DOT HS 811 296 March 2010

NHTSA Tire Aging TestDevelopment Project -Tire Innerliner Analysis

DISCLAIMER

This publication is distributed by the U.S. Department of Transportation, National Highway Traffic Safety Administration in the interest of information exchange. The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Department of Transportation or the National Highway Traffic Safety Administration. The United States Government assumes no liability for its contents or use thereof. If trade names, manufacturers’ names, or specific products are mentioned, it is because they are considered essential to the object of the publication and should not be construed as an endorsement. The United States Government does not endorse products or manufacturers.

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TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No.

DOT HS 811 296 2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

NHTSA Tire Aging Test Development Project - Tire Innerliner Analysis

5. Report Date

March 2010 6. Performing Organization Code

7. Author(s)

Uday Karmarkar1, Ana Barbur1, Edward R. Terrill, Ph.D.1, Mark Centea1, Larry R. Evans2, James D. MacIsaac Jr.3 1Akron Rubber Development Laboratory, Inc., 2Transportation Research Center Inc., 3National Highway Traffic Safety Administration

8. Performing Organization Report No.

9. Performing Organization Name and Address

Akron Rubber Development Laboratory, Inc. 2887 Gilchrist Rd. Akron, Ohio 44305

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTNH22-03-D-08660, DTNH22-07-D-00060

12. Sponsoring Agency Name and Address

National Highway Traffic Safety Administration 1200 New Jersey Avenue SE. Washington, D.C. 20590

13. Type of Report and Period Covered

Final 14. Sponsoring Agency Code

15. Supplementary Notes

Project support, testing, and analysis services provided by the Akron Rubber Development Laboratory, Smithers Scientific Services, Inc., Standards Test Labs, and Transportation Research Center, Inc. 16. Abstract

As a result of the TREAD Act of 2000, NHTSA initiated an effort to develop a laboratory-based accelerated service life test for light vehicle tires (herein referred to as a “tire aging test”). Scientific literature attributes the changes in properties of the tire rubber compounds and their interfaces to thermal-oxidation, a chemical reaction that involves heat and oxygen. Since the innerliner is the main barrier to permeation of the pressurized inflation gas (air containing degradative oxygen) through the tire, it was desired to know material composition, thickness, and permeability of a large cross-section of passenger vehicle tire innerliners in order to understand their influence on whole-tire performance in a tire aging test. Though example formulations for tire innerliner compounds are common in literature, the actual composition of a given tire’s innerliner is not publicly available. Currently there is no published analytical method for determining the exact material composition of the innerliner, which led to the development of the methodology outlined in this paper. Once an optimal innerliner analysis methodology was determined, the innerliners of six tire models collected from on-vehicle service in Phoenix, AZ, and 37 additional models used in laboratory phases of the project were analyzed. Microscopy analysis was used to determine innerliner gauge and placement. Innerliner permeability at two temperatures was measured on extracted innerliner slices. The air permeability results were correlated with the innerliner compositional results. Also completed were indentation modulus profiles of the innerliners of tires retrieved from service and after accelerated laboratory aging, which were benchmarked against new tires of each model. Results showed changes in the innerliner as a function of age (for in-service tires), as well as during accelerated laboratory aging tests. It is hypothesized that the observed changes in innerliner modulus during service or accelerated aging may affect the liner’s permeability and/or flexibility over time. 17. Key Words

Tire, aging, innerliner, butyl, polymer, permeability, tire safety, Phoenix, spare tire, accelerated service life

18. Distribution Statement

Document is available to the public from the National Technical Information Service www.ntis.gov

19. Security Classif. (of this report)

Unclassified 20. Security Classif. (of this page)

Unclassified 21. No. of Pages

104 22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

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TABLE OF CONTENTS EXECUTIVE SUMMARY .......................................................................................................... vii BACKGROUND ............................................................................................................................ 1 TEST TIRES ................................................................................................................................... 2

In-Service (Field) Tires ............................................................................................................... 2 Oven Aged Tires ......................................................................................................................... 2 Wheel-Tested (LTDE and P-END) Tires ................................................................................... 2

EXPERIMENTAL TECHNIQUES ................................................................................................ 2 Fourier Transform Infrared Spectroscopy (FTIR) ...................................................................... 3 Beilstein ...................................................................................................................................... 3 Energy Dispersive X-ray Spectroscopy (EDAX) ....................................................................... 3 X-ray Fluorescence (XRF) .......................................................................................................... 4 Pyrolysis-Gas Chromatography/Flame Ionization Detector (GC/FID) ...................................... 5 Pyrolysis-Gas Chromatography/Mass Spectroscopy (GC/MS) .................................................. 5 Thermal Gravimetric Analysis (TGA) ........................................................................................ 6 Extraction .................................................................................................................................... 6 Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-AES) ................................. 7 Oxygen Content (Fixed Oxygen by Weight) .............................................................................. 8 Permeability ................................................................................................................................ 8 Microscopy ................................................................................................................................. 9 Indentation Modulus ................................................................................................................... 9 ASTM D 2240 Type A Durometer Hardness ........................................................................... 10

INNERLINER FORMULA RECONSTRUCTION ..................................................................... 11 REGRESSION ANALYSIS ......................................................................................................... 13 RESULTS ..................................................................................................................................... 13

Part I - Model Liner Compound Chemical Analysis ................................................................ 13 Part II - Chemical Analysis of the Innerliner from Six Tire Models Retrieved from Service in Phoenix, AZ .............................................................................................................................. 26 Part II - Chemical Analysis of the Innerliners from Addition Tire Models .............................. 29 Part IV - Permeability of Model Compounds ........................................................................... 48 Part V - Permeability of Innerliners from Production Tires ..................................................... 54 Part VI - Microscopy of Innerliners from Production Tires ..................................................... 60 Part VII - Indentation Modulus of Innerliners from Production Tires ...................................... 62

CONCLUSIONS........................................................................................................................... 84 REFERENCES ............................................................................................................................. 91

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LIST OF FIGURES Figure 1. FTIR Test......................................................................................................................... 3 Figure 2. SEM/EDAX Test ............................................................................................................. 4 Figure 3. XRF Test ......................................................................................................................... 5 Figure 4. Pyrolysis GC/FID Test .................................................................................................... 5 Figure 5. TGA Test ......................................................................................................................... 6 Figure 6. Extraction Test ................................................................................................................. 7 Figure 7. ICP-AES Test .................................................................................................................. 8 Figure 8. Permeability Test ............................................................................................................. 9 Figure 9. Microscopy ...................................................................................................................... 9 Figure 10. Modulus Profiling Test ................................................................................................ 10 Figure 11. Overlay Plot of the TGA Weight Loss Curves ........................................................... 19 Figure 12. Overlay Plot of the TGA Derivative Curves .............................................................. 19 Figure 13. TGA Derivative Curves for Model Compounds 1, 18, 2, 3, 4, 5, and 6. .................... 20 Figure 14. TGA Derivative Curves for Model Compounds 7, 8, 9, 10: Increasing Levels of Natural Rubber with Chlorobutyl ................................................................................................. 21 Figure 15. TGA Derivative Curves for Model Compounds 1, 13, 14, 15, 16, 17: Increasing Levels of oil-extended SBR with Bromobutyl.............................................................................. 21 Figure 16. TGA Derivative Curves for Model Compounds 1, 7, 11: ........................................... 22 Figure 17. FTIR of Model Liner Compounds 1, 3, 5, 7, 9 ............................................................ 23 Figure 18. Correlation between XRF Bromine Content and phr Bromobutyl .............................. 24 Figure 19. Correlation between XRF Chlorine Content and phr Chlorobutyl .............................. 25 Figure 20. Correlation between Bromine Intensity and phr Bromobutyl ..................................... 26 Figure 21. Correlation between Chlorine Intensity and phr Chlorobutyl ..................................... 26 Figure 22. Pyrolysis-GC/FID Analysis of SBR (1502) Gum Polymer ......................................... 38 Figure 23. Pyrolysis-GC/FID Analysis of BIIR Gum Polymer .................................................... 38 Figure 24. Pyrolysis-GC/FID Analysis of Natural Rubber Gum Polymer ................................... 39 Figure 25. Pyrolysis-GC/FID Calibration Curve for Polyisobutylene Based on Isobutylene ...... 39 Figure 26. Pyrolysis-GC/FID Calibration Curve for Polyisoprene Based on Isoprene ................ 40 Figure 27. Pyrolysis-GC/FID Calibration Curve for Styrene Butadiene Polymer Based on Styrene .......................................................................................................................................... 40 Figure 28. Pyrolysis-GC/FID Calibration Curve for Styrene Butadiene Polymer Based on Butadiene ...................................................................................................................................... 41 Figure 29. Pyrolysis-GC/MS Calibration Curve for Polyisobutylene Based on Isobutylene ....... 43 Figure 30. Pyrolysis-GC/MS Calibration Curve for Polyisobutylene Based on Isobutylene Tetramer ........................................................................................................................................ 44 Figure 31. Pyrolysis-GC/MS Calibration Curve for Polyisoprene Based on Isoprene ................. 44 Figure 32. Pyrolysis-GC/MS Calibration Curve for Polyisoprene Based on Isoprene Dimer ..... 45 Figure 33. Pyrolysis-GC/MS Calibration Curve for Styrene Butadiene Polymer Based on Styrene....................................................................................................................................................... 45 Figure 34. Pyrolysis-GC/MS Calibration Curve for Styrene Butadiene Polymer Based on Butadiene Dimer ........................................................................................................................... 46 Figure 35. Permeability of Model Compounds at 21°C as a Function of Butyl Content ............. 51 Figure 36. Permeability of Model Compounds at 70°C as a Function of Butyl Content ............. 51 Figure 37. Permeability of Model Compounds at 21°C as a Function of Butyl Content ............. 53

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Figure 38. Permeability of Model Compounds at 65°C as a Function of Butyl Content ............. 53 Figure 39. Permeability of Tire Innerliners at 21°C as a Function of Butyl Content ................... 57 Figure 40. Permeability of Tire Innerliners at 65°C as a Function of Butyl Content ................... 59 Figure 41. Microscopy Innerliner Analysis of Production Tires .................................................. 62 Figure 42. Indentation Modulus Test Samples and Plots for a Phoenix-Retrieved Tire .............. 63 Figure 43. Average Indentation Modulus of Shoulder Region Innerliner as a Function of Age .. 64 Figure 44. Average Change in Indentation Modulus of Shoulder Region Innerliner for Six Tire Models During Service in Phoenix, AZ ........................................................................................ 65 Figure 45. Average Change in Indentation Modulus of the Shoulder Region Innerliner Versus LTDE Roadwheel Hours ............................................................................................................... 67 Figure 46. Average Change in Indentation Modulus of the Shoulder Region Innerliner Versus P-END Roadwheel Hours ................................................................................................................. 68 Figure 47. Average Change in Indentation Modulus of Shoulder Region Innerliner for Capped-Inflation Oven Aging .................................................................................................................... 70 Figure 48. Model Prediction of Innerliner Indentation Modulus with Capped-Inflation Oven Aging............................................................................................................................................. 71 Figure 49. Change in Average Indentation Modulus of Innerliner in Shoulder Region for 8 Weeks Oven Aging @ 65°C with 23-hour Break-in .................................................................... 74 Figure 50. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 3 or 5 Weeks Oven Aging @ 65°C with 2-hour Break-in ...................................................................... 76 Figure 51. Average Indentation Modulus of Innermost Layer of Bead Region for Five Phoenix Tire Models ................................................................................................................................... 78 Figure 52. Average Indentation Modulus of Innermost Layer in Bead Region for Capped-Inflation Oven Aging .................................................................................................................... 79 Figure 53. Change in Average Indentation Modulus of Innerliner in Bead Region for 8 Weeks Oven Aging @ 65°C with 23-hour Break-in ................................................................................ 80 Figure 54. Change in Average Indentation Modulus of Innerliner in Bead Region for 3 or 5 Weeks Oven Aging @ 65°C with 2-hour Break-in (at 50 mph) ................................................... 82

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LIST OF TABLES Table 1. Model Innerliner Formulation ........................................................................................ 12 Table 2. Analyses Used in Formula Reconstruction Estimates for Innerliner Compounds ......... 12 Table 3. Model Bromobutyl/Natural Rubber Liner Compounds .................................................. 14 Table 4. Model Chlorobutyl/Natural Rubber Liner Compounds .................................................. 15 Table 5. Model Bromobutyl/SBR Liner Compounds ................................................................... 16 Table 6. Six Additional Model Compounds for Liner Permeability Testing ............................... 16 Table 7. Acetone Extraction of Model Liner Compounds ............................................................ 17 Table 8. Oxygen Content of Model Liner Compounds ................................................................ 17 Table 9. Ash Composition of Model Liner Compounds............................................................... 18 Table 10. TGA Compositional Analysis (wt%) ............................................................................ 20 Table 11. Actual Compositional Analysis (wt%) ......................................................................... 20 Table 12. FTIR Analysis ............................................................................................................... 22 Table 13. XRF Analysis Results of Model Compounds ............................................................... 24 Table 14. EDAX of Model Compounds ....................................................................................... 25 Table 15. List of Six Phoenix-Retrieved Tire Models .................................................................. 27 Table 16. Acetone Extractables (wt%) of the Six Phoenix Tire Models ...................................... 27 Table 17. ICP-AES Analysis of the Six Phoenix Tire Models ..................................................... 27 Table 18. TGA Compositional Analysis of the Six Phoenix Tire Models (wt%) ........................ 28 Table 19. Beilstein and FTIR Results ........................................................................................... 28 Table 20. XRF Analysis Results ................................................................................................... 28 Table 21. EDAX Results for Chlorine and Bromine Analysis ..................................................... 29 Table 22. EDAX Prediction for Chlorobutyl and Bromobutyl ..................................................... 29 Table 23. EDAX Results for Other Elements Analysis ................................................................ 29 Table 24. Thirty Seven Additional Production Tires Models Analyzed by Extraction, TGA, XRF, Pyrolysis-GC/MS .......................................................................................................................... 30 Table 25. Acetone Extractables (wt%) of Additional Tires .......................................................... 31 Table 26. Composition Analysis by TGA..................................................................................... 32 Table 27. XRF Analysis of 31 Tire Innerliners ............................................................................ 35 Table 28. EDAX Results (for Bromine and Chlorine) ................................................................. 36 Table 29. EDAX Prediction of Tire Innerliner Polymers ............................................................. 36 Table 30. EDAX Results (for Other Elements) ............................................................................ 37 Table 31. Pyrolysis-GC/FID Peak Identification .......................................................................... 37 Table 32. Pyrolysis-GC/FID Analysis Summary .......................................................................... 41 Table 33. Pyrolysis-GC/MS Peak Identification .......................................................................... 43 Table 34. Pyrolysis-GC/MS Analysis Summary .......................................................................... 47 Table 35. Summary of Average GC Innerliner Composition by Tire Manufacturer .................... 48 Table 36. Conversion Table .......................................................................................................... 49 Table 37. Air Permeability Literature Values ............................................................................... 49 Table 38. Model Liner Compound Air Permeability Data ........................................................... 50 Table 39. 21°C Model Compound Permeability Data (66.4 cm2 Cell Size) ................................ 52 Table 40. 65°C Model Compound Permeability Data (66.4 cm2 Cell Size) ............................... 52 Table 41. Innerliner Permeability Data at 21°C for the Six Field Tire Models ............................ 55 Table 42. Innerliner Permeability Data at 21°C for Subsequent Test Tires ................................. 56 Table 43. Innerliner Permeability Data at 65°C for Six Field Tire Models .................................. 58

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Table 44. Innerliner Permeability Data at 65°C for Subsequent Test Tires ................................. 58 Table 45. Microscopy Innerliner Analysis of Production Tires ................................................... 60 Table 46. Average Change in Indentation Modulus of Shoulder Region Innerliner During Service in Phoenix, AZ .............................................................................................................................. 66 Table 47. Average Change in Indentation Modulus of the Shoulder Region Innerliner During LTDE Testing ............................................................................................................................... 67 Table 48. Oven Aging Conditions with Capped Inflation Gas - Six Phoenix Tire Models ......... 69 Table 49. Average Change in Indentation Modulus of Shoulder Region Innerliner During Capped-Inflation Oven Aging ....................................................................................................... 70 Table 50. Regression Analysis of Innerliner Modulus as a Function of Oven Temperature and Tire Type ....................................................................................................................................... 72 Table 51. Oven Aging Conditions with Vent and Refill of Inflation Gas - 21 Additional Tire Models........................................................................................................................................... 73 Table 52. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 8 Weeks Oven Aging @ 65°C with 23-hour Break-in ................................................................................ 75 Table 53. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 3 or 5 Weeks Oven Aging @ 65°C with 2-hour Break-in ...................................................................... 77 Table 54. Change in Avg. Indentation Modulus of Innerliner in Bead Region During Service in Phoenix, AZ .................................................................................................................................. 78 Table 55. Average Change in Indentation Modulus of Innermost Layer in the Bead Region During Capped-Inflation Oven Aging .......................................................................................... 79 Table 56. Change in Average Indentation Modulus of Innerliner in Bead Region for 8 Weeks Oven Aging @ 65°C with 23-hour Break-in (at 50 mph) ............................................................ 81 Table 57. Change in Avg. Indentation Modulus of Innerliner in Bead Region for 3 or 5 Weeks Oven Aging @ 65°C with 2-hour Break-in .................................................................................. 83 Table 58. Summary Table of Average Change and Rate of Change in Innerliner Modulus by Condition....................................................................................................................................... 84

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EXECUTIVE SUMMARY

In reviewing potential upgrades to the Federal Motor Vehicle Safety Standards (FMVSS) for tires, the United States Department of Transportation, National Highway Traffic Safety Adminis-tration initiated an effort to develop a laboratory-based accelerated service life test for light ve-hicle tires (herein referred to as a “tire aging test”). Laboratory tire aging tests attempt to simu-late, in an accelerated manner, the degradative process that tires experience while in service, and then evaluate the durability of the tire in an “aged” state. It is believed that if such a test method was successful, then light vehicle tires could eventually be required to meet standards that would make them more resistant to operational degradation and possibly reduce their failure rate during normal highway service. Scientific literature attributes the changes in properties of the tire rubber compounds and their interfaces to thermal-oxidation, a chemical reaction that involves heat and oxygen. A key tire component affecting thermal-oxidation in tires is the innerliner, since it slows the diffusion of air (more importantly oxygen in air) from the pressurized internal tire cavity through the tire struc-ture during service. The permeation of inflation gas out of the tire also reduces inflation pressure, which must be continually maintained by the consumer or the tire will be operated in an underin-flated state. Operation of the tire while underinflated is known to increase rolling resistance and wear, and with increasing amounts of underinflation can lead to thermal flex-fatigue damage or destruction of the tire. Therefore, modern tubeless radial tires employ a low-permeability inner-liner layer that lessens the permeation of the inflation gas through the tire. Innerliner polymer compositions, filler levels, thicknesses, and placement techniques vary widely between manufac-turers. The overall thickness and construction features of a tire also factor into the inflation gas permeation rates. For instance, a thick light truck tire may have a lower inflation pressure loss rate than a thin high performance passenger tire at the same pressure when using identical inner-liner compounds and thicknesses. Therefore, for each tire design, the manufacturer determines a desired balance between innerliner cost, production constraints, and performance. Since the innerliner is the main barrier to permeation of the pressurized inflation gas (containing degradative oxygen) through the tire, it was desired to know material composition, thickness, and permeability of a large cross-section of passenger vehicle tire innerliners in order to understand their influence on whole-tire performance in a tire-aging test. Though example formulations for tire innerliner compounds are common in literature, the actual composition of a given tire’s in-nerliner, which can vary in formulation even between tires from the same plant, is not publicly available. The authors were unable to identify a published analytical method for determining the exact material composition of an innerliner. Therefore, model innerliner compounds with known formulations were used to establish analytical baselines in the development of a methodology to determine a tire’s innerliner composition. Once an optimal analysis methodology was determined, the innerliners of six tire models col-lected from on-vehicle service in Phoenix, AZ, as well as 37 additional models used in laborato-ry phases of the project were analyzed. Microscopy analysis of tire cross-sections was used to determine innerliner gauge and placement. Innerliner permeability was measured on extracted liner slices. The air permeability results were correlated with the innerliner compositional results, for which butyl content was determined to be a major factor affecting permeability rates.

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The next topic examined was whether or not the modulus of tire innerliners changed during ser-vice. First, results from six tire models retrieved from service in Phoenix, AZ indicated that the innerliner in the shoulder region of the tires increased by approximately 0.21 MPa per year, and the innermost layer of the bead region (not always innerliner) increased 0.23 MPa per year. Total increases of 1.79 MPa in the shoulder region and 4.76 MPa in the bead region were observed during long terms of service. The second topic compared the changes in the modulus of tire in-nerliners during accelerated aging to the magnitudes observed in tires retrieved from on-vehicle service. For the original six tire models collected in Phoenix, both the roadwheel and oven acce-lerated aging tests could produce changes in innerliner modulus that were similar to those ob-served in on-vehicle tires. The magnitude of the increase in innerliner modulus of the six models could exceed levels observed after up to seven years of service when tires were exposed to 500 hours of LTDE roadwheel testing or eight weeks of capped-inflation oven aging. The 22 addi-tional tire models subjected to three to eight weeks of oven aging with vent and refilled inflation showed average changes in innerliner/innermost layer modulus in the shoulder and bead region that were within the ranges of values observed in in-service tires. It is hypothesized that the ob-served changes in innerliner modulus during service or accelerated aging may affect the liner’s permeability and/or flexibility over time.[1]

Future evaluations of accelerated aging tests will examine possible correlations between the in-nerliner properties of each tire model documented in this report to each tire model’s whole-tire performance in proposed accelerated aging tests.

BACKGROUND

Tires of six of the models used in this paper were collected from on-vehicle service in Phoenix, Arizona and analyzed by NHTSA during development of an accelerated tire durability test.[2] Scientific literature primarily attributes the changes in properties of the rubber compounds and their interfaces to other components to thermal-oxidation.[4-15] A key tire component affecting thermal-oxidation in tires is the innerliner since it slows the diffusion of oxygen from the pressu­rized tire cavity through the tire structure during service. As explained by Niziolek, Nelsen, & Jones (2000):

“The innerliner is one of the most critical components affecting the durability of tubeless

pneumatic tires. The function of the innerliner is to provide an effective barrier that main­

tains the correct inflation pressure and also minimizes the flow of oxygen and water va­

por from the inflation air through the tire structure. Maintaining the correct inflation pres­

sure is related to the diligence of the vehicle owner/operator but is greatly facilitated by

the effectiveness of the innerliner as an air barrier by avoiding the need for frequent air

pressure checks and adjustments. To preserve carcass integrity the flow of inflation air

and accompanying oxygen and water vapor into interior components of the tire must be

minimized in order to prevent separations and failures due to the buildup of intracarcass

pressure, and oxygen and water induced degradation and loss of adhesion.”[14]

Several authors have described the effect of liner composition on liner permeability.[3,16-17] These studies have also demonstrated the effects of liner permeability and liner gauge on intra­carcass pressure and inflation pressure retention. The effect of compound variables on innerliner permeability has been studied.[17-19] Coddington (1979) examined correlations between inner-liner permeability, oxidation, and belt edge durability during roadwheel testing.[3] Tokita, Sig­worth, Nybakkan, & Ouyang (1985) concluded that liner permeability and gauge had a strong influence on the generation of belt edge separations in radial tires.[20] Waddell (2006-07) found strong correlations between innerliner permeability, or whole tire air loss rate, on intra-carcass pressurization, belt edge separation, and time to failure in roadwheel durability test (both with and without accelerated aging), among tires of the same design with varied innerliner formula­tions.[21-26] However, he found no correlation between inflation pressure loss rate and perfor­mance in a stepped-up load roadwheel test across dissimilar models of new tires from different manufacturers.[24,26] Therefore, the research implies that construction features of the tire beyond innerliner permeability and air loss rate also strongly factor into the performance of the tire during roadwheel testing.

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TEST TIRES

In-Service (Field) Tires The field tires consisted of six brands with a wide age range collected from Phoenix, Arizona (the NHTSA Phoenix Tire Dataset).[2] The “DOT age” variable was the time between the tire’s production date and collection date. The mileage was based on odometer reading at collection date for original equipment (OE) tires. Mileage was estimated for replacement tires by using the average number of miles per year accumulated on the vehicle multiplied by the age of the tire.

Oven Aged Tires A wide variety of oven aging conditions were evaluated during the multiple phases of the test program. For some tires, a pre-oven roadwheel break-in was applied. The break-in used in the earliest phase of test development was 50/50 O2/N2 inflation, maximum sidewall pressure, max­imum sidewall load, for 24 hours at 75 mph. A subsequent phase used air inflation, sidewall pressure corresponding to maximum sidewall load, maximum sidewall load, for 23 hours at 50 mph. The final phase used air inflation, sidewall pressure corresponding to maximum sidewall load, maximum sidewall load, for 2 hours at 50 mph. The tires were oven-aged from 2 to 12 weeks at 55�C to 70�C using 50/50 O2/N2 inflation gas. The inflation pressure used in the earliest phase of test development was the maximum pressure listed on the sidewall. Later phases used the pressure that corresponded to the maximum sidewall load from the Tire & Rim Association or equivalent tables. The tire cavity pressure was either capped, which allowed the pressure and gas composition to change over the test period, or the inflation gas was replenished weekly, by vent and re-inflate.

Wheel-Tested (LTDE and P-END) Tires Two roadwheel tests were evaluated. The first roadwheel aged endurance test was the Long Term Durability and Endurance (LTDE) test. The LTDE test was developed by Michelin and shared with NHTSA.[27] The roadwheel hours on the LTDE test were varied by NHTSA from 100 to 508 hours, which was thought to impart 1-5 years of equivalent aging. The second method is called the Passenger Tire Endurance (P-END) test. The P-END test was developed by Conti­nental Tire and submitted to NHTSA on a confidential basis. The details of the methods will not be discussed in this paper. The roadwheel hours on the P-END test were varied by NHTSA from 96 to 240 hours, which was also thought to impart 1-5 years of equivalent aging.

EXPERIMENTAL TECHNIQUES

The tires were dissected to remove the innerliner compound for testing. The innerliner compound was taken from the inside tire surface in a slice that was typically about 0.5-1 mm (20-40 mil) thick. The innerliners from the three groups of tires were subjected to the following chemical and physical analyses:

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Fourier Transform Infrared Spectroscopy (FTIR) This method provided polymer identification.[28,29] Polymer identification was performed by FTIR (ASTM D 3677-90 [1995]) using a Perkin Elmer Spectrum BX Spectrometer. Transmit­tance was measured as a function of wavelength using a sodium chloride crystal. The polymers were identified two ways, by the examination of pyrolysis products or cast films. The sample was extracted with an organic solvent to remove the organic additives (plasticizers, antioxidants, antiozonants, waxes, oils, etc.) and purify the polymers. The polymer is then thermally degraded and the resulting pyrolyzate is examined using infrared spectroscopy. For cast film samples, the polymer was dissolved in a suitable solvent, filtered, and cast on a sodium chloride plate. The infrared spectra were compared to known reference spectra that have been generated at ARDL to identify the polymers. Figure 1 shows the FTIR equipment and test sample. The use of FTIR for polymer identification is well known.[30-35]

Figure 1. FTIR Test Equipment Test Sample

Beilstein This chemical test is a qualitative flame that was used to determine whether halogens are present. In this study, the test was used to detect the presence of chlorine or bromine halogens (i.e., chlo­ro- or bromo-butyl rubber) in the innerliner compound.

Energy Dispersive X-ray Spectroscopy (EDAX) This chemical test was used to identify chlorine, bromine and zinc levels semi-quantitatively. The sample was prepared by placing the tire innerliner on an aluminum pin mount coated with double-sided carbon adhesive tape. EDAX was used in conjunction with the scanning electron microscope providing chemical analysis (Figure 2). EDAX can detect all elements except H, He, Li, and Be. Tire innerliners were analyzed using a Cambridge S150T SEM interfaced with an EDAX PV9800 X-ray detector and IXRF EDS2004 X-ray analysis computer software. The Backscatter Detection (BSD) mode was used for imaging. Energy Dispersive X-ray (EDX) anal­ysis was done on elements above Sodium (Na) in the periodic table in the energy range from 0 KeV to 20 KeV. The x-ray spectral lines were calibrated using a copper/aluminum standard to assure correct identification of the elements. Automatic baseline correction is used and only those elements above the background matrix are reported. Results should be considered as being

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semi-quantitative. It should be kept in mind that only an area approximately 1.1 mm2 was being analyzed, and the sample may not be homogenous over a larger area. The beam energy used was 20 KeV, which would penetrate the surface to a depth of about 7µm. The results reflect the rela­tive amounts of the elements present in the surfaces of the samples to this depth. All samples were analyzed in the same manner using ZAF correction for the semi-quantitative analysis at a sample tilt of 20�. Contained in Figure 2 is an EDX spectrum of a sample. All data for each sam­ple was normalized to 100%.

Figure 2. SEM/EDAX Test Test Equipment Output

X-ray Fluorescence (XRF) The method used a Jordan Valley EX-3600M TEC Laboratory Spectrometer for qualitative de­termination of solid samples for elements of atomic mass greater than sodium (Figure 3).[36,37] The results are reported in three different concentration groups, i.e. major (>1%), minor (100ppm-1%), traces (<100ppm). The sample was placed into a disposable cup. The X-ray source was a palladium tube using a 45kV accelerating voltage. One set of spectra was the result of analysis with a titanium target. In the titanium secondary target analysis, the source was pointed at the target and the target element was excited and fluoresced. Then the target fluores­cence was used to excite the sample. The titanium target increased the sensitivity for the light elements (see figure). This was utilized for the analysis and detection of the following elements (Sulfur, Silicon, Potassium, and Calcium). The second sets of spectra were analyzed with a Col­limator. A collimator was placed between the source and sample to reduce signal (background). This technique was also used to determine remaining elements (Bromine, Iron, Zinc, and Chlo­rine) (see figure). The elements contained in the sample are thereby excited to emit the element-specific X-ray fluorescence radiation. A liquid nitrogen cooled light element detector (LED) Si(Li) measured the fluorescent and scattered x-rays from the sample as a multichannel analyzer and software assigned each pulse an energy value, thus producing the spectrum.

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Figure 3. XRF Test Test Equipment Output for Light ElementsOutput for Heavy Elements

Pyrolysis-Gas Chromatography/Flame Ionization Detector (GC/FID) This test method provided quantification of butyl rubber, natural rubber, polybutadiene rubber, and styrene butadiene rubber in rubber compounds.[38,39] The analytical system consisted of a PerkinElmer Clarus 500 GC/FID interfaced with a CDS Analytical Pyroprobe 5000 Pyrolysis Autosampler (Figure 4). Samples were loaded into the pyroprobe and rapidly pyrolyzed at 550�C. The volatiles and degradation products were automatically introduced into the GC carrier stream and transferred to the GC column equipped with a non-polar capillary column for analysis by GC/FID. Only monomer peaks (isobutylene, isoprene, styrene, and butadiene) having the highest intensity were used for the calibration. A piece of sample about 0.5 mg was used. To have sufficient separation between isobutylene and 1,3 butadiene, the GC oven was cooled down to -20�C, using liquid nitrogen. The test’s duration was about 40 minutes. The detection limits are about +/-5 weight percent for the polymer components in the formulation. The peak assign­ments and calibration are in the discussion section.

Figure 4. Pyrolysis GC/FID Test Test Equipment Loading Sample into Pyroprobe

Pyrolysis-Gas Chromatography/Mass Spectroscopy (GC/MS) This method also provided quantification of butyl rubber, natural rubber, polybutadiene rubber, and styrene butadiene rubber in rubber compounds.[40-48] The analytical system consisted of a PerkinElmer Clarus 500 GC/ 560D MS interfaced with a CDS Analytical Pyroprobe 5000 Pyro­

5

lysis Autosampler. Samples were rapidly pyrolyzed at 550�C. The volatiles and degradation products were automatically introduced into the GC carrier stream and transferred to the GC col­umn equipped with a non-polar capillary column for analysis by GC/MS. A piece of sample about 0.2 mg was used. The tests duration was about 40 minutes. The detection limits are about +/-5 weight percent for the polymer components in the formulation. The peak assignments and calibration are in the discussion section.

Thermal Gravimetric Analysis (TGA) TGA is a useful tool for characterizing polymers.[49-54] TGA has been utilized to characterize the polymer type in blends.[55] The weight loss as a function of temperature has been used to determine polymer loading, rubber chemical loading, carbon black loading and ash levels. For polymers with very different thermal stabilities, the TGA curves can be used to determine the amount of each polymer present. Thermogravimetric analysis (TGA) was performed using about 10 mg of sample (Figure 5). The purge (He) gas flow rate to the TGA was set at 10ml/min during weight loss measurements. The heating rate was 10�C/min to improve the resolution of small variations in the decomposition curves. At 600�C, the purge gas was switched over to air for car­bon black combustion. The total analysis time was approximately 1.5 hours.

Figure 5. TGA Test Test Equipment Loading Sample

Extraction Solvent extraction with acetone was used to remove non-polymerized organic components. Ex­tractable content was measured per ASTM D297-93 with acetone solvent. To perform the analy­sis, a sample was placed in a paper thimble and extracted for 16 hours with acetone at reflux conditions using an extraction apparatus (Figure 6). The solvent removed plasticizers, processing aids, organic accelerators or their decomposition products, fatty acids, antioxidants, antiozonants, resins, free sulfur, and other organic additives. The extractable content was used in the calcula­tion of the rubber hydrocarbon content (RHC).

6

Figure 6. Extraction Test Test Equipment Loading Sample

Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-AES) Inductively Coupled Plasma (ICP) – Atomic Emission Spectroscopy (AES) was used to quantita­tively determine inorganic content. The metal contents were determined according to ASTM D 1971-02. Atomic emission spectroscopy (AES) used quantitative measurement of the optical emission from exited atoms to determine their concentration. The sample was ashed and dis­solved in acid. The metals were acid digested on a hot plate to solubilize the elements of interest. The digested solutions were pumped into the plasma as a liquid stream at the rate of about 1 mL per minute with a peristaltic pump and introduced to the Spectro FTP-08 ICP Analyzer (Figure 7). The solution was aspirated into the excitation region where they were desolvated, vaporized, and atomized in Argon plasma. All the compounds are dissociated and yield atomic emission spectra. The inductively coupled plasma (ICP) was at a very high temperature (7000-8000�K) for excitation. The high temperature atomization source promoted the atoms into high energy levels. The atoms decay back to lower levels by emitted light. Since all atoms in the sample were ex­cited simultaneously, they can be detected simultaneously. The results are reported in parts per million of the sample, typically quantitative analysis of 21 elements.

7

Figure 7. ICP-AES Test Test Equipment Loading Sample

Pump Starting Test

Oxygen Content (Fixed Oxygen by Weight) This method measures oxygen content (elemental oxygen analysis) of an organic material ex­pressed in weight percent of elemental oxygen per weight of sample. The equipment is a Perkin Elmer PE 2400 Oxygen Elemental Analyzer with furnace temperature of 1200�C, carrier gas He/H2, and specimen size of 2 mg. The calibration involves purging the unit with carrier gas (He/H2) for 10 to 30 minutes and running three (3) blanks to get an average blank value. Then run three (3) benzoic acid standards to determine the calibration coefficient. The samples were tested after establishing the blank (correction) and calibration coefficient.

Permeability The innerliner sample’s permeability to gas transmission was measured at two temperatures (21�C and 65�C). Method ASTM D1434-82, procedure V was used.[56-60] The units on per­meability are cubic centimeter oxygen at STP1-cm/cm2-sec atm. The apparatus by which per­meability was measured works on the principles described by G. J. van Amerongen.[60] The gas cell is made of two parts of steel, containing gas chambers separated from each other by a rubber membrane ( Figure 8 ). The testing was performed with either a 66.4 cm2 or an 8.04 cm2 surface area permeability cell. The gas was introduced into the lower chamber. The upper chamber was

1 Standard Temperature and Pressure of 273K (0°C) and 1 atmosphere (101.325 kPa)

8

connected to a volume gauge. The volume changes were recorded and permeability calculated using the equations in ASTM D1434.

Figure 8. Permeability Test Test Equipment Sample and Fixture

Microscopy Microscopy measurements were used to determine innerliner thickness. Measurements were tak­en on tire “omega” sections (a cross-section of the tire from bead to bead). All measurements were taken on scanned, polished cross-sections using measurement software and NIST-traceable calibration standards (Figure 9). The individual component thicknesses in each cross-section were measured and entered into Excel spreadsheets.

Figure 9. Microscopy Test Equipment Micrograph of a Tire Cross-Section

Indentation Modulus Indentation modulus profiling was conducted to map the modulus (akin to hardness) of the rub­ber compound across the thickness of the innerliner. The indentation modulus measurements (for modulus profiling) were performed in accordance with the methodology published by Gillen,

9

Figure 10. Modulus Profiling Test Test Equipment Schematic

Probe Probe in Contact with Sample

Terrill, & Winter (2001). The equipment in Figure 10 was used to acquire indentation modulus measurements of the rubber components in 0.1 mm increments from interior to exterior surface of the region studied (innerliner to tread for the shoulder region, innerliner to sidewall for bead region). Test specimens were obtained with minimal heat input in an embedment medium suita­ble for grinding and polishing in order to obtain a flat surface for measurement. A single radial scan was performed on tread tire in the shoulder of the crown and the lower sidewall at the rim flange.

ASTM D 2240 Type A Durometer Hardness Durometer hardness measurements were conducted on the innerliner to measure the bulk hard­ness of the innerliner components as an indicator of initial cure and state of oxidation. Two in­nerliner samples were measured from each tire, one sample from the centerline of the crown at 0 degrees from the Tire Identification Number (TIN or “DOT Code”), and one sample from the centerline of the crown at 180 degrees from the TIN. Five ASTM D 2240 Type A Durometer hardness measurements were performed on each sample.

10

INNERLINER FORMULA RECONSTRUCTION

To estimate the composition of the innerliner compound a variety of steps are necessary. An in­nerliner compound contains a variety of components, however the type of materials and their functions are generally known in the industry. There are numerous techniques that can be used in concert to provide complementary information to estimate the components of a rubber com­pound. These include such general categories as:

• Measuring the amount of ingredients by physical separation of the components, for in­stance by volatility using pyrolysis or thermogravimetric analysis (TGA), or solubility us­ing solvent extraction. The separated components can be subjected to further analysis.

• Measuring the energy emission or absorption of atoms or chemical groups. For instance, x-ray emission spectroscopy measuring the characteristic energy released by an atom struck by x-rays, or Fourier transform infrared spectroscopy (FTIR) measuring the ab­sorption of infrared energy corresponding to specific chemical bonding.

• Measuring the interaction of a component with a medium. For instance, gas chromato­graphy (GC) measuring the interaction with a defined surface as molecules in the gas phase are moved along.

• Measuring the reaction of a component. For instance, the Beilstein test turns a flame green when a copper wire has been reacted with a compound containing halogen.

• Measuring the size or mass of a component. For instance, mass spectrometry (MS) corre­lating the molecular mass of a component with its reaction to a magnetic field.

By combining techniques, either in series (e.g. pyrolysis/GC/MS) or in parallel (TGA and FTIR) there are a wide variety of ways to determine composition of a compound. The analytical tech­niques used in this study are only a small sampling of those available, and new techniques with greater sensitivity and selectivity are being introduced to the field on a regular basis.

A typical model compound formulation is shown in Table 1 below.[62] Rubber compounds are normally specified in parts per hundred rubber (phr), where the amount of rubber is set to 100, and all other components are specified as a ratio to the amount of rubber. The percent by weight is also shown for comparison. Using this compound as an example, the process used to estimate the formulation of the innerliners in this study is shown in Table 2. Detailed explanations of the test techniques are found in the Experimental Techniques section of this report. It should be noted that the materials were identified based on well-known compounding practices. For in­stance, the presence of isobutylene groups and bromine atoms is assumed to indicate the use of bromobutyl polymer, and not some heretofore-unknown use of isobutylene rubber and a bromi­nated flame retardant in a tire innerliner.

11

Table 1. Model Innerliner Formulation

Ingredient phr % by weight

Brominated Polyisobutylene Rubber (HIIR) 70 30.77 Natural Rubber (NR) 30 13.19 Carbon Black 60 26.37 Clay 40 17.58 Stearic Acid 1 0.44 Processing Oil 10 4.40 Tackifier Resin 15 6.59 Zinc Oxide 5 2.20 Sulfur 0.5 0.22 Accelerator 1 0.44

Total 227.5 100

Table 2. Analyses Used in Formula Reconstruction Estimates for Innerliner Compounds Compound Analysis Technique Employed Comments

Thermal Gravimetric Analysis (TGA) is used to es­timate the amount of:

• moisture, stearic acid, processing oil, anti­oxidants, antiozonants, unreacted sulfur, ac­celerator fragments, and tackifier resin

• polymer, including small amounts of reacted sulfur and accelerator

• carbon black • inorganic material, in this example zinc oxide

and clay.

Base amount of polymer and phr carbon black determined. Total parts per hun­dred (phr) of volatile and inorganic ma­terial determined.

Inductively Coupled Plasma-Optical Emission Spec­troscopy (ICP-AES) of inorganic ash quantitatively determines elements present:

• zinc Ł zinc oxide • aluminum Ł clay (aluminosilicate) • magnesium Ł talc (magnesium silicate) • calcium Ł calcium carbonate

The phr of zinc oxide, clay, talc or cal­cium carbonate determined.

Solvent extraction with acetone to remove non-polymerized organic components, such as processing oil, tackifier resin, etc., followed by dissolving the polymer and analysis by Fourier Transform Infrared Spectroscopy (FTIR).

Type of polymer(s) identified.

Pyrolysis/Gas Chromatography/Mass Spectroscopy (GC/MS).

Provides best quantitative data for ratio of polymer type in compound.

Energy Dispersive X-ray Spectroscopy (EDAX) Identifies chlorine, bromine and zinc semi-quantitatively.

12

Beilstein test. Presence of chlorine or bromine identi­fied.

Energy Dispersive X-Ray Fluorescence Spectroscopy (XRF).

Identifies chlorine or bromine semi-quantitatively.

Pyrolysis/Gas Chromatography/Flame Ionization De­tection (GC/FID).

Provides quantitative data for ratio of polymer type in compound.

Oxygen Content of innerliner. Determines elemental oxygen content per weight of sample. Can be used as an indicator of oxidation of the material.

Physical Analysis Technique Employed Comments Permeability of innerliner sample. Measures the permeation of gas through

the innerliner material using ASTM D1434 protocols.

Microscopy of tire cross-section to measure innerlin­er thickness.

Innerliner thickness varies throughout the bead-to-bead cross-section of a tire. The location(s) of each microscopy measurement must be consistent from sample to sample.

Indentation modulus profiles of tire shoulder region. Measures innerliner modulus (akin to hardness) values at the shoulder. Can be used to map the modulus of the com­pound across the thickness of the inner-liner. Indicator of the state of cure for new tires and can track the evolution of modulus properties across the compo­nent profile.

ASTM D 2240 Type A Durometer hardness at the innerliner centerline.

Yields the overall hardness of the inner-liner sample. Indicator of the state of cure for new tires and can track the evo­lution of bulk hardness properties.

REGRESSION ANALYSIS

Statistical software JMP professional edition version 5 release 5.0.1.2 was used to correlate the properties to the variables. The variables included tire age (in years), mileage (miles), and the interaction term (age*mileage). For example, JMP regression was used to determine the best model for innerliner indentation modulus of tires in service.

RESULTS

Part I - Model Liner Compound Chemical Analysis Model innerliner compounds were analyzed by chemical analysis, including oxygen content, TGA, ICP-AES, EDAX, and FTIR. The model compounds are shown below (Table 3-Table 6). Although these techniques were quite illustrative, newer techniques (including pyrolysis-gc/ms)

13

were used later in this report to more precisely characterize the compositions of liners extracted from tires.

Table 3. Model Bromobutyl/Natural Rubber Liner Compounds Compound Liner

1 Liner

2 Liner

3 Liner

4 Liner

5 Liner

6 Liner

18 Ingredient parts parts parts parts parts parts parts Bromobutyl (BIIR) Exxon grade 2222

100.00 80.00 60.00 50.00 40.00 20.00 95.00

Natural Rubber (SMR 20) 20.00 40.00 50.00 60.00 80.00 5.00 N660 Carbon Black 60.00 60.00 60.00 60.00 60.00 60.00 60.00 Naphthenic oil, Calsol 810 or equivalent

8.00 8.00 8.00 8.00 8.00 8.00 8.00

Struktol 40MS 7.00 7.00 7.00 7.00 7.00 7.00 7.00 SP 1068 Resin 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Stearic Acid 1.00 1.00 1.00 1.00 1.00 1.00 2.00 Magnesium Oxide 0.15 0.15 0.15 0.15 0.15 0.15 0.19 Zinc Oxide 1.00 1.00 1.00 1.00 1.00 1.00 1.31 Sulfur 0.50 0.50 0.50 0.50 0.50 0.50 0.65 MBTS (mercapto benzo­thiazyl sulfenamide)

1.25 1.25 1.25 1.25 1.25 1.25 1.58

Total 182.90 182.90 182.90 182.90 182.90 182.90 184.73

14

Table 4. Model Chlorobutyl/Natural Rubber Liner Compounds Compound Liner

7 Liner

8 Liner

9 Liner

10 Liner

11 Liner

19 ingredient parts parts parts parts parts parts Chlorobutyl Rubber (CIIR) Exxon-Mobil Grade 1066

100.00 80.00 75.00 60.00

Natural Rubber (SMR 20) 20.00 25.00 40.00 100.00 Butyl Exxon (IIR) grade 365 (or equivalent)

100.00

N660 60.00 50.00 60.00 50.00 60.00 60.00 Nonblack Filler, CACO3 40.00 40.00 Naphthenic oil 8.00 5.00 8.00 8.00 Paraffinic Processing Oil, Flexon 876 4.00 4.00 Struktol 40MS 7.00 10.00 7.00 10.00 7.00 7.00 SP 1068 Resin 4.00 7.00 4.00 4.00 Tackifying Resin, Escorez 1102 4.00 4.00 Stearic Acid 1.00 1.00 7.00 1.00 2.00 1.00 Magnesium Oxide 0.15 0.20 7.00 0.20 Zinc Oxide 1.00 3.00 3.00 3.00 5.00 5.00 Sulfur 0.50 0.50 0.50 0.50 2.00 1.50 MBTS 1.25 1.50 1.50 1.50 0.50 Accelerator, Vultac 5 0.20 0.20 TMTD (tetramethylthiuram disulfide) 1.00 CBS (cyclohexyl benzothiazyl sulfe­namide)

1.50

Total 182.90 214.40 198.00 214.40 189.50 188.00

15

Table 5. Model Bromobutyl/SBR Liner Compounds

Compound Liner 13 Liner 14 Liner 15 Liner 16 Liner 17

ingredient parts parts parts parts parts Bromobutyl Exxon grade 2222 95.00 90.00 70.00 50.00 SBR (SBR 1712) 6.88 13.75 41.25 68.75 137.50 Natural Rubber (SMR 20) N660 60.00 60.00 60.00 60.00 60.00 naphthenic oil 8.00 8.00 8.00 8.00 aromatic oil 8.00 Struktol 40MS 7.00 7.00 7.00 7.00 SP 1068 Resin 4.00 4.00 4.00 4.00 Stearic Acid 2.00 2.00 2.00 2.00 2.00 Magnesium Oxide 0.19 0.19 0.19 0.19 6PPD 2.00 TMQ 1.00 Zinc Oxide 1.31 1.38 1.62 1.88 3.00 Sulfur 0.65 0.68 0.81 0.93 2.50 MBTS 1.58 1.65 1.80 2.05 Santocure MOR 2.00

Total 186.61 188.65 196.67 205.80 217.00

Table 6. Six Additional Model Compounds for Liner Permeability Testing

Compound L21150­154-1

L21150­154-2

L21150­154-3

L21150­154-4

L21150­154-5

L21150­154-6

ingredient parts parts parts parts parts parts Bromobutyl Exxon grade 2222 100.00 80.00 80.00

CIIR 1068 100.00 80.00 NR (SMR 20) 20.00 100.00 20.00 SBR (SBR 1712) 27.50 N660 60.00 60.00 60.00 60.00 60.00 60.00 naphthenic oil 8.00 8.00 8.00 8.00 8.00 8.00 Struktol 40MS 7.00 7.00 7.00 7.00 7.00 7.00 SP 1068 Resin 4.00 4.00 4.00 4.00 4.00 4.00 Stearic Acid 2.00 1.00 2.00 1.00 2.00 1.00 Magnesium Oxide 0.15 0.15 0.15 0.15 0.15 Zinc Oxide 1.00 1.00 1.00 5.00 3.00 3.00 Sulfur 0.50 0.50 0.50 1.50 0.50 0.50 MBTS 1.20 1.25 1.25 1.50 1.50 CBS 1.50

Total 183.85 182.90 191.40 188.00 186.15 185.15

16

Acetone Extraction of Model Liner Compounds

Model innerliner compounds were analyzed by acetone extraction to determine rubber chemical levels (Table 7). The acetone extraction results were comparable to the rubber chemical values determined by TGA technique.

Table 7. Acetone Extraction of Model Liner Compounds Compound 1 2 3 4 5 6 7 8 9 10

Acetone Extraction (Wt %) 6.68 6.47 9.99 6.45 7.31 6.65 6.22 8.1 9.41 6.83

Oxygen Content of Model Liner Compounds

Five model compounds were analyzed for oxygen content (Table 8). For reference, only the dif­ferences in compound formulations are listed in the table. Holding all other ingredients constant, innerliner samples using 100 parts of halobutyl rubber had the lowest oxygen content.

Table 8. Oxygen Content of Model Liner Compounds Compound 1 3 5 7 9 Bromobutyl (BIIR) Exxon grade 2222 (parts) 100.00 60.00 40.00 -Chlorobutyl Rubber (CIIR) ExxonMobil Grade 1066 (parts) - 100.00 75.00

Natural Rubber (SMR 20) (parts) - 40.00 60.00 - 25.00 Naphthenic oil (parts) 8.00 5.00 SP 1068 Resin 4.00 7.00 Stearic Acid 1.00 7.00 Magnesium Oxide 0.15 7.00 Zinc Oxide 1.00 3.00 MBTS 1.25 1.50 Oxygen Content (Wt %) 1.52 2.11 1.81 1.71 2.14

ICP-AES of Model Liner Compounds

Five model compounds were analyzed by ICP (Table 9). The zinc level varied with the recipe zinc oxide (ZnO) loading. The magnesium level was approximately related to the recipe magne­sium oxide (MgO) loading. The titanium, aluminum, nickel, and sodium levels seemed to be re­lated to the butyl loading, possibly from catalyst residues. Phosphorous appeared to be related to the natural rubber loading. Phosphorous is a catalyst in the biosynthesis of natural rubber latex.

17

Table 9. Ash Composition of Model Liner Compounds Element Liner 1 Liner 3 Liner 5 Liner 7 Liner 9

1 Aluminum, ppm 64.10 238.60 76.06 89.25 58.65 2 Antimony, ppm < 2.50 < 2.85 < 2.30 3.74 14.42 3 Arsenic, ppm 6.70 4.64 17.02 2.34 < 3.26 4 Berylium, ppm < 0.01 < 0.02 < 0.01 < 0.01 < 0.03 5 Bismuth, ppm < 2.33 < 2.65 < 2.14 < 2.04 < 4.46 6 Boron, ppm 2.10 2.31 1.20 2.01 2.76 7 Cadmium, ppm < 0.43 < 0.49 < 0.40 < 0.38 < 0.82 8 Calcium, ppm 695.17 594.68 447.11 639.38 388.69 9 Chromium, ppm < 1.04 < 1.19 < 0.96 < 0.91 < 2.00

10 Cobalt, ppm < 1.63 < 1.86 < 1.50 < 1.43 < 3.12 11 Copper, ppm 12.56 6.81 4.36 29.72 23.63 12 Iron, ppm 25.00 57.79 44.75 61.76 63.50 13 Lead, ppm < 0.87 < 1.00 < 0.80 < 0.77 1.94 14 Magnesium, ppm 366.19 479.01 75.83 58.17 574.64 15 Manganese, ppm < 0.60 < 1.72 3.08 5.53 < 1.15 16 Nickel, ppm 3.12 3.03 1.14 14.08 5.59 17 Phosphorous, ppm < 33.34 < 110.50 126.20 < 29.20 146.47 18 Potassium, ppm 44.56 163.30 138.47 92.21 184.69 19 Selenium, ppm 4.97 10.48 28.08 17.71 47.12 20 Silicon, ppm 249.97 375.36 179.32 99.88 60.52 21 Silver, ppm < 2.80 < 3.20 < 2.58 < 2.46 < 5.38 22 Sodium, ppm 183.49 177.81 94.88 328.75 190.11 23 Thallium, ppm < 13.89 < 15.83 < 12.78 < 12.17 < 26.65 24 Titanium, ppm 3.09 8.59 4.35 2.41 2.77 25 Vanadium, pm 4.65 5.99 3.76 13.79 2.63 26 Zinc, ppm 1763.29 3810.31 9533.74 4889.45 14375.45

TGA of Model Liner Compounds

Five model compounds were analyzed by TGA. The weight loss curves (Figure 11) and weight loss derivative curves (Figure 12) showed differences with change in polymer composition. Lin­er 1 (100% bromobutyl) had the highest decomposition temperature. Liner 7 (100 phr chloro­butyl) had similar decomposition temperatures. Liner 9 (25 phr natural rubber), liner 3 (40 phr natural rubber), and liner 5 (60 phr natural rubber) exhibited lower decomposition temperatures in that order. Natural rubber content reduced the decomposition temperature. The derivative curves showed the growth of a peak at about 375�C which increased with natural rubber level. Addition of natural rubber increased the decomposition temperature of the carbon black, for which no explanation is known.

From the TGA data, the level of rubber chemicals, polymer, carbon black, and ash were assessed (Table 10) and compared to the formulation values (Table 11). The rubber chemical levels were determined by the weight losses before the polymer weight loss began (as indicated by the

18

Figure 11. Overlay Plot of the TGA Weight Loss Curves

120

liner 1 100

liner 3 liner 5 80

Wei

ght (

%) liner 7

60 liner 9

40

20

0 0 100 200 300 400 500 600 700 800

Temperature (deg C)

Figure 12. Overlay Plot of the TGA Derivative Curves

1

-1

Deri

vativ

e (w

t%/m

in)

-3 liner 1

-5 liner 3

liner 5 -7 liner 7

liner 9 -9

-11 0 100 200 300 400 500 600 700 800

Temperature (deg C)

change in slope associated with rapid loss from polymer). The carbon black levels were the weight losses above 515�C. The ash levels were the weight after heating to 800�C. The agree­ment between TGA calculated values for polymer and ash levels were very close. The TGA cal­culated values for rubber chemicals and carbon black differed from the actual levels. Presuma­bly, not all of the rubber chemicals were removed at the lower temperatures. In future work, ex­traction will be used for the rubber chemical levels, thereby yielding proper carbon black levels by calculation.

19

Figure 13. TGA Derivative Curves for Model Compounds 1, 18, 2, 3, 4, 5, and 6. Increasing Levels of Natural Rubber with Bromobutyl

1

-1

-3 liner 1

(wt%

/min

)

-5 liner 18 liner 2

-7

e tiv liner 3

-9

Der

iva

liner 4 liner 5

-11 liner 6

-13 0 100 200 300 400 500 600 700 800

Temperature (deg C)

Table 10. TGA Compositional Analysis (wt%) Compound Liner 1 Liner 3 Liner 5 Liner 7 Liner 9

rubber chemicals 6.6 6.9 5.8 9.2 6.3 polymer 55.8 56 58.2 54.9 58.0 carbon black 37 36.2 34.7 35.0 33.8 ash 0.66 0.78 1.26 0.79 1.84

Table 11. Actual Compositional Analysis (wt%)

Compound Liner 1 Liner 3 Liner 5 Liner 7 Liner 9 rubber chemicals 11.8 11.8 11.8 11.8 11.7 polymer 54.7 54.7 54.7 54.7 54.0 carbon black 32.8 32.8 32.8 32.8 32.4 ash 0.70 0.71 0.71 0.71 1.78

Eighteen model compounds were analyzed by TGA as standards for tire innerliner polymer iden­tification. The model compound compositions are shown in Table 3-Table 5. The TGA deriva­tive curves were characteristic of the polymers, and used in polymer identification of the tire in­nerliners (Figure 13-Figure 16).

20

Figure 14. TGA Derivative Curves for Model Compounds 7, 8, 9, 10: Increasing Levels of Natural Rubber with Chlorobutyl

1

-1

Der

ivat

ive

(wt%

/min

)-3

liner 7

liner 8 -5 liner 9

liner 10 -7

-9

-11 0 100 200 300 400 500 600 700 800

Temperature (deg C)

Figure 15. TGA Derivative Curves for Model Compounds 1, 13, 14, 15, 16, 17:

Increasing Levels of oil-extended SBR with Bromobutyl

1

-1

Der

ivat

ive

(wt%

/min

)

liner 1 -3 liner 13

liner 14 -5 liner 15

liner 16 -7 liner 17

-9

-11 0 100 200 300 400 500 600 700 800

Temperature (deg C)

21

Figure 16. TGA Derivative Curves for Model Compounds 1, 7, 11: Bromobutyl, Chlorobutyl and Butyl Rubber

-11

-9

-7

-5

-3

-1

1

0 100 200 300 400 500 600 700 800

liner 1 liner 7 liner 11

FTIR of Model Liner Compounds

Five model compounds were analyzed by FTIR. The composition summary is shown in Table 12 and Figure 17. The results were qualitative only, not quantitative. The polyisoprene peaks were observed at 3024, 1660, 1126, 1086, and 831 wave number with increasing absorbance, sequen­tially with natural rubber loading (liner 9, liner 3, and liner 5). The presence of natural rubber at 25 phr loading in liner 9 was scarcely detectable. For this reason, subsequent work used pyroly­sis-gc/fid and pyrolysis-gc/ms to quantify the polymer levels in the innerliner compounds.

Table 12. FTIR Analysis

Compound Polymer Identification 1 Halobutyl 3 Halobutyl & Polyisoprene 5 Halobutyl & Polyisoprene 7 Halobutyl 9 Halobutyl & Polyisoprene

22

40

50

60

70

40

50

60

Tran

smis

sion

(%)

Tran

smis

sion

(%)

Figure 17. FTIR of Model Liner Compounds 1, 3, 5, 7, 9

Liner #1 Liner #3 100 90

90 80

80 70

Tran

smis

sion

(%)

60

50

40

30 30

20 20

10 36004000 3200

Liner #5

1600200024002800

Wave Number (cm-1)

1200 800 400

10 36004000 3200

Liner #7

1600200024002800

Wave Number (cm-1)

1200 800 400

90 100

80 90

70 80

Tran

smis

sion

(%)

70

60

50

40

30 30

20 20

10 10 4000 3600 3200 2800 2400 2000 1600 1200 800 400 4000 3600 3200 2800 2400 2000 1600 1200 800 400

Wave Number (cm-1) Wave Number (cm-1) Liner #9

100

90

80

Tran

smis

sion

(%)

70

60

50

40

30

20

10 4000 3600 3200 2800 2400 2000 1600 1200 800 400

Wave Number (cm-1)

23

Figure 18. Correlation between XRF Bromine Content and phr Bromobutyl

0.0001

0.001

0.01

0.1

1

10

0 20 40 60 80 100

BIIR (phr)

Brom

ine

(%) (m

ajor

) (m

inor

)(tr

ace)

(z

ero)

Beilstein of Model Liner Compounds

Five model compounds (1, 3, 5, 7, and 9) were analyzed by Beilstein (qualitative flame identifi­cation test for halogens). The results were slight positive (for the presence of halogen) for all the five model compounds.

XRF Analysis of Model Liner Compounds

Six model compounds were analyzed by X-ray Fluorescence (XRF) (Table 13). Calibration curves were determined from the model compound data (Figure 18 & Figure 19). The results were grouped in categories: Major (>1%), Minor (<100 ppm to 1%), Trace (<100 ppm) by per­cent weight in the sample (wt/wt).

Table 13. XRF Analysis Results of Model Compounds

Barcode Bromine Chlorine Sulfur Calcium Iron Potassium Zinc Liner #1 Major Major Minor Trace Major Liner #4 Major Major Minor Trace Minor Major Liner #7 Minor Major Minor Trace Minor Major Liner #9 Minor Major Minor Trace Minor Major Liner #11 Major Minor Trace Major Liner #19 Major Trace Trace Minor Major *Grouped in categories: Major (>1%), Minor (<100 ppm to 1%), Trace (<100 ppm)

24

Figure 19. Correlation between XRF Chlorine Content and phr Chlorobutyl

0.0001

0.001

0.01

0.1

1

10

0 20 40 60 80 100 CIIR Content (phr)

Chlo

rine

(%) (m

ajor

) (m

inor

)(tr

ace)

(z

ero)

EDAX of Model Liner Compounds

Five model compounds were analyzed by EDAX (Table 14). The zinc levels correlated with the ZnO in the compound. The bromine intensity correlated with the phr of bromobutyl (Figure 20) and the chlorine intensity correlated with chlorobutyl loading (Figure 21).

Table 14. EDAX of Model Compounds

Element Liner 1 Liner 3 Liner 5 Liner 7 Liner 9

Intensity (c/s) Intensity (c/s) Intensity (c/s) Intensity (c/s) Intensity (c/s) Silicon 37.6 58.3 63.5 32.0 20.6 Sulfur 455.3 525.4 1083.9 705.3 652.2

Chlorine 368.7 264.6 Potassium 17.5 11.0 Calcium 62.1 40.0 26.8 28.2 19.5

Zinc 76.2 68.8 122.8 63.4 161.8 Bromine 31.4 17.6 13.8

25

Figure 20. Correlation between Bromine Intensity and phr Bromobutyl

y = 0.311x + 0.138 R2 = 0.996

0 5

10 15 20 25 30 35 40

0 20 40 60 80 100

phr Bromobutyl

Brom

ine

Inte

nsity

(c/s

)

bromobutyl

Figure 21. Correlation between Chlorine Intensity and phr Chlorobutyl

y = 3.637x - 0.628 R2 = 0.999

0 50

100 150 200 250 300 350 400

0 20 40 60 80 100 phr Chlorobuty

Chlo

rine

Inte

nsity

(c/s

)

chlorobutyl

Part II - Chemical Analysis of the Innerliner from Six Tire Models Retrieved from Service in Phoenix, AZ

The six tire models that were retrieved from on-vehicle service in Phoenix, AZ are shown in Ta­ble 15. New tires of each tire model were used for innerliner analysis.

26

Table 15. List of Six Phoenix-Retrieved Tire Models Tire Type Tire Description Market Size Contains

Overlay Tire #

B B F Goodrich Touring T/A P195/65R15 OE Pass No 1001-1100 C Goodyear Eagle GA P205/65R15 OE Pass Yes 1501-1600 D Michelin LTX M/S P235/75R15 OE Pass No 1101-1200 E Firestone Wilderness AT P265/75R16 OE Pass No 1301-1400

H Kelly Pathfinder ATR A/S LT245/75R16/E Repl LT Some* 1201-1300

L General Grabber ST 255/65R16 OE Pass Yes 1401-1500 *The presence of overlays in the Type H light truck tires is build date dependent.

Acetone Extraction of the Six Phoenix Tire Models

The innerliners from six tire models were analyzed by acetone extraction to determine rubber chemical levels (Table 16). The acetone extraction results were comparable to the rubber chemi­cal values determined by TGA technique.

Table 16. Acetone Extractables (wt%) of the Six Phoenix Tire Models Tire Number 1030 1132 1227 1337 1427 1530

NHTSA Tire Type B D H E L C Acetone extractable (wt%) 7.35 6.88 8.12 6.72 11.11 8.13

ICP-AES of the Six Phoenix Tire Models

The six tire innerliners were analyzed by ICP (Table 17). The results suggest that the zinc levels were similar to model compounds, while some tire innerliner silicon levels were significantly higher.

Table 17. ICP-AES Analysis of the Six Phoenix Tire Models Tire Number 1037 1137 1237 1335 1437 1537 NHTSA Tire Type B D H E L C Element Silicon, ppm 89.15 1348.63 3076.23 853.25 871.57 2025.03 Zinc, ppm 15910.67 8480.03 15960.17 30118.67 17864.00 9841.87

TGA of the Six Phoenix Tire Models

Six tire innerliners were analyzed by TGA (Table 18). From the TGA data, the levels of rubber chemicals, polymer, carbon black, and ash were assessed (Table 12). The polymer composition results were not quantitative. For that reason, the tire innerliner polymer composition work was switched to pyrolysis-gc/fid and pyrolysis-gc/ms.

27

Table 18. TGA Compositional Analysis of the Six Phoenix Tire Models (wt%) Tire Number 1030 1132 1227 1337 1427 1530 NHTSA Tire Type B D H E L C rubber chemicals 8.8 8.8 9.8 7.9 7.6 12.5 polymer 56.3 55.5 50.2 49.7 51.0 49.0 carbon black 33.7 32.5 35.4 39.5 39.5 34.7 ash 1.17 3.20 4.64 2.93 1.89 3.76

Beilstein and FTIR of the Six Phoenix Tire Models

The six tire innerliners were analyzed by Beilstein and FTIR (Table 19). All of the six tire inner-liners were positive for halogen. The polymer compositions results were not quantitative.

Table 19. Beilstein and FTIR Results

Tire Number NHTSA Tire Type Polymer Identification 1037 B Halobutyl Rubber 1137 D Halobutyl Rubber 1237 H Halobutyl Rubber 1335 E Halobutyl Rubber and 10-20 phr SBR 1437 L Halobutyl Rubber 1537 C Halobutyl Rubber

XRF Analysis of the Six Phoenix Tire Models

The six tire innerliners were analyzed by X-ray Fluorescence (XRF) (Table 20). The X-ray fluo­rescence data was used to determine the halogen type in the butyl polymer. The results were grouped in categories: Major (>1%), Minor (<100 ppm to 1%), Trace (<100 ppm) by weight in the sample. Note that no evidence of chlorine was found in the samples.

Table 20. XRF Analysis Results

Barcode NHTSA

Tire Type

Bromine Sulfur Calcium Iron Potassium Zinc Silicon

1030 B Major Minor Minor Minor Trace Minor Minor 1132 D Major Minor Minor Minor Minor 1227 H Major Minor Minor Minor Minor 1337 E Major Minor Minor Minor Major 1427 L Major Minor Minor Minor Trace Minor 1530 C Major Minor Minor Minor Minor

*Grouped in categories: Major (>1%), Minor (<100 ppm to 1%), Trace (<100 ppm)

28

EDAX of the Six Phoenix Tire Models

The six tire innerliners were analyzed by EDAX (Table 21). The results (Table 22) suggest that tire D innerliner is 100-phr bromobutyl and tires B, E, H, L, and C are based primarily on bro­mobutyl. The EDAX results (Table 23) indicate the element levels are in the range of those of the model compounds, with the exception of the higher silicon levels in some tire innerliners. Also, Ti, Fe, and Cu were observed in some tire innerliners. Ti and Fe could be polymerization catalyst residues.

Table 21. EDAX Results for Chlorine and Bromine Analysis Tire Number 1037 1137 1237 1335 1437 1537 NHTSA Tire Type B D H E L C

Element Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Chlorine 0.0 0.0 0.0 55.9 0.0 0.00 Bromine 23.6 32.9 16.8 26.4 17.5 25.53

Table 22. EDAX Prediction for Chlorobutyl and Bromobutyl Tire Number 1037 1137 1237 1335 1437 1537 NHTSA Tire Type B D H E L C polymer phr phr phr phr phr phr chlorobutyl 0.2 0.2 0.2 15.5 0.2 0.17 bromobutyl 76 105 53 84 56 82

Table 23. EDAX Results for Other Elements Analysis Tire Number 1037 1137 1237 1335 1437 1537 NHTSA Tire Type B D H E L C

Element Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Si 105 127 356 186 128 276 S 950 788 801 604 811 679 K 0 31 0 0 31 15 Ca 55 61 103 92 51 55 Ti 0 0 169 0 0 133 Fe 0 13 17 11 10 10 Cu 12 11 12 14 13 11 Zn 65 84 103 196 93 66

Part II - Chemical Analysis of the Innerliners from Addition Tire Models An additional thirty seven tire innerliners (Table 24) were analyzed by acetone extraction, TGA, X-ray fluorescence or EDAX, pyrolysis-gc/fid, and pyrolysis-gc/ms. Also, the six tire models from the original NHTSA dataset were included in the pyrolysis-gc/fid and pyrolysis-gc/ms ana­lyses.

29

Table 24. Thirty Seven Additional Production Tires Models Analyzed by Extraction, TGA, XRF, Pyrolysis-GC/MS

Barcode Tire Type

Plant Code

Market Tread Design

Man. Brand Model Size Load Range

Speed Rating

2012 P1 UT Repl. All Season

Cooper Futura [Pep Boys]

Dakota H/T P265/75R16 114 S

2039 P2 UP Repl. All Season

Cooper Futura [Pep Boys]

Scrambler A/P (LT)

LT235/85R16 120 (E)

N

2040 P3 UT Repl. All Season

Cooper Futura [Pep Boys]

Scrambler A/P (P-XL)

P235/75R15XL 108 S

2065 U2 EU OE Run Flat

Goodyear Dunlop SP Sport 4000 DSST (Run Flat)

P225/60R17 098 T

2113 G1 PD Repl. Winter Goodyear Goodyear Ultra Grip P235/75R15XL 108 S 2126 G2 PJ Repl. All

Season Goodyear Goodyear WRANGLER

SilentArmor LT235/85R16 120

(E) R

2135 R2 XL OE All Season

Pirelli Pirelli Scorpion STR LT265/75R16 123 (E)

R

2140 Y2 CC Repl. All Season

Yokohama Yokohama Geolandar A/T+II

LT285/75R16 122 (D)

Q

2165 N1 UP Repl. Winter Cooper Nokian Hakkapeliitta 10LT

LT235/85R16 120 (E)

-

2178 N2 YL Repl. Winter Nokian Nokian Hakkapeliitta LT

LT265/75R16 119 (D)

-

2212 B4 EJ Repl. All Season

Bridgestone Bridgestone DUELER A/T 693

LT285/75R16 122 (D)

Q

2226 B6 7X OE All Season

Bridgestone Bridgestone DUELER H/T 689

P245/70R16 106 S

2250 B7 VN OE All Season

Bridgestone Firestone Wilderness AT I P265/75R16 114 S

2269 B1 EP Repl. Winter Bridgestone Bridgestone Blizzak DM-Z3 235/75R16 105 Q 2270 B8 0B OE All

Season Bridgestone Bridgestone B450 P205/65R15 092 S

2313 O5 U9 Repl. All Season

Cooper Big O [Big O Tire]

MERIT FOUR SEASON Black

P195/65R15 089 S

2326 O3 UP Repl. All Season

Cooper Big O [Big O Tire]

ASPEN P205/65R15 092 S

2339 O1 PJ Repl. All Season

Goodyear Big O [Big O Tire]

BIGFOOT A/T (LT235)

LT235/85R16 120 (E)

Q

2352 O2 PJ Repl. All Season

Goodyear Big O [Big O Tire]

BIGFOOT A/T (LT265)

LT265/75R16 123 (E)

Q

2365 O4 UT Repl. All Season

Cooper Big O [Big O Tire]

X/T BIG FOOT (356)

LT265/75R16 123 (E)

N

2378 D2 PJ Repl. All Season

Goodyear Arizonian [Discount Tire]

Silver Edition P195/65R15 089 S

2391 D3 U9 Repl. All Season

Cooper Dominator [Discount Tire]

All Season P205/65R15 092 S

2404 D6 PB Repl. All Season

Goodyear Mohave [Discount Tire]

RS P205/65R15 092 R

2417 D5 UP Repl. All Season

Cooper Dominator [Discount Tire]

Sport A/T LT265/75R16 123 (E)

Q

2429 D4 3D Repl. All Season

Cooper Dominator [Discount Tire]

Durango Radial A/T

LT285/75R16 122 (D)

N

30

2438 J1 PJ Repl. All Season

Goodyear Kelly Safari SJR LT265/75R16 112 (C)

-

2456 C3 A3 OE All Season

Continental Continental CONTITRAC P235/70R16 104 T

2469 M1 B7 Repl. All Season

Michelin Michelin Cross Terrain SUV

P265/75R16 114 S

2482 M3 ED Repl. Winter Michelin Michelin X-Ice 205/65R15 094 Q 2495 C5 AC OE All

Season Continental Continental TouringContact

AS P205/65R15 092 T

2501 B9 7X OE All Season

Bridgestone Bridgestone Duravis M773 II LT265/75R16 123 (E)

-

2526 C7 A3 OE All Season

Continental Continental Contitrac TR P265/70R17 113 S

2551 C8 P5 OE All Season

Continental General Ameri G4S P205/65R15 092 T

2576 H3 T7 OE All Season

Hankook Hankook DynaPro AS LT245/75R16 120 (E)

-

2601 M10 B7 OE All Season

Michelin Michelin LTX A/S LT245/75R16 120 (E)

R

2626 S1 V4 Repl. All Season

Sumitomo Sumitomo HTR+ 225/60R16 098 V

2651 T2 9T Repl. All Season

Toyo Toyo 800 Ultra P235/60R16 099 T

Acetone Extraction of Thirty Seven Tire Innerliners

Thirty-seven tire innerliners were analyzed by acetone extraction to determine rubber chemical levels (Table 25). The acetone extraction results were comparable to the rubber chemical values determined by the TGA (weight loss) technique.

Table 25. Acetone Extractables (wt%) of Additional Tires Plant Code Brand NHTSA Barcode Acetone Extraction 0B Bridgestone 2270 9.13% 3D Dominator [Discount Tire] 2429 10.50% 7X Bridgestone 2226 7.69% 7X Bridgestone 2501 8.23% 9T Toyo 2651 8.29% A3 Continental 2456 9.43% A3 Continental 2526 9.93% AC Continental 2495 9.85% B7 Michelin 2469 5.58% B7 Michelin 2601 3.59% CC Yokohama 2140 7.65% ED Michelin 2482 10.26% EJ Bridgestone 2212 7.26% EP Bridgestone 2269 8.18% EU Dunlop 2065 6.50% P5 General 2551 11.76% PB Mohave [Discount Tire] 2404 11.81%

31

PD Goodyear 2113 9.83% PJ Goodyear 2126 7.98% PJ Big O [Big O Tire] 2339 8.04% PJ Big O [Big O Tire] 2352 7.40% PJ Arizonian [Discount Tire] 2378 11.59% PJ Kelly 2438 8.83% T7 Hankook 2576 8.13% U9 Big O [Big O Tire] 2313 11.89% U9 Dominator [Discount Tire] 2391 12.13% UP Futura [Pep Boys] 2039 8.56% UP Nokian 2165 9.42% UP Big O [Big O Tire] 2326 10.95% UP Dominator [Discount Tire] 2417 7.62% UT Futura [Pep Boys] 2012 11.23% UT Futura [Pep Boys] 2040 9.99% UT Big O [Big O Tire] 2365 9.46% V4 Sumitomo 2626 7.21% VN Firestone 2250 8.70% XL Pirelli 2135 7.06% YL Nokian 2178 7.10%

TGA of Thirty Seven Tire Innerliners

Thirty-seven tire innerliners were analyzed by TGA. The results are summarized in Table 26. From the TGA data, the level of rubber chemicals, polymer, carbon black, and ash were as­sessed. The polymer composition was qualitatively identified.

Table 26. Composition Analysis by TGA

Plant Code Brand Barcode

Polymer Types Oils (chem­

icals) (wt %)

Polymer (wt %)

Carbon black

(wt %)

Ash (wt %)

Butyl (wt %)

NR (wt %)

SBR (wt %)

PBD (wt %)

0B Bridgestone 2270 100 9.3 49.8 38.9 2.0 3D Dominator

[Discount Tire]

2429 100 7.7 49.8 39.5 3.0

7X Bridgestone 2226 100 8.0 52.2 38.1 1.7 7X Bridgestone 2501 100 8.9 49.9 39.1 2.1 9T Toyo 2651 53 47 6.3 48.5 34.5 10.7 A3 Continental 2456 55 45 6.7 51.9 39.5 1.9 A3 Continental 2526 100 8.3 53.0 37.5 1.2 AC Continental 2495 67 33 6.9 51.2 38.8 3.1

32

Table 26. Composition Analysis by TGA

Plant Code Brand Barcode

Polymer Types Oils (chem­

icals) (wt %)

Polymer (wt %)

Carbon black

(wt %)

Ash (wt %)

Butyl (wt %)

NR (wt %)

SBR (wt %)

PBD (wt %)

B7 Michelin 2469 100 8.0 54.0 33.4 4.6 B7 Michelin 2601 100 6.0 55.7 34.1 4.2 CC Yokohama 2140 67 33 6.7 49.6 38.0 5.7 ED Michelin 2482 100 8.6 53.0 35.0 3.4 EJ Bridgestone 2212 100 7.2 50.6 39.3 2.9 EP Bridgestone 2269 100 8.0 50.9 36.4 4.7 EU Dunlop 2065 65 35 7.0 45.2 36.7 11.1 P5 General 2551 54 46 7.9 52.6 36.3 3.2 PB Mohave

[Discount Tire]

2404 73 27 11.0 53.5 28.5 7.0

PD Goodyear 2113 100 9.5 51.5 36.1 2.9 PJ Arizonian

[Discount Tire]

2378 53 47 8.6 53.3 33.2 4.9

PJ Big O [Big O Tire] 2339 100 10.0 49.4 36.1 4.5

PJ Big O [Big O Tire] 2352 100 9.0 49.3 36.2 5.5

PJ Goodyear 2126 100 7.5 51.1 36.7 4.7 PJ Kelly 2438 100 10.1 48.5 36.6 4.8 T7 Hankook 2576 70 32 5.2 55.0 36.5 3.3 U9 Big O [Big

O Tire] 2313 70 30 7.3 52.4 37.0 3.3

U9 Dominator [Discount Tire]

2391 100 8.8 50.9 37.9 2.4

UP Big O [Big O Tire] 2326 100 8.2 49.0 39.1 3.7

UP Dominator [Discount Tire]

2417 100 7.0 50.5 39.7 2.8

UP Futura [Pep Boys] 2039 100 7.2 50.3 39.6 2.9

UP Nokian 2165 100 6.4 52.2 39.2 2.2 UT Big O [Big

O Tire] 2365 100 8.3 50.1 38.9 2.7

UT Futura [Pep Boys] 2012 100 8.4 50.2 37.2 4.2

UT Futura [Pep Boys] 2040 100 7.0 51.0 38.4 3.6

V4 Sumitomo 2626 52 48 5.7 48.8 36.9 8.6

33

Table 26. Composition Analysis by TGA

Plant Code Brand Barcode

Polymer Types Oils (chem­

icals) (wt %)

Polymer (wt %)

Carbon black

(wt %)

Ash (wt %)

Butyl (wt %)

NR (wt %)

SBR (wt %)

PBD (wt %)

VN Firestone 2250 100 8.6 51.1 38.7 1.6 XL Pirelli 2135 61 39 7.3 53.3 29.6 9.8 YL Nokian 2178 62 38 5.8 50.6 29.6 14.0

XRF Analysis of Thirty One Tire Innerliners

Thirty-one tire innerliners were analyzed by X-ray Fluorescence (XRF) (Table 27). The results were grouped in categories: Major (>1%), Minor (<100 ppm to 1%), Trace (<100 ppm) by weight in the sample (wt/wt). The calibration curves (Figure 18 and Figure 19) from the model compounds were used to determine the butyl type (halogen type). The X-ray fluorescence data was combined with the pyrolysis-gc/fid data to determine the halogen type in the butyl polymer (Table 32). The halogen type in six of the thirty-seven innerliners was determined by EDAX, which is discussed in the next section.

34

Table 27. XRF Analysis of 31 Tire Innerliners Plan

t Code

Brand Bar­code

Bro­mine

Chlo­rine

Sul­fur

Cal­cium Iron Potas­

sium Zinc Sili­con Tin Tita­

nium

0B Bridges-tone 2270 Major Minor Minor Mi­

nor Minor Mi­nor Minor

3D Dominator [Discount Tire]

2429 Major Major Minor Mi­nor Minor Mi­

nor Major Ma­jor

7X Bridges-tone 2226 Major Minor Minor Mi­

nor Minor Mi­nor Minor

7X Continental 2501 Major Minor Minor Mi­nor Minor Major Trace

9T Sumitomo 2651 Major Major Minor Mi­nor

Mi­nor Minor

A3 Bridges-tone 2526 Major Minor Minor Mi­

nor Trace Mi­nor Major Trace

A3 Kelly 2456 Minor Minor Minor Mi­nor Minor Mi­

nor Minor

AC Michelin 2495 Major Major Minor Mi­nor Minor Mi­

nor B7 Continental 2469 Major Minor Minor Mi­

nor Minor Mi­nor Minor

B7 Hankook 2601 Major Minor Minor Mi­nor Minor Major Major

CC Yokohama 2140 Minor Minor Minor Mi­nor Minor Major Major

ED Michelin 2482 Major Minor Minor Mi­nor Minor Mi­

nor Minor

EJ Bridges-tone 2212 Major Trace Minor Minor Mi­

nor Minor Major Major Trace

EP Bridges-tone 2269 Major Minor Minor Mi­

nor Minor Mi­nor

EU Dunlop 2065 Trace Minor Minor Major Mi­nor

Mi­nor Minor

PD Goodyear 2113 Major Minor Minor Mi­nor Trace Mi­

nor Major

PJ Big O [Big O Tire] 2339 Major Minor Minor Mi­

nor Minor Mi­nor Minor

PJ Big O [Big O Tire] 2352 Major Minor Minor Mi­

nor Trace Mi­nor Minor

PJ Dominator [Discount Tire]

2438 Minor Minor Minor Mi­nor Minor Mi­

nor Minor

PJ Goodyear 2126 Major Minor Minor Mi­nor Minor Mi­

nor Minor

T7 General 2576 Major Minor Minor Mi­nor Minor Major Minor

U9 Arizonian [Discount Tire]

2391 Trace Minor Minor Minor Mi­nor Minor Mi­

nor Major

UP Big O [Big O Tire] 2326 Major Major Minor Mi­

nor Minor Mi­nor Major

UP Mohave [Discount Tire]

2417 Major Major Minor Mi­nor Minor Mi­

nor Major

UP Nokian 2165 Minor* Minor Minor Minor Mi­nor Minor Mi­

nor Minor

UT Big O [Big O Tire] 2365 Trace Minor Minor Minor Mi­

nor Trace Mi­nor Major

35

UT Futura [Pep Boys] 2012 Trace Minor Minor Mi­

nor Minor Mi­nor Major

UT Futura [Pep Boys] 2040 Trace Minor Minor Minor Mi­

nor Minor Mi­nor Major

V4 Michelin 2626 Minor Major Minor Mi­nor Minor Major Minor

XL Pirelli 2135 Major Minor Minor Mi­nor Minor Mi­

nor Major

YL Nokian 2178 Trace Minor Minor Major Trace Minor Mi­nor Minor

*Suspected outlier, may have missed bromine peak.

EDAX of Six Tire Innerliners (Six Additional Tire Innerliners)

Six tire innerliners were analyzed by EDAX (Table 28-Table 30). EDAX was used to determine the type of butyl polymer in the tire innerliner. The calibration curves (Figure 20 and Figure 21) from the model compounds were used to determine the butyl type (halogen type). The EDAX data was combined with the pyrolysis-gc/fid data to determine the halogen type in the butyl po­lymer (Table 32).

Table 28. EDAX Results (for Bromine and Chlorine) Plant Code UP VN U9 PJ PB P5

Brand

Futura [Pep Boys] Firestone

Big O [Big O Tire]

Arizonian [Discount

Tire]

Mohave [Discount

Tire] General Barcode 2039 2250 2313 2378 2404 2551

Element Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity (c/s) Intensity (c/s) Intensity

(c/s) Chlorine 0.00 34.6 200 17.0 11.1 137 Bromine 24.5 23.3 0.00 3.40 2.84 3.83

Table 29. EDAX Prediction of Tire Innerliner Polymers Plant Code UP VN U9 PJ PB P5

Brand Futura

[Pep Boys] Firestone

Big O [Big O Tire]

Arizonian [Discount

Tire] Mohave [Dis­count Tire] General

Barcode 2039 2250 2313 2378 2404 2551 Polymer phr phr phr phr phr phr Chlorobutyl 0 0 55 0 0 38 Bromobutyl 78 74 0 0 0 0

36

Table 30. EDAX Results (for Other Elements) Plant Code UP VN U9 PJ PB P5

Brand

Futura [Pep Boys] Firestone

Big O [Big O Tire]

Arizonian [Discount

Tire]

Mohave [Discount

Tire] General Barcode 2039 2250 2313 2378 2404 2551

Element Intensity

(c/s) Intensity

(c/s) Intensity

(c/s) Intensity (c/s) Intensity (c/s) Intensity

(c/s) Si 106 83 160 336 694 130 S 759 482 730 839 690 840 K 20 11 14 19 22 21 Ca 61 54 48 79 25 56 Ti 86 124 Fe 16 21 21 14 10 17 Zn 96 165 92 183 162 128

Pyrolysis - Gas Chromatography/Flame Ionization Detector (Pyrolysis-GC/FID) Analysis of Forty Three Tire Innerliners

Forty-three tire innerliners were analyzed by Pyrolysis-GC/FID. The calibration of the pyrolysis-gc/fid for polymer identification and quantification included seventeen standards (model liner compounds). The peak identifications are shown in Table 31 and Figure 22-Figure 24 for SBR (type1502), BIIR (ExxonMobil 2222), and NR (SMR-L) respectively. The peaks for isobutylene, isoprene, butadiene, and styrene were used for the calibration curves (Figure 25-Figure 28). The innerliner analysis results are shown in Table 32. Two tire innerliners were run twice (1030 and 1132) and showed good repeatability. The pyrolysis-gc/fid analysis was combined with XRF (bromine and chlorine determination) to determine qualitatively the butyl polymer types. The butyl type in six tires (tire numbers 2039, 2250, 2313, 2378, 2404, and 2551) were determined by EDAX.

Table 31. Pyrolysis-GC/FID Peak Identification Chemical Peak Location (min)

Isobutylene 3.9-4.1 Isobutylene trimer (probably) 22.5 Isobutylene trimer (probably) 23.1 Isoprene 8.9-9.1 Isoprene dimer 22.8 Butadiene 4.3 Butadiene dimer 16.99 Styrene 19.95-20.0

37

Figure 22. Pyrolysis-GC/FID Analysis of SBR (1502) Gum Polymer

Figure 23. Pyrolysis-GC/FID Analysis of BIIR Gum Polymer

38

Figure 24. Pyrolysis-GC/FID Analysis of Natural Rubber Gum Polymer

Figure 25. Pyrolysis-GC/FID Calibration Curve for Polyisobutylene Based on Isobutylene

y = 8.804E-08x + 8.905E-03 R2 = 9.639E-01

0.0

0.2

0.4

0.6

0 1000000 2000000 3000000 4000000 5000000

Isobutylene Peak Area (uV*sec)

Pol

yiso

buty

lene

(gm

)

39

Figure 26. Pyrolysis-GC/FID Calibration Curve for Polyisoprene Based on Isoprene

Figure 27. Pyrolysis-GC/FID Calibration Curve for Styrene Butadiene Polymer Based on Styrene

y = 3.591E-07x + 5.081E-03 R2 = 9.556E-01

0.0

0.2

0.4

0 200000 400000 600000 800000 1000000

Isoprene Peak Area (uV*sec)

Poly

isop

rene

(gm

)

y = 1.05E-06x - 2.23E-03 R2 = 9.97E-01

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 50000 100000 150000 200000 250000 300000

Styrene Peak Area (uV*sec)

Styr

ene

Buta

dine

Pol

ymer

(gm

)

40

Figure 28. Pyrolysis-GC/FID Calibration Curve for Styrene Butadiene Polymer Based on Butadiene

y = 1.39E-06x + 1.46E-03 R2 = 9.89E-01

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0 50000 100000 150000 200000 250000

Butadiene Peak Area (uV*sec)

Sty

rene

But

adie

ne P

olym

er (g

m)

Table 32. Pyrolysis-GC/FID Analysis Summary

Plant Code

Tire Type Brand Barcode Pyr-GC/FID

Composition (%)

Butyl Type based

on XRF (or EDAX)

0B B8 Bridgestone 2270 81/17/2­IIR/NR/SBR BIIR

3D D4 Dominator [Discount Tire] 2429 85/15-IIR/NR BIIR

7X B6 Bridgestone 2226 83/17-IIR/NR BIIR 7X B9 Bridgestone 2501 81/19-IIR/NR BIIR 9T T2 Toyo 2651 53/47-IIR/NR BIIR

A3 C3 Continental 2456 56/38/6­IIR/NR/SBR BIIR

A3 C7 Continental 2526 66/21/13­IIR/NR/SBR BIIR

A3 L General 1427 70/30-IIR/NR BIIR

AC C5 Continental 2495 61/30/9­IIR/NR/SBR BIIR

AP B BFGoodrich 1030 #1 100 IIR* BIIR AP B BFGoodrich 1030 #2 100 IIR* BIIR B3 D Michelin 1132 #1 100 IIR* BIIR B3 D Michelin 1132 #2 100 IIR* BIIR B7 M1 Michelin 2469 100 IIR* BIIR B7 M10 Michelin 2601 100 IIR* BIIR CC Y2 Yokohama 2140 72/28-IIR/NR BIIR

41

ED M3 Michelin 2482 89/11-IIR/NR BIIR EJ B4 Bridgestone 2212 85/15-IIR/NR BIIR EP B1 Bridgestone 2269 83/17-IIR/NR BIIR EU U2 Dunlop 2065 70/30-IIR/NR CIIR M6 C Goodyear 1530 92/6/2-IIR/NR/PBD BIIR

P5 C8 General 2551 55/37/8­IIR/NR/SBR CIIR

PB D6 Mohave [Discount Tire] 2404 82/18-NR/SBR N/A

PD G1 Goodyear 2113 93/7-IIR/NR BIIR

PJ D2 Arizonian [Discount Tire] 2378 65/35-NR/SBR N/A

PJ G2 Goodyear 2126 92/8-IIR/NR BIIR

PJ H Pathfinder [Discount Tire] 1227 84/7/9-IIR/NR/PBD BIIR

PJ J1 Kelly 2438 90/8/2-IIR/NR/PBD BIIR

PJ O1 Big O [Big O Tire] 2339 87/11/2­IIR/NR/SBR BIIR

PJ O2 Big O [Big O Tire] 2352 85/8/7-IIR/NR/PBD BIIR T7 H3 Hankook 2576 70/30-IIR/NR BIIR

U9 D3 Dominator [Discount Tire] 2391 89/11-IIR/NR CIIR

U9 O5 Big O [Big O Tire] 2313 73/23/4­IIR/NR/PBD CIIR

UP D5 Dominator [Discount Tire] 2417 83/17-IIR/NR BIIR

UP N1 Nokian 2165 83/17-IIR/NR BIIR UP O3 Big O [Big O Tire] 2326 82/18-IIR/NR BIIR UP P2 Futura [Pep Boys] 2039 83/17-IIR/NR BIIR UT O4 Big O [Big O Tire] 2365 86/14-IIR/NR CIIR UT P1 Futura [Pep Boys] 2012 84/16-IIR/NR CIIR UT P3 Futura [Pep Boys] 2040 83/17-IIR/NR CIIR

V4 S1 Sumitomo 2626 43/47/11­IIR/NR/SBR BIIR

VN B7 Firestone 2250 85/15-IIR/NR BIIR VN E Firestone 1337 86/14-IIR/SBR BIIR XL R2 Pirelli 2135 72/28-IIR/NR BIIR

YL N2 Nokian 2178 48/37/15­IIR/NR/PBD CIIR

* Polystyrene resin detected.1,2

1 e.g., United States Patent 7425591. 2 According to the Polymeric Material Encyclopedia, polymerization of butyl rubber in the presence of chlorinated polystyrene or poly(styrene-co-butadiene) can provide a compound with special melt and viscoelastic properties that result in processability improvements. [Salomone, J.C., Editor, 1996, Polymeric Material Encyclopedia, Vol. 1 A­B, p. 897, CRC Press, Inc., Salem, MA].

42

Pyrolysis-gas Chromatography/Mass Spectroscopy (Pyrolysis-GC/MS) Analysis of Twenty Two Tire Innerliners

Twenty-two tire innerliners were analyzed by Pyrolysis-GC/MS to confirm their compositional analysis. The seventeen standards (model liner compounds) were analyzed by Pyrolysis-GC/MS for polymer identification. The peak identifications are shown in Table 33. The peaks for isobu­tylene, isobutylene tetramer, isoprene, isoprene dimer, styrene, and butadiene dimer were used for the calibration curves (Figure 29-Figure 34). The innerliner analysis is shown in Table 34. One tire’s innerliner was run twice (2126) and showed good repeatability.

Table 33. Pyrolysis-GC/MS Peak Identification Chemical Pyrolysis-gc/ms peak location

Isobutylene 2.74-2.83 Isobutylene tetramer 26.78-26.81 Isoprene 7.33-7.60 Isoprene dimer 20.84-20.88 Styrene 18.13-18.15 Butadiene dimer 16.79-16.84

Figure 29. Pyrolysis-GC/MS Calibration Curve for Polyisobutylene Based on Isobutylene

y = 6.573E-11x - 7.763E-03 R2 = 9.313E-01

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.0E+00 5.0E+08 1.0E+09 1.5E+09

Isobutylene Peak Area (uV*sec)

Poly

isob

utyl

ene

(mg)

43

Figure 30. Pyrolysis-GC/MS Calibration Curve for Polyisobutylene Based on Isobutylene Tetramer

Figure 31. Pyrolysis-GC/MS Calibration Curve for Polyisoprene Based on Isoprene

y = 3.862E-10x + 8.460E-04 R2 = 9.766E-01

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.0E+00 1.0E+08 2.0E+08 3.0E+08

Isobutylene Tetramer Peak Area (uV*sec)

Poly

isob

utyl

ene

(mg)

y = 8.678E-11x - 2.777E-03 R2 = 9.342E-01

0.00

0.05

0.10

0.0E+00 5.0E+08 1.0E+09

Isoprene Peak Area (uV*sec)

Poly

isop

rene

(mg)

44

Figure 32. Pyrolysis-GC/MS Calibration Curve for Polyisoprene Based on Isoprene Dimer

y = 6.359E-11x + 1.620E-03 R2 = 9.152E-01

0.00

0.05

0.10

0.0E+00 5.0E+08 1.0E+09 1.5E+09

Isoprene Dimer Peak Area (uV*sec)

Poly

isop

rene

(mg)

Figure 33. Pyrolysis-GC/MS Calibration Curve for Styrene Butadiene Polymer Based on Styrene

y = 2.610E-19x2 + 2.571E-11x - 6.665E-05 R2 = 9.979E-01

0.00

0.02

0.04

0.06

0.08

0.E+00 2.E+08 4.E+08 Styrene Peak Area (uV*sec)

Styr

ene

But

adin

e Po

lym

er (m

g)

45

Figure 34. Pyrolysis-GC/MS Calibration Curve for Styrene Butadiene Polymer Based on Butadiene Dimer

y = 4.513E-10x + 1.434E-04 R2 = 9.982E-01

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.E+00 2.E+07 4.E+07 6.E+07 8.E+07 1.E+08

Butadiene Dimer Peak Area (uV*sec)

Styr

ene

But

adie

ne P

olym

er (m

g)

46

Table 34. Pyrolysis-GC/MS Analysis Summary Plant Code

Tire Type

Brand Barcode Pyrolysis-GC/MS Best Composition (%)

0B B8 Bridgestone 2270 85/13/2-IIR/NR/SBR 7X B6 Bridgestone 2226 84/16-IIR/NR 7X B9 Bridgestone 2501 81/19-IIR/NR A3 L General 1427 72/23/5-IIR/NR/PBD B3 D Michelin 1132 100 IIR* EP B1 Bridgestone 2269 84/16-IIR/NR EU U2 Dunlop 2065 75/25-IIR/NR M6 C Goodyear 1530 92/3/5-IIR/NR/PBD PJ G2 Goodyear 2126 90/5/4-IIR/NR/SBR PJ G2 Goodyear 2126 92/7/1-IIR/NR/SBR PJ H Pathfinder [Discount Tire] 1227 89/4/7-IIR/NR/PBD PJ J1 Kelly 2438 85/7/8-IIR/NR/PBD PJ O1 Big O [Big O Tire] 2339 92/4/4-IIR/NR/SBR PJ O2 Big O [Big O Tire] 2352 87/8/5-IIR/NR/SBR T7 H3 Hankook 2576 67/33-IIR/NR U9 D3 Dominator [Discount Tire] 2391 87/11/3-IIR/NR/PBD U9 O5 Big O [Big O Tire] 2313 78/20/2-IIR/NR/PBD UT P3 Futura [Pep Boys] 2040 82/18-IIR/NR V4 S1 Sumitomo 2626 39/51/10-IIR/NR/SBR VN B7 Firestone 2250 87/13-IIR/NR VN E Firestone 1337 91/9-IIR/SBR XL R2 Pirelli 2135 68/32-IIR/NR YL N2 Nokian 2178 48/38/14-IIR/NR/PBD

*1phr polystyrene resin detected.

In order to estimate the variability of the procedures to measure the polymer content of the inner-liner, the calculated composition of tires of the same brand were compared. Many samples showed small amounts of SBR and/or PBD rubber, which could be spurious data, or could come from small amounts of these polymers that may have been added as recycled rubber. The addi­tion of small amounts of uncured tire compounds (work-away) is less common in modern radial tires. However, the use of finely ground tire compounds in innerliners is increasing in popularity. The average formulations were similar by either method of identification (pyrolysis-gc/fid and pyrolysis-gc/ms). The Bridgestone tires were estimated as an 85/15 bromobutyl/natural rubber compound. The Continental tires were approximately a 65/35 bromobutyl/natural compound. The Cooper tires were approximately 85/15 halobutyl/natural formulations, with chlorobutyl or bromobutyl rubber, varying by plant. The Goodyear tires were approximately a 90/10 bromo­butyl/natural rubber formulation. Finally, the Michelin tires were approximately 100-phr bromo­butyl compound, containing a high styrene resin. These results are summarized in Table 35.

47

Table 35. Summary of Average GC Innerliner Composition by Tire Manufacturer

Tire Brand Number of

Samples (GC/FID : GC/MS)

HIIR Content by FID

HIIR Content by MS

NR Content by FID

NR Content by MS

SBR / PBD

Content by FID

SBR / PBD

Content by MS

Bridgestone 7 : 6 83.4 ± 2.0 85.3 ± 12.8

14.3 ± 6.4 12.9 ± 6.7 2.3 ± 5.2 (SBR)

1.8 ± 3.6 (SBR)

Continental 5 : 1 61.6 ± 6.4 72 31.2 ± 6.8 23 7.2 ± 4.8 (SBR)

5 (PBD)

Cooper 10 : 3 83.1 ± 4.1 82.3 ± 4.5 16.5 ± 3.1 16.3 ± 4.7 0.4 ± 1.3 (PBD)

1.7 ± 1.5 (PBD)

Goodyear 7 : 7 89.0 ± 3.7 89.6 ± 2.8 7.9 ± 1.6 5.4 ± 1.9 1.3 ± 2.6 (SBR) 2.0 ± 2.2 (PBD)

2.0 ± 2.2 (SBR) 2.9 ± 3.7 (PBD)

Michelin 7 : 1 98.4 ± 4.2 100 1.6 ± 4.2 0 0 0

Part IV - Permeability of Model Compounds Air Permeability of Model Compounds

Model compounds (L21150-154-1 to 6 and liner 2, 4, 5, 6, 7, 8, 9, 10) were analyzed for air per­meability by ASTM method D1434-82 (Table 38). The permeability results from the first six model compounds were compared to literature values (Table 37).[30,56,60,63] The experimental results compared closely to literature data. The results were reported in units of cm3STP-cm/cm2­sec-atm, but a conversion table is supplied in Table 36. The testing was performed with a 66.4 cm2 surface area permeability cell and an 8.04 cm2 surface area permeability cell at 21�C and 70�C (Table 38, Figure 35, and Figure 36).

Air Permeability of Ten Model Compounds

The air permeability method (ASTM method D1434-82) was further verified with an additional twelve model compounds (liners 1-10, 11 and 19) (Table 39 and Table 40). The results were re­ported in units of cm3STP-cm/cm2-sec-atm. The permeability values of the model compounds were compared to literature values and good agreement was observed. The testing was per­formed with 66.4 cm2 surface area at 21�C and 65�C (Figure 37 and Figure 38).

48

Table 36. Conversion Table Sample # permeability

(cm3STP-cm/cm2-sec-atm)

permeability (cm3STP-cm/cm2-

sec-Pa)

permeability (cm3STP-cm/cm2-

sec-cmHg) L21150-154-1(example) 5.30E-09 5.23E-14 6.97E-11 Unit Conversion 1 9.86E-06 1.316E-02

Table 37. Air Permeability Literature Values Polymer Temperature (�C) Permeability

(cm3STP-cm/cm2-sec-atm) at 21�C

Reference

BIIR 21 3.0E-09 64 BIIR 21 3.6 to 4.6E-9 19 BIIR 25 3.2E-09 17 BIIR 25 3.8E-09 18 BIIR 65 2.7E-08 17 BIIR 65 4.3 to 7.0E-8 64 BIIR 65 2.8E-08 18 NR 21 3.6E-08 64 NR 25 4.2E-08 17 NR 65 2.1E-07 17

49

Table 38. Model Liner Compound Air Permeability Data Compound # Temperature

(deg C) BIIR CIIR IIR NR SBR Permeability

(cm3STP­cm/cm2-sec-atm)

Cell Size

(cm2) L21150-154-1 21 100 5.3E-09 66.4 L21150-154-2 21 80 20 9.2E-09 66.4 L21150-154-3 21 80 20 8.1E-09 66.4 L21150-154-4 21 100 5.0E-08 66.4 L21150-154-5 21 100 6.4E-09 66.4 L21150-154-6 21 80 20 9.8E-09 66.4 L21150-154-1 21 100 1.8E-08 8.04 L21150-154-2 21 80 20 1.5E-08 8.04 L21150-154-3 21 80 20 1.3E-08 8.04 L21150-154-3 21 80 20 1.8E-08 8.04 L21150-154-4 21 100 6.4E-08 8.04 L21150-154-5 21 100 2.3E-08 8.04 L21150-154-6 21 80 20 1.9E-08 8.04 Liner 2 70 80 20 3.9E-08 66.4 Liner 4 70 50 50 6.6E-08 66.4 Liner 5 70 40 60 1.3E-07 66.4 Liner 6 70 20 80 1.8E-07 66.4 Liner 7 70 100 3.0E-08 66.4 Liner 8 70 80 20 3.8E-08 66.4 Liner 9 70 75 25 6.4E-08 66.4 Liner 10 70 60 40 1.3E-07 66.4

50

Figure 35. Permeability of Model Compounds at 21�C as a Function of Butyl Content

Figure 36. Permeability of Model Compounds at 70�C as a Function of Butyl Content

0.0E+00

1.0E-08

2.0E-08

3.0E-08

4.0E-08

5.0E-08

6.0E-08

7.0E-08

0 20 40 60 80 100

Butyl Content (phr)

Perm

eabi

lity

(cm

3 -cm

/cm

2 -s-a

tm)

66.4 cm2 8.04 cm2 Literature

0.0E+00

5.0E-08

1.0E-07

1.5E-07

2.0E-07

2.5E-07

0 20 40 60 80 100 Butyl Content (phr)

Perm

eabi

lity

(cm

3 -cm

/cm

2 -s-a

tm)

66.4 cm2 Literature

51

Table 39. 21�C Model Compound Permeability Data (66.4 cm2 Cell Size) Sample

ID Temperatur

e (deg C) phr IIR

phr CIIR

phr BIIR

phr NR

Permeability (cm3*cm/(cm2*s*atm

)) Liner #1 21 100 7.04E-09 Liner #2 21 80 20 7.00E-09 Liner #3 21 60 40 2.03E-08 Liner #4 21 50 50 5.53E-09 Liner #5 21 40 60 2.14E-08 Liner #6 21 20 80 4.61E-08 Liner #7 21 100 7.97E-09 Liner #8 21 80 20 8.67E-09 Liner #9 21 75 25 5.25E-09 Liner #10 21 60 40 1.02E-08 Liner #11 21 100 5.03E-09 Liner #19 21 100 5.32E-08

Table 40. 65�C Model Compound Permeability Data (66.4 cm2 Cell Size) Sample

ID Temperatur

e (deg C) phr IIR

phr CIIR

phr BIIR

phr NR

Permeability (cm3*cm/(cm2*s*atm

)) Liner #1 65 100 5.23E-08 Liner #2 65 80 20 6.66E-08 Liner #3 65 60 40 1.29E-07 Liner #4 65 50 50 2.22E-07 Liner #5 65 40 60 1.62E-07 Liner #6 65 20 80 2.99E-07 Liner #7 65 100 4.33E-08 Liner #8 65 80 20 7.86E-08 Liner #9 65 75 25 7.17E-08 Liner #10 65 60 40 7.03E-08 Liner #11 65 100 5.09E-08 Liner #19 65 100 4.06E-07

52

Figure 37. Permeability of Model Compounds at 21�C as a Function of Butyl Content

0.E+00

1.E-08

2.E-08

3.E-08

4.E-08

5.E-08

6.E-08

7.E-08

0 20 40 60 80 100

Butyl content (phr)

Perm

eabi

liyt (

cm3 -c

m/c

m2 -s

-atm

)66.4 cm2 Literature

Figure 38. Permeability of Model Compounds at 65�C as a Function of Butyl

Content

0.E+00

1.E-07

2.E-07

3.E-07

4.E-07

5.E-07

0 20 40 60 80 100 Butyl content (phr)

Perm

eabi

liyt (

cm3 -c

m/c

m2 -s

-atm

)

66.4 cm2 Literature

53

Part V - Permeability of Innerliners from Production Tires The innerliners from new tires of each of the six models collected by NHTSA from service in Phoenix were analyzed for permeability by ASTM method D1434-82 (Table 41). Four or five tires of each model were analyzed for good repeatability and data confidence. The testing was performed with the 8.04-cm2 surface area permeability cell at 21�C because of the size limita­tions associated with removing large flat slices of innerliner from tires. The testing was then conducted on a single tire’s innerliner from each of the thirty-seven tires used in subsequent por­tions of the test development program (Table 42). This testing was then repeated for samples at 65�C to simulate in-service running1,2 and accelerated oven-aging temperatures (Table 43 & Ta­ble 44). The permeability values of extracted innerliners at 21�C (Figure 39) and 65�C (Figure 40) were plotted against butyl content and compared to literature values.[56,60,63-64] Some data scatter may come from thickness non-uniformity, as some innerliners have a non-uniform pattern imprint from the curing bladder that could not be removed. Error bars are shown on the six inner-liners that had repeat measurements. The confidence was about +/- 25%. The actual permeability measured for the innerliners at 21�C and 65�C was similar to literature values for compounds with high butyl content, but measured higher than literature values for compounds with no butyl content (natural rubber). However, plot against butyl content alone cannot capture the effects of other constituents in the innerliner such as fillers and oils, which vary from one liner formulation to another. The average permeability of an innerliner at 65�C was over 500% (6X) higher than its permeability at 21�C (1.14E-07 versus 1.83E-08 cm^2/(sec*atm)).

1 “Typically, the internal temperature of a tire fitted to a standard passenger car lies between 20 and 90�C, depend­ing on the type of tire, the way the car is driven and the ambient temperature.”, The Pneumatic Tire, Edited by A.N. Gent and J.D. Walter, The University of Akron, August 2005, p. 490.2 “A tire operating at normal speeds can achieve internal temperatures in excess of 180°F [82�C].” , Transportation Research Board Special Report 286, Tires and Passenger Vehicle Fuel Economy, National Research Council of the National Academies, 2006, p. 33.

54

Table 41. Innerliner Permeability Data at 21�C for the Six Field Tire Models Plant Code

Tire Type

Barcode Pyrolysis -GC/FID Composition

phr Butyl Gas Permeability (cm^2/(sec*atm)) First Test Second Test Third Test Average Std Dev Confidence

AP B 1030 100 IIR 100 1.64E-08 1.05E-08 3.14E-09 2.41E-09 1025 1.19E-08 1.33E-08 1026 8.03E-09 1027 7.76E-09 8.37E-09 9.13E-09 1028 7.35E-09 1.26E-08

B3 D 1132 100 IIR 100 1.72E-08 1.00E-08 5.35E-09 4.48E-09 1125 1.47E-08 6.67E-09 1126 1.71E-08 5.56E-09 1127 7.93E-09 1128 6.23E-09 4.81E-09

PJ H 1227 84/7/9­IIR/NR/PBD

82 1.60E-08 1.04E-08 4.86E-09 4.06E-09 1225 1.39E-08 1226 7.05E-09 7.60E-09 1227 1.82E-08 8.29E-09 5.06E-09 1228 7.36E-09

VN E 1337 86/14­IIR/SBR

86 2.58E-08 1.79E-08 1.13E-08 8.70E-09 1306 1.98E-08 5.73E-09 1308 1.90E-08 1.22E-08 1319 4.27E-08 9.06E-09 1333 1.82E-08 8.84E-09

A3 L 1427 70/30­IIR/NR

70 2.46E-08 1.82E-08 5.44E-09 4.19E-09 1425 2.74E-08 1.73E-08 1426 2.02E-08 1.41E-08 1.08E-08 1427 1.70E-08 1.25E-08 1428 1.95E-08

M6 C 1530 92/6/2­IIR/NR/PBD

92 1.10E-08 1.06E-08 4.41E-09 3.16E-09 1525 1.40E-08 9.83E-09 1526 1.46E-08 1527 1.55E-08 1.27E-08 9.50E-09 1528 1.29E-08 4.48E-09 1530 1.96E-09

55

Table 42. Innerliner Permeability Data at 21�C for Subsequent Test Tires Plant Code

Tire Type

Barcode Pyrolysis -GC/FID Composition

phr Butyl

Gas Permeability (cm^2/(sec*atm))

0B B8 2270 81/17/2-IIR/NR/SBR 81 1.11E-08 3D D4 2429 85/15-IIR/NR 85 2.47E-08 7X B6 2226 83/17-IIR/NR 83 1.18E-08 7X B9 2501 81/19/-IIR/NR 81 1.30E-08 9T T2 2651 53/47-IIR/NR 53 1.86E-08 A3 C3 2456 56/38/6-IIR/NR/SBR 56 1.38E-08 A3 C7 2526 66/21/13-IIR/NR/SBR 66 1.79E-08 AC C5 2495 61/30/9-IIR/NR/SBR 61 2.28E-08 B7 M1 2469 100 IIR 100 1.29E-08 B7 M1 2469 100 IIR 100 1.78E-08 B7 M10 2601 100 IIR 100 2.06E-08 CC Y2 2140 72/28-IIR/NR 72 1.28E-08 ED M3 2482 89/11-IIR/NR 89 1.28E-08 EJ B4 2212 85/15-IIR/NR 85 2.20E-08 EP B1 2269 83/17-IIR/NR 83 2.24E-08 EU U2 2065 70/30-IIR/NR 70 2.76E-08 PB D6 2404 82/18-NR/SBR 0 7.05E-08 PD G1 2113 93/7-IIR/NR 93 1.96E-08 PJ D2 2378 65/35-NR/SBR 0 2.52E-08 PJ D2 2378 65/35-NR/SBR 0 8.39E-08 PJ G2 2126 92/8-IIR/NR 92 1.45E-08 PJ J1 2438 90/8/2-IIR/NR/PBD 92 1.65E-08 PJ O1 2339 87/11/2-IIR/NR/SBR 87 7.93E-09 PJ O2 2352 85/8/7-IIR/NR/PBD 83 5.55E-09 T7 H3 2576 70/30-IIR/NR 70 1.87E-08 U9 D3 2391 89/11-IIR/NR 89 1.65E-08 U9 O5 2313 72/23/5-IIR/NR/PBD 72 2.52E-08 UP D5 2417 83/17-IIR/NR 83 1.18E-08 UP N1 2165 83/17-IIR/NR 83 2.82E-08 UP O3 2326 82/18-IIR/NR 82 1.36E-08 UP P2 2039 83/17-IIR/NR 83 1.50E-08 UT O4 2365 86/14-IIR/NR 86 2.03E-08 UT P1 2012 84/16-IIR/NR 84 1.07E-08 UT P3 2040 83/17-IIR/NR 83 1.66E-08 V4 S1 2626 43/47/11-IIR/NR/SBR 43 2.04E-08 V4 S1 2626 43/47/11-IIR/NR/SBR 43 9.75E-09 VN B7 2250 85/15-IIR/NR 85 2.02E-08 XL R2 2135 72/28-IIR/NR 72 1.65E-08 YL N2 2178 48/37/15-IIR/NR/PBD 47 2.64E-08 YL N2 2178 48/37/15-IIR/NR/PBD 47 1.99E-08

56

Figure 39. Permeability of Tire Innerliners at 21�C as a Function of Butyl Content

0.0E+00

1.0E-08

2.0E-08

3.0E-08

4.0E-08

5.0E-08

6.0E-08

7.0E-08

8.0E-08

0 20 40 60 80 100

Butyl Content (phr)

Perm

eabi

lity

(cm

2 /se

c-at

m)

Tire Innerliners Literature

57

Table 43. Innerliner Permeability Data at 65�C for Six Field Tire Models Plant Code

Tire Type

Barcode Pyrolysis -GC/FID Composition

phr Butyl Gas Permeability (cm^2/(sec*atm)) First Test Second Test Third Test Average Std Dev Confidence

AP B 1030 100 IIR 100 6.26E-08 6.79E-08 6.94E-08 1.79E-08 1.38E-08 1029 9.49E-08 7.96E-08 1031 3.81E-08 6.46E-08 1032 9.42E-08 5.79E-08 1028 6.51E-08

B3 D 1132 100 IIR 100 5.11E-08 6.62E-08 6.57E-08 2.66E-08 2.23E-08 1129 6.35E-08 4.59E-08 1130 1.18E-07 5.23E-08 1131 9.11E-08 3.74E-08

PJ H 1229 82/6/12­IIR/NR/PBD

82 7.01E-08 4.28E-08 5.92E-08 1.57E-08 1.32E-08 1230 4.38E-08 7.22E-08 1231 3.90E-08 1232 8.17E-08 5.97E-08 1226 6.43E-08

VN E 1337 86/14­IIR/SBR

86 5.78E-08 6.51E-08 2.04E-08 1.70E-08 1357 1.07E-07 6.68E-08 1359 5.53E-08 1368 3.57E-08 5.68E-08 1308 7.07E-08 7.03E-08

A3 L 1429 70/30­IIR/NR

70 6.29E-08 8.18E-08 9.70E-08 2.78E-08 2.14E-08 1430 6.03E-08 1.11E-07 1431 1.29E-07 1.04E-07 1432 9.71E-08 8.48E-08 1426 1.42E-07

M6 C 1530 92/6/2­IIR/NR/PBD

92 4.76E-08 7.95E-08 7.74E-08 2.09E-08 1.40E-08 1529 7.27E-08 1.13E-07 1531 4.96E-08 8.08E-08 1532 6.71E-08 8.90E-08 6.92E-08 1527 1.10E-07 1528 7.34E-08

Table 44. Innerliner Permeability Data at 65�C for Subsequent Test Tires Plant Code

Tire Type Barcode Pyrolysis -GC/FID

Composition phr Butyl

Gas Permeability (cm^2/(sec*atm))

0B B8 2270 81/17/2-IIR/NR/SBR 81 5.26E-08 3D D4 2429 85/15-IIR/NR 85 5.21E-08 7X B6 2226 83/17-IIR/NR 83 8.88E-08 7X B9 2501 81/19/-IIR/NR 81 1.36E-07 9T T2 2651 53/47-IIR/NR 53 1.51E-07 A3 C3 2456 56/38/6-IIR/NR/SBR 56 1.61E-07 A3 C7 2526 66/21/13-IIR/NR/SBR 66 5.18E-08 AC C5 2495 61/30/9-IIR/NR/SBR 61 7.52E-08 AC C5 2495 61/30/9-IIR/NR/SBR 61 6.90E-08 B7 M1 2469 100 IIR 100 1.02E-07 B7 M10 2601 100 IIR 100 7.58E-08 CC Y2 2140 72/28-IIR/NR 72 1.22E-07 ED M3 2482 89/11-IIR/NR 89 8.56E-08

58

EJ B4 2212 85/15-IIR/NR 85 1.45E-07 EP B1 2269 83/17-IIR/NR 83 1.80E-07 EU U2 2065 70/30-IIR/NR 70 6.83E-08 PB D6 2404 82/18-NR/SBR 0 4.86E-07 PD G1 2113 93/7-IIR/NR 93 1.57E-07 PJ D2 2378 65/35-NR/SBR 0 5.16E-07 PJ D2 2378 65/35-NR/SBR 0 5.05E-07 PJ O1 2339 87/11/2-IIR/NR/SBR 87 1.62E-07 PJ O2 2352 85/8/7-IIR/NR/PBD 83 1.36E-07 T7 H3 2576 70/30-IIR/NR 70 2.11E-07 U9 D3 2391 89/11-IIR/NR 89 7.31E-08 UP D5 2417 83/17-IIR/NR 83 1.56E-07 UP O3 2326 82/18-IIR/NR 82 1.19E-07 UP P2 2039 83/17-IIR/NR 83 1.66E-07 UT O4 2365 86/14-IIR/NR 86 3.79E-08 UT P1 2012 84/16-IIR/NR 84 1.50E-07 UT P3 2040 83/17-IIR/NR 83 1.20E-07 V4 S1 2626 43/47/11-IIR/NR/SBR 43 1.86E-07 YL N2 2178 48/37/15-IIR/NR/PBD 47 1.35E-07 YL N2 2178 48/37/15-IIR/NR/PBD 47 5.58E-08

Figure 40. Permeability of Tire Innerliners at 65�C as a Function of Butyl Content

0.0E+00

1.0E-07

2.0E-07

3.0E-07

4.0E-07

5.0E-07

6.0E-07

7.0E-07

0 20 40 60 80 100

Butyl Content (phr)

Perm

eabi

lity

(cm

2 /se

c-at

m)

Tire Innerliners Literature

59

Part VI - Microscopy of Innerliners from Production Tires The innerliner thickness in the crown region was measured by microscopy in 294 tires, from 40 tire models, from 38 different plants. The average innerliner gauge was computed from three lo­cations (serial side shoulder, tread centerline, and opposite serial side shoulder) and is shown in Table 45 with the standard deviation. Across the 41 unique tire model/plant code combinations, the average innerliner thickness in the crown was 0.96 mm, with an average standard deviation of –0.15 mm. The results displayed graphically in Figure 41 are ordered by manufacturer, plant code, maximum sidewall pressure, and tire model type designation. In many cases, the higher inflation pressure light truck tires have thicker innerliners than the passenger tires. When possi­ble, the innerliner placement (i.e. extent of coverage) was determined by visual microscope in­spection of polished omega cuts and generally documents how far down the innerliner coverage extends. Innerliners can be placed to wrap fully from bead toe to bead toe, or terminate at the bead toe, or terminate some distance down each sidewall for partial coverage. Often the place­ment was difficult to determine and varied from tire-to-tire, side-to-side in some tire models; hence the “about xx-yy mm above the toe” terminology in the Innerliner Placement column.

Table 45. Microscopy Innerliner Analysis of Production Tires Tire Size Plant

Code Tire Type

Data Points

Avg. of Inner-liner Thickness

(mm)

Std. Dev. of Innerliner Thickness

(mm)

Innerliner Placement

205/65R15 ED M3 3 1.12 0.09 225/60R16 V4 S1 9 0.94 0.07 Innerliner ends about

3-30 mm above toe 235/75R16 EP B1 3 0.66 0.16 255/65R16 A3 L 96 0.70 0.12 Innerliner wraps

around toe LT235/85R16 PJ G2 3 0.72 0.04

O1 6 0.99 0.11 UP N1 3 1.22 0.06

P2 6 1.27 0.14 LT245/75R16 B7 M10 9 1.85 0.11 Innerliner wraps

around toe PJ H 90 1.20 0.27 Innerliner ends about

30 mm above toe T7 H3 9 0.76 0.07 Innerliner ends at bot­

tom of toe or wraps around toe

LT265/75R16 7X B9 9 1.05 0.17 Innerliner ends about 8-15 mm above toe

60

Table 45. Microscopy Innerliner Analysis of Production Tires Tire Size Plant

Code Tire Type

Data Points

Avg. of Inner-liner Thickness

(mm)

Std. Dev. of Innerliner Thickness

(mm)

Innerliner Placement

PJ O2 6 0.96 0.17 UP D5 3 1.49 0.20 UT O4 3 1.42 0.20 XL R2 6 1.09 0.23 YL N2 3 0.76 0.18

LT285/75R16 3D D4 9 1.23 0.15 CC Y2 3 0.64 0.07 EN B4 3 0.88 0.21

P195/65R15 AP B 162 0.84 0.13 Innerliner ends about 28 mm above toe

PJ D2 6 1.47 0.47 U9 O5 6 0.92 0.15

P205/65R15 0B B8 6 0.74 0.05 Innerliner ends about 11-20 mm above toe

M6 C 113 0.77 0.18 Innerliner ends about 20 mm above toe

P5 C8 9 0.67 0.05 Innerliner wraps around toe or ends at bottom of toe

PB D6 3 0.48 0.09 U9 D3 6 0.86 0.14 UP O3 6 0.97 0.15

P225/60R17 EU U2 9 0.68 0.22 Innerliner ends about 13-21 mm above toe

P235/60R16 9T T2 9 0.87 0.16 Innerliner ends about 9-33 mm above toe

P235/75R15XL B3 D 111 0.98 0.14 Innerliner ends at bot­tom of toe

PD G1 3 0.72 0.03 UT P3 15 0.90 0.22 Innerliner wraps

around toe P245/70R16 7X B6 8 0.91 0.08 P265/70R17 A3 C7 9 0.83 0.08 Innerliner ends about

13-24 mm above toe P265/75R16 B7 M1 3 1.22 0.12

UT P1 3 1.04 0.12 VN B7 6 0.86 0.23

E 75 0.88 0.27 Innerliner ends about 33 mm above toe W2 E 30 0.69 0.15

Average by Tire Type & Plant Code 0.96 0.15

61

Figure 41. Microscopy Innerliner Analysis of Production Tires

Part VII - Indentation Modulus of Innerliners from Production Tires The indentation modulus for all production tires in the study was measured at 0.1mm increments across the shoulder belt-edge region and bead area, yielding modulus (similar to hardness) results for all rubber layers in that region, including the innerliner (Figure 42).

62

Figure 42. Indentation Modulus Test Samples and Plots for a Phoenix-Retrieved Tire Shoulder Region Sample Shoulder Region Plot

Innerliner

i

nner

liner

p

lyco

at

s

houl

der w

edge

b

elt 1

coa

t

g

umst

rip

b

elt 2

coa

t

t

read

bas

e

t

read

4 5 6 7 8 9

10 11 12 13 14 15

Mod

ulus

(MPa

)

0 1 2 3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Position (mm)

Bead Region Sample Bead Region Plot

Innerliner

i

nner

liner

toe

guar

d

in

ne

rlin

er

p

lyco

at

ape

x

p

lyco

at t

oegu

ard

s

ide

wa

ll

10

15

20

25

30

35

40

0

5

0 1 2 3 4 5 6 7 8 9 10 11 12

63

Indentation Modulus - Shoulder Region Innerliner

Indentation Modulus - Shoulder Region Innerliner, In-Service Tires For the six tire models retrieved from service in Phoenix, AZ (Types B, C, D, E, H, and L), in­nerliners from tires of various ages and mileages were compared to innerliners from new tires of each model (Figure 43). Five of the six tire models had innerliners from the shoulder region that exhibited an increase in modulus with increasing age. The correlation coefficient (R2) of the li­near fits was greater than 0.9 in tire types B, C, and L. The indentation modulus of the innerliner from the tire type D did not increase with age. The aging behavior of the innerliner is almost cer­tainly affected by compounding. Butyl rubber is known to have better oxidation resistance than SBR and NR polymers, and is thus more resistant to hardening. However, butyl content alone was not the main determinant. For instance, observe the dissimilar behavior of tire types B and D, with innerliners thought to both use 100% bromobutyl.

Figure 43. Average Indentation Modulus of Shoulder Region Innerliner as a Function of Age

The average change of the indentation modulus for the innerliner in the shoulder region of each of the six Phoenix-retrieved tires is shown in Figure 44 and Table 46. Modulus values ranged from an initial softening of 0.5 MPa after 0.5 years of service to an increase of up to 1.8 MPa after 7.4 years of service. The average rate of change in the average innerliner modulus value for the six tire models was 0.21 MPa/yr of service.

64

Figure 44. Average Change in Indentation Modulus of Shoulder Region Innerliner for Six Tire Models During Service in Phoenix, AZ

65

Table 46. Average Change in Indentation Modulus of Shoulder Region Innerliner During Service in Phoenix, AZ

Tire Type

DOT Age (yrs)

Avg. Innerliner Modulus (MPa)

Change in Avg. Modulus (MPa)

Rate of Change in Avg. Modulus (MPa/yr)

B 1.37 2.31 0.02 0.01 2.51 2.90 0.61 0.24 2.53 2.76 0.47 0.19 4.66 3.52 1.23 0.26 6.04 3.66 1.37 0.23 7.38 4.08 1.79 0.24

C 1.81 3.04 0.17 0.09 5.45 3.51 0.64 0.12

D 1.58 3.05 0.60 0.38 3.87 2.44 -0.01 0.00

E 0.53 3.51 -0.56 -1.06 2.91 4.87 0.80 0.27 3.27 5.18 1.11 0.34

H 1.36 2.78 0.81 0.60 1.99 3.15 1.18 0.59 2.99 3.48 1.51 0.51 5.96 2.99 1.02 0.17

L 1.06 3.39 0.29 0.27 1.24 3.57 0.47 0.38 2.65 4.11 1.01 0.38

Average 0.21

Indentation Modulus - Shoulder Region Innerliner, Roadwheel Tested Tires Thirty-one new tires of the six original tire models collected from service in Phoenix were sub­jected to various durations of the Michelin Long Term Durability Endurance (LTDE) roadwheel test. In Figure 45 the average change in innerliner modulus in the shoulder region for each model is plotted against hours on the roadwheel test. The approximate innerliner polymer composition from Pyrolysis-GC-MS or Pyrolysis-GC-FID analysis is listed with each tire model. As observed in service, innerliners from the shoulder region in tire types B, C, E, L, and H hardened with in­creasing roadwheel hours and innerliners from the Type D tires exhibited no change. The aver­age modulus change and rates of change are calculated in Table 47 for the in-service tires.

66

Figure 45. Average Change in Indentation Modulus of the Shoulder Region Innerliner Versus LTDE Roadwheel Hours

Table 47. Average Change in Indentation Modulus of the Shoulder Region Innerliner During LTDE Testing

Tire Type

Number of Tires

Avg. Innerliner Modulus (MPa)

Change in Avg. Modulus (MPa)

Rate of Change in Avg. Modulus (MPa/100 hrs)

B 6 3.43 1.14 0.40 C 4 3.42 0.55 0.17 D 6 2.51 0.06 0.04 E 7 5.35 1.28 0.33 H 4 3.07 1.10 0.86 L 4 4.20 1.10 0.57

Average 3.74 0.87 0.37

Only five tires were subjected to indentation modulus testing after running on the Continental Passenger Endurance (P-END) test (Figure 46). Therefore, there were insufficient data to make a similar analysis of rates of change in the innerliner modulus for the P-END test. Though there are only five data points, a similar trend to service and LTDE testing is observed in P-END test­ing. Tire Types B, C, E, and L showed an increase in average innerliner modulus during roadw­heel aging, and Type D showed a slight decrease.

67

Figure 46. Average Change in Indentation Modulus of the Shoulder Region Innerliner Versus P-END Roadwheel Hours

Indentation Modulus - Shoulder Region Innerliner, Oven Aged Tires

New tires of types B, C, D, E, L, and H were subjected to one of three accelerated oven-aging conditions listed in Table 48 and compared to new, unaged tires of each model. In the initial phase of test development capped inflation with 50/50 N2/O2 was used (i.e. the tire was filled to test pressure, valve stem cap installed, and the inflation gas and pressure were not changed throughout the oven aging sequence).

68

Table 48. Oven Aging Conditions with Capped Inflation Gas - Six Phoenix Tire Models Name Temp

(�C) Duration (weeks)

Inflation Gas

Inflation Maintenance

Pre-Oven Roadwheel Break-in

Oven - 55C - 12 wks - 50/50 ­

Capped

55 12 50/50 N2/O2

Capped (none) None

Oven - 65C - 8 wks - 50/50 ­

Capped

65 8 50/50 N2/O2

Capped (none) None

Oven - 65C - 8 wks - 50/50 ­

Capped ­24/75BI- 50/50

65 8 50/50 N2/O2

Capped (none) 24 hrs, 75 mph, 100% max sidewall load, 100% max sidewall

pressure, 50/50 N2/O2 inflation

The innerliner in the shoulder region of all six models exhibited some hardening during the capped oven aging (Figure 47). The approximate innerliner polymer composition from Pyrolysis-GC-MS or Pyrolysis-GC-FID analysis is listed with each tire model. The average change in modulus and rate of change in modulus for each test condition are displayed in Table 49. In some cases, the long capped-inflation oven aging sequences (8-12 weeks) produced larger innerliner modulus changes than were observed after up to 7 years of service. The rates of change per week of aging were higher for 65�C oven aging than 55�C.

Some of these test tires were subjected to the third test condition in Table 48 that includes a 24­hour roadwheel break-in prior oven aging. The combination of oven aging after a roadwheel break-in is called “hybrid aging.” The break-in did not appear to significantly affect the innerlin­er modulus. JMP software effect screening analysis of innerliner indentation modulus showed that the best model fit was oven temperature and tire type (Figure 48). The effect of aging time was not significant, probably, in part, because the tire inflation gas was capped during the expe­riment and becomes depleted during the 8-12 weeks of oven aging (Table 50).

69

Figure 47. Average Change in Indentation Modulus of Shoulder Region Innerliner for Capped-Inflation Oven Aging

Table 49. Average Change in Indentation Modulus of Shoulder Region Innerliner During Capped-Inflation Oven Aging

Tire Type

Oven - 55C - 12 wks - 50/50 ­Capped

Oven - 65C - 8 wks - 50/50 ­Capped

Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI- 50/50

Average Modulus

(MPa)

Average Change in Mod­

ulus (MPa)

Rate of Change in Avg.

Modulus (MPa/

wk)

Average Modulus

(MPa)

Average Change in Mod­

ulus (MPa)

Rate of Change in Avg.

Modulus (MPa/

wk)

Average Modulus

(MPa)

Average Change in Mod­

ulus (MPa)

Rate of Change in Avg.

Modulus (MPa/

wk) B 4.01 1.72 0.14 4.60 2.31 0.29 5.20 2.91 0.36 C 3.79 0.92 0.08 4.38 1.51 0.19 4.62 1.75 0.22 D 3.00 0.55 0.05 2.50 0.05 0.01 2.86 0.41 0.05 E 6.06 1.99 0.17 6.29 2.22 0.28 H 2.94 0.97 0.08 3.50 1.53 0.19 3.17 1.20 0.15 L 4.78 1.68 0.14 5.08 1.98 0.25 4.84 1.74 0.22 Average 4.01 1.72 0.14 4.60 2.31 0.29 5.20 2.91 0.36

70

Figure 48. Model Prediction of Innerliner Indentation Modulus with Capped-Inflation Oven Aging

1

2

3

4

5

6

7

Inne

rline

r_Av

g_M

od_M

Pa A

ctua

l

1 2 3 4 5 6 7 Innerliner_Avg_Mod_MPa Predicted P<.0001 RSq=0.92 RMSE=0.4218

B C D E H L

Tire_Type

71

aTable 50. Regression Analysis of Innerliner Modulus as a Function of Oven Temperature

and Tire Type

RSquare RSquare Adj Root Mean Square Error Mean of Response Observations (or Sum Wgts)

0.917023 0.889363 0.421798 3.8628

25

Summary of Fit

Model Error C. Total

Source 6

18 24

DF 35.391664 3.202440 38.594104

Sum of Squares 5.89861 0.17791

Mean Square 33.1544

F Ratio

<.0001 Prob > F

Analysis of Variance

Nominal factors expanded to all levels Continuous factors centered by mean, scaled by range/2

Intercept Temperature (degC) Tire_Type[B] Tire_Type[C] Tire_Type[D] Tire_Type[E] Tire_Type[H] Tire_Type[L]

Term 3.8625222 0.8409045 0.0069453 0.0046109 -1.207889 1.6721109 -1.015389 0.5396109

Scaled Estimate 0.084657 0.098871 0.177307 0.191938 0.191938 0.191938 0.191938 0.191938

Std Error 45.63 8.51 0.04 0.02 -6.29 8.71 -5.29 2.81

t Ratio <.0001 <.0001 0.9692 0.9811 <.0001 <.0001 <.0001 0.0116

Prob>|t|

Scaled Estimates

Inne

rline

r_Av

g_M

od_M

P

6.29

1.97

3.869467

Temperature (degC)

0 6544.4

Tire_Type

B C D E H L

Prediction Profiler

Subsequent phases of the aging test development project subjected an additional 21 tire models to oven aging conditions that used weekly vent and refill of the 50/50 N2/O2 inflation gas. The vent and refill procedure was conducted to mitigate the observed depletion of oxygen during the

72

oven aging testing and perhaps shorten the required duration of oven aging. These test conditions are listed in Table 51.

Table 51. Oven Aging Conditions with Vent and Refill of Inflation Gas - 21 Additional Tire Models

Name Temp (�C)

Duration (weeks)

Inflation Gas

Inflation Maintenance

Pre-Oven Roadwheel Break-in

Oven - 65C - 8 65 8 50/50 Weekly vent & 23 hrs, 50 mph, 100% wks - 50/50 - N2/O2 refill max sidewall load, 100% WRFL - max pressure for max 23/50BI - Air sidewall load, air infla­

tion Oven - 65C - 3 65 3 50/50 Weekly vent & 2 hrs, 50 mph, 100% max wks - 50/50 - N2/O2 refill sidewall load, 100% max WRFL - pressure for max sidewall 2/50BI - Air load, air inflation Oven - 65C - 5 65 5 50/50 Weekly vent & 2 hrs, 50 mph, 100% max wks - 50/50 - N2/O2 refill sidewall load, 100% max WRFL - pressure for max sidewall 2/50BI - Air load, air inflation

Twelve new tire models were subjected to a 23-hour roadwheel break-in at 50 mph (80.5 km/h), with air inflation, at 100% of the maximum rated load and corresponding pressure, followed by 8 weeks oven aging at 65�C with 50/50 N2/O2 inflation that was vented and refilled weekly. The results are compared to unaged, new tires of each model in Figure 49. Table 52 details the aver­age change in modulus and average rate of change. The average increase in modulus of the in­nerliner in the shoulder region for the twelve tire models was 1.04 MPa, which is well within the range of values observed for the original six tire models retrieved from service. The average rate of change in the average innerliner modulus value for the twelve tire models was 0.13 MPa per week of aging.

73

Figure 49. Change in Average Indentation Modulus of Innerliner in Shoulder Region for 8 Weeks Oven Aging @ 65�C with 23-hour Break-in

74

Table 52. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 8 Weeks Oven Aging @ 65�C with 23-hour Break-in

Tire Mfg. Test IP

(kPa)

Estimated In­nerliner Com­position

Tire Type

Average Modulus

(MPa)

Average Change in Modulus

(MPa)

Rate of Change in

Avg. Modulus (MPa/wk)

Bridgestone 240 84/16 - BIIR/NR B6 4.47 1.30 0.16 87/13 - BIIR/NR B7 6.64 2.67 0.33

Continental 240 56/38/6 - BI­IR/NR/SBR

C3 4.67 0.76 0.10

61/30/9 - BI­IR/NR/SBR

C5 4.63 -0.16 -0.02

Cooper 240 78/20/2 -CIIR/NR/PBD

O5 3.44 0.90 0.11

82/18 - BIIR/NR O3 4.17 1.38 0.17 87/11/3 -CIIR/NR/PBD

D3 3.26 0.21 0.03

280 82/18 - CIIR/NR P3 4.17 1.36 0.17 450 85/15 - BIIR/NR D4 4.38 1.60 0.20 550 83/17 - BIIR/NR P2 4.18 1.26 0.16

Goodyear 240 65/35 - NR/SBR D2 2.84 0.03 0.00 550 87/8/5 - BI­

IR/NR/SBR O2 3.41 1.19 0.15

Average 4.19 1.04 0.13

The analysis was again completed for an additional 10 tire models were subjected to a 2-hour roadwheel break-in at 50 mph (80.5 km/h), with air inflation, at 100% of the maximum rated load and corresponding pressure, followed by 3 or 5 weeks of oven aging at 65�C with weekly vent and refill of the 50/50 N2/O2 inflation gas. The results are compared to unaged, new tires of each model in Figure 50 and Table 53. The average increase in innerliner modulus was 1.64 MPa for the 3-week oven aging condition and 1.45 MPa for the 5-week oven aging condition, which are again within the range of values observed for tires retrieved from service. The average rate of change in the average innerliner modulus value for the ten tire models was 0.55 and 0.29 MPa per week of aging for the 3 week and 5 week oven aging times respectively. It was expected that the longer oven aging condition (5 weeks) would produce a larger increase in the average inner-liner modulus than the shorter oven aging condition (3 weeks). However, that was not the case for this mix of tire types. The tires with high percentages of natural rubber (NR) and/or styrene­butadiene rubber (SBR) in the innerliner were observed to initially harden and then soften with increased time in the oven. For these innerliners, thermal reversion likely begins to dominate at the longer oven periods.

75

Figure 50. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 3 or 5 Weeks Oven Aging @ 65�C with 2-hour Break-in

76

Table 53. Change in Avg. Indentation Modulus of Innerliner in Shoulder Region for 3 or 5 Weeks Oven Aging @ 65�C with 2-hour Break-in

Tire Mfg. Tes t IP kPa

Estimated Innerliner

Composition

Tire Typ

e

Oven - 65C - 3 wks - 50/50 ­WRFL - 2/50BI - Air

Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

Average Mod­ulus

(MPa)

Average Change in Mod­ulus (MPa)

Rate of Change in Avg.

Modulus (MPa/wk

)

Average Mod­ulus

(MPa)

Average Change in Mod­ulus (MPa)

Rate of Change in Avg.

Modulus (MPa/wk

) Bridges-tone

240 85/13/2 -BI­IR/NR/SBR

B8 6.31 2.27 0.76 6.16 2.12 0.42

550 81/19 - BI­IR/NR

B9 4.72 1.73 0.58 4.88 1.89 0.38

Continen­tal

240 55/37/8 -CIIR/NR/SB R

C8 6.07 2.54 0.85 4.47 0.94 0.19

66/21/13 -BI­IR/NR/SBR

C7 5.91 3.20 1.07 4.68 1.97 0.39

Cooper 280 82/18 -CIIR/NR

P3 4.39 1.07 0.36 4.77 1.45 0.29

Goodyear 240 75/25 -CIIR/NR

U2 5.26 0.98 0.33 5.90 1.62 0.32

Hankook 550 67/33 - BI­IR/NR

H3 5.46 1.65 0.55 5.17 1.36 0.27

Michelin 550 100 - BIIR M10 3.53 0.26 0.09 3.82 0.55 0.11 Sumitomo 240 39/51/10 -

BI­IR/NR/SBR

S1 6.31 2.01 0.67 6.54 2.24 0.45

Toyo 240 53/47 - BI­IR/NR

T2 4.19 1.24 0.41 3.36 0.41 0.08

Average 5.14 1.64 0.55 4.96 1.45 0.29

Indentation Modulus - Bead Region Innermost Layer

As documented in Table 45, innerliners can be placed to wrap fully from bead toe to bead toe, terminate at the bead toe, or terminate some distance down each sidewall for partial coverage. Therefore, the indentation modulus measurements in the bead region represent the innermost rubber compound in the bead, not necessarily true innerliner material. The indentation modulus profile of the bead region was measured for the five of the six tire models retrieved from service in Phoenix, AZ (Figure 51). No tires of Type C were available for this particular test. The inner­most layer in the Type B did exhibit an increase in average modulus with increasing age. One Type B tire exhibited an average 4.76 MPa increase in modulus of the innermost layer after 7.38 years of service. The average rate of change in modulus for the six tire models was 0.23 MPa per year. The test was not performed on tires following P-END or LTDE roadwheel testing.

77

Figure 51. Average Indentation Modulus of Innermost Layer of Bead Region for Five Phoenix Tire Models

Table 54. Change in Avg. Indentation Modulus of Innerliner in Bead Region During Service in Phoenix, AZ

Tire Type

DOT Age (yrs)

Avg. Innerliner Modulus (MPa)

Change in Avg. Modulus (MPa)

Rate of Change in Avg. Modulus (MPa/yr)

B 2.53 4.49 1.95 0.77 4.66 3.61 1.07 0.23 7.38 7.3 4.76 0.64

D 1.58 3.29 0.38 0.24 3.87 2.74 -0.17 -0.04

E 2.91 3.93 -0.74 -0.25 H 1.99 2.82 0.7 0.35 L 1.06 3.12 -0.14 -0.13

Average 0.23

New tires of types B, C, D, E, L, and H were subjected to one of three accelerated oven aging conditions with capped inflation pressure (Table 48) and compared to new, unaged tires of each model in Figure 52. The average change in modulus and rate are listed in Table 55. The magni­tudes of the changes in modulus observed during capped-inflation oven aging were well within the range of values observed in field tires.

78

Figure 52. Average Indentation Modulus of Innermost Layer in Bead Region for Capped-Inflation Oven Aging

Table 55. Average Change in Indentation Modulus of Innermost Layer in the Bead Region During Capped-Inflation Oven Aging

Tire Type

Oven - 55C - 12 wks - 50/50 - Capped

Oven - 65C - 8 wks - 50/50 ­Capped

Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI- 50/50

Avg. Mod. (MPa)

Avg. Change in Mod. (MPa)

Rate of Change in Avg. Mod. (MPa/

wk)

Avg. Mod. (MPa)

Avg. Change in Mod. (MPa)

Rate of Change in Avg. Mod. (MPa/

wk)

Avg. Mod. (MPa)

Avg. Change in Mod. (MPa)

Rate of Change in Avg. Mod. (MPa/

wk) B 3.36 0.82 0.07 - - - 3.65 1.11 0.14 C 4.38 1.05 0.09 4.14 0.81 0.10 4.62 1.29 0.16 D 3.04 0.13 0.01 3.38 0.47 0.06 3.22 0.31 0.04 E 5.61 0.94 0.08 - - - 4.65 -0.02 0.00 H 2.98 0.86 0.07 2.97 0.85 0.11 3.68 1.56 0.20 L 4.09 0.83 0.07 4.57 1.31 0.16 5.30 2.04 0.26

Avg. 3.91 0.77 0.06 3.77 0.86 0.11 4.19 1.05 0.13

The results for 12 new tire models subjected to 8 weeks oven aging at 65�C with 23-hour roadw­heel break-in are compared to unaged, new tires of each model in Figure 53 and Table 56. The

79

average increase in modulus for the twelve tire models during the 8-week oven aging was 1.30 MPa, which is well within the range of values observed for the six tire models retrieved from service. The average rate of change in the average innerliner modulus value for the twelve tire models was 0.16 MPa per week of aging.

Figure 53. Change in Average Indentation Modulus of Innerliner in Bead Region for 8 Weeks Oven Aging @ 65�C with 23-hour Break-in

80

Table 56. Change in Average Indentation Modulus of Innerliner in Bead Region for 8 Weeks Oven Aging @ 65�C with 23-hour Break-in (at 50 mph)

Tire Mfg. Test IP kPa

Tire Type

Average Modulus

(MPa)

Average Change in Modulus

(MPa)

Rate of Average Change in Modulus

(MPa/wk) Bridgestone 240 B6 4.69 1.60 0.20

B7 7.54 4.05 0.51 Continental 240 C3 4.58 1.10 0.14

C5 4.70 0.51 0.06 Cooper 240 O5 4.61 1.17 0.15

O3 4.41 1.33 0.17 D3 4.44 0.50 0.06

280 P3 5.37 2.12 0.27 450 D4 4.45 1.47 0.18 550 P2 4.28 0.93 0.12

Goodyear 240 D2 2.72 -0.53 -0.07 550 O2 2.95 0.51 0.06

Average 4.62 1.30 0.16

The analysis was again completed for an additional 10 tire models subjected to 3 or 5 weeks of oven aging at 65�C with a 2-hour roadwheel break-in (Figure 54 and Table 57). The average in­crease in innerliner modulus was 1.56 MPa for the 3-week oven aging condition and 1.87 MPa for the 5-week oven aging condition, which are again within the range of values observed for the six tire models retrieved from service. The average rate of change in the average innerliner mod­ulus value for the ten tire models was 0.52 and 0.36 MPa per week of aging for the 3-week and 5-week aging times respectively. Again, the tires with high percentages of natural rubber (NR) and/or styrene-butadiene rubber (SBR) in the innerliner were observed to initially harden and then soften with increased time in the oven. For these innerliners, thermal reversion likely begins to dominate at the longer oven periods.

81

Figure 54. Change in Average Indentation Modulus of Innerliner in Bead Region for 3 or 5 Weeks Oven Aging @ 65�C with 2-hour Break-in (at 50 mph)

82

Table 57. Change in Avg. Indentation Modulus of Innerliner in Bead Region for 3 or 5 Weeks Oven Aging @ 65�C with 2-hour Break-in

Tire Mfg. Test IP

(kPa)

Tire Type

Oven - 65C - 3 wks - 50/50 ­WRFL - 2/50BI - Air

Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

Avg. Mod. (MPa)

Avg. Change

in Mod. (MPa)

Rate of Avg.

Change in Mod.

(MPa/wk)

Avg. Mod. (MPa)

Avg. Change

in Mod. (MPa)

Rate of Avg.

Change in Mod.

(MPa/wk) Bridgestone 240 B8 5.98 2.00 0.67 6.68 2.70 0.54

550 B9 4.68 1.73 0.58 4.62 1.67 0.33 Continental 240 C8 5.16 2.44 0.81 4.32 1.60 0.32

C7 6.29 2.70 0.90 4.70 1.11 0.22 Cooper 280 P3 4.63 1.38 0.46 6.02 2.77 0.55

Goodyear 240 U2 7.16 2.31 0.77 7.38 2.53 0.51 Hankook 550 H3 3.63 -0.45 -0.15 4.57 0.49 0.10 Michelin 550 M10 3.64 0.69 0.23 4.07 1.12 0.22

Sumitomo 240 S1 8.91 2.67 0.89 9.81 3.57 0.71 Toyo 240 T2 3.50 0.26 0.09 3.44 0.20 0.04

Avg. 5.29 1.56 0.52 5.60 1.87 0.37

Summary - Indentation Modulus Results

The results of the innerliner analysis are summarized in Table 58. With the exception of the 8­week, capped-inflation pressure oven aging tests, the magnitudes of the average change in inner­liner/innermost layer modulus for the accelerated aging tests were within the range of values ob­served in the six tire models retrieved from service. The tires with high percentages of natural rubber (NR) and/or styrene-butadiene rubber (SBR) in the innerliner were observed to initially harden and then soften with increased time in the oven. For these innerliners, thermal reversion likely begins to dominate at the longer oven periods.

83

Table 58. Summary Table of Average Change and Rate of Change in Innerliner Modulus by Condition

Tire Models Condition Shoulder Region Bead Region Avg.

Change in Mod. (MPa)

Rate of Avg. Change in

Mod.

Avg. Change in

Mod. (MPa)

Rate of Avg. Change in

Mod. B, C, D, E, H,

L Service in Phoenix -0.56 to 1.79 0.21 MPa/yr -0.74 to 4.76 0.23 MPa/yr

LTDE 0.87 0.37 MPa/100 hrs

- -

Oven - 55C - 12 wks - 50/50 ­

Capped

1.72 0.14 MPa/wk 0.77 0.06 MPa/wk

Oven - 65C - 8 wks - 50/50 - Capped

2.31 0.29 MPa/wk 0.86 0.11 MPa/wk

Oven - 65C - 8 wks - 50/50 - Capped ­

24/75BI- 50/50

2.91 0.36 MPa/wk 1.05 0.13 MPa/wk

B6, B7, C3, C5, D2, D3, D4, O2, O3, O5,

P2, P3

Oven - 65C - 8 wks - 50/50 - WRFL ­

23/50BI - Air

1.04 0.13 MPa/wk 1.30 0.16 MPa/wk

B8, B9, C7, C8, H3, M10, P3,

S1, T2, U2

Oven - 65C - 3 wks - 50/50 - WRFL ­

2/50BI - Air

1.64 0.55 MPa/wk 1.56 0.52 MPa/wk

Oven - 65C - 5 wks - 50/50 - WRFL ­

2/50BI - Air

1.45 0.29 MPa/wk 1.87 0.37 MPa/wk

CONCLUSIONS

Since the innerliner is the main barrier to permeation of the pressurized inflation gas (containing degradative oxygen) through the tire, it was desired to know material composition, thickness, and permeability of a large cross-section of passenger vehicle tire innerliners in order to understand their influence on whole-tire performance in a tire-aging test. Model innerliner compounds with known chemical formulations were used to evaluate a wide range of laboratory analysis methods. A final methodology was developed to allow estimation of innerliner compound formulation. The analysis indicated that tire innerliners were primarily comprised of polymer blends of halo­butyl (bromobutyl or chlorobutyl), natural (isoprene), styrene butadiene, and polybutadiene rub­ber, with one manufacturer using small amounts of polystyrene resin. The innerliner compounds also contained varying levels of carbon black, inorganic material (such as clay, zinc oxide, mag­nesium oxide, talc, or calcium carbonate), stearic acid, processing oils, antioxidants, antiozo­nants, unreacted sulfur, accelerator fragments, and tackifier resin. This methodology was applied to estimate the innerliner composition of six tire models collected from service in Phoenix, AZ,

84

as well as an additional 37 tire models used in subsequent phases of the project. Microscopy of cross-sections of each tire model was used to measure the thickness of the innerliner at the center and two edges of the crown region, as well as the amount of coverage of the innerliner. The in­nerliner compounds of the production tires varied significantly in composition, thickness, and placement, even within the same manufacturer. Across the 41 unique tire model/plant code com­binations, the average innerliner thickness in the crown was 0.96 mm, with an average standard deviation of –0.15 mm.

Sections of the innerliner were removed from all tire models and measured for permeability at room temperature (21�C) and approximate in-service running temperature (65�C). The measured permeability for the innerliners at 21�C and 65�C was similar to literature values for compounds with high butyl content, but measured higher than literature values for compounds with no butyl content. The average permeability for an innerliner sample at 21�C increased over 500% when tested at 65�C (1.14E-07 versus 1.83E-08 cm^2/(sec*atm)). This would imply that the more a tire is in operation (i.e., where it experiences higher operating temperatures), the faster the per­meation of inflation gas through the innerliner layer. A large amount of scatter was seen in the permeability data due to the non-uniform pattern imprint on the innerliner left from the curing bladder. Since average of the three innerliner thickness measurements in the crown ranged from 0.5 to 1.9 mm, shaving slices to smooth uniform thicknesses for permeability testing would be a major technical challenge. Readers are cautioned that innerliner permeability does not necessari­ly scale to whole tire inflation pressure loss rate, as many other size and construction parameters affect the whole tire loss rate.

The indentation modulus technique was employed to map the modulus (hardness) profile of the rubber components in the shoulder and bead region of tires retrieved from Phoenix and used in accelerated aging experiments. The first topic examined was whether or not the modulus of tire innerliners changed during service. Results from six tire models retrieved from service in Phoe­nix, AZ indicated that the innerliner in the shoulder region of the tires increased by approximate­ly 0.21 MPa per year, and the innermost layer increased 0.23 MPa per year in the bead region. Total increases of 1.79 MPa in the shoulder region and 4.76 MPa in the bead region were ob­served. The second topic examined was whether or not the modulus of tire innerliners changed during accelerated aging and if the magnitudes of the change matched or eventually exceed those observed during service. For the original six tire models collected in Phoenix, both the roadwheel and oven accelerated aging tests could produce changes in innerliner modulus that were similar to those observed in on-vehicle tires. The magnitude of the increase in innerliner modulus of the six models could exceed levels observed after up to seven years of service after the tires expe­rienced 500 hours of LTDE roadwheel testing or eight weeks of capped-inflation oven aging. The 22 additional tire models subjected to three to eight weeks of oven aging with vent and re­filled inflation showed average changes in innerliner/innermost layer modulus in the shoulder and bead region that were within the ranges of values observed in in-service tires. It is hypothe­sized that the observed changes in innerliner modulus during service or accelerated aging may affect the liner’s permeability and/or flexibility over time.

Future evaluations of accelerated aging tests will examine possible correlations between the in­nerliner properties of each tire model documented in this report to each tire model’s whole-tire performance in proposed accelerated aging tests.

85

APPENDIX 1. INDENTATION MODULUS INNERLINER DATA, SHOULDER & BEAD Tire Type

Test Description Barcode DOT Number Age (yrs)

Est. Mileage

(mi)

Avg. Shoulder Innerliner Mod­

ulus (MPa)

St. Dev. Shoul­der Innerliner

Modulus (MPa)

Avg. Bead In­nerliner Mod­

ulus (MPa)

St. Dev. Bead Innerliner Mod­

ulus (MPa)

Notes

B New 1094 APC6BB113803 0 0 2.54 0.65 B New 1040 APC6BB113803 0 0 2.29 0.2 B New 1042 APC6BB113803 0 0 2.29 0.09 B Phoenix 0027 APC6BB114301 1.37 24593 2.31 0.15 B Phoenix 0042 APC6BB113800 2.51 6049 2.9 0.21 B Phoenix 0049 APC6BB213700 2.53 32028 2.76 0.16 4.49 1.36 B Phoenix 0063 APC6BB11308 4.66 27337 3.52 0.12 3.61 0.06 B Phoenix 0002 APC6BB11117 6.04 51392 3.66 0.12 B Phoenix 0064 APC6BB11455 7.38 44385 4.08 0.31 7.3 2.22 B LTDE - 60 mph - 100 hrs 1074 APC6BB113803 0 0 2.44 0.17 B LTDE - 60 mph - 100 hrs 1058 APC6BB113803 0 0 2.94 0.19 B LTDE - 60 mph - 292 hrs 1080 APC6BB113803 0 0 2.86 0.19 B LTDE - 60 mph - 292 hrs 1059 APC6BB113803 0 0 4.53 0.44 B LTDE - 60 mph - 508 hrs 1084 APC6BB113803 0 0 3.12 0.13 B LTDE - 60 mph - 508 hrs 1060 APC6BB113803 0 0 4.68 0.35 B Oven - 55C - 12 wks - 50/50 ­

Capped 1081 APC6BB113803 0 0 4.01 0.37 3.36 0.49

B Oven - 65C - 8 wks - 50/50 ­Capped

1076 APC6BB113803 0 0 4.6 0.25 5.74 Only one data point for innerliner, not used.

B Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1086 APC6BB113803 0 0 5.2 0.48 3.65

B P-END - 240 hrs 1057 APC6BB113803 0 0 3.18 0.14 Tire failed @ 240 hrs -Liner Split

B4 Oven - 65C - 8 wks - 50/50 ­WRFL - 23/50BI - Air

2208 ENLFDAC5204 0 0 4.55 0.2 4.38 0.33 Failed in oven at week 7 due to: Sidewall blister

B6 New 2222 7X9LPDW3205 0 0 3.17 0.26 3.09 0.28 B6 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2221 7X9LPDW1905 0 0 4.47 0.29 4.69 0.18

B7 New 2249 VN73WM00105 0 0 3.97 0.29 3.49 0.49 B7 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2234 VN73WM00105 0 0 6.64 0.22 7.54 0.27

B8 New 2286 0BURB411606 0 0 4.04 0.25 3.98 0.48 B8 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2289 0BURB411606 0 0 6.31 0.42 5.98 0.54

B8 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2290 0BURB411606 0 0 6.16 0.34 6.68 0.97

B9 New 2517 7XW8P7M1806 0 0 2.99 0.22 2.95 0.34 B9 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2520 7XW8P7M1806 0 0 4.72 0.11 4.68 0.32

B9 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2521 7XW8P7M1806 0 0 4.88 0.15 4.62 0.29

C New 1542 M6URFJ2R4802 0 0 2.87 0.12 3.33 0.16 C Phoenix 0309 M6URFJ2R1901 1.81 11897 3.04 0.29 C Phoenix 0311 M6URFJ2R417 5.45 43135 3.51 0.25

86

Tire Type

Test Description Barcode DOT Number Age (yrs)

Est. Mileage

(mi)

Avg. Shoulder Innerliner Mod­

ulus (MPa)

St. Dev. Shoul­der Innerliner

Modulus (MPa)

Avg. Bead In­nerliner Mod­

ulus (MPa)

St. Dev. Bead Innerliner Mod­

ulus (MPa)

Notes

C LTDE - 60 mph - 100 hrs 1574 M6URFJ2R4802 0 0 2.98 0.22 C LTDE - 60 mph - 292 hrs 1579 M6URFJ2R4802 0 0 3.48 0.29 C LTDE - 60 mph - 292 hrs 1559 M6URFJ2R4802 0 0 3.37 0.14 Failed LTDE @ 292 hrs

- BdTuCr C LTDE - 60 mph - 508 hrs 1584 M6URFJ2R4802 0 0 3.84 0.31 C Oven - 55C - 12 wks - 50/50 ­

Capped 1581 M6URFJ2R4802 0 0 3.79 0.51 4.38 0.21

C Oven - 65C - 8 wks - 50/50 ­Capped

1576 M6URFJ2R4802 0 0 4.38 0.26 4.14 0.52

C Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1586 M6URFJ2R4802 0 0 4.62 0.61 4.62 0.41

C P-END - 240 hrs 1557 M6URFJ2R4802 0 0 3.08 0.13 C3 New 2444 A30846JB1505 0 0 3.91 0.28 3.48 0.1 C3 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2452 A30846JB1505 0 0 4.67 0.28 4.58 0.32

C5 New 2487 ACUR3K42005 0 0 4.79 0.58 4.19 0.14 C5 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2491 ACUR3K42005 0 0 4.63 0.16 4.7 0.28

C7 New 2542 A3T645RW2206 0 0 2.71 0.12 2.72 0.15 C7 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2545 A3T645RW2206 0 0 5.91 0.37 5.16 0.47

C7 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2546 A3T645RW2206 0 0 4.68 0.27 4.32 0.42

C8 New 2567 P5UR4421806 0 0 3.53 0.18 3.59 0.21 C8 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2570 P5UR4421806 0 0 6.07 0.46 6.29 0.24

C8 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2571 P5UR4421806 0 0 4.47 0.41 4.7 0.09

D New 1142 B3DD462X2903 0 0 2.45 0.16 2.91 0.09 D Phoenix 0108 B3DDBDUX3201 1.58 23381 3.05 0.29 3.29 0.13 D Phoenix 0077 B3DD570X199 3.87 31396 2.44 0.16 2.74 0.15 D LTDE - 60 mph - 100 hrs 1174 B3DD462X2903 0 0 2.47 0.22 D LTDE - 60 mph - 100 hrs 1158 B3DD462X2903 0 0 2.63 0.09 D LTDE - 60 mph - 292 hrs 1159 B3DD462X2903 0 0 2.27 0.03 D LTDE - 60 mph - 292 hrs 1179 B3DD472X2003 0 0 2.65 0.44 D LTDE - 60 mph - 508 hrs 1160 B3DD462X2903 0 0 2.5 0.05 Failed LTDE @ 377.35

hrs - ILS/BdD/TAL D LTDE - 60 mph - 508 hrs 1184 B3DD472X2003 0 0 2.56 0.19 D Oven - 55C - 12 wks - 50/50 ­

Capped 1181 B3DD472X2003 0 0 3 0.22 3.04 0.11

D Oven - 65C - 8 wks - 50/50 ­Capped

1176 B3DD472X2003 0 0 2.5 0.18 3.38 0.15

D Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1186 B3DD472X2003 0 0 2.86 0.29 3.22 0.25

D P-END - 096 hrs 1115 B3DD462X2903 0 0 2.22 0.03 D2 New 2371 PJC6XTLR2505 0 0 2.81 0.22 3.25 0.28

87

Tire Type

Test Description Barcode DOT Number Age (yrs)

Est. Mileage

(mi)

Avg. Shoulder Innerliner Mod­

ulus (MPa)

St. Dev. Shoul­der Innerliner

Modulus (MPa)

Avg. Bead In­nerliner Mod­

ulus (MPa)

St. Dev. Bead Innerliner Mod­

ulus (MPa)

Notes

D2 Oven - 65C - 8 wks - 50/50 ­WRFL - 23/50BI - Air

2374 PJC6XTLR2405 0 0 2.84 0.56 2.72 0.19

D3 New 2387 U9URTT93105 0 0 3.05 0.14 3.44 0.27 D3 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2386 U9URTT93105 0 0 3.26 0.28 4.61 0.2

D4 New 2430 3D40B8W1505 0 0 2.78 0.22 2.98 0.08 D4 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2425 3D40B8W1505 0 0 4.38 0.14 4.45 0.71

D5 New 2412 UPW8XDJ0805 0 0 3.38 0.14 3.95 0.24 D5 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2413 UPW8XDJ0805 0 0 4.38 0.31 Failed in oven at week 7

due to: Shoulder crack­ing

E New 1372 VN73WMB0302 0 0 4.07 0.33 E New 1319 VN73WMB0502 0 0 4.67 0.27 E Phoenix 0200 VN73WMB3502 0.53 5554 3.51 0.24 E Phoenix 0210 VN73WMA150 2.91 40594 4.87 0.23 3.93 0.4 E Phoenix 0201 W273WMB499 3.27 5.18 0.6 E LTDE - 60 mph - 100 hrs 1325 VN73WMB0902 0 0 4.16 0.21 E LTDE - 60 mph - 100 hrs 1330 VN73WMB4002 0 0 4.22 0.06 E LTDE - 60 mph - 292 hrs 1338 VN73WMB4002 0 0 5.62 0.16 E LTDE - 60 mph - 292 hrs 1366 VN73WMB1602 0 0 4.88 0.18 E LTDE - 60 mph - 500 hrs 1654 VN73WM03205 0 0 6.69 0.6 E LTDE - 60 mph - 508 hrs 1311 VN73WMB4002 0 0 5.5 0.41 E LTDE - 60 mph - 508 hrs 1354 VN73WMB4002 0 0 6.35 0.15 E Oven - 55C - 12 wks - 50/50 ­

Capped 1383 VN73WMB0702 0 0 6.06 0.23 5.61 0.68

E Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1394 VN73WMB1402 0 0 6.29 0.33 4.65 0.13

E P-END - 168 hrs 1373 VN73WMB0502 0 0 4.47 0.07 G2 New 2126 PJ0RY5HV3305 0 0 2.1 0.15 1.88 0.07 G2 Oven - 65C - 8 wks - 50/50 ­

WRFL 2119 PJ0RY5HV3205 0 0 3.79 0.4 3.21 0.18

G2 Oven - 65C - 8 wks - 50/50 ­WRFL - 23/50BI - Air

2122 PJ0RY5HV3305 0 0 2.94 0.1 2.02 0.14 Failed in oven at week 1 due to: Turn-up blowout at bead

H New 1242 PJ11FKKV4403 0 0 1.97 0.19 2.12 0.15 H Phoenix 0145 PJ11FKKV4501 1.36 15411 2.78 0.23 H Phoenix 0167 PJ11FKKV1201 1.99 42669 3.15 0.3 2.82 0.17 H Phoenix 0146 PJ11FKKV1300 2.99 64062 3.48 0.19 H Phoenix 0147 PJ11FKKV147 5.96 51053 2.99 0.33 H LTDE - 60 mph - 100 hrs 1266 PJ11FKKV4403 0 0 3.14 0.42 H LTDE - 60 mph - 100 hrs 1258 PJ11FKKV4403 0 0 2.75 0.34 Failed LTDE @ 100 hrs

- BdD H LTDE - 60 mph - 100 hrs 1263 PJ11FKKV4403 0 0 2.87 0.25 H LTDE - 60 mph - 292 hrs 1259 PJ11FKKV4403 0 0 3.51 0.11 Failed LTDE @ 268.45

88

Tire Type

Test Description Barcode DOT Number Age (yrs)

Est. Mileage

(mi)

Avg. Shoulder Innerliner Mod­

ulus (MPa)

St. Dev. Shoul­der Innerliner

Modulus (MPa)

Avg. Bead In­nerliner Mod­

ulus (MPa)

St. Dev. Bead Innerliner Mod­

ulus (MPa)

Notes

hrs H Oven - 55C - 12 wks - 50/50 ­

Capped 1281 PJ11FKKV4403 0 0 2.94 0.14 2.98 0.22

H Oven - 65C - 8 wks - 50/50 ­Capped

1276 PJ11FKKV4403 0 0 3.5 0.22 2.97 0.37

H Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1286 PJ11FKKV4403 0 0 3.17 0.14 3.68 0.35

H3 New 2592 T7XD5JNH4905 0 0 3.81 0.15 4.08 0.19 H3 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2595 T7XD5JNH4905 0 0 5.46 0.27 3.63 0.49

H3 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2596 T7XD5JNH4905 0 0 5.17 0.53 4.57 0.43

L New 1442 A33X3HB3003 0 0 3.1 0.21 3.26 0.1 L Phoenix 0275 A33X3HB0702 1.06 10992 3.39 0.14 3.12 0.2 L Phoenix 0261 A33X3HB4901 1.24 22051 3.57 0.22 L Phoenix 0262 A33X3HB3100 2.65 54125 4.11 0.22 L LTDE - 60 mph - 100 hrs 1474 A33X3HB3003 0 0 4.51 0.46 L LTDE - 60 mph - 292 hrs 1480 A33X3HB3003 0 0 3.68 0.13 L LTDE - 60 mph - 292 hrs 1459 A33X3HB3003 0 0 4.08 0.36 L LTDE - 60 mph - 500 hrs 1424 A33X3HB0304 0 0 4.52 0.24 Tire failed @ 412 hrs -

Bead Torn into Sidewall L Oven - 55C - 12 wks - 50/50 ­

Capped 1481 A33X3HB3003 0 0 4.78 0.35 4.09 0.26

L Oven - 65C - 8 wks - 50/50 ­Capped

1476 A33X3HB3003 0 0 5.08 0.19 4.57 0.16

L Oven - 65C - 8 wks - 50/50 ­Capped - 24/75BI - 50/50

1486 A33X3HB3003 0 0 4.84 0.21 5.3 0.76

L P-END - 240 hrs 1457 A33X3HB3003 0 0 4.2 0.2 Tire failed @ 240 hrs -Bead turn up sep, liner sep

M10 New 2617 B72K2EHX1106 0 0 3.27 0.12 2.95 0.3 M10 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2620 B72K2EHX1106 0 0 3.53 0.28 3.64 0.31

M10 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2621 B72K2EHX1106 0 0 3.82 0.31 4.07 0.65

O1 New 2337 PJ0RH6LV3305 0 0 2.3 0.22 2.19 0.16 O1 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2334 PJ0RH6LV3305 0 0 3.06 0.18 2.56 0.1 Failed in oven at week 2

due to: Sidewall blo­wout

O2 New 2344 PJW8KDKV3405 0 0 2.22 0.27 2.44 0.1 O2 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2348 PJW8JLLV3405 0 0 3.41 0.13 2.95 0.07

O3 New 2324 UPURTX33205 0 0 2.79 0.13 3.08 0.24 O3 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2321 UPURTX33305 0 0 4.17 0.11 4.41 0.25

O5 New 2312 U9C6HTE3305 0 0 2.54 0.06 3.94 0.37

89

Tire Type

Test Description Barcode DOT Number Age (yrs)

Est. Mileage

(mi)

Avg. Shoulder Innerliner Mod­

ulus (MPa)

St. Dev. Shoul­der Innerliner

Modulus (MPa)

Avg. Bead In­nerliner Mod­

ulus (MPa)

St. Dev. Bead Innerliner Mod­

ulus (MPa)

Notes

O5 Oven - 65C - 8 wks - 50/50 ­WRFL - 23/50BI - Air

2308 U9C6HTE3305 0 0 3.44 0.17 4.44 0.29

P1 New 2013 UT73B9J2705 0 0 2.71 0.12 3.24 0.21 P2 New 2028 UP0RPAL2005 0 0 2.92 0.37 3.35 0.17 P2 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2035 UP0RPAL2005 0 0 4.18 0.19 4.28 0.42

P3 New 2018 UTHLPAN3205 0 0 2.81 0.16 3.12 0.13 P3 Oven - 65C - 8 wks - 50/50 ­

WRFL - 23/50BI - Air 2022 UTHLPAN3205 0 0 4.17 0.28 5.37 0.17

P3 New 2056 UTHLPAN2806 0 0 3.84 0.21 3.38 0.12 P3 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2059 UTHLPAN2806 0 0 4.39 0.28 4.63 0.39

P3 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2060 UTHLPAN2806 0 0 4.77 0.23 6.02 0.62

R2 Oven - 65C - 8 wks - 50/50 ­WRFL - 23/50BI - Air

2134 XLW8E4231603 0 0 3.18 0.16 3.6 0.28 Failed in oven at week 8 due to: Sidewall blister

S1 New 2642 V4A64MCR5005 0 0 4.3 0.44 6.24 0.16 S1 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2649 V4A64MCR5005 0 0 6.31 0.41 8.91 0.22

S1 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2646 V4A64MCR5005 0 0 6.54 0.21 9.81 0.16

T2 New 2667 9TKU93A0706 0 0 2.95 0.29 3.24 0.11 T2 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2670 9TKU93A0706 0 0 4.19 0.22 3.5 0.12

T2 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2671 9TKU93A0706 0 0 3.36 0.3 3.44 0.16

U2 New 2081 EUFC3TMR4705 0 0 4.28 0.01 4.85 0.38 Run Flat Tire U2 Oven - 65C - 3 wks - 50/50 ­

WRFL - 2/50BI - Air 2084 EUFC3TMR4705 0 0 5.26 0.19 7.16 0.6 Run Flat Tire

U2 Oven - 65C - 5 wks - 50/50 ­WRFL - 2/50BI - Air

2085 EUFC3TMR4705 0 0 5.9 0.11 7.38 0.3 Run Flat Tire

90

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DOT HS 811 296March 2010