Performance and Processing Enhancements ofAromatic Polyurea Elastomer Systems Preparedfrom High 2,4’-MDI Isocyanates Aureliano Perez, Jr.

Huntsman CorporationAustin Research Laboratories7114 North Lamar BoulevardAustin, Texas 78752USA

Jay A. Johnston Huntsman Polyurethanes2190 Executive Hills BoulevardAuburn Hills, Michigan 48326USA

ABSTRACT

Polyurea elastomer systems have beenformulated to produce high performance, rapidcuring coatings and caulks that can be applied inadverse climates that would normally inhibit theuse of other conventional chemistries. It is theinherently rapid reaction rate of isocyanates andamines that allows for the unique gel and curerates that enables the consistent application ofpolyurea elastomers over a broad temperatureand humidity range. These fast reaction rates,though favorable to the experienced applicator,can be an initial challenge to those who are newto this technology. In an effort to reduce thereaction rates of these polymer systems,sterically hindered amines and isocyanates havebeen examined. Recent studies have revealedthat aromatic isocyanates with a high 2,4’-MDIisomer content do impart steric disruptions thateffectively reduce the reaction rates of typicalpolyurea spray coatings and dual-syringe appliedpolyurea caulks. The longer open times of thesesystems allow for reductions in processingpressures and temperatures of the pluralcomponent spray machines typically used forpolyurea spray applications. The extendedprocessing time also leads to elastomers withimproved flow, leveling, and adhesion to avariety of substrates. In addition, significantperformance enhancements of tensile strength,tear strength, elongation, and modulus of theresulting cured elastomers have been observedby using these high 2,4’-MDI isomers versussimilar polyurea systems that utilizedisocyanates with lower 2,4’-MDI isomer content.This presentation illustrates the physicalproperties and processing enhancements ofpolyurea spray coatings and dual-syringe appliedpolyurea caulk products that are achieved usingthese new, high 2,4’-MDI products.

INTRODUCTION

Polyurea spray technology continues to rapidlygrow and is becoming increasingly visible due toits specification and use in several new, high-profile applications. The Boston Tunnel Project,the Inchon Airport in Korea, and most recently,the San Mateo Bridge in California have allspecified polyurea spray elastomers in large,coating aspects of these projects. Thoughpolyurea spray coating technology is only tenyears old, it already has gained global confidenceand approvals as a high performance coatingsystem. The many successful case histories andthe truly unique performance and processingcharacteristics of polyurea have made it atechnology that can compete in niche areas onceexclusively held by the more mature coatingsystems.

A continued area of interest lies in theextension of gel and tack-free times of aromaticpolyurea spray systems. The technologydeveloped in the early to mid 1990’s entails veryrapid reactions (3 second gel times) and can bequite challenging to those who are inexperiencedin handling polyurea systems. The challenge ofextending gel times without sacrificing thecoating performance is once again beingaddressed by the recognized leaders in polyureaspray technology. Huntsman Polyurethanes hasrecently introduced several new isocyanate pre-polymers that focus on the issue of systemreactivity. These new products contain varyinglevels of the 2,4’-MDI isomer, which introducessteric kinks into the polymer matrix whenblended with the standard 4,4’-MDI isomer. The2,4’-MDI isomer effectively reduces thereactivity of polyurea elastomers prepared viathe reaction of primary and/or secondary amineswith isocyanates. Primeaux reported thatincreased levels of the 2,4’-MDI isomerextended the gel-time of aromatic polyurea

systems and provided improvements in theperformance of the cured polyurea elastomers.(1)

Broekaert and Pille-Wolf reported similarobservations upon investigation of the influenceof isocyanate isomer composition. A secondaspect of their study probed the influence ofisocyanate functionality on gel time andperformance of polyurea spray systems.(2) Theirwork examined the performance of polyureaelastomers after typical laboratory cureschedules.

As an extension of that earlier work, long termcure schedules of systems utilizing higher 2,4’-MDI products were undertaken. To betterunderstand the effect of the 2,4’-MDI isomercontent on performance, a study using new,commercially-available isocyanate pre-polymerswith varying 2,4’-MDI isomer content wasconducted. This paper introduces these newaromatic isocyanate pre-polymers and examinesthe effect that the varying isomer content impartsupon the performance properties of the curedpolyurea elastomer products.

EXPERIMENTAL

Materials and Methods

The materials utilized in this study are availablefrom the sources listed in Table 1. Four newisocyanate pre-polymers were examined in theseexperimental aromatic polyurea spray starting-point formulations. The polyurea elastomers

Table 1. List of chemicals and suppliers

COMPOUND MANUFACRUBINATE® 9009RUBINATE® 9495RUBINATE® 9480RUBINATE® 9483RUBINATE® 9495

HUNTSMAN POLY

JEFFAMINE® D-2000JEFFAMINE® T-5000JEFFAMINE® M-2005

HUNTSMAN C

TIOXIDE® TiO2 HUNTSMAN CETHACURE® 100 ALBAMAUNILINK® 4200 UOP LL

CABOSIL M-5 CABOSilane A-187 Witco

were produced with a GUSMER® Marksmanproportioning unit and GUSMER® GX-7 Series400 spray gun. The block and hose heatersattached to the Marksman unit were set at 160°Fwith the system pressure being set to 2500pounds per square inch (psi). A detailedexplanation of the equipment and procedures ofprocessing polyurea coatings in this manner canbe found in a study by Primeaux and Anglin.(3)

Elastomer samples were obtained by applicationof the polyurea spray coatings onto plastic panelsmeasuring 12” x 12” that were first coated with awater-borne release agent. After de-molding,tensile and tear specimens were die cut from thevarious elastomer profiles after the requisiteroom temperature cure times, then tested forphysical properties. Concrete and steelsubstrates were also coated with theexperimental formulations. Sixteen gauge steelpanels, measuring 5” x 5”, were sandblasted toan approximate 2-mil blast profile as specifiedby the National Association of CorrosionEngineers (NACE).

In addition to the polyurea spray coatings,experiments were conduct on dual-syringe, staticmix sealant/caulk formulations using the newisocyanate pre-polymers and alternative amineresin blends. Polyurea sealants offer very rapidgel-times and excellent performance forconstruction sealant and caulking applications.RUBINATE 9483 has been formulated with avery high 2,4’-MDI isomer content for use in

TURE DESCRIPTION

URETHANES Isocyanate pre-polymer

HEMICAL Polyetheramine

HEMICAL Titanium dioxideRLE Amine chain extenderC Hindered amine chain

extenderT Fumed silica

Epoxy functional silane

.

caulk applications. This pre-polymer isexamined in the caulk section of this work.Polyurea caulk resins (“B” component) caneasily be blended in high speed/ high shearmixers. The isocyanate and resin componentscan be dispensed and applied through manual,pneumatic, or hydraylic dual-syringe, static mixequipment. For our testing we utilized amanually operated MixPac model DM-400dispense gun and model MC-13-32 static mixtubes (15” long by ½ inch diameter with 32elements).

Testing of the cured elastomer samples wasperformed using an Instron Model number 4201,electro-mechanical test machine, with acrosshead speed (pull rate) set at 20 inches perminute. The standard test methods performedwere as follows:

Tensile Strength ASTM D638Percent Elongation ASTM D638Modulus ASTM D638Tear Strength ASTM D624Hardness ASTM D2240-81Elcometer Adhesion ASTM D-4541Moisture Vapor Transmission ASTM E96-80Taber Abrasion ASTM D4060Flexural Modulus ASTM D790Impact Resistance ASTM D3763Water Absorption ASTM D570-95

Table 3. Huntsman Polyurethan

2,4’-MDIIsomerContent

%NCO

RUBINATE® 9009 low 15.8RUBINATE® 9495 low 15.2RUBINATE® 9480 high 15.4RUBINATE® 9483 highest tested 15.0RUBINATE® 9484 high 16.0

RESULTS AND DISCUSSION

The objective of this work was to examine thephysical properties and performancecharacteristics of aromatic polyurea systemsbased upon several new isocyanate prepolymers.The influence of the 2,4’-MDI isomer content onthe processing and performance properties of theelastomers can be correlated to the increasinglevel of the 2,4’-MDI isomer content of the pre-polymers. It should be noted that other factorssuch as the co-reactant selected (polyol,polyamine, etc.) and the functionality of theisocyanate pre-polymer can also influence theprocessing and performance properties. Thisstudy primarily focuses on the 2,4’-MDI isomercontent of the pre-polymers and the impact thatvaried isomer content has on the coatingproperties.

As a reference standard, RUBINATE® 9009,an isocyanate pre-polymer with a low 2,4’-MDIisomer content, has been included in this study.RUBINATE® 9009 was one of the firstisocyanate preplymers that was formulatedspecifically for use in polurea spray applications.In 1993 the former ICI Polyurethanes, nowHuntsman Polyurethanes, co-developed this pre-polymer with researchers at Huntsman ChemicalThis pre-polymer has been available to theindustry for over 7 years and has been usedsuccessfully in many commercial applications.Data pertaining to the RUBINATE® 9009 and

es Isocyanate Prepolymers

FunctionalitySpecific Gravity

25°CIsocyanateEquivalent

Weight2.1 1.12 266

2.04 1.14 2762.0 1.1439 2762.0 1.1403 2622.0 1.14 262

the other new Huntsman isocyanates analyzed inthis study can be found in Table 3.

A standard resin blend (B component) wasprepared and used for a series of spray and caulksystems. A matrix of the experimental starting-point formulations used for the sprayexperiments is listed in Table 4. Note that theresin blend for experimental spray formulations“A” through “D” is constant, while a slight

adjustment was necessary to experimental resinblend “E” to maintain a consistent system indexand volume mix ratio.

Processing Characteristics

Highlighted in Table 5 are the gel and tack-freetimes, and the surface gloss of the experimentalsystems. The four systems exhibited

Table 4. Polyurea spray experimental formulations.

Isocyanate Component A B C D

RUBINATE® 9009 100 ----- ----- -----RUBINATE® 9495 ----- 100 ----- -----RUBINATE® 9480 ----- ----- 100 -----RUBINATE® 9484 ----- ----- ----- 100

Resin Blend

JEFFAMINE® D-2000 54.8 54.8 54.8 54.8JEFFAMINE® T-5000 9.6 9.6 9.6 9.6ETHACURE® 100 25.4 25.4 25.4 25.4TIOXIDE® TiO2 10.2 10.2 10.2 10.2Silane A-187 0.9 0.9 0.9 0.9

ProcessingIndex 1.10 1.10 1.10 1.10Iso/Resin volume ratio 1.00 1.00 1.00 1.00Iso/Resin weight ratio 1.01 1.05 1.03 1.03

Table 5. Gel time, tack free time and gloss.

Gel Time(seconds)

Tack Free Time(seconds)

Gloss(20°°°°/60°°°°)

RUBINATE 9009 System 2.5 5.0 48/81RUBINATE 9495 System 3.5 5.5 40/77RUBINATE 9480 System 4.0 7.5 59/83RUBINATE 9484 System 4.0 6.5 69/86

different processing characteristics. Appreciablegel and tack-free time variations wereencountered. The systems that incorporated thehigher 2,4’-MDI isomer pre-polymers gavelonger gel and tack free times as expected.

The RUBINATE 9009 and 9495 systemsexhibited noticeable regions of “orange peel”morphology on the surface of the cured films.The RUBINATE 9480 and 9484 systems did notdisplay any such visible “orange peel” surfacedefect. The higher 2,4’-MDI isomer contenteffectively extended the gel and tack free timesof the systems and improved flow and leveling.This resulted in coatings with improved surfaceappearance and performance properties. Higher

gloss values correlated with a smootherappearance of the coating surface.

Performance versus Time

While short gel and tack-free times of polyureaspray coatings have been well-documented andpromoted within the industry, a detailed study ofthe curing and/or annealing time necessary toachieve optimal performance properties ofpolyurea elastomers has not been presented. Inthis study, elastomer samples were examined atroom temperature cure time intervals rangingfrom 10 minutes to one year. The following datatables detail the performance that developed over

a given time period for the experimentalformulations.

Table 6 illustrates the performancedevelopment of an aromatic polyurea spraysystem that utilized the isocyanate test standard,RUBINATE® 9009, as the pre-polymer. Forthis series of testing, approximately 90% of thetensile strength of the system is achieved afternearly five hours of room temperature cure time.

Table 6. Performance/Time u

10minute

cure

1 hourcure

5 hourcure

24c

Tensilestrength(psi)

699 1273 2250 2

Percentelongation(%)

76 184 256 2

TearStrength(pli)

206 275 325 3

Shorehardness(0sec/10sec)

D43/30

D48/39

D48/41 5

Modulus,100% (psi)

----- 1112 1474 1

Modulus300% (psi)

----- ----- ----- -

Plots of the data corresponding to the tensile,tear, and percent elongation properties arepresented in Figures 1, 2 & 3. The tensilestrength of the RUBINATE 9009 system peakedafter 24 hours, while peak elongation propertieswere achieved after approximately five hours.The ultimate tear strength of the systemdeveloped after seven days of cure; however,over 90% of the strength was developed afterjust three days.

sing RUBINATE 9009

hourure

3 daycure

7 daycure

4 weekcure

1 yearcure

640 2525 2744 2287 2541

61 252 244 241 235

43 414 417 357 357

D0/43

D50/43

D51/44

D46/39

D47/40

685 1623 1735 1477 1595

---- ----- ----- ----- -----

0

500

1000

1500

2000

2500

3000

3500

4000

10 min 1 hr 5 hr 24 hr 3 day 7 day 4 wk 1 yr

TIME

RUBINATE® 9009 RUBINATE® 9495

RUBINATE® 9480 RUBINATE® 9484

Figure 1. Development of tensile strength over time.

0

100

200

300

400

500

600

700

10 min 1 hr 5 hr 24 hr 3 day 7 day 4 wk 1 yr

TIME

RUBINATE® 9009 RUBINATE® 9495 RUBINATE® 9480 RUBINATE® 9484

Figure 2. Development of tear strength over time.

0

100

200

300

400

500

600

10 min 1 hr 5 hr 24 hr 3 day 7 day 4 wk 1 yr

Time

% E

long

atio

n

RUBINATE® 9009 RUBINATE® 9495

RUBINATE® 9480 RUBINATE® 9484

Figure 3. Elongation properties as a function of cure time

In a second system RUBINATE 9495 wasutilized as the isocyanate pre-polymer. Thegreater 2,4’-MDI isomer content in this pre-polymer resulted in a 40% increase in the geltime (3.5 seconds versus 2.5 seconds) and a 10%increase in the tack-free time versus RUBINATE9009. Performance development data for theRUBINATE 9495 system is presented in Table7. Figures 1, 2 & 3 illustrate trends similar to theinitial performance development profile of theRUBINATE 9009 system. While this profileinitially parallels that of the standardRUBINATE 9009 system, the RUBINATE 9495system begins to overtake the performance of thestandard system after seven days. The Shore Dhardness development of both systems is similar,with the RUBNINATE 9495 system producing aslightly harder elastomer.

The third system in this test series usedRUBINATE 9480 as the isocyanate pre-polymer.This material provided a 60% increase in the gel-time and a 50% increase in the tack-free time ofthe sprayed elastomer versus RUBINATE 9009.Extended processing times were expected due tothe increased 2,4’-MDI isomer content. Theperformance development data for this system

are shown in Table 8. Figures 1, 2 & 3 illustratea significant difference in the development of theperformance properties versus those of thestandard. Interestingly, the percent elongation ofthe RUBINATE 9480 system undergoes a sharpincrease at the five hour cure time and plateausafter three days (in contrast, the elongation of thestandard system builds at a moderate rate up tothe five hour cure time). The initial tensilestrength of the RUBINATE 9480 system is only64% of the test standard and builds at a slowerrate. However, at the seven day cure point, theRUBINATE 9480 system overtakes theRUBINATE 9009 system and continues to buildto an ultimate strength that is approximately 20%greater than the standard. The final Shore Dhardness of both systems is very similar,although the 9480 system is much softer duringthe first 24 hours of cure.

The final isocyanate pre-polymer systemexamined in this study was RUBINATE 9484.This isocyanate pre-polymer has been formulatedto offer enhanced waterproofing capabilities forcured polyurea elastomer systems. Thisimprovement/modification is illustrated by the

Table 7. Performance/Time for RUBINATE 9495 system

10minute

cure

1 hourcure

5 hourcure

24 hourcure

3 daycure

7 daycure

4 weekcure

1 yearcure

Tensilestrength(psi)

721 881 1637 2315 2086 2411 3087 3035

Percentelongation(%)

64 102 245 256 219 225 269 318

TearStrength(pli)

170 233 349 386 414 432 470 458

Shorehardness(0sec/10sec)

D36/24

D42/32

D47/38

D47/40

D49/41

D52/43

D55/47

D54/47

Modulus,100% (psi)

----- ----- 1195 1497 1501 1695 1949 1753

Modulus300% (psi)

----- ----- ----- ----- ----- ----- ----- 3035

low water absorption values summarized inTable 10. The 2,4’-MDI isomer content ofRUBINATE 9484 was similar to that ofRUBINATE 9480, and not surprisingly exhibitedsimilar cure and performance developmentprofiles as illustrated in Figures 1, 2 & 3. TheRUBINATE 9484 system did provide the highestultimate tensile and tear strength of the systemsexamined in this series, further suggesting thatthe 2,4’-MDI isomer does indeed play a role inthe performance of aromatic polyurea spraysystems.

ADDITIONAL PERFORMANCE TESTING

The experimental formulations listed in Table1 were also subjected to physical testing after a14 day room temperature cure period. Table 10contains the test data obtained for each system.Elcometer adhesion studies indicated excellentadhesion to blasted steel and concrete for all ofthe polyurea systems tested.

The blast profile of the steel is crucial forproper adhesion of polyurea coatings tounprimed steel. Perez and House et al. showedthat adhesion of aliphatic polyurea coatingscould be increased from 350 psi on smooth steelto 1300 psi when the steel surface was properlyblasted.(4) An epoxy functional silane adhesionpromoter was incorporated into the testformulations to enhance the adhesion of thepolyurea coatings to the steel substrate’s surface.Detailed studies of silane adhesion promotersand their use can be found in works byPlueddemann.(5) While an adhesion promoter isnot usually necessary in applications of polyureacoatings to concrete surfaces due to porosity ofthe concrete surface, it is highly recommendedthat old concrete be shot blasted prior to coatingwith polyurea to ensure adequate adhesion toconcrete. This treatment makes certain thatsurface contaminants that could inhibit adhesionof the applied coating are removed. (Blasting of

Table 8. Performance/Time for RUBINATE 9480 system

10 minutecure

1 hourcure

5 hourcure

24 hourcure

3 daycure

7 daycure

4 weekcure

1 yearcure

Tensile strength(psi) 447 567 783 1439 1919 2724 2876 3001

Percentelongation (%) 52 84 161 318 431 496 519 465

Tear Strength(pli) 82 133 244 364 392 430 485 546

Shore hardness(0sec/10sec)

A81/72

A86/81

D38/28

D44/35

D44/36

D48/40

D47/44

D49/41

Modulus, 100%(psi)

----- ----- 751 1003 1046 1209 1230 1376

Modulus 300%(psi)

----- ----- ----- ----- 1543 1875 1896 2147

Table 9. Performance/Time for RUBINATE 9484 system

10 minutecure

1 hourcure

5 hourcure

24 hourcure

3 daycure

7 daycure

4 weekcure

1 yearcure

Tensilestrength (psi) 436 678 817 1836 2406 2338 3113 3335

Percentelongation (%) 33 64 87 386 447 433 514 536

Tear Strength(pli) 80 137 211 357 414 411 508 581

Shore hardness(0sec/10sec)

A81/72

A 86/82D 40/28

D41/31

D48/39

D49/40

D48/40

D50/43

D46/39

Modulus,100% (psi)

----- ----- ----- 1143 1250 1269 1400 1447

Modulus 300%(psi)

----- ----- ----- 1596 1839 1845 2115 2187

Table 10. Performance properties of the tested systems

RUBINATE 9009SYSTEM

RUBINATE 9495SYSTEM

RUBINATE 9480SYSTEM

RUBINATE 9484SYSTEM

ElcometeradhesionASTM D-4541

Steel:>1300 psi *

Concrete:750 psi(CF of concrete)

Steel:>1275 psi *Concrete:

700 psi(CF of concrete)

Steel:>1000 psi*Concrete:

900 psi(30% CF concrete,70% AF coating)

Steel:>1200 psi*Concrete:

450 psi(95% CF of

concrete)

Moisture VaporTransmissionASTM E96-80

Perm value< 0.10

Perm value<0.10

Perm value<0.10

Perm value<0.10

Taber AbrasionASTM D4060

0.4 mg weight loss 0.5 mg weight loss 0.5 mg weight loss 0.6 mg weight loss

FlexuralModulusASTM D790

36,000 psi 48,902 psi 35,000 psi 49,000 psi

ImpactResistanceASTMD3763

6.6 ft-lb@ 23 °°°°C

0.6 ft-lb@ -40°°°°C

6.84 ft-lbs@23°°°°C

0.28 ft-lbs@ -40°°°°C

4.4 ft-lb@ 23 °°°°C

0.2 ft-lb@ -40°°°°C

6.5ft-lb@ 23 °°°°C

0.3 ft-lb@ -40°°°°C

WaterAbsorptionASTMD570-95

1.94 weight percentabsorption

Not tested 2.26 weight percentabsorption

1.60 weight percentabsorption

*adhesive failure of the glue used to adhere the test dolly to the coating surface occurred before thepolyurea coating or substrate failed.

CF = cohesive failureSF = substrate failure

fresh concrete is usually not necessary if thesurface is uncontaminated.)

Moisture vapor transmission testing of eachsystem resulted in perm values below 0.10,indicating that all of the systems have excellentwaterproofing capabilities. A pronouncedimprovement in the waterproofing capabilities ofthe RUBINATE 9484 system is illustrated by itshaving the lowest water absorption value of the

series. This was the result of extensive researchto produce an isocyanate pre-polymer withenhanced hydrophobic character.

Taber abrasion test results show excellentabrasion resistance for all of the systems tested.The values are quite similar and indicate that theabrasion resistance of polyurea elastomers is notgreatly affected by variations in the 2,4’-MDIisomer content.

CAULK APPLICATIONS

The sealant industry has expressedconsiderable interest in polyurea caulk andsealant products. While these systems alsoexhibit rapid gel and tack-free times,considerable differences exist between thesealant products and the spray elastomer analogs.Polyurea spray systems require hightemperature/high pressure, impingement mixequipment while polyurea sealant products canbe applied via dual-syringe, static mixdispensing equipment. (Pour guns can be fittedto the high temperature/high pressure sprayequipment, which enable the dispensing of caulkproducts from this type of equipment).

These caulk formulations incorporated ahindered, secondary diamine chain extender, incombination with the high 2,4’-MDI pre-polymers, to extend the gel time of polyureasystems for caulking applications. The use ofthe Unilink®4200 chain extender (UOP LLC)has been described by House, et al. (6) and byPrimeaux (7). Additionally, the caulk productsincorporated a mono-functional polyether amine,JEFFAMINE® M-2005, which functions as a“reactive plasticizer”. The amine group reactswith an isocyanate group in the pre-polymer,while the unreactive end, now appended from thepolymer matrix functions in a manner similar to

Table 11. Experimental starting-point form

A BRUBINATE 9480 100 ----RUBINATE 9495 ----- 100RUBINATE 9483 ----- ----RUBINATE 9484 ----- ----

JEFFAMINE D-2000 50.5 50.5JEFFAMINE M-2005 9.9 9.9ETHACURE 100 10.9 10.9UNILINK 4200 18.8 18.8TIOXIDE TiO2 6.8 6.8CABOSIL M-5 3.0 3.0

INDEX 1.3 1.3Iso/Resin volumeratio

1.0 1.0

Iso/Resin weight ratio 1.05 1.06

a traditional plasticizer. A benefit of this type ofplasticizer is that it is covalently bonded to thepolymer backbone and avoids the volatilityissues common to inert plastisizers. Cabosil M-5was incorporated as a thixotrope, and thisuntreated, fumed silica was successful in keepingthe products suspended when loaded at a 3%minimum level in the amine resin blend.Interestingly, treated fumed silica (Cabosil TS-720), unlike the Cabosil M-5, caused a highdegree of rapid bubble formation with thebubbles remaining trapped in the surface of thecoating. Huntsman TiOxide® was used as acolor pigment.

Difficulty is encountered when isocyanate pre-polymers containing low levels of the 2,4’-MDIisomer are used in caulk formulations. Thereactivity of these pre-polymers, in general, istoo great, and the corresponding caulk productshave a tendency to gel before exiting the staticmix tube.

Table 11 lists the experimental starting-pointformulations that were used for caulk analysis.As previously discussed with the sprayexperiments, a common amine resin blend (Bcomponent) was used, while a minor formulationadjustment to the RUBINATE 9484 containingsystem was necessary to maintain a consistentindex and volume mix ratio for the series.

ulations for polyurea joint sealants

C D- ----- -----

----- ------ 100 ------ ----- 100

50.5 49.489.9 10.68

10.9 10.718.8 18.46.8 6.73.0 3.0

1.3 1.31.0 1.0

1.05 1.06

In all runs the experimental polyurea caulksdispensed easily from the static mix equipment.The gel-time of these products in a 100 grammass was approximately two minutes. A rapidexotherm build-up was encountered in the 100gram mass testing and led to shorter gel timesdue to the heat generated. These caulk productsare expected to have longer open times whenused as joint fillers and sealers for concretebecause the concrete can function as a heat sinkand help to dissipate the exothermic heat thatbuilds in the reacting product.

The data in Table 12 illustrates improvementsin the elongation and abrasion resistance for thehigh 2,4’-MDI pre-polymer systems. TheRUBINATE 9483 exhibited excellentelongation, abrasion resistance, and reducedShore D hardness. The RUBINATE 9495system, with a lower 2,4’-MDI isomer content,was high in tensile strength but lower in percentelongation, modulus, and abrasion resistance.The Shore D hardness of this system was alsohigher than that of the RUBINATE 9483 system.Thus, the RUBINATE 9483 isocyanate pre-polymer, with its high 2,4’-MDI isomer content,does offer considerable improvements inpolyurea caulk/sealant applications

Table 12. Performance properties

RUBINATE 9480SYSTEM

Gel-time (100 gram mass) ~2 minutes

Tensile strength (psi) 894

Percent elongation 432

Tear strength 298

Shore D hardness 41

Modulus, 100% 628

Modulus, 300% 793

Moisture Vapor Transmission 0.047

Taber Abrasion 1.0 mg weight loss

CONCLUSIONS

Polyurea spray coating technology continues toenjoy rapid proliferation of commercialsuccesses in unique, niche application areas thatpose considerable challenges to traditionalcoatings technologies. The extension of gel andtack-free times has been accomplished throughthe use of high 2,4’-MDI isomer pre-polymers.In addition, high performance polyurea caulk andsealant formulations based upon these same pre-polymers have been introduced. The rapidformation of coatings and sealants, which can beapplied in extreme climate conditions and putinto service shortly after application, will ensurecontinued phenomenal growth of polyureaapplication technology. To assist in theendeavors of polyurea blenders and applicators,technological enhancements and developmentswill continue to be introduced by the industryleading materials suppliers. The new isocyanatepre-polymers from Huntsman are the latestoffering to the polyurea market and, as shown inthis study, exhibit the performance andprocessing enhancements sought by the industry.These new high 2,4’-MDI isomer pre-polymers,developed by reseachers at HuntsmanPolyurethanes, are one of the key aspects (whichcompliment the integral JEFFAMINEpolyetheramines) of this exciting coatingstechnology.

for polyurea caulk systems.

RUBINATE 9495SYSTEM

RUBINATE 9483SYSTEM

RUBINATE 9484SYSTEM

~2 minutes ~2 minutes ~2 minutes

1391 834 963

286 438 412

298 293 332

44 36 41

286 649 742

----- 768 884

0.042 0.049 0.047

1.1 mg weight loss 0.9 mg weight loss 0.8 mg weight loss

ACKNOWLEDGMENTS

The authors would like to thank Ken Hillmanfor his expertise and diligence in preparing all ofthe polyurea spray systems used in this study,and Don Crow for his expertise in thecoordination and testing of the preparedspecimens. Many thanks go to Dr. JerryReddinger for his input and assistance in thepreparation of this manuscript.

References

1. Primeaux II, D.J, “Polyurea SprayTechnology in Commercial Applications”,60 Years of Polyurethanes: InternationalSymposium and Exhibition, 1998.

2. Broekaert, M., Pille-Wolf, W., “TheInfluence of Isomer Composition andFunctionality on the Final Properties ofAromatic Polyurea Spray Coatings”,UTECH 2000 Conference Paper, TheHague, Netherlands.

3. Primeaux II, D.J., Anglin, K.C., “TheProcessing of Spray Polyurea ElastomerSystems”, Polyurethanes 92, Proceedings ofthe SPI 34th Annual Technical/MarketingConference, 1992.

4. Perez, A., Hillman, K.M., House, D.W.,Scott, Jr., R.V., Ilijevski, D., “ SecondaryAliphatic Diamine Chain Extenders inAliphatic Polyurea Spray Applications”,UTECH 2000 Conference Paper, TheHague, Netherlands.

5. Plueddemann, Edwin P., “Silane CouplingAgents”, 2nd edition, Plenum Press, NewYork, 1991.

6. House, D.W., Scott, Jr., R.V., Wetherall, J.,“The Versatility of UOP Unilink andClearlink Diamines in Polyurethane andPolyurea Systems”. UOP LLC TechnicalPublication.

7. Primeaux II, D.J., “Spray PolyureaElastomers Offer Performance Advantages”,Modern Paint and Coatings, June 1991.

BIOGRAPHY

Aureliano Perez, Jr.

Aureliano Perez, Jr.earned his bachelor’sdegree in chemistryfrom Wayne StateUniversity in Detroit,Michigan in 1991.He has previouslyheld productdevelopmentpositions with Ciba-Geigy, Schnee-Morehead, Chem-Trend and Sika.Aureliano currentlyholds the position of

Applications Chemist with the Polyurea SprayTechnology Group at Huntsman. He is active inthe National Association of Corrosion Engineers(NACE) and the Society for Protective Coatings(SSPC). He holds one US patent in the area ofurethane sealants and has published papers inepoxy and polyurea coatings.

Jay A. JohnstonJay A. Johnstongraduated with aPh.D. in polymerchemistry from theUniversity of Akronin 1991. He is atechnical associate inthe ACE (Adhesives,Coatings andElastomers) group atHuntsmanPolyurethanes inAuburn Hills, MI.Jay joined ICIPolyurethanes (now

Huntsman Polyurethanes) in 1994. Previously,he completed postdoctoral fellowships at GeneralElectric’s Corporate R&D and at the Universityof Akron’s Institute of Polymer Science. JayJohnston is currently responsible fordevelopment of isocyanates and prepolymers forthe ACE market.