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NEW HIGH PERFORMANCE DISPERSANTS FOR WATER BASED VOC-FREE PIGMENT DISPERSIONS

Ayaz KHAN, Dr. Lichang ZHOU and Brian VEST

Solvay USA Inc. Research & Innovation Center - Bristol, 350 George Patterson Boulevard, Bristol, PA 19007, U.S.A.

ABSTRACT With evolving regulatory requirements related to VOC-free and APE-free colorant systems, there is a need for new technologies which will help formulators simultaneously meet both regulatory and performance requirements. A new series of high performance dispersants will be introduced which provide exceptional color strength development, higher pigment loading at lower viscosity, improved stability and higher gloss development. The new high performance dispersants also provide excellent pigment wetting and dispersion with difficult to disperse pigments such as small particle size or conductive carbon blacks. These products are especially suited for VOC-free and APE free pigment dispersions for architectural, industrial and ink applications and enable high performance while meeting sustainability protocols. New high performance dispersants can be used to formulate coatings that are compliant with sustainability protocols. Keywords: Pigment, VOC, Dispersions INTRODUCTION: Glycol based colorants has been the industry standard for years until regulations, limiting the use levels of VOC containing solvents, were introduced, thereby all but eliminating the use of Glycols in water based applications. Furthermore, these glycol based colorants also utilize Nonylphenol Ethoxylates (NPE) based surfactants which are now being regulated in certain parts of the world (legislation in Europe; green movement in US, Canada and other Regions restricting use of NPE). These changes in VOC content coupled with limitations on use of NPE based surfactants have posed a very serious challenge for pigment dispersion and coatings formulators. With the increasing demand for colorants that are VOC-free and more compliant with Green Seal and Ecolabel Standards, the need for high performance dispersants have also significantly increased and formulators are demanding the same, if not better, performance in compliant colorants, when compared to their VOC and APE surfactant containing predecessors. There is also a big push in the Coatings Industry for use of more sustainable raw materials as this lowers the dependence on fossil fuel feedstocks and helps to avoid the price volatility associated with such materials. MECHANISM OF DISPERSION: Most pigments are manufactured to specifications that would typically provide the best performance properties. However, during the pigment manufacturing process, pigment particles come into contact with each other, often resulting in the formation of aggregates or agglomerates which then requires further processing by the colorant manufacturer to separate them into primary particles during the colorant manufacturing process. The mechanical breakdown or dispersion of the aggregates and agglomerates occurs in three stages as outlined in Figure 1.

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Figure 1: Overview of the dispersion process

Stabilization, which is by far, the most important step of the dispersion process, occurs either by steric, electrostatic or electro-steric repulsion. The goal of the dispersion process is to produce a liquid color concentrate which is not only stable but also compatible when combined with different water borne paint systems. Since the dispersion phase is the most time and energy consuming stage of the manufacturing process, selecting the right equipment and using the correct dispersant is critical to the overall success and economic viability of the process. PIGMENT STABILIZATION – CHALLENGES: The major challenges encountered in the Industry today are:

• Maintaining storage stability of pigment concentrates over longer time periods • Maintaining the compatibility of these pigment concentrates with different coating

systems after enduring longer storage time • Good color acceptance and color development in tinted systems using pigment

concentrates that were stored for prolonged periods IMPROVED STORAGE STABILITY: Anchoring of dispersant onto the pigment surface is key to improved storage stability and helps to

• Prevent flocculation • Prevent sedimentation • Improve compatibility

Wetting: Liquid replaces air on the surface of the pigment particles by decreasing the interfacial tension.

Separation: Mechanical breakdown of agglomerates.

Stabilization: Electrostatic, steric or electro-steric repulsion

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If the dispersants selected for use have poor anchoring abilities, then this will lead to pigment flocculation which will increase the rate of sedimentation and compatibility will be definitely compromised. PIGMENT PROPERTIES : INORGANIC VS. ORGANIC Table 1: Comparison of pigment properties

Table 1 shows a comparison of properties for inorganic and organic pigments. The inorganic pigments, which are typically metal oxides, are generally low in tint

strength, high in opacity, low in brightness and are fairly easy to disperse. They also have excellent weathering properties. The organic pigments on the other hand are high in tint strength, high in brightness but are very difficult to disperse. This has created demand for high performance dispersants to help improve the overall dispersion process and while maintaining good feasibility and manufacturing economics. PRODUCTS EVALUATED: Table 2: New High Performance Dispersants and Benchmarks

The new high performance dispersants numbered 1, 5 and 7 were evaluated against four commercial Benchmark dispersants, numbered 1, 2, 3 and 4 respectively, as shown in the Table 2. Dispersant 1 and 5 are non-ionic while

Dispersant 7 is anionic. Competitive Benchmarks are polymeric types. EXPERIMENTAL DESIGN: Dispersant demand curves were run for each pigment tested to determine the optimized dispersant and pigment usage level. Competitive dispersants were used at their respective recommended levels. Pigment loadings were kept constant for both the new HP Dispersants and the Benchmark products. Based on the optimized dispersant and pigment levels, respective pigment slurries were prepared using the starting point formula shown below. Water was adjusted in the formula

Property Inorganic Organic Solubility Generally insoluble, non-

bleeding Slightly soluble

Tint Strength Low High Hiding Power High, opaque Low, more transparent Ease of Dispersion Fairly easy to disperse Difficult Specific Gravity High Low Heat Resistance High Low Weathering Excellent Poor Brightness (Intensity) low High

Product Name % Actives Description Dispersant 1 85 Proprietary APE-free, non-ionic

wetting/dispersing agents for organic pigments for low to VOC-free waterborne

pigment dispersions Dispersant 5 70

Dispersant 7 97 Proprietary APE-free, anionic

wetting/dispersing agent for conductive carbon black pigments

Product Name % Actives Description Benchmark 1 40 Block copolymer with pigment affinic

groups Benchmark 2 40 Aqueous solution of a copolymer with

groups of high pigment affinity Benchmark 3 40

Benchmark 4 100 Modified polyether with groups of high pigment affinity

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based on dispersant and pigment loading. A basket mill attached to a high speed Dispermat, shown in picture below, was used for all pigment slurry preparations. Pigment dispersion stabilities were monitored at both room temperature and after seven days heat aging in an oven at 50 °C. The resulting slurries were also tested in WB Architectural and Industrial Tint Bases for color properties. The CIE L*a*b* color System was used for color measurements.

• Tint Strength (98% - 102%; 2% Colorant addition) • Pigment is tested in a base containing TiO2

• Masstone (95% - 105%; 12% Colorant addition)

• Pigment is tested in a base that does NOT contain TiO2

• Color compatibility/development (∆E ± 1)

Typical Starting Point Formula Raw Materials Weight %

DI water 50 Defoamer 1 Dispersant 8

pH neutralizer 1 Pigment 40

Total 100 EVALUATION OF STANDARD PAINT PROPERTIES: Gloss readings were performed using a BYK Gardner Micro-TRI-Gloss gloss meter. Low shear viscosity reported in Centipoise (cPs), was measured on a LV Viscometer (Brookfield). Drawdowns were done on Leneta charts using a 3 mils bird blade. PIGMENTS TESTED: Carbon Black Grades shown in the Table 3 were evaluated using the new HP dispersants versus industry benchmarks. The carbon blacks were divided into three categories:

• Architectural • Industrial • Conductive

As can be seen in the table, particle size decreased while oil absorption and surface area increased as you go from Architectural grades to Conductive grade.

CIE L*a*b* Color System

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Table 3: Carbon Black grades evaluated and properties

Properties

Architectural Industrial Conductive

Raven 500

Raven 1170

Raven 5000

Ultra II

Color Black Emperor 2000

Printex XE-2B FW

171 FW 200

FW 255

FW 285

Particle Size (nm) 53 21 8 11 13 11 11 11 30

Surface Oxidized No No Yes Yes Yes Yes Yes - No

% Volatiles 1.2 1.8 10.5 3.0 20.0 12 5.0 - 0.0

Oil Absorption 80 60 95 110 160 106 175 - 410

NSA Surface area (m2/g) 44 107 583 650 550 - 350 - 1100

CARBON BLACK PB 7 – RAVEN® 1170 – Architectural Grade Figure 2: Dispersant demand curve for Raven 1170

Dispersant demand curves were run for Raven 1170 carbon black pigment using Dispersants 1, 5 and 7 to establish dispersant and pigment usage levels. Results are shown in Figure 2. From the dispersion demand curves, optimum usage level was determined to be between 14% - 24% active dispersant based on a 35% pigment loading. A usage level of 18% was selected for

further evaluations versus competitive product. From the dispersant demand curves, it was seen that the resulting viscosities were all very low. Since the dispersion phase is the most energy intensive and cost sensitive part of the process, grinding a much higher loading of pigment for the same amount of time and imparting the same amount of energy would help to improve the overall economics of the process. Figure 3: Viscosity of pigment concentrates

Using the same 18% active dispersant based on pigment loading, the carbon black content was increased from 35% to 45%. Dispersant 1 was exceptional in producing the lowest viscosity at the higher pigment loading as shown in Figure 3. Dispersant 7 was the weakest performer of the three dispersants tested and was excluded from further testing.

Dispersant 5

Dispersant 1

Dispersant 7

Optimum usage level: 14-24% on total pigment weight 18% usage level was selected for other dispersant evaluation

Dispersant 5Dispersant 1

Dispersant 7

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Based on the above results, pigment dispersions using Raven 1170 carbon black at 35% loading using 18% active dispersant based on pigment weight were prepared using Dispersants 1, Dispersant 5 and an industry benchmark product BM 1, respectively. The dispersions were allowed to sit overnight to allow for equilibration. The equilibrated viscosities of the respective dispersions were measured and results are shown in the table below. Equilibrated viscosities were all under 100 cPs and thus comparable. The dispersions were then tested in a semi-gloss and a flat paint (white and clear tint bases respectively) for color properties such as tint strength (white bases), masstone (clear bases), color acceptance and development. Results obtained are listed in table 4. Table 4: Performance properties and final results Properties Benchmark 1 Dispersant 1 Dispersant 5 Active dispersant (% dry/dry) 18 18 18 BF 12 rpm, #3 spindle 90 50 70 Semi-Gloss White Base Flat White Base Test BM 1 Disp. 1 Disp. 5 BM 1 Disp. 1 Disp. 5 Tint Strength - % 100 98 96 100 101 99 Rub up - ∆E 0.65 0.42 0.76 0.09 0.13 0.16 Masstone Semi-Gloss White Base Flat White Base Masstone - % 100 99 100 100 100 99 Color difference - ∆E 0.73 0.39 0.23 0.09 0.27 0.57 Gloss (24 hrs dry) 20°/60° 16/49 18/53 16/50 X X X

The final results from all testing conducted shows that Dispersant 1 is comparable in performance to industry Benchmark 1. Dispersant 5 was a little weak in Tint Strength in the semi-gloss white base paint. Carbon Black – Raven® 5000 Ultra® II – Industrial Grade Dispersant demand curves were run for Raven 5000 Ultra II carbon black pigment using Dispersants 1 and 5 to establish dispersant and pigment usage levels. Dispersant 1 did not perform well and was excluded from further testing. Results are shown in Figure 4. From the dispersion demand curves, optimum usage level was determined to be ~ 50% active dispersant based on a 20% pigment loading. Figure 4: Dispersant demand curve for Raven 5000

Based on the above results, pigment dispersions using Raven 5000 carbon black at 20% loading using Dispersant 1 at 50% actives and an Industry dispersant Benchmark 2 using 60% actives based on pigment weight were prepared respectively. The initial, equilibrated and heat aged viscosities of the respective dispersions were measured and results are shown in the table 5. While

initial and equilibrated viscosities were comparable, heat aged results showed Dispersant 5 to be superior to Benchmark 2 in performance.

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Table 5: Performance properties and final results Properties Benchmark 2 Dispersant 5 Pigment – Raven 5000 % 20 20 Dispersant % (solids on pigment) 60 50 Viscosity, cPs, BF, 12 rpm, #3 spindle Initial 30 28 Equilibrated 30 44 7 days at 50°C 5029 92 Stability at room temperature, 7 days Soft settling good Tint: Acrylic Gloss White Base, Industrial Tint Strength - % 100 106 Rub up - ∆E 0.43 0.24 Masstone: DTM Acrylic Clear Base Masstone - % 100 100 Color difference - ∆E Std 0.40 Gloss 20°/60° 39/69 51/81

The dispersions were then tested in an Industrial acrylic gloss white base and a DTM acrylic clear base paint respectively, for color properties such as tint strength (white base), masstone (clear base), color acceptance and development. Results obtained are listed in table 5. The final results from all testing conducted showed that Dispersant 5 is more efficient and superior in performance when compared to Industry Benchmark 2. Also, higher gloss was developed in the DTM clear base using Dispersant 5 based dispersion as compared to that of the Benchmark 2 based dispersion. This is further indication of the superior dispersion properties of Dispersant 5 in Industrial grade Carbon black pigments. Carbon Black – Printex® XE-2B Conductive Figure 5: Dispersant demand curve for Printex XE-2B

Dispersant demand curves were run for Printex® XE-2B carbon black pigment using Dispersant 7 to establish dispersant and pigment usage levels. Results are shown in Figure 5 From the dispersion demand curves, optimum usage level was determined to be ~ 80% active dispersant based on a 10% pigment loading.

Pigment dispersions using Printex® XE-2B carbon black at 10% loading using Dispersant 7 at 80% actives and an Industry dispersant Benchmark 3 using 70% actives based on pigment weight were prepared respectively. Initial viscosities were measured and the dispersions were allowed to sit overnight to allow for equilibration. The initial, equilibrated and heat aged viscosities of the respective dispersions were measured and results are shown in table 6. While initial viscosity was comparable, equilibrated and heat aged results showed Dispersant 7 to be far superior in performance when compared to Benchmark 3, which gelled after heat aged testing.

Printex XE-2B (10%) with Dispersant 7

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Table 6: Performance properties and final results Properties Benchmark 3 Dispersant 7 Printex XE-2B % 10 10 Dispersant solids on pigment, % 70 80 Initial viscosity, cPs 1304 268 Equilibrated viscosity, cPs 4189 192 7 days heat aging at 50ºC Syneresis/settling gelled none Viscosity, cPs gelled 302

RESULTS AND DISCUSSIONS – CARBON BLACK PIGMENTS: As shown in table 7, various grades of Carbon Black pigments were used to evaluate the performance of the new High Performance dispersants versus Industry Benchmarks. Overall, the new High Performance Dispersants demonstrated excellent efficiency across the different grades of Carbon Black pigments when compared to the Industry Benchmarks. Table 7: Summary of results and dispersant recommendations

Properties

Architectural Industrial Conductive

Raven 500

Raven 1170

Raven 5000

Ultra II

Color Black Emperor 2000

Printex XE-2B FW

171 FW 200

FW 255

FW 285

Particle Size (nm) 53 21 8 11 13 11 11 11 30 Surface Oxidized No No Yes Yes Yes Yes Yes - No % Volatiles 1.2 1.8 10.5 3.0 20.0 12 5.0 - 0.0 Oil Absorption 80 60 95 110 160 106 175 - 410 NSA Surface area (m2/g) 44 107 583 650 550 - 350 - 1100

Recommended Dispersant Rhodoline 3100 Rhodoline 3500 Rhodoline

3700 % Usage level 15-20 45-50 80-90

For the Architectural grade carbon blacks, Dispersant 1 was recommended at a dosage of 15-20% active dispersant based on total pigment weight. For the Industrial grade carbon blacks, Dispersant 5 was recommended at a dosage of 45-50% active dispersant based on total pigment weight. For the Conductive grade carbon blacks, Dispersant 7 was recommended at a dosage of 80-90% active dispersant based on total pigment weight. Organic Pigments: Organic pigments shown in Table 8 were evaluated using the new HP dispersants versus industry benchmarks. Table 8: Organic pigments tested

Organic Pigments Tested Phthalo Blue PB 15:2 Violet Pigment PV 19 Phthalo Blue 15:4 Organic Yellow PY 65, PY 74, PY 83, PY 97 DPP Red PR 254 Organic Yellow PY 151 Organic Red PR 122 Phthalo Green PG 7 Organic Red PR 188 Pigment Orange PO 34

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Organic Yellow PY 83 Dispersant demand curves were run for Organic Yellow PY 83 pigment using Dispersant 1 to establish dispersant and pigment usage levels. From the dispersion demand curves shown in Figure 6, optimum usage level was determined to be ~ 10% active dispersant based on a 43% pigment loading. Pigment dispersions using Organic Yellow PY 83 at 43% loading were made using Dispersant 1 at 10% actives and an Industry dispersant Benchmark 4 at 15% actives based on pigment weight respectively. The dispersions were allowed to sit overnight to allow for equilibration. Figure 6: Dispersant demand curve for PY-83

The equilibrated and heat aged viscosities of the respective dispersions were measured and results are shown in table 9. Equilibrated and heat aged results showed Dispersant 1 to be superior to Benchmark 4 in performance. The dispersions were then tested in an acrylic semi-gloss white base and an acrylic semi-gloss clear base paint respectively, for color properties such as tint strength (white base), masstone

(clear base), color acceptance and development. Results obtained are listed in the table 9. Table 9: Performance properties and final results Properties Benchmark 4 Dispersant 1 Pigment - % 43 43 Active dispersant (% dry/dry) 15 10 Results Equilibrated BF 12 rpm, #3 spindle 2870 530 Results 7 days at 50°C BF 12 rpm, #3 spindle 1630 450 Tint: Semi-Gloss White Base Tint Strength - % 100 108 Rub up - ∆E 0.21 0.57 Masstone: Semi-Gloss Clear Base Masstone - % 100 100 Color difference - ∆E Std 0.13

The final results from all testing conducted showed that Dispersant 1 is much more efficient and superior in performance when compared to industry Benchmark 4. Excellent tint strength and equal masstone along with good color acceptance were all achieved using Dispersant 1. DPP Organic Red PR 254 Dispersant demand curves were run for DPP Organic Red PR254 pigment using Dispersants 1, 5 and 7 to establish dispersant and pigment usage levels. Results are shown in the Figure 7. From the dispersion demand curves, optimum usage level was determined to be between 4% - 10% active dispersant based on a 40% pigment loading.

Dispersant 1Dispersant 1

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Figure 7: Dispersant demand curve – PR254 Dispersant 1 at a usage level of 8% based on total pigment weigh was selected for further evaluations versus Benchmark product. Based on the above results, pigment dispersions using DPP Organic Red PR 254 at 40% loading using Dispersant 1 at 8% actives and an Industry dispersant Benchmark 2 using 30% actives based on pigment weight were prepared respectively. The dispersions were allowed to sit overnight to allow for

equilibration before further testing. The dispersions were then tested in an acrylic gloss white base and an acrylic gloss clear base paint respectively, for color properties such as tint strength (white base), masstone (clear base), color acceptance and development. Results obtained are listed in the table 10. Table 10: Performance properties and final results Properties Benchmark 2 Dispersant 1 Pigment - % 40 40 Active dispersant (% dry/dry) 30 8 Tint Strength – Gloss White Base Tint Strength - % 100 98 Rub up - ∆E 0.33 0.61 Masstone – Acrylic Gloss Clear Base Masstone - % 100 98 Color difference - ∆E Std 0.44

The final results from all testing conducted showed that Dispersant 1 is a much more efficient dispersant when compared to industry Benchmark 2. Comparable tint strength and masstone along with good color acceptance was achieved using Dispersant 1. Orange PO 34 Figure 8: Dispersant demand curve – PO34

Dispersant 1

Dispersant 5

Dispersant demand curves were run for Orange PO 34 pigment using Dispersants 1 and 5 to establish dispersant and pigment usage levels. Results are shown in Figure 8.

Dispersant 5

Dispersant 1

Dispersant 7

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From the dispersion demand curves, optimum usage level was determined to be between 4% - 12% active dispersant based on a 45% pigment loading. Dispersants 1 and 5 at usage levels of 8% based on total pigment weight was selected for further evaluations versus Benchmark product. Based on the above results, pigment dispersions using Orange PO 34 pigment at 40% loading using Dispersants 1 and 5 at 8% actives and an Industry dispersant Benchmark 4 also using 8% actives based on pigment weight were prepared respectively. The dispersions were allowed to sit overnight to allow for equilibration before further testing. The equilibrated and heat aged viscosities of the respective dispersions were measured and results are shown in the table below. Equilibrated and heat aged results showed Dispersant 1 to be better than Benchmark 4 in performance. Dispersant 5 was comparable to Benchmark 4 in initial viscosity but much better on heat aged viscosity. The dispersions were then tested in an acrylic semi-gloss white base and an acrylic semi-gloss clear base paint respectively, for color properties such as tint strength (white base), masstone (clear base), color acceptance and development. Results obtained are listed in table 11. Table 11: Performance properties and final results Properties Benchmark 4 Dispersant 1 Dispersant 5 Pigment - % 45 45 45 Active dispersant (% dry/dry) 8 8 8 Results Equilibrated BF 12 rpm, #3 spindle 640 170 810 Results 7 days at 50°C BF 12 rpm, #3 spindle 3849 560 760 Tint: Semi-Gloss White Base Tint Strength - % 100 99 93 Rub up - ∆E 0.65 0.33 0.61 Masstone: Semi-Gloss Clear Base Masstone - % 100 99 96 Color difference - ∆E Std 0.09 0.64 Gloss (24 hrs dry) 20°/60° 16/52 16/52 18/53 The final results from all testing conducted showed that Dispersants 1 and 5 were equal in efficiency when compared to industry Benchmark 4. However, Dispersant 1 had the best overall viscosity stability. Comparable tint strength and masstone along with good color acceptance was achieved using Dispersant 1. However Dispersant 5 was lower in both tint strength and masstone and higher in color numbers.

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RESULTS AND DISCUSSIONS – ORGANIC PIGMENTS: As shown in the table 12, various Organic pigments were used to evaluate the performance of the new High Performance dispersants versus Industry Benchmarks. Overall, the new High Performance Dispersants demonstrated excellent efficiency across the different Organic pigments when compared to the Industry Benchmarks. Dispersant 1 showed much better versatility that Dispersant 5 across the range of Organic Pigments. Table 12: Summary of results and dispersant recommendations Pigments Tested Dispersant 1 Dispersant 5 Usage Level Phthalo Blue PB 15:2 ++ + 10 - 20% Phthalo Blue 15:4 ++ + 5 - 15% DPP Red PR 254 ++ - 5 - 15% Organic Red PR 122 + ++ 12 - 20% Organic Red PR 188 ++ + 5 – 12% Violet Pigment PV 19 ++ ++ 10 – 20% Organic Yellow PY 65, PY 74, PY 83, PY 97 ++ + 5 – 20% Organic Yellow PY 151 ++ + 4 – 10% Phthalo Green PG 7 + + 10 – 25% Pigment Orange PO 34 ++ + 5 – 10%

++ Recommended; + Suitable; - Not Recommended CONCLUSIONS: The new High Performance Dispersants exhibited very good performance across the range of Carbon Black and Organic pigments when compared to Industry Benchmark products. The new high performance dispersants provide exceptional color strength development, higher pigment loading at lower viscosity, improved stability and higher gloss development. The new high performance dispersants also provide excellent pigment wetting and dispersion with difficult to disperse pigments such as small particle size or conductive carbon blacks. The new high performance dispersants are especially suited for VOC-free and APE free pigment dispersions for architectural, industrial and ink applications and enable high performance while meeting sustainability protocols. The new high performance dispersants can also be used to formulate coatings that are compliant with sustainability protocols. REFERENCES: (1). Patton, Temple C., Paint Flow and Pigment Dispersion, 2nd Ed., John Wiley & Sons Inc., 1979. (2). Paul, Swaraj, Surface Coatings Science & Technology, 2nd Ed., John Wiley & Sons Inc., 1996. (3). Tracton, Arthur A., Coatings Technology Handbook, 3rd Ed., Taylor & Francis Group LLC, 2006. (4). Wicks, Jr., Zeno W., Jones, Frank N., and Pappas, S. Peter, Organic Coatings Science and Technology, 2nd Ed., Wiley-Interscience, 1998. (5). Calbo, Leonard J., Handbook of Coatings Additives Volume 2, Marcel Dekker Inc., 1992