Paint & Coatings Industry - November 2008 - (Page 72)

Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings (e) Impact Impact resistance was determined using a Tubular Impact Tester (Sheen, UK). Values were reported in cm at which the film passed the impact test using a weight of 2 lb (approx. 0.91kg). Impact test results are presented in Table 3. It is clear from the data that films having higher HEMA content, had high impact resistance, because HEMA is known to impart flexibility to the coating films. That could be the possible reason why impact resistance decreased progressively from TSA1 to TSA4. (f) Gloss A Triglossometer (Sheen, UK) was used to measure films at a 60º angle; all coating films had good gloss (Table 3). presence of free hydroxyl groups when they were immersed in distilled water up to a period of 2 weeks. TSA4 films were unaffected because of the higher degree of crosslinking (Table 4). (d) Solvent All films exhibited good solvent resistance when immersed in non-polar solvents like xylene and mineral turpentine oil. But, when exposed to low-polar MEK, a slight loss in gloss was observed in TSA1, TSA2 and TSA3. This film behavior might be due to the fact that even after crosslinking, the presence of some unreacted OH-functional groups leads to moderate polarity in coated films. On immersion into ethanol, almost all films of TSAs showed slight loss in gloss due to the attack of moderatly polar ethanol on moderate polar films. In the coating films of TSA1 loss in gloss along with slight softening was observed due to the presence of a lesser degree of crosslinking, which leads to high polarity in the films (Table 4). Chemical Resistance Cured coating films were tested for their chemical resistance properties and data is presented in Table 4. (a) Acid Coating films were immersed in 1.0 N sulfuric acid up to a period of 7 days. The films of TSA1 and TSA2 were highly affected (loss in gloss along with slight softening) by the acid solution due to their alkaline nature. Films of TSA3, due to their slight alkaline nature, showed only slight loss in gloss. This behavior can be attributed to the fact that after crosslinking some unreacted hydroxyl groups were present in the coating films. The TSA4 film was unaffected by acid solution due to the presence of a sufficient degree of crosslinking (Table 4). Conclusion Four TSA resin samples were prepared successfully in the presence of varying amounts of 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). On comparing the performance properties, TSA4 outperforms TSA1, TSA2 and TSA3, except that it has low impact resistance. Among all the coating compositions, films of TSA4 showed good optical, mechanical and chemical resistance properties. This behavior of TSA4 might be due to the presence of a higher degree of crosslinking. Therefore, it can be concluded that water-thinable TSA coatings based on the developed copolymer/ resin prepared by using AA and HEMA in the molar ratio of (1:1) can be used as protective coatings for automobiles and other industrial applications, as eco-friendly coatings with no/negligible evolution of VOCs and hazardous air pollutants. (b) Alkali Coating films were immersed in 1.0 N sodium hydroxide for 1 week. All coating films were unaffected by alkali solution due to their alkaline nature (Table 4). (c) Water Coating films of TSA1, TSA2 and TSA3 were slightly affected due to moderate polarity because of the TABLE 4 | Chemical resistance properties of cured films. Results S.No. 1. 2. 3. 4. 5. 6. 7. References 1 2 3 Chemical 1.0 N H2SO4 1.0 N NaOH Distilled water Mineral turpentine oil Methyl ethyl ketone Xylene Ethyl alcohol TSA1 2 0 1 0 1 0 2 TSA2 2 0 1 0 1 0 1 TSA3 1 0 1 0 1 0 1 TSA4 0 0 0 0 0 0 1 4 5 6 7 Bijckmann, A.J.P.; Nabuurs, T.; Overbeek, G.C. PCI 2002, 10, 96. Maity, N.C. Paintinida 1984, XXLIV,6,10. Patel, J.N.; Dolia, M.B.; Patel, K.H.; Patel, R.M. J. Poly. Research 2006, 13, 3, 219. Winnik, M.A. JCT 2002, 74, 925, 49. Raval, D.A.; Patel, V.M. Paintindia 2005, LV, 3, 51. Tilak, G.Y. Paint and Resin 1983, 2, 37. OCCA. Australia : Surface Coatings, 1993, Chapman & Hall, London, III Ed., 1,4. Basu, M.; Pradhan, S. G.; Maity, N.C. Prog. Org. Coatings 1988, 16,19. 8 For further information contact pramod.hbti@yahoo.co.in. 70 NOV EMBER 2008 | W W W . P C I M A G . C O M http://WWW.PCIMAG.COM

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Paint and Coatings Industry - November 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News HiTone Resins for Enhanced Pigment Affinity of Powder Coatings New Water-Based Interior Coatings Combine Innovation and Quality With Respect for the Environment Novel, UV-Curable Nanotechnology-Enabled Coatings Highly Weather-Resistant Radiation-Curable Monomers and Oligomers for Exterior Applications Konica Minolta — Sensing Success for Viracon Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings Paint and Criminal Forensic Science Supplier and Application/Curing Showcases Materials Watch Classifieds Advertiser Index

Paint & Coatings Industry - November 2008

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