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834013 
Journal Article 
Effect of the polyester chemical structure on the stability of polyester-melamine coatings when exposed to accelerated weathering 
Batista, MAJ; Moraes, RP; Barbosa, JCS; Oliveira, PC; Santos, AM 
2011 
1 
Progress in Organic Coatings
ISSN: 0300-9440 
71 
3 
265-273 
English 
WOS:000291909700008 
The effect of the polyester chemical structure on the degradation of polyester/melamine coatings was studied. Four different polyesters were synthesized using different diacid monomers: (i) isophthalic acid (IPA) and mixtures of hexahydrophthalic anhydride (HHPA) with (ii) terephthalic acid (TA). (iii) phthalic anhydride (PAN) and (iv) 1,4 cyclohexanedicarboxylic acid (1,4-CHDA). Varnishes were prepared using melamine resin and submitted to accelerated degradation cycles. The process was monitored in terms of photooxidation index (POI), based on FTIR analysis, and in terms of changes in films' hardness, level of gloss and surface morphology. The monomers which contributed the most to polymer degradation were the couple HHPA and 1,4-CHDA. The most important factor to degradation was the high number of hydrogen atoms attached to tertiary and secondary carbons in the polymer structure, due to their high sensitivity to abstraction, which favors the photooxidation reactions. The monomer IPA presented the lowest POI and the highest gloss retention. (C) 2011 Elsevier B.V. All rights reserved. 
Polyester synthesis; Polyester/melamine coatings; Accelerated weathering; Degradation; Photo degradation