Degradation profiles of polyester-urethane (hydroxylated polyester/diphenylmethane diisocyanate) and polyester-melamine (hydroxylated polyester/hexamethoxymethyl-melamine) coatings: An accelerated weathering study

The successful material performance of coatings depends on the environmental conditions to which they are exposed. The effects of the diol structure and acetoacetylation on the weathering degradation of hydroxylated polyester (HP)/hexamethoxymethylmelamine and HP/diphenylmethane diisocyanate clear coatings were studied. The acetoacetylation of HPs led to better performance for higher application solids than the acetoacetylation of their base counterparts. Weathering degradation profiles were investigated with dynamic mechanical thermal analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The structural variations of the building blocks and aceto-acetylation were found to be important for enhancing the stability of coatings at higher application solids. Polyester-urethane coatings were more stable toward weathering than polyester-melamine coatings. (c) 2005 Wiley Periodicals, Inc.