Abstract
A new weatherability test method for coatings has been developed. The method is a cyclic treatment of A; 2h UV irradiation in 3wt % aqueous hydrogen peroxide solution at 40°C and B; 20h UV irradiation in 0.8 atm oxygen and 0.2 atm water vapor at 80°C.UV fluorescence lamp and metal halide lamp were employed for treatment A and B, respectively. Four alkyd/melamine type coatings containing titanium oxide pigment were subjected to treatment A, B, the cyclic test, and outdoor exposure in Okinawa. The treatment A produces small pits around titanium oxide pigment near the coatings surface. The pits are shaped by loss of resin around the pigment caused by photo-catalysis oxidation. The treatment B yields small waviness on the coatings surface. The waviness is formed by resin shrinkage caused by hydrolysis and oxidation. The cyclic treatment of A and B reproduces gloss loss and surface morphology of outdoor-exposed coatings in 100 times, acceleration.
