Effect of artificial weathering on surface properties of unsaturated polyester (UP) resin

Unsaturated polyester resin samples were exposed to artificial weathering environment for different time intervals. The change of appearance, morphology, chemical structure and contact angle on unsaturated polyester resin surface before and after exposure in this environment was monitored by spectrophotometer, gloss meter, microscope, Specula Reflection Fourier Transform Infrared (SR-FTIR) spectroscopy and optical contact angle measuring device. The results showed that the surface of unsaturated polyester resin turned darker and yellower in the first stage and then remained nearly unchanged during further ageing. Gloss reached maximum when the sample was aged for 12 days and then decreased. With increasing aging time, small cracks appeared and developed on the unsaturated polyester resin surface. Hydroxyl and carbonyl groups produced in aging process increased the wettability of unsaturated polyester resin surface.