Consequences of photoageing on the durability of plastic glasses for automotive applications

Polycarbonate is one of the most attractive polymers for plastic glasses because of its excellent physical properties such as its transparency. To improve its photochemical resistance, a coating is generally applied on the surface. The efficiency of the coating depends on its ability to reduce the intensity of UV light. The present study focuses on the weathering of polycarbonate/polyurethane (PC/PU) structures under conditions of accelerated photoageing. Spectrophotometrics show that photooxidation results from the high reactivity of the C–H bond in the α-position of the urethane group, a rapid consumption of the urethane function and, as a consequence, chain scission. The consequences on the durability of the complex were assessed by mechanical experiments to test modifications of the adhesion of the PU coating on the PC substrate. A significant diminution of the cohesion energy with oxidation was noted.