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

Polycarbonate is one of the most attractive polymers for plastic glasses be cause of its excellent physical properties such as its transparency. To imp rove its photochemical resistance, a coating is generally applied on the su rface. The efficiency of the coating depends on its ability to reduce the i ntensity of UV light. The present study focuses on the weathering of polyca rbonate/polyurethane (PC/PU) structures under conditions of accelerated pho toageing Spectrophotometrics show that photooxidation results from the high reactivi ty of the C-H bond in the alpha -position of the urethane group, a rapid co nsumption of the urethane function and, as a consequence, chain scission. T he consequences on the durability of the complex were assessed by mechanica l experiments to test modifications of the adhesion of the PU coating on th e PC substrate. A significant diminution of the cohesion energy with oxidat ion was noted. (C) 2001 Elsevier Science Ltd. All rights reserved.