Effects of temperature on the weathering lifetime of coated polycarbonate

Abstract The lifetime of polycarbonate (PC) coated with silicone hardcoats containing UV absorber is shorter at elevated temperatures. The activation energy ( E a ) for delamination was found to be 18 ± 2 kJ/mol (4.3 ± 0.5 kcal/mol) at the 95% confidence level in this study. This E a is the consequence of the sensitivity of the substrate and the UV absorber to temperature. The E a for PC photodegradation was previously found to be 17–21 kJ/mol (4–5 kcal/mol). The E a for loss of absorbance in the second-generation silicone hardcoat was found to be 28.5 ± 5.4 kJ/mol (6.8 ± 1.3 kcal/mol) at the 95% confidence level. Results are consistent with experimental findings when these activation energies are used in published predictive models. Since the E a for coating delamination depends on the E a of UV absorber loss, coating systems different from the one in this study will need to be investigated separately.