Degradation of polycarbonate sheeting on outdoor exposure. Relationship between changes in molecular weight and tensile properties

To obtain better understanding of surface microcracking of polycarbonate (PC) glazing during outdoor exposure, and to determine the effect of weathering on its fracture resistance, changes in molecular weight and tensile properties during outdoor and various artificial weathering were studied. During outdoor weathering, the ultimate elongation and ultimate tensile stress decreased showing that PC became less ductile and more susceptible to fracture. The occurrence of surface microcracking of PC is attributed to a combination of a decrease in ultimate tensile stress and ductility of surface layer due to UV radiation, and alternating stresses due, primarily, to temperature changes.