Environmental degradation of highly loaded polypropylene

Six formulations of polypropylene (PP) containing combinations of calcium carbonate (CaCO,), stearic acid, and a light stabilizer were prepared and placed in the environment for their degradation. Samples were taken at proper time intervals for following the consequences of the outdoor conditions. Impact resistance and elongation at rupture were evaluated as mechanical properties. On the other hand, size exclusion chromatography, chemiluminescence, and infrared spectroscopy (FTIR) were used to follow chemical changes. Polypropylene by itself showed a slow but stable aging, while PP + CaCO, had improved initial mechanical properties but was more sensitive to degradation. The treatment of CaCO, with stearic acid before its addition to PP resulted in an improved material but with an induction time to degradation greatly reduced to 2 weeks of environmental exposure. The addition of the W stabilizer reduced the negative effect of the stearic acid to some extent but did not compensate for it completely.