Reactivity of weathered polyolefinic samples studied by means of TGA

The reactivity of polyolefin films having different environmental exposure times was assessed by thermogravimetric curves. Tests in air at 200 °C of all polyethylene samples show an initial steady weight time, an intermediate weight increase due to oxygen absorption and, subsequently, a continuous weight loss. The highest weight gain is obtained with weathered samples containing many oxygenated functional groups. In the same conditions no polypropylene sample displays the intermediate weight increase. Thermogravimetric data can be used to determine how the environmental stress affects oxidation, crosslinking and scission reactions in pristine and recycled polyolefins. Furthermore, the concept of induction time of the degradation can be redefined.