Ultra high molecular weight polyethylene - II. Thermal- and photo-oxidation

Thermal- and photo-oxidation of ultra high molecular weight polyethylene (UHMWPE) has been studied using FTIR and derivatisation techniques. The species responsible for the initiation of the oxidative process are peroxides. produced by mechano-oxidative degradation. which evolve through a nonradical concerted mechanism and form ester and acid species. A second oxidative process takes place. It has an induction period and is similar to those described in the literature for linear low density polyethylene (LLDPE). The main difference between thermo-and photo-oxidation processes is the larger amount of acids formed in photo-oxidation. As far as the mechanism is concerned beta-scission prevails in thermo-oxidative conditions whereas Norrish I and Norrish II reactions are the most relevant in photo-oxidation. (C) 1997 Elsevier Science Limited.