Kinetic identification of individual reactions determining molecular weight variation of polymers during thermal oxidative degradation

Abstract

IT IS well known tha t thermal oxidative degradation of most polymers is a radical chain process with degenerate branching. During degradation, as well as formation of functional groups containing oxygen, the molecular weight and molecular weight dis tr ibut ion of polym e r s is modified. Even in the case of inhibited thermal oxidation of polymers subject to random degradation, a marked molecular weight variat ion is observed during the induction period [1]. Therefore, the problem of identifying the main individual reactions determining this change is very essential. Kinetic equations based on the generally adopted system of oxidation satisfactorily describe oxygen absorption and the accumulation of some of the products of oxidation. However, the kinetics of variat ion of polymer molecular weight during degradat ion remain obscure. Assumptions have boon made in the l i terature concerning reactions resulting in variat ion of molecular weight during degradation [2]. Reduction of polymer molecular weight in part icular has boon related to isomerization in the decomposit ion of macroradicals. These assumptions, however, have not boon confirmed by kinetic analysis.