DEGRADATION OF VINYLIDENE-CHLORIDE METHYL ACRYLATE COPOLYMERS IN THE PRESENCE OF AMINES

Because of the prominence of vinylidene chloride/methyl acrylate copolymers in barrier plastic packing applications the degradation of these materials continues to be the focus of much interest. The prominent degradation process at moderate temperatures (less than 200-degrees-C) is dehydrochlorination. This reaction is a typical radical chain process with distinct initiation, propagation and termination phases. A principal defect structure responsible for the initiation of degradation is unsaturation along the polymer backbone. Although most stabilization packages for these polymers contain basic components to absorb hydrogen chloride as it is generated, materials sufficiently basic to abstract hydrogen chloride might actually enhance the rate of degradation by introducing double bonds into the polymer structure. That this is the case has been established by the thermogravimetric examination of the degradation of a methyl acrylate (5 mol.%)/vinylidene chloride copolymer in the presence of amines of varying base strength. In general, the initiation rate constant k(i) for the degradation process is enhanced in the presence of amine.