Thermal degradation of vinylidene chloride/butyl acrylate copolymers

Vinylidene chloride/acrylate copolymers display a good barrier to the transport of small molecules (oxygen, carbon dioxide, water, etc.) as well as to flavor and aroma constituents of food items. For this reason, they occupy a place of prominence in the barrier plastic packaging industry. However, at process temperatures, these materials tend to undergo degradative dehydrochlorination. This is a typical radical chain process with distinct initiation, propagation, and termination phases and if unchecked can lead to the development of coloration which may be objectionable in some applications. To examine the influence of an aliphatic side chain on this process, a series of vinylidene chloride/butyl acrylate (4, 8, 12, 18, 20 wt.%) copolymers have been sythesized and fully characterized by chromatographic, thermal, and spectroscopic methods and by thermogravimetry. Increasing levels of butyl acrylate in the copolymer have little impact on the rate of initiation of degradation but do modestly decrease the propagation rate for the degradation.