THERMAL-DEGRADATION STUDIES OF ALTERNATING COPOLYMERS .2. THE COPOLYMER OF VINYL-ACETATE AND CROTONIC ACID

As the temperature is progressively raised, the alternating copolymer of vinyl acetate and crotonic acid degrades in two main stages: in the first (up to about 270-degrees-C), acetic acid is lost through a lact onisation reaction between the dissimilar chain units, accompanied by a parallel reaction involving decarboxylation of some of the crotonic acid groups. At higher temperatures, some further acetic acid loss occ urs, but the main degradation products are carbon dioxide, from decomp osition of the gamma-lactone rings, and chain fragments from the lacto nised backbone formed at lower temperatures. A variety of minor volati le products are also formed in the second degradation stage. Unlike po ly(vinyl acetate), the copolymer degrades almost without residue by 50 0-degrees-C.