THERMAL-DEGRADATION STUDIES OF POLY(VINYL CHLORIDE) AND ETHYLENE-VINYL CHLORIDE COPOLYMER

The thermal degradation behavior of suspension-polymerized poly(vinyl chloride) (PVC) and ethylene-vinyl chloride copolymer (E-VC) in the ea rly stages was compared by continuous measurement of the extent of deh ydrochlorination. The behavior of E-VC was different from that of PVC; the rate of dehydrochlorination of E-VC decreased as a function of he ating time whereas that of PVC was constant. It was presumed that the dehydrochlorination reaction was terminated at the ethylene units in t he polymer backbone. At a very early degradation stage, however, the r ate of dehydrochlorination of E-VC was greater than that of PVC. This degradation behavior arose from structural defects in the polymer, i.e . the content of tertiary chlorine increased according to the increase in ethylene content in E-VC during suspension polymerization.