Zum Mechanismus der Thermische Abspaltung von Chlorwasserstoff aus Polyvinylchlorid. I. Mitteilung: Thermische Zersetzung von Copolymeren aus Vinylchlorid und Fumarsäurediäthylester, Isobutylen, Vinylbromid und 2‐Chlorpropen

Abstract

Investigation of the thermal behavior of copolymers of vinyl chloride (VC) and diethylfumaric ester (FDE), isobutene (IBu), vinyl bromide (VBr), and 2‐chloropropene (2CP) gives an insight into the mechanism of thermal dehydrochlorination in an inert atmosphere. The rate of decomposition at 180°C. increases in the following order: VC‐homopolymer < VC–FDE‐copol. < VC‐IBu‐copol. < VC‐VBr‐copol. < VC‐2CP‐eopol. The thermal elimination of hydrogen chloride from the copolymers in a nitrogen atmosphere starts from the comonomer unit. The first step of the decomposition of the VC‐VBr and the VC‐2CP‐copolymers requires a sequence of at least two neighboring comonomer units. The behavior of the 2CP‐copolymers indicates that the thermal decomposition of PVC can start from branches. The growth of the forming polyene sequences is stopped at the FDE‐ or IBu‐units Thus shorter sequences result, in reference to the VC‐homopolymer. However, the length of the polyene sequences increases from PVC to VC‐VBr‐copolymers to VBr‐homopolymer. The activation energies of hydrogen halide elimination from VC–VBr‐ and VC–2CP‐copolymers are lower than that of PVC.