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The concentration and possible source of unstable sites in PVC
Author(s) -
Berens A. R.
Publication year - 1974
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760140503
Subject(s) - copolymer , vinyl chloride , chlorine , branching (polymer chemistry) , degree of unsaturation , materials science , polymer chemistry , polymerization , thermal decomposition , polymer , thermal stability , reactivity (psychology) , chemistry , organic chemistry , composite material , medicine , alternative medicine , pathology , metallurgy
Copolymers of vinyl chloride with 2‐chloropropene were prepared as models for tertiary‐chlorine branching in PVC. Rates of thermal dehydrochlorination of copolymers containing up to 2 mol percent 2‐chloropropene were found to be a linear function of composition. By comparing the decomposition rates of the copolymers with that of PVC prepared under similar conditions, we estimate the maximum tertiary‐chlorine content of PVC at 0.1 to 0.2 mol percent. This figure is of the same magnitude as estimates of the content of tertiary‐chlorine, random unsaturation, and long‐chain branching obtained in previously published studies of PVC. Possible mechanisms for tertiary‐chlorine branch formation include chain‐transfer to polymer and copolymerization with unsaturated chain‐ends. By applying the conventional copolymerization equation, using the reactivity ratios of the vinyl chloride/2‐chloropropene system, it is shown that the copolymerization mechanism predicts a tertiary‐chlorine branch content close to the estimated value. Both mechanisms also agree qualitatively with reported effects of polymerization temperature and conversion on branching and thermal stability.