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Reaction mechanisms of polyacrylonitrile on thermal treatment
Author(s) -
Kim J.,
Kim Y. C.,
Ahn W.,
Kim C. Y.
Publication year - 1993
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.760332203
Subject(s) - polyacrylonitrile , itaconic acid , dpph , differential scanning calorimetry , radical , materials science , reaction mechanism , polymer chemistry , nitrile , copolymer , photochemistry , chemistry , organic chemistry , catalysis , antioxidant , polymer , composite material , physics , thermodynamics
A high‐temperature radical scavenger, 2,2‐diphenyl‐l‐picryl hydrazyl (DPPH), has been used to study the reaction mechanisms of polyacrylonitrile (PAN) on thermal treatment. The effect of DPPH on the cyclization reaction of PAN in both air and nitrogen, investigated by differential scanning calorimetry (DSC), helped to verify the proposed reaction mechanisms, i.e., the free radical and the ionic ones. For PAN homopolymer, the peak temperature of the reaction exotherm shifted to higher temperatures and the heat of reaction was decreased with increasing DPPH concentration. For PAN copolymer with methylacrylate and itaconic acid, however, the effects of DPPH on DSC thermograms were insignificant. The effects of IPPH suggest that the reaction of the nitrile groups proceeds by free radicals for the homopolymer while by ions for the copolymer. The activation energies for the thermal reactions of PAN in both air and nitrogen were also estimated by the dynamic DSC method, and they proved to be highly dependent on reaction mechanism, environment of thermal treatment, and DPPH concentration.