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Effect of heat treatment on the dielectric relaxation of polyacrylonitrile. III. Role of duration of heat treatment
Author(s) -
Gupta A. K.,
Singhal R. P.,
Agarwal V. K.
Publication year - 1983
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1983.070280906
Subject(s) - polyacrylonitrile , dielectric , nitrile , relaxation (psychology) , glass transition , materials science , degree (music) , thermodynamics , dielectric loss , chemistry , polymer chemistry , composite material , organic chemistry , polymer , medicine , physics , optoelectronics , acoustics
Dielectric relaxation of polyacrylonitrile (PAN) heat‐treated at 120°C in vacuum for durations varying from 4 to 24 h is studied in order to investigate the effect of the duration of heat treatment. Decrease in dielectric constant increment and loss peak height and an increase in relaxation temperature on heat treatment are observed at all durations of heat treatment. At the studied temperature of heat treatment the observed changes in dielectric relaxation were found to increase with duration of heat treatment showing maxima at a 16 h duration and then a decrease at a higher duration of heat treatment. The results are discussed in terms of the variation of degree of intermolecularly bound nitrile groups with the duration of heat treatment. Glass transition temperature calculated from the dielectric data, through WLF theory, showed a variation, similar to that of the degree of bound nitrile groups, with duration of heat treatment. The observed variation of T g is attributed to the interlinking effect produced by the bound nitrile group pairs on the segmental mobility.