Premium
Thermal stability of polyacrylonitrile in the melt formed by hydration
Author(s) -
Min Byung Ghyl,
Son Tae Won,
Jo Won Ho,
Choi Soo Ghil
Publication year - 1992
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.1992.070461010
Subject(s) - annealing (glass) , differential scanning calorimetry , enthalpy of fusion , polyacrylonitrile , thermodynamics , crystallization , nitrile , fusion , materials science , polymer chemistry , thermal stability , glass transition , melting point , intrinsic viscosity , polymer , chemistry , chemical engineering , composite material , organic chemistry , linguistics , physics , philosophy , engineering
Differential scanning calorimetry (DSC) and intrinsic viscosity measurement have been used to investigate the thermal stability of PAN‐based copolymer in the melt formed by hydration. Samples containing various water contents were annealed at temperatures between 160 and 180°C for periods up to 60 min. The melting point ( T m ) and crystallization temperature ( T c ) increased with annealing time, irrespective of annealing temperature and water content. The increase in T m with annealing time was interpreted in terms of thermodynamic parameters. The decrease in the heat of fusion (Δ H f ) with the increase of annealing time implies that the number of nitrile groups is reduced during annealing in the melt. The decrease in the entropy of fusion (Δ S f ) calculated from T m and Δ H f suggests that the polymer chain becomes more rigid as the annealing time (or temperature) increases; however, the intrinsic viscosity does not increase during annealing. From both thermodynamic analysis and intrinsic viscosity, it is concluded that the increase in T m is caused by chain rigidity mainly due to the intramolecular cyclization of nitrile groups. © 1992 John Wiley & Sons, Inc.