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Volume contraction and its significance in structural formation during the thermal stabilization of acrylic fibers
Author(s) -
Takaku Akira,
Shimizu Jiro
Publication year - 1984
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.1984.070290425
Subject(s) - materials science , composite material , ultimate tensile strength , contraction (grammar) , stacking , isothermal process , polymerization , polymer , thermodynamics , chemistry , organic chemistry , medicine , physics
The length changes of acrylic fibers during isothermal treatment at temperatures from 208°C to 270°C were measured under constant tensile stresses. In order to elucidate the relation between the length and structural changes during heat treatment, the measurements of density, the elemental composition, and the aromatization index determined from X‐ray diffraction were made for the fibers heat‐treated at 252°C for various periods of time. It is shown that a contraction in length which accompanied a volume contraction occurred during extended heat treatment, even when the fibers were subjected to high tensile stresses. The volume contraction is attributed to the fact that planar cyclized polymer segments, formed by additional polymerization of the nitrile side groups, are built up and construct a stacking which is denser than the original fiber structure. The orientation of the stacking of the cyclized segments was measured for the fibers heat‐treated in the fixed state giving a high orientation, which is comparable to that of the fibers heat‐treated under a high tensile stress giving an extension to the fibers in the initial periods of heat treatment. These results were explained by considering the interaction of external constraint and volume contraction which occurs during heat treatment.