Study of the kinetics of thermal stabilization of a polyacrylonitrile fiber

Results are presented from studies of the change in the internal stress of a polyacrylonitrile fiber during heat treatment. It is shown that the increase in stress during deformation and heat treatment and its decrease during relaxation can be explained by representing the structure of the polymer in the form of stable and unstable grids superimposed on one another. The sub-units of the grids are formed by chains of the amorphous phase, the stable nodes are formed by crystallites and chemical bonds, and the unstable nodes are formed by microscopic blocks of the amorphous phase and van der Waals interactions.