Effect of the thermal stabilization temperature on the change in the texture of polyacrylonitrile fiber

The effect of temperature of isothermal treatment on the change in sizes $L_{010}$ of coherent scattering regions and texture of a polyacrylonitrile fiber during its transition to the structure of a thermally stabilized fiber is analyzed using X-ray structure analysis. An increase in the thermostabilization temperature at a constant stretching load stimulates simultaneously a more active increase in size $L_{010}$ and texturing of polyacrylonitrile fibers at the initial stage. Active evolution of the phase transformation at temperatures 275–290$^\circ$C during further thermostabilization is accompanied by a substantial decrease in the texture of the polymer that has not experienced the phase transformation by this instant.