Improving stabilization degree of stabilized fibers by pretreating polyacrylonitrile precursor fibers in nitrogen

Polyacrylonitrile fibers were heat-treated in nitrogen before oxidation to make the nitrile groups cyclized partially, and then were sufficiently stabilized and oxidated in air atmosphere. Fourier transform infrared spectroscopy showed that the stabilization degree of the stabilized fibers was improved by 2.9% and more conjugated nitrile groups were formed by heating precursor fibers in nitrogen, when the resultantly modified and conventionally stabilized fibers were stabilized to the same density of 1.39 g/cm(3). Thermal gravimetric analysis of the resultant stabilized fibers showed the carbon yield at carbonization of 900 degrees C was enhanced by 1.7% attributed to the higher stabilization degree. The crystallite width and mechanical properties of the resultant carbon fibers were improved compared to the carbon fibers manufactured by the conventional method. (C) 2012 Elsevier B.V. All rights reserved.