Observations Concerning the Carbonization of Viscose Rayon Yarn

Abstract

The course of carbonization of continuous filament viscose rayon yarn was followed, using various experimental techniques. The disappearance of the cellulose hydroxyl function in the early stages of carbonization was determined by chemical means, and the factors of weight loss, shrinkage, carbon level, and resistivity were also determined. In addition, observations of selected samples using DTA and scanning electron micros copy techniques were also carried out. The experimental data indicate that the reaction which occurs at 230-260°C involving a major loss in weight of the viscose is preceded by a cross-linking reaction involving the cellulosic hydroxyl groups. As the treatment temperature is increased, the yarn undergoes various other changes in properties, including a sharp reduction in resistivity beginning at a temperature of approximately 500°C. After exposure at approximately 1400°C, the carbon content of the yarn increases to a level of approximately 95%. Examination of the surface of carbon fibers with the scanning electron microscope shows a relatively unmarked surface bearing similar striations to the viscose precursor.