EXAMINATION OF THE OXIDATIVE STABILIZATION REACTION OF THE PITCH-BASED CARBON-FIBER THROUGH CONTINUOUS MEASUREMENT OF OXYGEN-CHEMISORPTION AND GAS-FORMATION RATE

Stabilization is an important step for producing pitch-based carbon fiber. In this paper, gas formation rates and weight change during oxidative stabilization, which is most commonly employed as the stabilization method, were measured continuously for three pitch-based yarns, using a mass spectrometer and a thermogravimetric analyzer, respectively. From these measurements, change in the amount of oxygen incorporated in the yam could be estimated continuously and accurately. A large difference was found between the amount of incorporated oxygen measured by the presented method and the amount estimated from only weight change. The amount of oxygen incorporated during the oxidative stabilization was found to be fairly large (12.3 similar to 17.6 wt%), and was almost equal to the amount of H2O produced. The changes in the micropore distribution and the oxygen functional groups of the yam during the stabilization were measured. Step response experiments of O-18(2) were also performed to examine the mechanism of gas formation. Based on these measurements, the mechanism of the oxidative stabilization was discussed.