INFRARED-SPECTROSCOPY STUDIES OF THE PETROLEUM PITCH CARBON-FIBER .2.THE DISTRIBUTION OF THE OXIDATION-PRODUCTS BETWEEN THE SURFACE AND THE BULK

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used to study the distribution of the oxidation products between the s urface and the bulk of the precursor carbon fiber during the stabiliza tion process, and to evaluate the degree of oxidation in the near surf ace of the stabilized fiber. The distribution of the oxidation product s is homogeneous during the first 70 min of the stabilization process. In the last 10 min of the process, however, the near surface of the c arbon fiber is completely oxidized, whereas the bulk has a lower degre e of oxidation. It was also found that incomplete oxidation in the nea r surface of a precursor carbon fiber may cause inferior mechanical pr operties of the fiber. An increase in the rate of temperature increase in the programmed stabilization process reduces the degree of oxidati on in both the near surface and the bulk of the precursor carbon fiber . In this research, FT-IR/PAS has demonstrated the ability to differen tiate the near surface of a carbon fiber from its bulk. It is a useful technique for the analysis of carbon fibers.