Infrared spectroscopy studies of the petroleum pitch carbon fiber—I. The raw materials, the stabilization, and carbonization processes

Abstract

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used for the characterization of the petroleum pitch, the green fiber, and the stabilization and carbonization processes of the petroleum pitch precursor carbon fiber. Various substituted aromatic ring structures, saturated and unsaturated aliphatic hydrocarbon groups, as well as small amounts of carbonyl and hydroxyl were detected in the green fiber. Both the saturated and unsaturated hydrocarbons were gradually oxidized during the stabilization process. The oxidation products included alcohol/phenol, ketone/aldehyde, carboxylic acid, ester and anhydride. Dehydration and elimination of carbonyls and hydrocarbons in the stabilized carbon fiber were detected in the carbonization process. The aromatic ring condensation started to take place when the temperature reached above 500°C. All the functional groups were eliminated at 900°C.