Oxidation kinetics of polyacrylonitrile-based carbon fibers in air and the effect on their tensile properties

Polyacrylonitrile-based carbon fibers are oxidized by air at temperatures from 400 to 700 degrees C. The mass loss, morphology, graphitic structure and residual properties are investigated. The activation energy is about 111 kJ/mol and is independent of carbonization temperature. With increasing oxidation temperature, the crystallite height decreases gradually, while the d(002) spacing increases presumably due to combination of oxygen with carbon. The tensile strength decreases significantly, while the tensile modulus remains nearly unchanged. The increase in carbon fiber density after oxidation suggests that glass-like carbon in the fiber is easier to burn off than the more graphitic carbon. (C) 2011 Elsevier Ltd. All rights reserved.