Formation of non-graphitizing carbon fibers prepared from poly(p-phenylene terephthalamide) precursor fibers

Abstract

The effect of carbonization temperature on the structure and properties of poly(p-phenylene terephthalamide)- based carbon fibers from commercially available Twaron00AE; (PPTA) presursor is reported. Turbostratic PPTA-based carbon fibers were produced using a single step procedure in an inert atmosphere at temperatures ranging from 600 to 1100 °C. In the present study, fiber diameter, mass yield, density, elemental analysis, X-ray diffraction, Raman spectroscopy, tensile testing and electrical conductivity measurements were performed and evaluated to follow and monitor the properties and structural transformations of carbon fibers with rising temperature. The increase of heat-treatment temperature to 1100 °C. decreased the interlayer d-spacing (d002) and increased the in-plane size (La) and thickness (Lc) of the graphene layers. The intensity ratios of D to G bands in the Raman spectra increased with rising temperature, suggesting, in agreement with the X-ray diffraction measurements, that the in-plane size (La) of the graphene planes increased with temperature. The density, carbon content, C/H ratio, apparent crystallite size (La and Lc), electrical conductivity and tensile properties of the resultant carbon fibers were enhanced with rising temperature. It has been shown that the gage length of the carbon fibers tested has a significant effect on the tensile strength obtained. After taking into account the effects of gage length and porosity dependence, the carbonization of PPTA precursor fibers prepared at 1100 °C. gave a tensile strength of 191 MPa and a tensile modulus of 83 GPa, respectively.