Stabilization time and temperature influence on the evolution of the properties of mesophase pitch stabilized fibers and carbon fibers

Abstract

The structure of a mesophase pitch carbon fiber is primarily developed during the fiber spinning process and is refined in stabilization and carbonization steps. Stabilization of mesophase pitch filaments was performed in a thermogravimetric apparatus (TGA) using a multivariate approach to investigate the influence of the initial and final temperature of stabilization and the step time on the changes that occur during the stabilization stage. Different levels of stabilization were observed: insufficient, proper, and over-oxidation. Through Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Photoelectron Spectroscopy (XPS), it was found that the chemical composition of the stabilized fibers was highly dependent on the mass evolution of this thermal treatment. Excessive stabilization induced defects in the structure of the fibers that negatively reflected on their tensile strength and modulus. Stabilization at lower final temperatures led to low mass increase but in turn provided carbon fibers with the highest modulus. Carbon fibers differing solely in their initial stabilization temperature did not exhibit statistically different tensile strength and modulus, proving that industrial stabilization can be shortened without compromising the fibers' properties.