Preparation and Composition Analysis of Modified Asphalt for Preparing Carbon Fiber from Coal Direct Liquefaction Asphalt

The modified asphalt with high softening point was prepared by air oxidation polymerization with coal liquefied asphalt as raw material. The quality control model regarding the coking value and softening point of the product were established based on the DFSS (Design for Six Sigma) and RSM (response surface method). By means of elemental analysis, infrared, XPS, XRD, nuclear magnetic, MALDI-TOF and other characterization methods, the composition and structure characteristics of the modified asphalt were analyzed. Using the target product as raw material, general base asphalt carbon fiber was prepared by spinning, pre-oxidation and carbonization. The results show that the fitting effect of the quality control model about the coking value and softening point of the product is good, and the operating window range of the polymerization process parameters corresponding to the preparation of target product is wide. It can be found that the oxidation time and oxidation temperature has the most significant effect on the coking value and softening point of products, respectively, and all of them show a positive correlation. The dealkylation reaction and oxidative crosslinking reaction were carried out at the same time, and the bridging products of methylene bridging products, ether–oxygen bonds, carbonyl bonds, anhydride bonds and other oxygen-containing groups were generated. The properties of carbon fiber prepared with the target product are better: the tensile strength is 775 MPa, the elastic modulus is 68.6 GPa and the elongation at break is 1.13%.