Isotropic Carbon and Graphite Fibers from Chemically Modified Coal-Tar Pitch

A precursor for a general purpose carbon fiber was prepared from coal tar pitch (CP) modified with 10% p-benzoquinone (BQ) at 380°C for 3 hours. Such a modification raised the softening of the pitch from 85°C to 271°C at a yield of 43%. The modified pitch was spun smoothly at a rate of 480 m/min into a fiber of 20 μm diameter. The fiber was stepwise stabilized at 236°C (5°C/min) and 312°C (1°C/min) for 3 hours at each temperature. Successively, carbonization and graphitization were performed at 1,000°C and 2,400°C, respectively, for one hour. Both the carbonized and graphitized fibers exhibited tensile strength of 570 MPa. The structural parameters of carbon and graphite fibers were their orientation values of 56.2 and 58.1 %, relatively low Lc(002) of 11.24 and 25 Å, and large interlayer spacing (d₀₀₂) of 3.86 and 3.49 Å, respectively.