Preparation of microbead from coal tar pitch with chemical modification

In this study, microbeads were prepared by heat treatment of the mixtures of two kinds of pitches which have different molecular weights. They were THF (tetrahydrofuran) soluble coal-tar pitch(CP) and that of chemically modified(MCP) with 30 wt.% benzoquinone for 1 hour at 150 degrees C, 250 degrees C. The compositions of CP/MCP chosen were 3/7, 5/5, 7/3 wt.% ratio. The microbeads were separated by solvent extraction with pyridine. The concentration of the pyridine insoluble increased with an increase in MCP concentration. All the samples in 30 minutes showed isotropic under polarized light microscope, however, the microbeads were observed in the 5/5 (CP/MCP) sample with isotropic property under SEM. With an increase in heat treatment time, following behaviors were observed: an increase in fraction of pyridine insoluble, growth in bead size, coalescence of the beads; ultimate transformation to bulk mesophase. Microstructure and optical textures of carbonized products were characterized by using X-ray diffractometer and polarized light microscope. With an increase in concentration of MCP, the stack height (L(c002) value) reduced, which represents that the molecules of high M(w) suppressed the mobility of molecules resulting mosaic texture.