SYTHESIS OF BORON SUBSTITUTED POLYAROMATIC MESOPHASE

Boron substituted polyaromatic mesophase was synthesized by co pyrolysis of a coal tar pitch with pyridine borane complex at the pressure of 1 MPa,pyrolysis temperature of 400 ℃ and reaction time of 10 h. The boron contents in raw material were increased step by step up to 3 %. The effects of the boron content on the properties and microstructure of the resulting polyaromatic mesophases were investigated. It was found that although the yield of mesophase pitches decreased with the increase of boron content at the starting mixture at the same reaction condition, the yield of microbeads increased gradually. The diameter of microbeads decreased. The results indicate a cross linking effect of boron in the formation of mesophase pitches.