Influence of Coexistent Materials on the Formation of Carbonaceous Mesophase in Pitch (2)

Abstract

Meso-carbon microbeads were added in various pitches; coal-tar pitch, quinoline soluble coal-tar pitch (QS coal-tar pitch) and asphalt pitch, and these pitches were heat-treated at 400-430°C. A correlation between the microbeads added and the mesophase formed in pitch was investigated by using a polarized light microscope.The obtained results are follows;(1) In the case of addition of the microbeads of Type-M in QS coal-tar pitch, the growth of Type-M is observed but new mesophase is not formed in the pitch. For Type-P in QS coal-tar pitch, new mesophase spherules are formed in the pitch and their growth is predominant rather than the growth of Type-P . This is similar to the case of addition of Type-C and Type-M in asphalt pitch. From these results, it is considered that the growth of the added microbeads as well as the coalescence of new mesophase and the added microbeads requires similarity in molecular structure between pitch and meso-carbon microbeads.(2) In the case of addition of the microbeads of Type-C, Type-P and Type-M in coal-tar pitch containing metaphase, the microbeads added do not grow, and new mesophase spherules surrounded with metaphase are nucleated and grown. Thus the metaphase in pitch plays an important role in the formation of mesophase . In particular, the formation of mesophase spherules at the surface of metaphase in pitch is predominant than at the surface of microbeads themselves or of metaphase on Type-M. From these results, it is suggested that the metaphase in pitch has active site on itself for the formation of mesophase.(3) In the case of addition of Type-P in coal-tar pitch or addition of Type-C and Type-M in asphalt pitch, the microbeads added are dispersed in the pitch over the wide range, and coalesced with new mesophase formed in the pitch. It seems that coal-tar pitch is able to mix and melt homogeneously with asphalt pitch through the medium of mesophase.