Production and sintering of mesophase pitch from anthralene oil

Abstract

When certain oils and polymers are heated under an inert atmosphere, a high viscosity liquid forms. Examples include crude oil, coal tar, and PVC. Upon further heating, this liquid becomes a progressively harder solid called pitch. Pitch that contains crystalline areas is called mesophase pitch. Mesophase pitch is required for the production of graphite. The purpose of the research was to investigate whether anthracene oil can be used for the production of mesophase pitch for sintering purposes. Sintering involves heating a powder under pressure to produce a solid. Anthracene oil is a low-value by-product of coke production from coal. Despite its low market value, it has unique properties. It consists primarily of polycyclic aromatic hydrocarbons and it is free of primary quinoline insoluble material. Polycyclic aromatic hydrocarbons are the precursors for mesophase pitch formation, while quinoline insoluble material hinders mesophase growth. These attributes make it a good potential starting material for the production of mesophase pitch, which may be used for sintering and carbon fibre production. In the search for a mesophase pitch that can be sintered, a variety of pitches were produced from anthracene oil. This was done by varying the heat treatment time and temperature. The pitches produced were characterised to determine their glass transition temperature, melting temperature, carbon yield and optical microstructure. This was done to determine their sintering potential. A high mesophase content, high softening temperature and high carbonisation yield were considered essential for effective sintering. Pitches with a high mesophase content were produced. Longer heat treatment led to higher carbon yields, higher glass transition temperatures, higher softening temperatures and higher mesophase content.