Characterisation of coal tar pitches by thermal analysis, infrared spectroscopy and solvent fractionation

Abstract

Four commercially available coal tar pitches have been characterised through the combination of conventional techniques used for pitch characterisation, like elemental analysis and solvent fractionation, and infrared spectroscopy (FTIR) and thermal analysis (thermogravimetry (TG)-differential thermal analysis (DTA)). The results obtained from this set of experiments provide suitable information to establish differences between the materials according to their industrial origin and preparation method. The differences found are a consequence of the distinct chemical composition of the pitches (determined by FTIR), as well as the dissimilar chemical interaction that exists between the molecules of different fractions of the parent pitch (evidenced from DTA). These observations are responsible of the clear differences found between a given pitch and its respective insolubles, and affect their applications, i.e. in the area of carbon fibre preparation.