Modification of coal tar pitch by solvent extraction for high density C/C composites

Abstract

C/C composites have excellent mechanical and thermal properties even in extreme environments. Thus, they are used in various fields such as aircraft, automobiles, rockets and etc. The characteristics of the raw materials are very important to reduce the swelling or pores that occur during the carbonization. In this study, the properties of coal tar pitch were controlled, one of the raw materials for C/C composites, using three solvents (acetone, toluene, and tetrahydrofuran (THF)). Using the solvent extraction method, the insoluble (CTP-AceI, CTP-TI, CTP-THFI) and soluble (CTP-AceS, CTP-TS, CTP-THFS) are separated and used as a binder and impregnation pitch, respectively. As a result, when CTP-TI is used as a binder, density is 1.75 g/cm3, which is the highest. And the highest density appeared in the order of CTP-TI, CTP-THFI, CTP-AceI, and CTP-Raw. This coincided with the order in which β-resin, which is an important parameter for binders. Additionally, the volatile matter that causes swelling could be reduced from 22.33 wt% to 9.30 wt%. Thus, the swelling was suppressed efficiently. When CTP-AceS was used as the impregnation pitch, the density was 1.89 g/cm3, the impregnation rate was 60 %, and the porosity was 2.5 %. The impregnation rates were higher in the order of CTP-AceS, CTP-TS and CTP-THFS. This is because QI reduces fluidity and interrupt penetration into pores.