Evaluation of naphthalene-derived mesophase pitches as a binder for carbon-carbon composites

Binding properties of the mesophase pitches produced catalytically from naphthalene with HF/BF₃ were examined in terms of their carbon value, fluidity, thermal stability and oxidative stabilization reactivity. The present pitches with 100% anisotrophy and low softening points of 207-275°C provided very high coke yields of 80-88 wt% under atmospheric pressure and 90-95 wt% under 30 atm. Pitches with softening points of 207 and 224°C exhibited strikingly low viscosity below 1 Pa{black diamond suit}s at 350°C. It is noted that viscosity-temperature profiles of a series of the present pitches cover the complete area of the processing window for the manufacture of carbon-carbon composites, whose processes typically include impregnation of mesophase pitch into a two-dimensional carbon fiber preform, oxidative stabilization and successive carbonizations. The pitches were thermally stable under nitrogen at 300°C, keeping the melt viscosity constant for longer than 100 h to assure easy handling. At the same time, they were very reactive for the oxidation in air at 200°C for rapid stabilization.