Microstructure of Pitch-Based Carbon Fibers

Abstract

Graphitized carbon fibers for use in composite materials have been made from pitch for several years. 1,2 Two types of pitch have been used for producing carbon fibers. Aromatic pitch, which is isotropic, needs a high strain rate and rapid quenching to spin into a highly oriented fiber. The other type, known as high molecular weight pitch, forms an anisotropic liquid (mesophase) upon heating and spins at a relatively low speed to form oriented fiber. Usually commercial pitch contains both of these types. The pitch is melt-spun so that the mesophase will form rod-like elongated fibrils embedded in an isotropic matrix. The fiber is oxidized to thermoset the isotropic pitch and then carbonized and graphitized at higher temperature to form a completed 1Oμm diameter carbon fiber.