Production of carbon fibers by the direct carbonization of polybenzimidazole fiber

Abstract

An improved process is provided for readily transforming a relatively low denier (i.e. 0.5 to 10 denier per filament) polybenzimidazole fibrous material to a carbonaceous fibrous material which contains at least 90 percent carbon by weight. The polybenzimidazole fibrous material initially is reacted with a solution of an acid (as described) to form a polybenzimidazonium salt, and the fibrous material subsequently is heated in a non-oxidizing atmosphere to form the carbonaceous fibrous material which retains the original fibrous configuration intact. A preferred acid solution for use in the present process is a dilute solution of sulfuric acid. The resulting carbon fibers are useful as fibrous reinforcement in the resinous or metallic matrix material.

Description