ABSTRACT
Polyaramid fibers, such as Kevlar, are polymeric textile fibers. They have stiffness and strength intermediate between that of glass and graphite, and they have great potential for reinforcement purposes due to their excellent specific stiffness and strength. As in the case of graphite, they are available in tows or yarns of various weights and may be converted into woven cloth and chopped mat products. Glass fibers are manufactured by drawing molten glass from a die to form a strand of fibers. Graphite and carbon fibers are prepared from polymer precursors, mainly polyacrylonitrile and cellulose but also from pitch. In general, graphite fibers are more easily handled than glass so that elaborate finishes are not necessary. The as-manufactured fibers are usually subjected to a surface treatment which is designed to improve the adhesion between fiber and matrix in the final molded product. With the exception of asbestos, reinforcing fibers are first manufactured in the form of continuous filaments.
