NOVEL COMPOSITES BY HOT COMPACTION OF FIBERS

The production of solid section products from highly oriented fibers b y a novel compaction procedure is described for melt-spun and gel-spun polyethylene fibers, poly(ethylene terephthalate) and polypropylene f ibers and Vectran liquid crystalline copolyester fibers. Differential scanning calorimetry and electron microscopy have been used to study t he structure of the compacted polymers. For the most successful compac tion, selective surface melting of a small fraction of each fiber enab les the formation of a fiber composite of high integrity, where the ma trix phase is formed by epitaxial crystallization of the melted fracti on on the initial fibers, retaining a high proportion of their initial strength and stiffness. A nide range of potential applications is env isaged for the composites produced by hot compaction, In many cases th ese composites will be produced by thermoforming. In addition to the o bvious advantages of high stiffness and strength, in several instances the unrestricted exploitation of unique properties of the fibers such as transparency to microwave radiation or low thermal expansion coeff icients offer additional incentives for the use of these hot compacted materials rather than conventional fiber/resin composites.