Reinforced Plastics

Only a few years ago，the term reinforced plastics was used to refer to a group of low-pressure molding materials fabricated by using a thermosetting resin to coat or impregnate a cloth, random fiber, or continuous filaments. Now, the term is used to designate any resin type, either thermosetting or thermoplastic，which has some type of reinforcing material incorporated with the resin. The result is a compounded raw material ready to be processed by injection, compression, transfer, or extrusion. If the raw material is thermosetting and in sheet form, it may be stamped, die cut, or hand cut to make layer type preforms for molding in a hot mold. Reinforced thermoplastic resin is generally pelletized for hopper loading into an injection machine. It should be obvious that the term reinforced plastics covers a wide range of materials and a wide range of applications. Switch gear parts, automobile components (particularly body parts), air frames, and aircraft panels are only a few of the many possible applications. The fibrous reinforcements covers the entire range of fibers, such as aramid, glass, carbon, thermoplastic (such as acrylic and nylon), and the hybrid combinations of any of the foregoing.

Note that fillers and extenders may be fibrous in nature, but the resulting material would not be termed reinforced plastics. Fillers and extenders generally refer to low-cost (as compared to the cost of the resin) materials such as clay, wood-flour, minerals, etc. Reinforcing fibers may be considerably more expensive than the base resin, and in all cases increase the difficulty of processing into marketable molded parts. The requirements of the precise application are the determining factors in the choice of the base resin. Then, the degree and purpose of reinforcement determines the choice of fiber and its method of preprocessing prior to compounding with the resin. Books on fibers and reinforcement are readily available to cover this extensive field.