Ahmad K Elshennawy, George F Schrader
Published By: SME
This chapter presents the fundamentals of nonmetallic materials, including plastic materials, plastics processing, design of plastic parts, and ceramics. Manufacture of plastics is economical because most products can be entirely finished by molding and forming without secondary operations. A plastic may be in one or more of three forms in the raw material state. First are powders, flakes, or granules for molding plastic pieces. Second are liquids for castings, impregnated laminates, adhesives, paints, and mixed molding compounds. Third are the filaments, films, sheets, rods, and tubes to be fabricated into finished articles, such as by weaving into cloth, cutting and joining into wrappers, or machining. One major class of plastics, called the thermoplastic materials, is composed of materials having chemically separate long molecules. A second major class of plastics, called thermosetting materials, is composed of materials having long molecules linked to each other in three dimensions by primary or valence bonds. There are other forms of plastic materials such as elastomers (rubbers), siliconses, and adhesives. Plastic objects are formed by compression, transfer, and injection molding. Other processes are casting, extrusion and pultrusion, laminating, filament winding, sheet forming, joining, foaming, and machining. Others forms of nonmetallic materials include clay products, glass, cermets, and ceramic cutting tools. Because of their high electrical resistance and magnetic properties ceramics are suitable for certain applications.