2. Glass fiber

Definition: A family of reinforcing materials for reinforced plastics based on single filaments of glass ranging in diameter from 3 to 19 micrometers (0.00012 inch to 0.00075 inch). Single filaments are produced by mechanically drawing molten glass streams. Next, the filaments are usually gathered into bundles called strands or rovings. The strands may be used in continuous form for filament winding; chopped into short lengths for incorporation into molding compounds or use in spray-up processes; or formed into fabrics and mats of various types for use in hand coatings with a material known as a coupling agent, which serves to promote adhesion of the glass to the specific resin being used. Glass fiber reinforcements are classified according to their properties. At present there are five major types of glass used to make fibers. The letter designation is taken from a characteristic property: 1) A-glass is a high-alkali glass containing 25% soda and lime, which offers very good resistance to chemicals, but lower electrical properties. 2) C-glass is chemical glass, a special mixture with extremely high chemical resistance. 3) E-glass is electrical grade with low alkali content. It manifests better electrical insulation and strongly resists attack by water. More than 50% of the glass fibers used for reinforcement is E-glass. 4) S-glass is a high-strength glass with a 33% higher tensile strength than E-glass. 5) D-glass has a low dielectric constant with superior electrical properties. However, its mechanical properties are not so good as E-or S-glass. It is available in limited quantities. Glass fibers coated with nickel, by the electron beam deposition process, are used in molding compounds and as reinforcements for electrically conductive parts. The major disadvantage of glass fiber is its unidirectional reinforcement which leads to uneven shrinkage and warpage.