ABSTRACT

Plastic materials quite literally revolutionized the automobile industry, primarily because plastics offer many significant mechanical and manufacturing advantages over wood and metal components. They are easily moldable into complex shapes; they are almost entirely corrosion resistant; they can be produced in a variety of colors without the need for painting; they can be used in plating procedures to make lightweight chrome

parts; and they resist denting and fracture. They can be made very rigid and strong like polycarbonates, soft and durable like polyurethanes, and either opaque or clear, depending on the degree of crystallinity in the polymer. In general, amorphous materials like glass are clear, since they lack long-range ordered arrangements of atoms that can block light. Some of the disadvantages of polymers include a lower resistance to temperature than metals and the possibility for photochemical reactions that may degrade either the polymer structure or pigmentation. However, the low cost, light weight, and workability of plastics often outweigh the disadvantages. Since plastics are organic polymers, polymer chemistry and definitions are required to discuss the chemistry of plastics and plastic production. Some basic polymer definitions and example polymers used in automotive plastics can be found in Appendix C. It is recommended that a reader unfamiliar with polymers read this section before continuing on in this chapter.