FIGURE 3.5 High-performance alloys are now used extensively in the demanding exterior body applications of automobiles. For example, front fenders are molded from a PPO-nylon alloy that can withstand paint oven temperatures of 400°F and above. They are chosen for their class-A surface, dimensional stability, impact strength, and corrosion and chemical resistance. The side claddings on these vehicles are molded of a resin that is a polyester-polycarbonate alloy, chosen for its cold temperature impact strength, chemical resistance, and quality surface. For the front and rear bumper fascias, a copolyester elastomer is used, characterized by its cold temperature ductility, class-A surface, chemical resistance, and on-line paintability at temperatures exceeding 280°F. More than 60 pounds of engineering thermoplastics can be found on many of the vehicles. SOURCE: Photograph courtesy of GE Plastics, Southfield, Michigan.

Toughening by the addition of rubber was first practiced for commodity polymers, such as polystyrene, poly(vinyl chloride), polypropylene, and poly(methyl methacrylate) (PMMA). Widely different processes and product designs were required to achieve optimal products. Now this approach is being applied to engineering thermoplastics and thermosets in order to move these materials into applications that require stringent mechanical performance under demanding conditions. This ensures an excellent growth opportunity for a variety of toughening agents. Elastomers with low glass transition temperatures are needed to impart toughness at low use temperatures, while thermal and oxidative

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