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Syndiotactic potystyrene (SPS) is a new semi-crystalline polymer under development by Dow Plastics, a business group of The Dow Chemical Company. The material is differentiated from conventional styrenic polymers in terms of microstructure and physical properties and represents the basis for an entirely new family of materials derived from crystalline polystyrene. SPS exhibits excellent thermal performance with a melting point of 270° C (520° F) combined with resistance to moisture and automotive fluids. Products produced from SPS demonstrate exceptional electrical performance, low specific gravity, competitive toughness and high modulus relative to other semi-crystalline engineering polymers. A wide range of products have been formulated including impact modified and glass reinforced resins for use in specific markets.

Thermoplastics are rapidly gaining acceptance throughout the automotive industry as an attractive alternative to steel for exterior automotive body panel applications. The transition from steel to thermoplastic is driven primarily by the unique balance of physical properties derived from this new class of engineering polymers. These properties include corrosion resistance, dent resistance and reduced production costs. However, it is recognized that thermoplastic parts must be designed such that the stresses imposed on the component in service are minimized. By minimizing the strain and corresponding stress, the designer could help prevent problems associated with cracking induced by solvents or constraint at the panel attachment locations. This paper proposes a new methodology for analysis of full field stresses in thermoplastic exterior body panels. The methodology utilizes photoelastic stress analysis techniques to define areas of maximum stress in injection molded components.

Environmental stress crack resistance, ESCR, of several candidate plastics for instrument panels was studied using both constant load and constant strain methods. Poly-carbonate/ABS blends demonstrated significantly better ESCR properties than the polystyrene modified polyphenylene oxide system. The mechanism of failure was followed using SEM microscopy which showed that the load carrying phase was polycarbonate. Furthermore, a fracture mechanics study under dry conditions and in the presence of the aggressive environment was done. The data, based on the critical stress intensity factor in and away from the stress cracking environment, explains the behavior of polycarbonate/ ABS blends relative to the modified polyphenylene oxide system.