No matter what kind of coating process is used for the surface quality of automobiles, the surface quality of the plastic parts of the car body must meet the requirements of Class A. Therefore, plastics must have good processing fluidity. In addition, in order to ensure the smallest possible gap size between parts under extreme temperature conditions, the thermal expansion coefficient of the body plastic parts must be small. If the body plastic part is used as the skin of the metal substrate, the quality of the appearance can only be guaranteed when the thermal expansion coefficient of the substrate and the surface layer are close. Generally, the coefficient of thermal expansion of thermoplastics is much larger than that of steel. Fillers are generally added to reduce the coefficient of thermal expansion. However, the addition of fillers tends to always reduce the surface quality. Fiber-reinforced thermosetting plastics can mostly meet the requirements of car body structural parts in terms of strength and rigidity, but its surface quality is often difficult to meet the A-level requirements. In addition, it is difficult to paint fiber reinforced plastics.
Another option to solve this problem is to use an injection compounding process, that is, a highly filled plastic and a colored high-quality film/sheet are compounded by injection. The composite parts produced no longer need to be painted and can meet the requirements of Class A surface quality. BASF cooperated with other companies to study the injection and compounding of long-fiber reinforced ABS with polymethyl methacrylate and ASA co-extruded film to produce the tail cover (luggage compartment cover) of the car; GE produced a polycarbonate co-extruded film. Extruded sheet (model: Sollx), which has been used in the production of body parts for mini-cars 2 Current status of the application of plastics on car bodies 2.1 Plastics for body parts are light in weight, good in processability, high in design freedom, and multi-functional The ability of plastics to be integrated in the application of car body parts is one of the most interesting aspects of plastics as a body material. Especially in today’s era where individualization is emphasized, the style of the car has a great influence on the customer’s desire to buy. The plastics currently used as bodywork mainly include sheet molding compound (SMC), reinforced reaction injection polyurethane (PUR-RRIM) and glass fiber reinforced thermoplastics. All three types use glass fiber reinforcement, mainly to meet the rigidity requirements of the car body.
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