Bumpers

Bumper pads Bumpers Bump materials BunaN... 

Electroplating. The second-largest appHcation for nickel chemicals is as electrolytes ia nickel electroplating (qv). In ordinary plating systems, nickel present ia the electrolyte never forms on the finished workpiece the latter results from dissolution and transfer from nickel anodes. Decorative nickel plating is used for automobile bumpers and trim, appHances, wire products, flatware, jewelry, and many other consumer items. A comprehensive review of nickel electroplating has been compiled (164). 

Automotive appHcations account for about 116,000 t of woddwide consumption aimuaHy, with appHcations for various components including headlamp assembHes, interior instmment panels, bumpers, etc. Many automotive appHcations use blends of polycarbonate with acrylonitrile—butadiene—styrene (ABS) or with poly(butylene terephthalate) (PBT) (see Acrylonitrile polymers). Both large and smaH appHances also account for large markets for polycarbonate. Consumption is about 54,000 t aimuaHy. Polycarbonate is attractive to use in light appHances, including houseware items and power tools, because of its heat resistance and good electrical properties, combined with superior impact resistance. 

PC-PET better chemical resis-tance, processibihty. tubing, auto bumpers, and business 335,336, 313... 

As with SMC, appHcations are limited to high volume because of the capital investment in equipment and tooling. Thermoset compression molders require additional heating and material Handling equipment to adapt their process to thermoplastic sheet fabrication. AppHcations include automotive bumper beams, load floors, radiator supports, battery trays, and package shelves. Chair sheUs, military containers, material Handling pallets, trays, and concrete foaming pans are also produced. 

By employing additives to improve interfacial adhesion and the cohesive strength of the mbber phase, natural mbber can compete with ethylene—propylene mbbers as an impact modifier for polypropylene. These hard grades, containing between 15 and 25% natural mbber, have the potential for use in the automotive and domestic markets, eg, in bumpers, spoilers, grilles, electrical connectors, and floor tiles. 

The polyDCPD has good flexural modulus and exceUent impact resistance (61). Current uses for polyDCPD are in golf carts, snowmobiles, and automotive bumpers (62). The polymer is viewed as having a high potential, especially in automotive body panel appHcations. 

Butyl-type polymers exhibit high damping, and the viscous part of the dynamic modulus is uniquely broad as a function of frequency or temperature. Molded mbber parts for damping and shock absorption find wide appHcation in automotive suspension bumpers, auto exhaust hangers, and body mounts. 

Considerable amounts of EPM and EPDM are also used in blends with thermoplastics, eg, as impact modifier in quantities up to ca 25% wt/wt for polyamides, polystyrenes, and particularly polypropylene. The latter products are used in many exterior automotive appHcations such as bumpers and body panels. In blends with polypropylene, wherein the EPDM component may be increased to become the larger portion, a thermoplastic elastomer is obtained, provided the EPDM phase is vulcanked during the mixing with polypropylene (dynamic vulcani2ation) to suppress the flow of the EPDM phase and give the end product sufficient set. 

The properties of PBT and PC resins and of a blend of these two resins are given in Table 18. The chemical resistance of crystalline PBT is reduced, but that of amorphous PC is increased. Hydrolytic stabiUty is good throughout. Impact performance is lower than that of the components. It can be improved by modifiers. A commercial example of this type of resin blend is the General Electric Xenoy resin which is used in automotive bumpers. 

Friend, W.H., Murphy, C.L., and Shanfield, I., Review of Meteoroid-Bumper Interaction Studies at McGill University, National Aeronautics and Space Administration Contract Report No. NASA CR-54857, Cleveland, OH, 187 pp., August 1966. 

If (as with body panels) elastic deflection is what counts, the logical comparison is for a panel of equal stiffness. And if, instead, it is resistance to plastic flow which counts (as with bumpers) then the proper thing to do is to compare sections with equal resistance to plastic flow. 

Both thermoplastics and thermosets can be formed by compression moulding (Fig. 24.5). The polymer, or mixture of resin and hardener, is heated and compressed between dies. The method is well suited to the forming of thermosets (casings for appliances, for instance) and of composites with a thermosetting matrix (car bumpers, for example). Since a thermoset can be removed while it is still hot, the cycle time is as short as 10 seconds for small components, 10 minutes for large tliick-walled mouldings. Pressures are lower than for injection mouldings, so the capital cost of the equipment is much less. 

Polyamide PPOs are manufactured by General Electric (Noryl GTX), BASF having now withdrawn from marketing their product (Ultranyl). Usage of the blends has so far been mainly in the automobile field for such applications as valance panels, wheel trims, grilles, rear quarter panels, front bumpers and tailgates. 

Blends of PBT with polycarbonates have been widely used for car bumpers. Interest in PBT/PET blends and PBT/ASA has arisen because of the good surface finish possible even with glass-reinforced grades. Copolyesters based on PBT but with some longer chain diol or acid are also now produced. 

The RIM process was originally developed for the car industry for the production of bumpers, front ends, rear ends, fascia panels and instrument housings. At least one mass-produced American car has RIM body panels. For many of these products, however, a number of injection moulding products are competitive, including such diverse materials as polycarbonate/PBT blends and polypropylene/EPDM blends. In the shoe industry the RIM process has been used to make soling materials from semi-flexible polyurethane foams. 

The development of new polymer alloys has caused a lot of excitement in recent years but in fact the concept has been around for a long time. Indeed one of the major commercial successes of today, ABS, is in fact an alloy of acrylonitrile, butadiene and styrene. The principle of alloying plastics is similar to that of alloying metals - to achieve in one material the advantages possessed by several others. The recent increased interest and activity in the field of polymer alloys has occurred as a result of several new factors. One is the development of more sophisticated techniques for combining plastics which were previously considered to be incompatible. Another is the keen competition for a share of new market areas such as automobile bumpers, body panels etc. These applications call for combinations of properties not previously available in a single plastic and it has been found that it is less expensive to combine existing plastics than to develop a new monomer on which to base the new plastic. 

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