Bumper, automotive polymers

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. 

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. 

Information is presented in some detail on Du Pont Polymers proeess for reeovery of used polyesters from produets sueh as automotive bumpers. The process is reported to use a methanolysis teehnique and is reported to be able to separate pure monomer ingredients from reinforeed, painted or otherwise eontaminated polymers. DU PONT DE NEMOURS E.I., ... 

Blends are physical mixtures of polymers. Depending on the extent and type of blend the properties may be characteristic of each blend member or may be some blend of properties. Immiscible blends are phase-separated with the phases sometimes chemically connected. They are generally composed of a continuous and discontinuous phase. HIPS is an example of an immiscible blend. Miscible blends occur when the two blended materials are compatible. Often the properties are a mixture of the two blended materials. The plastic automotive panels and bumpers are generally made from a miscible blend of PE and a copolymer of PE and PP. 

Reaction injection molding (RIM) is a fast, low-pressure, low-temperature, low-cost process for one-step conversion of reactive liquids into large finished solid plastic products. Liquid polyol and liquid diisocyanate are mixed by impingement, pumped instantly to fill a large mold cavity, and polymerize/ cure rapidly to form a thermoset polyurethane product. The cured polymer may be a stiffly flexible product such as automotive bumper covers, front ends, and trim or a rigid foamed product such as furniture and housings (cabinets) for computers, business machines, TY and radio. 

Major polymer applications automotive, car bumper, wire insulation, hose tube, sheet... 

The automotive industry started to use plastics in 1946. Since then, its content steadily increases (see Figure 16.4). Today, the plastics for automotive apphcations are dominated by polymer alloys, blends, and composites. The reason for it is the need for automotive parts to show a wide range of performance characteristics that are virtually impossible to meet using a single-component polymer. Thus, for example, in Saturn, front fenders and rear quarter panels are from PA/PPE, door outer skins are from PC/ABS, the bumper fascias are TPO, etc. 

Rubbers have physical characteristics and a chemical composition that precludes their successful identification by infrared spectroscopy due to their inherent elasticity and highly filled composition. In contrast, no such difficulties are encountered with Py-GC. Crime scene rubber evidence from automotive tires and rubber vehicle components is found in hit-and-run cases and in soles of shoes worn by offenders in offenses against property. Discrimination of vehicle bumper rubbers by Py-GC has been reported. Volatile and polymeric components of rubbers and other polymers have been analyzed by Py-GC and the inorganic residue recovered for subsequent analysis. The technique may also be used to quantitate rubber blends by measuring the ratios of characteristic pyrolysis products. Figure 8.8 shows examples of the pyrograms of three common types of rubber. 

Blending two or more polymers offers yet another method of tailoring resins to a specific application. Because blends are only physical mixtures, the resulting polymer usually has physical and mechanical properties that lie somewhere between the values of its constiment materials. For instance, an automotive bumper made from a blend of PC resin and thermoplastic polyurethane elastomer gains rigidity from the PC resin and retains most of the flexibility and paintability of the polyurethane elastomer. For business machine housings, a blend of PC and ABS (acrylonitrile—butadiene—styrene copolymer) resins offers the enhanced performance of PC flame retar-dance and ultraviolet (UV) stability at a lower cost. 

---