Automotive bumpers

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. 

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. 

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. 

Automotive bumpers, grills, handles, over-riders, hubcaps, exhaust trim, locks, aerials, ash-trays, knobs. 

Polyurethane, thermoset TSUs have du-rometers range from soft cushion to glass hard with superior wear resistance. Use includes skateboard wheels, solid tires, floor coatings, marine finishes, etc. A major use for soft-foam is automotive bumpers another is upholstery. Property improvements are made with different added fibers and fillers in... 

The basic steps of the IM process produce unique structures in all molded products, whether they are miniature (micro) electronic components, compact discs, or large automotive bumpers. These structures have frequently been compared to plywood with several distinct layers, each with a different set of properties. In all IM products, a macroscopic skin-core structure results from the flow of melt into an empty cavity. Identifiable zones or regions within the skin are directly... 

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., ... 

Adhesion of, e.g., paint on polymeric materials such as in automotive bumper material may be poor because of silicon grease being present at the surface as a result of handling the bumper before applying the paint. By using ESCA such problems can be tackled easily and customer complaints can be refuted or accepted. 

TPO applications are in automotive bumpers and dashboards because of their higher toughness than conventional polypropylene copolymers. 

The advantages offered by the use of expanded polypropylene in automotive bumper cores and other applications are considered, and its properties are compared with other materials traditionally used in such applications in terms of impact strength, energy absorption, resilience, and compressive strength. 

Details are given of planned capacity increases in expandable polypropylene by the JSP Gronp, in both the US and Europe. A doubling of combined prodnction capacities is planned for the material which is nsed in the foam of automotive bumper core materials. 

HIPS is an immiscible blend that is used in many applications and was employed as material for many of the automotive bumpers. The PS portion is strong and inflexible, whereas the polybutadiene particles are flexible allowing an impact to be distributed over a larger area. The polybutadiene rubbery portion allows the bumper to bend and indent and protects the PS from fracturing while the PS phase resists further deformation. This combination gives a strong flexible material. 

Addition of about 1% of an EPM is used today to achieve most of our multiviscosity oils. These copolymers were developed as part of Exxon s program that Ed Kresge and fellow researchers were involved with that also produced the miscible blends used to make automotive bumpers and panels (Section 7.8). 

As noted earlier, new materials must fight-it-out with existing materials for existing and developing areas. This is particularly true in the automotive area. Thus, PE-PE-copolypro-pylene panels and bumpers have replaced rubber HIPS as automotive bumpers. Other materials were available with greater toughness and scratch resistance, but they were also more expensive. Here, classical monomers were employed to develop nonclassical materials. 

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. 

With the pressures in the mixing head at between 1,500 to 3,000 psi (10.3 to 20.6 MPa), the in-mold pressures are significantly lower than in many of the other molding processes. When comparing a typical RIM in-mold pressure of 50 to 150 psi (0.4 to 1.1 MPa) with the 5000 to 30,000 psi (34.5 to 206.7 MPa) required for thermoplastic injection molding (Chapter 4), it becomes apparent why RIM is particularly suitable for larger parts. Automotive bumpers are routinely produced on RIM presses with 100 to 150 tons of clamping force, while comparable injection molded parts require presses of 3500 tons or more. 

The most important commercial blends of BPA-PC are poly(acrylonitrile-butadiene-styrene) (PC/ABS) and polybutylene terephthalate (PC/PBT) or polyethylene terephthalate (PET). Commercial grades of PC/ABS include CYCOLOY (GE), Bayblend (Bayer), and PULSE (Dow). PC/ABS blends exhibit improved flow and processability and enhanced low-temperature impact strength in comparison to PC (Fig. 3). These blends are widely used in applications requiring enhanced impact resistance, such as interior automotive parts and computer and electronics applications such as computer housings and cell phones. Non-halogenated flame-retardant PC/ABS blends are widely available. Poly(acrylic-styrene-acrylonitrile) (PC/ ASA) blends (GELOY , GE Luran , BASF) provide improved weatherability for outdoor applications such as exterior automotive parts, but exhibit reduced impact performance at low temperatures in comparison to PC/ABS. PC/PBT or PET blends (XENOY , GE Makroblend , Bayer) provide enhanced chemical resistance and weatherability for applications such as lawn and garden equipment and automotive bumpers and fasdas. 

The use of polyurethane elastomers for automotive bumpers and body parts is a rapidly growing transportation market. 

Symalit GMT. [Symaliti MBS Mastics] Glass mat leMorced tiiennqdastics for automotive bumper systems, front end, under-hood, underbody panels. 

PC/PBT low temperature impact, dimensional stability, and chemical resistance. Apphcations in automotive bumpers. 

The current annual consumption of TPO blends in transportation alone is 50 Mton/y in the USA and is projected to grow at >10%/yr [Spencer, 1990]. The use of TPOs in automotive bumper covers is expected to grow even more at an annual rate of about 30% [Evans and Mosier, 1991]. 

Typical applications in development with these PP/PS alloys include automotive bumper beams, pillars, sporting and recreational equipment, sledge hammer handles and other consumer tools appliance components. The lighter weight (lower... 

PP/EPDM automotive bumpers since the early 1990 s, bumper recycling has been commercial in Europe)... 

PVC botties, roofing sheets, blister packag-ings, window profiles PBT/PC automotive bumpers PA containers, hub cups, electrical and electronic housings... 

Bexloy W Du Pont lonomeric alloys — Automotive bumper... 

In this temperature range, the viscosities of the two components are very similar and the mechanical shear can be effectively transferred to the mixture to enforce a good dispersion of the phases. Intensive mixing and high homogeneization levels are especially important when, for quality reasons, the modifying capability of the elastomer has to be optimized. This is the case, for instance, of the new family of elastomer modified polypropylene which has opened a major market for plastic materials in the field of the automotive bumpers. For this highly innovative utilization a severe set of properties has to be ensured by the material and in particular ... 

Resin type Automotive Body not/. Automotive body white Automotive bumper Low prof. V. high FR... 

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