Bumper fascia

The need to paint the blends has also resulted in new painting systems. Recently, a nonpolar color coat based on a hydrogenated polybutadiene diol and melamine resin for TPO bumper fascia was invented. The breakthrough technology allows the elimination of the TPO pretreatment step such as adhesion promoter, flame, or plasma during manufacturing. The paintability of two different types of E-plastomers was evaluated. The olefinic white paint was found to provide excellent paint adhesion for both types of metallocene plastomers. Paint peeling was not observed in any of the test... 

Bumpers, bumper fascias, exterior trims, headlight casings and rear light bases, spoilers, step pads, body side mouldings, wheel trims. .. 

Moulded-in-colour film laminate technology for bumper fascias. 

ABS/TPU blends are used mostly for automotive parts, e.g., paintable, soft bumper fascias. They are mosfly formed by injection molding or extrusion. 

Bumper fascias (TPO) are increasing in surface area and becoming more integrated into the body design. Thinner bumper fascia will require plastic to be stilfer, have better melt flow characteristics and still meet -30°C impact strength requirements. 

Reactor TPOs, reportedly offering better combination of toughness and stiffness, are gaining increasing penetration into the automotive market, in both the soft bumper fascia applications as well as other rigid applications replacing the more expensive engineering resins. 

A recent commercial blend of ABS contains thermoplastic polyurethane elastomer as the main blend component. The blend was introduced in 1990 by Dow Chemical Co., under the trade name Prevail . These blends characteristically exhibit low modulus (340 to 1000 MPa) and high impact strength at low temperamres, e.g. notched Izod values of 370 to 1500 J/m at -29°C. The TPU component of the blend imparts high toughness and also allows paintabihty without a primer. ABS component imparts heat resistance (for paint ovens) and good tensile strength in the blend. The blend is projected to find applications in the automotive markets, particularly as paintable, soft bumper fascias. Typical properties of commercial ABS/TPU blends are shown in Table 15.6. 

PBT/polycarbonate blend, first introduced in 1980 by General Electric (Xenoy ) has enjoyed a fast growth in automotive applications, particularly for bumpers. The blend was developed to meet the low temperature impact strength, dimensional stability and paintability requirements of rigid bumper fascias [Bertolucci and Delany, 1983], which accounted for the bulk of the current market volume for the PBT/PC blend (estimated 25 kton/y in the USA). The development of commercial PET/PC blends followed shortly after the initial success of PBT/PC blends. Currently there are several commercial blends of both PBT/PC and PET/PC blends available. 

Commercial PBT/copoly(ether-ester) blends are generally richer (> 50%) in the copoly(ether-ester) elastomer content. These blends were designed for the automotive, flexible bumper fascia market (Bexloy V, DuPont). Typical properties of these blends are shown in Table 15.32. Typically they exhibit low moduli (< 800 MPa), high elongation and toughness. The purpose of PBT in the blend is to lower the cost and improve the heat sag resistance required for paint oven capability. 

PBT/copoly(ether-ester) elastomer blend molded parts exhibit excellent surface finish and good paint adhesion without the need for primers. About 3 kton/y of this blend is being used for painted, flexible bumper fascias in selected luxury model cars in the USA. Because of the excellent surface esthetics of the blend, molded-in colors are also being evaluated to reduce the painting costs. Lower levels (< 20%) of copoly(ether-ester) elastomers have also been blended with PBT for high impact strength molding resin applications (Celanex , Hoechst-Celanese). 

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. 

Toyota, in conjunction with several Japanese resin compounders, recently introduced a super TPO, which consists of polypropylene islands in a rubber matrix. The resulting TPO is softer, ahs better scratch resistance, and is more easily molded for bumper fascia and interior applications than standard TPO products. 

There is considerable competition between materials in automotive markets. For example, a major shift is taking place from polyurethanes to TPO for bumper fascia. The TPOs, with molded-in color capability, light weight, relatively low cost, and ease of recycling, are poised to capture a large share of the fascia market both in North America and Europe. A significant cost saving is possible with a TPO fascia, especially if it is not painted. A polyurethane fascia, by contrast, must always be painted, which adds some 60% to the cost of a fascia. 

Many of the factors responsible for shifts in bumper fascia are also behind similar changes in side-body moldings. Various grades of TPO have effectively displaced PVC in this application. 

There is no single method for treating polymethane (PUR) waste, due to the different quantities, qualities, mixes, and cleanliness. It is estimated that some 125,000 t of RIM polyurethane is used worldwide, 85% in automotive parts, mainly in bumper fascias. Current technologies for physical recycling of PURs are mainly directed towards flexible and rigid foams, but systems have also been developed for recycling reinforced reaction injection molded (RRIM) PURs, on the... 

Stiffness plus low-temperature impact With their use growing at about 10% per year, TPOs can provide varying levels of impact resistance and varying flexural modulus values and are tailored for particular applications, from the most extreme exterior bumper fascia parts to softer interior components (Chapters 7 and 8). Other additives pair these properties with scratch-resistance (Chapter 17). 

An excellent example of a compatible system is the 1997 Buick Park Avenue bumper/fascia system. The fascia is a TPO material and the energy absorber is PP foam snap fit to the aluminum bumper beam. Signal markers and trim strips are also snap-fit for easy removal. Therefore, a large amount of compatible material can be quickly removed from it for recycling. There has been a trend toward molded-in-color fascias on certain types of vehicles. These not only reduce mass but also eliminate the environmental burdens associated with painting. Molded-in-color fascias have been used on a variety of small cars and some sport utility vehicles. 

Having been first commercialized in 1972, EPDM/PP TPOs are used mainly in external antomotive and electrical applications np to 80°C. Automotive uses include exterior trim such as bumpers, fascia, and nonsealing moldings however, under-the-hood nses are generally exclnded because of temperature and fluid-resistance requirements in the engine compartment. 

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