Polyurethane fascias

Extensive use of flexible polyurethane fascia on automobiles has established RIM (Reaction Injection Molding) as a viable plastic molding process. 

All the above factors taken together - damageability resistance, styling freedom, and weight savings - have led to a very rapid rise in the RIM polyurethane fascia and bumper cover market. Table I historically summarizes the market from 1977 to 1980. 

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. 

The first major growth of RIM processing, as noted earlier in this section, occurred in the United States with the development of automobile bumpers designed to meet Congressionally mandated safety standards in a 5-mph impact. Polyurethane fascia (a term applied to both the front and rear bumpers, as well as fenders and other automobile parts) were designed to cover steel beams mounted on shock absorbers. Later, glass-reinforced RIM (RRIM) products were introduced and applied to some fender and body parts. In 1987, about 150 million pounds (67, 500 metric tons) of material were used for the manufacture of RIM products in the United States. About half of this total is polyether polyol, and about half was used in automobiles. 

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. 

Polyurethane, thermoplastic TPU has excellent properties except for heat resistance (usually only up to 250°F 121°C). It is used in alloys with ABS or PVC for property enhancement. Typical uses are in automobile fascias and exterior body parts, tubing, cord, shoe soles, ski boots and other oil and wear resistant products. 

Polyurethanes Expo 99. Conference proceedings. Orlando, FI., 12th-15th Sept. 1999, p.377-82 NEW ERA OF POLYURETHANE RECYCLING -FASCIA TO ROOF RAIL SUSTAINABLE RECYCLING IN AUTOMOTIVE APPLICATIONS You K K Chang L P Witte E A Prokopyshen M H BASF Corp. DaimlerChrysler Corp. 

Low modulus elastomers are materials that have found wide use in the automobile industry for fascia, bumper covers, and trim parts. Other applications include integral window seals and a wide variety of applications where it is replacing molded rubber. Most of these materials are not pure polyurethane, but polyurethane/polyurea hybrids with improved processing and properties when compared with the earlier allurethane systems. 

Table VI contains the general properties for 50-60% HARD SEGMENT polymers. This table contains polymers which have been developed in the past such as the Polyurethanes in the 55 to 65 Shore D hardness (Fascia materials), as well as Poly(urea-urethanes) which are more recent developments. This hard segment range also covers 65 to 75D intermediate modulus materials which are in reality toughened plastics. The raw materials prices are for comparison purposes.

Polyurethane RIM (PU-RIM) was selected for the Initial RIM application of automotive fascia not only because 1t provides the required damage resistance and other performance requirements, but also because the reactivity of the urethane raw materials, Isocyanate and polyol, provide acceptable productivity. Because the urethane mnomers can be nucleated, high quality sink free surfaces that are suitable for automotive exteriors are produced at the time of demold. Little, 1f any, post mold surface repair 1s needed 1n preparation for painting the RIM part. 

RIM polyurethane elastomers are a natural to meet the regulations. The process is highly suitable for producing complicated large, thin fascia to cover the entire front end... 

MAJOR INGREDIENTS OF RIM ELASTOMERIC POLYURETHANES FOR FASCIA APPLICATIONS... 

AVERAGE USAGE OF MAJOR COMPONENTS OF RIM FASCIA POLYURETHANE SYSTEMS... 

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. 

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... 

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