Bumpers paint

Typical products are elastomer modified heterophasic copolymers (heco), as compounded or reactor TPOs. Talc, typically below 20%, is added for higher stiffness and lower coefficient of thermal expansion (LCTE). The latter is an important condition for zero-gap concepts, in which the bumper follows very closely the line of the body fascia. Now that bumpers painted in body colors have become a standard feature, paint adhesion and enhanced surface finish have become important criteria. These can be influenced by optimizing the polymer structure and rubber content. The recycling aspects are treated in the chapter on Bumper recycling technology in this book. 

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., ... 

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... 

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. 

Hard metal that is white in pure state but brilliantly colored as compounds in trace amounts it gives gems their colors used in paints, automobile bumpers, and stainless steel. 

These common uses only hint at all the things that transition metals can do. The copper penny, for instance, is mostly made of zinc, another transition metal. Chromium provides the shiny, mirror-like metal coating on chrome car bumpers, but is also added to some lasers to make their light shine red. Nickel and chromium combine in an alloy that can be coiled into the wires that heat toasters and hair dryers. Titanium dioxide is a very white reflective compound used in toothpaste and paints. The transition metal cadmium is used in brilliant and permanent colors such as cadmium yellow, red, and orange. Artists have used cadmium-based paints for hundreds of years, and manufacturers used the colors more recently in plastic products. However, the colors are rarely used now that scientists have discovered that cadmium pollution can cause cancer and other health problems. 

In Europe, car manufacturers first used a half product, a sheet molding compound (SMC) made of sheets of fibers pre-impreg-nated with resin. In the USA they used a different process named RIM (Reaction Injection Molding) which allowed the bumper to be painted the same color as the rest of the structure. 

Thus far, the technology has been used only to paint the bumpers of a two-wheel personal transportation system called Segway. A thin film, when heated it can be molded into shapes that correspond to parts of a car. While the film will be more expensive than paint, the process eliminates the need for paint lines and uses a plant s existing molding equipment. GE Plastics expects to announce its first contract with a carmaker in 2004. 

Steamic OOS, OOS D - micronized and finely ground talc for PP dashboards and bumpers IN, Extra 5/O-MlO, Prever, M8, MIOC, M8C, M30 - talc from Val Germanasca mine in Italy for rubber and plastics Paint grades... 

In the winter of 1984-1985, test samples on Plexiglass plates were exposed in each of the test cities. These included samples of bare weighed auto-body steel, weighed galvanized steel, and painted auto-body steel with stainless steel trim. Where painted panels were involved, cut edges were coated in the stainless steel trimmed panels, the ends of the stainless steel bolts used for electrical continuity were coated as well. Nylon bolts were used to attach the other test specimens to the Plexiglass plate which was mounted on the front bumper of an automobile. 

The diisocyanates are reacted with diols to produce polyurethanes that end up in consumer products, such as seat cushions, mattresses, insulation, car bumpers, swim suits, floor coatings, paints, and adhesives.12 The aromatic diisocyanates are cheaper, but yield less light-stable polymers than the aliphatic ones. 

When this work began, an important application for TPU elastomers was in automobile exterior body components associated with impact absorbing bumper systems. Cold impact strength, resilience, resistance to heat distortion at paint oven temperatures and rapid injection molding cycles were all required. 

Polynrethane (PU) was first synthesized in the 1930s by German chemist Otto Bayer (1902-1982), who was trying to prepare a nylonfike fiber. PU is a versatile polymer that is used for rigid and flexible foams, bristles, coatings, fibers, and automobile parts, such as bumpers. Other synthetics are nsed in products such as stretchable fabrics and binders for paints. 

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. 

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). 

Subam was the first manufacturer to offer fuUy recyclable PP/TPE bumpers for all car models. To recycle, the bumpers are chopped into sections and placed between rollers rotating at different speeds. This removes 99% of paints and coatings. The sections are then re-stabihzed and granulated, ready for re-use. Similarly, Nissan aims for 100% bumper-to-bumper recycling of PPE/PA. Fiat has a policy of 100% recycling its TPO bumpers into automotive parts that do not demand similar level of performance, viz. air ducts, liners, etc. The PP battery cases are being recycled as fender liners. 

Low temperature brittleness to pulverize, e.g., paints off bumpers surfaces or PVC from metal trim at the cryogenic temperatures. The powders are then removed by sieving. 

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. 

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. 

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