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Compounds Target Tough Problems
Design issues include ethanol, cost
Design News Staff -- Design News, August 8, 2008
The low-hanging fruit for new plastics' applications is largely gone. Design engineers are now asking suppliers to develop specialty materials aimed at solving very specific problems. Among the solutions are compounds for chrome plating, electronic housings and chemical pumps.
The use of two materials in one component where only one material is plated is a recent development in chrome plating. Sabic Innovative Plastics has a unique combination of materials that offers selective plating. When Xylex X7509 or X8409 resin grades are combined with the special Cycoloy and Cycolac resin grades and chrome plated, the Xylex resin will remain completely free from plating.
A new BASF nylon is dimensionally stable and absorbs almost no water. The development of Ultramid T included Bosch's sensor and ignition development departments, BASF's project managers in Germany and the U.S., and a car manufacturer.
TREND TOWARD CHROME
There's a resurgence of chrome in trim, door handles and other decorative touches to impart a high-end, luxury look to new cars. Special grades of Cycoloy polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) resin and Cycolac ABS resin feature low stress and superior adhesion to the metal layer and are aimed at helping automakers easily incorporate jewel-bright chrome details into designs.
Higher yields are especially important due to the relatively high cost of chrome plating. In addition, the use of plated plastic components versus all-metal parts avoids the expense of secondary operations including milling and polishing. Lightweight plastics also help with weight-out for improved fuel economy. Finally, plastics offer greater design flexibility than traditional metal. Chrome plating can be unforgiving in terms of quality. Even the slightest defects can create a negative impression of the entire vehicle. Target applications include exterior trim, interior trim, running boards, wheel covers, roof racks and mirror housings that require stiffness, impact strength and processability.
WEAR-RESISTANT PPS
A customized wear-resistant polyphenylene sulfide (PPS) compound from RTP Co. is being used by Tuthill Transfer Systems, a manufacturer of pumps and meters for the fast transfer of petroleum fuels and agricultural and industrial chemicals. Tuthill wanted to improve the plastic chamber of its Sotera chemical pump, which is designed to transfer thin to thick products including slurries and encapsulated chemicals. Fluids and chemicals such as weed and insect control chemicals, automotive fluids, mild acids and a variety of industrial materials can easily flow through the Sotera system. Re-designing the plastic chamber required rugged chemical-compatible materials. Wear resistance was also a critical requirement for improving the life of the product. “RTP customized a wear-resistant PPS compound with the best additives to meet the product needs,” says Dick Curtin, president of Tuthill Plastics Group. PPS is a crystalline polymer with a symmetrical, rigid backbone chain consisting of recurring p-substituted benzene rings and sulfur atoms.
NEW PLASTIC FOR ETHANOL
A new fuel tank pressure sensor from Robert Bosch GmbH uses BASF's Ultramid T KR 4355 G7, a partially aromatic polyamide (PA 6/6T) that fulfills a new and crucial requirement for materials used in electronic housings. Any material that comes into contact with modern fuels has to be able to resist not only gasoline but also water and alcohols such as methanol and ethanol. These substances are found in the tank, especially due to the emergence of flex fuels that contain alcohol. The new polyamide (also called nylon) can withstand the presence of zinc chloride. At the underbody area the sensor may come into contact with this zinc salt that can be formed at the zinc-plated car body due to splash water.
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