Where Miles is headed in RIM & engineering thermoplastics.

The slate of key technology developments for the Polymer Div. of Miles Inc., includes recycled RIM polyurethane automotive parts, Class-A SRIM body panels, intensified focus on Apec HT polycarbonate and polymer alloys utilizing thermoplastic polyurethane, and a push to commercialize plastic/metal hybrid structural components.

Recent interviews with company executives at Miles' Pittsburgh headquarters pinpointed these key focal points of current material and process R&D. Some of these developments have been individually previewed by the company during recent months, targeting commercial applications for the mid- to late-1990s. In the main, they are directed at the automotive sector, a key market for Miles.

RECYCLED RIM AUTO PARTS 

This year a 100% recycled RIM component will be introduced on a commercial domestic automotive platform, utilizing grinding and compression molding technology developed by Miles' German parent, Bayer AG.

The recycled part, an air deflector, fits behind the front bumper and manages air flow into the radiator. Currently in the final test development stage, it's believed to be the first fully recycled polyurethane RIM part to be specified for a commercial U.S. vehicle. (Similar recycled RIM parts last year won specification on BMW 850 models in Germany.)

The new application was developed jointly by Miles, one of Detroit's Big Three car builders, and an unnamed domestic molder. It involves compression molding of reground polyurethane RIM auto fascias. A key aspect of the process is "roll grinding" technology, developed by Bayer.

Scrap RIM fascias are roll-ground into a powder of about 300-micron average particle size. The powder is preheated to 320-350 F; the thermoset powder does not melt and remains dry and flowable. It's then compression molded in a tool heated to around 300 F. The urethane crosslinks chemically break and reform under heat and pressure, so that the regrind material flows and fills out the tool, producing a part in a 90-sec cycle.

CLASS-A SRIM PARTS

Miles is continuing development of "Class-A" SRIM technology, looking to capture automotive applications now using SMC. The company previewed this innovation at last year's SAE show in Detroit (see PT, April '92, p. 19) . Miles engineers say they can actually improve on the surface quality of SMC with Class-A SRIM, besides offering up to 30% weight savings. However, they concede that SMC so far maintains a stiffness advantage over SRIM.

Miles is working closely with an unnamed car company on developing horizontal body panels such as deck lids and hoods, with potential commercial applications targeted for the 1995 time frame.

Miles' approach to Class-A SRIM utilizes a proprietary, finely woven glass-fiber surfacing veil, which covers the part's structural glass mat, thus preventing a read-through of the glass fibers onto the part surface. Class-A technology development also involves Miles' Hennecke Machinery division.

NEW EMPHASIS ON APEC HT

After making the "painful decision" last year to drop its Tedur PPS line, Miles' is focusing on Apec HT polycarbonate as a main thrust in the high-temperature engineering thermoplastic arena, according to H. Lee Noble, president of Miles' Polymer Div (see PT, May '92, p. 83). Noble says Miles is refocusing development efforts on Apec HT. New products anticipated in coming months include flame-retardant, glass-filled, and uv-stable grades.

A proprietary copolymerization technique (combining a special bisphenol with standard bisphenol A) enables Miles to tailor the temperature performance capability of Apec HT, according to Peter R. Muller, v.p. of sales and marketing. Muller says the material now has an end-use temperature range that extends up to 390 F.

Bayer is negotiating with Albis Plastic GmbH, a plastics compounder in Hamburg, Germany, on sale or licensing of the Tedur linear PPS technology. It's anticipated Albis might market Tedur grades in North America, once negotiations are finalized. Albis (with offices in Rosenberg, Texas, and Pickering, Ontario) also is the North American distributor of Bayer's Pocan PBT and Petlon PET. Miles (then Mobay) ceased its own efforts to sell TP polyesters here in 1990.

ALLOYS WITH TP URETHANE

Muller identifies Miles' Texin thermoplastic PU as a key resin technology to be exploited in the company's future alloying efforts, especially as an impact modifier for PC. Texin will be an alloy ingredient in new injection molding, blown film extrusion, and blow molding grades, to be introduced in coming months.

Bayblend PC/ABS and Makroblend PC/PET are additional areas of Miles' alloy/blend development. The company will introduce this year Makroblend DP4-1377, which includes a proprietary flame retardant said to provide reduced windshield fogging in car interiors.

METAL/PLASTIC HYBRID

Another key research project for Bayer's and Miles' is developing a new plastic/metal hybrid concept for structural applications in automotive load-bearing parts, such as doors, instrument panels, and under-skin support members.

The process involves loading a perforated steel sheet into an injection mold, where it's overmolded with thermoplastic to provide structural ribbing as well as hinges and mounting points. Plastic flows through the metal perforations to form rivet-like bonds. Besides automotive, the concept has potential in household appliances, office equipment, and sporting goods.

Muller says the concept already has prompted several secret development projects, some aimed at commercial applications for 1995/96 vehicles. Current development work, going on both in U.S. and Germany, involves using Miles' Durethan BKV-130, an impact-modified, 30% glass-filled nylon 6 as the matrix resin.