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Old Rubber, Better Parts

This year, a new material developed in Detroit, its maker says, recycled 18,500 tires, removed five million pounds (cumulative) from seven domestic platforms, and saved one customer $185,000 annually-all from one plant.

Recycled Polymeric Materials, Inc. (RPM; Detroit, MI) is located in a seen-better-days section of Detroit in a building that formerly housed a tire distributor. This is ironic considering that the polyurethane product RPM makes within uses 25% post-consumer crumb rubber–the stuff that used to be tires. And that seals made from this substance take 1.5 lb out of Ford’s Taurus and Sable, and outperform the EPDM vulcanized rubber closures it replaces.

Technically, RPM produces parts from a recycled rubber polyurethane elastomer (RRPE) that utilizes an ambient temperature, reaction injection molding process. The isocyanate part of the mixture is bought on the global market, but the polyol (polyhydric alcohol) component is part of a proprietary blend that requires strict adherence to a unique recipe, and contains the crumb rubber. “We use a minimum of 25% recycled crumb rubber,” says Reuben Tandoh, one of RPM’s research and development chemists, “but the higher the density of the material, the more recycled rubber content we can use.” So mud flaps would have a higher concentration than interior foams, for example.

“Functionality and dimensional stability are of prime importance in many products, but especially when it comes to seals,” says Dennis Askew, New Business Development account manager. “The harsh underhood environment can wreak havoc on the seal material, and cause it to fail.” In testing conducted by RPM, their RRPE material outperformed EPDM in a number of tests. For example, heat resistance–measured as a change in compression deflection–was +5% after seven days at 70ºC and again at 22 hours at 125ºC. This compared to a +13% and +16% change for EPDM, which was still well under the OEM requirements of +30% and +25%, respectively. Similarly, compression set–the difference between the initial and new part height after compressing it to 50% of its original thickness–was down by 2.5% after 22 hours at room temperature, and 4.9% after 70 hours at 70°ºC for the RRPE. EPDM, on the other hand, lost 19% and 24% of its original thickness, respectively. “We can, therefore, design a piece that has an optimal circumference for a pass-through item,” says Askew, “and add a taper or bevel to the opening to decrease installation force to an acceptable level because we know our material won’t lose its shape.”

Its test for fluid resistance–in which the material’s resistance to gasoline, brake fluid, windshield washer solvent, anti-freeze, power steering fluid, transmission fluid and diesel at 70°ºC is measured–showed a marked difference between the RRPE and EPDM parts. Though OEM requirements demand no dimensional change, the EPDM pieces swelled to many times their original size after this particular test, while the RRPE parts looked and felt new. “When we show this to potential customers,” says Askew, “it really opens their eyes.”

Another eye opener are the material’s environmental benefits. The room temperature process doesn’t consume the energy found in a typical vulcanizing process, or use virgin rubber material. And the corrugated cardboard and release paper used to separate stacks of vulcanized parts also are eliminated. Says Askew, “We not only eliminated nine tons of landfill at one OEM’s plant, we can take any scrap and grind it up and reuse it.” Plus, die-cut pieces can be replaced by direct application of the material in a mold, which cuts both waste and cost.

RPM’s chemists are currently at work on RRPE engine mounts and encapsulated suspension pieces. “These have the most stringent requirements,” says Askew, “which is why we decided to tackle them first.” One domestic OEM currently imports an encapsulated suspension bracket from Germany at a cost Askew says is close to $7.00 per piece. “We can undercut that by 20%, and provide the same performance characteristics,” he claims before telling how variations on this material are being formulated for seat, armrest, and instrument panel foam; floor mats; carpet backing; and molded NVH and splash shields. “Give us a component and we’ll build a business case for it.”