Nanocomposite TPOs at GM

Together with Montell North America, GM R&D has been developing a nanocomposite TPO material suitable for exterior and interior automotive applications. Using the new technology, the partners have already produced prototype rear quarter and exterior door panels with further plans to develop additional applications for the TPO.

Currently, the new material (a proprietary grade of Hifax) is undergoing validation testing at GM, and the results are positive. According to Montell's Theo Zwygers, it consists of a sub-micron smectite clay in a TPO substrate. "Nanocomposite means the clay-reinforcing particle is at the nanometer level [10-9 m] in size," Zwygers says. "For comparison, if one nanoparticle were thumbnail-sized, talc particles would be basketballs, and glass fibers would be 5 ft in diameter. We've found that by using smectite clay in TPO, we can enhance physical properties without increased weight, loss of low temperature properties, or opacity."

Specifically, the research has proven that with only 5 percent clay, the resulting material has stiffness characteristics equal to 25 to 35 percent talc-filled TPO. Compared to conventional 25 percent talc-filled olefins, TPO nanocomposites offer a 20 percent weight reduction with equivalent stiffness, improved dimensional stability, and increased low-temperature impact performance. From a processing standpoint, the nano-TPO parts are molded on conventional injection presses with no modifications necessary. A lower filler level will also enhance recyclability, according to Montell's Bill Windscheif. "Achieving high stiffness with just 5 percent clay loading means that when recycled, the nanocomposite will actually enhance properties of the recyclate," he says. Also, because of its stiffness, the new TPO may be able to replace ABS and PC/ABS in the interior, facilitating a monomaterial strategy among OEMs.

To make the new TPO, Montell first exfoliates the clay, breaking it up as if it were a deck of cards broken into each individual card, to increase surface area. Then Catalloy chemistry is applied to make the TPO polymer compatible with the filler. Although this specific Hifax grade is dedicat-ed to GM, Windscheif confirms the nanocomposite technology will be translated into the Hifax family some time in the near future.