General Motors Corp. is jump-starting its use of nanocomposites, planning to employ an estimated 500,000 pounds of a thermoplastic polyolefin with nanometer-sized filler on exterior trim in its best-selling car.
The composite will be used on as many as 200,000 Chevrolet Impalas - a big move up from its first automotive appearance, in fewer than 10,000 optional minivan step assists.
``We needed a small-volume application to start with, but that gave us the confidence going forward,'' said William Rodgers, a research scientist for GM's nanocomposites and magnetorheological materials group.
``Now we're talking about real commercial volumes,'' he said.
The body side molding on the 2004 Impala went into production late last year - about 18 months after the material first launched in the steps on GMC Safari and Chevrolet Astro vans.
The nanocomposite study teamed GM researchers with those from Basell Polyolefins and Southern Clay Products Inc. to produce a thermoplastic using reinforcements on the microscopic level. The minute particles of the clay additive measure one-millionth of a millimeter thick, allowing for a lighter final component.
``We have much higher reinforcement properties because the action is taking place at the molecular scale,'' Alan Taub, executive director of GM's Research and Development Science Labs in Warren, said during a Jan. 27 news conference there.
The development team had to tweak the formula as it moved from the step assist to the side molding, in part to compensate for the color in nanocomposites compared with standard talc-filled material, Rodgers said. GM must continue adjusting, to adapt for shrinkage rates in trim that will be painted in the auto assembly plant along with the rest of the vehicle. Other refinements will be needed to prepare the material for interior use, he said.
The TPO is 7 percent lighter than standard reinforced components - a slight savings on a narrow body molding, but one that will come into play more as nanocomposites make it onto bigger parts such as bumper fascia.
``The driver has been ... weight and surface appearance,'' said Jeff Leone, senior vice president of Basell Polyolefins-Automotive.
Basell is compounding the resin, molded at Blackhawk Automotive Plastics, on production lines in Jackson, Tenn., that have been modified slightly for the filler. As demand for the material increases, Leone said he expects that the firm will refine the manufacturing process in screw designs and feeding systems.
While the material is very new for GM and its development partners, Karl Kamena, commercial manager for Gonzales, Texas-based Southern Clay, said that with each use, the future of nanocomposites improves.
``The more visible the application, the more exciting it is,'' Kamena said. ``This is a very significant step forward.''
Taub said GM and its researchers still are discovering new opportunities in nanocomposites.
``We are going to concentrate, and you'll see a series of applications going forward,'' Taub said. ``Logistical and technical issues are there, but we are well on the way to solving them. Materials are an enabler for our industry.''