DETROIT - General Motors 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. A nanometer is one-billonth of a meter.
The composite will be used on as many as 200,000 2004 model year 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," says William Rodgers, a research scientist for GM's nanocomposites group. "Now we're talking about real commercial volumes."
The body side molding on the 2004 Impala went into production last year - about 18 months after the material first was used in the steps on GMC Safari and Chevrolet Astro vans.
The nanocomposite study teamed GM researchers with those from Basell Polyolefins-Automotive 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," said Alan Taub, executive director of GM's Research and Development Science Labs in Warren, Mich.
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 says.
GM must continue adjusting, to adapt for shrinkage rates in trim that will be painted in the assembly plant along with the rest of the vehicle. Other refinements will be needed to prepare the material for interior use, he says.
