10/1/2001 | 4 MINUTE READ

Nano for Auto

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There are some big benefits to the use of the nanocomposites. Recyclability is enhanced. A fraction (~3% volume) of the filler ordinarily used can do the job; less filler means recycling is comparatively simplified.

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Mr. Spock of Star Trek fame came from the planet Vulcan. Ostensibly, that is a place with an advanced civilization, comparatively speaking. (OK: so Star Fleet was based on Earth. But you know that with Spock’s Pentium-style mind, Vulcan has to be quite the cutting edge locale.) The word “Vulcan” comes from the Latin Vulcanus. Which was applied to the Roman god of fire, Vulcan.

While some of you might be thinking that there must be some mistake here, as though the musing of a Star Trek fan has made its way into the wrong venue, here’s the point of this speculation about the planet Vulcan: It is an advanced place because of volcanoes. That’s right, volcanoes. Why? Because of the abundance of smectite that would be available on a volcanic planet. Smectite? Yes. It is the name of a family of minerals from which nanoclays come from. Nanoclays? These are organic materials derived from volcanic ash (along with other constituents such as aluminum, silicon, magnesium, and iron) that have oxidized under some very specific atmospheric conditions, conditions like those that existed on Earth some 85 million years ago. Put all of those things together, and voila! a montmorillonite material. A nanoclay.

Where am I going with this? To the step-up on a 2002 Chevy Astro or GMC Safari full-sized van. Because those step-ups are being molded by Blackhawk Automotive Plastics with a new material devised by researchers from GM working in association with Basell, a producer of polymers jointly owned by BASF and Shell; and Southern Clay Products, a supplier of smectite-based additives. The material is a thermoplastic olefin (TPO) nanocomposite.

“It’s not often we get to introduce a new structural material in our market,” says Alan I. Taub, executive director of science for GM Research and Development. According to Taub, this new material has promising application in a variety of external and internal automotive applications. Among them are cladding, body side moldings, rocker covers, sail panels, and toolbox covers.

(And as a side note, it is interesting that this development has been made in fairly short order: a joint development program began between GM and Montell, which is now subsumed into Basell, in June 1997. The optional van step-ups—bona fide production parts, not test parts—are being produced right now. While the vans may have a limited life span—according to Taub, they will be produced at least until sometime in ’03—it is said to be “enough commitment to learn” about the materials.)

Although “nano” means billion—as in a nanometer being one billionth of a meter—here are a couple of more picturesque ways to think about nanoclay, courtesy of Robert Briell, chief scientist for Southern Clay Products. One of the materials typically used to reinforce TPO is talc. As in powder. A very fine talc granule, which measures on the order of 1 to 2 microns, is “a boulder” compared to a nanoclay particle.

Or consider this: five grams of nanoclay can cover a football field.

One of the tricks of the nanocomposite is the way the clay disperses into the polymer. Homogeneous distribution of the filler is important to composite performance (simply put: You don’t want clumps in some areas and straight resin in others). Another analogy from Briell. Consider a big, thick dictionary. Ordinary fillers are like the dictionary. The 2D crystalline nanoclay is like a page in that dictionary. The technical description is “sheet morphology.” A method has been developed so that the “pages” are shingled throughout the TPO; this is known as “clay exfoliation.”

While it might seem that because the particles are a whole lot smaller than conventional fillers (on average, a thousand times smaller) that more nanomaterial would be needed, Taub says, “They have huge surface areas relative to the other additives we use, like talc, and the result is exceptional improvements in the properties of the plastics with only a fraction of the inorganic filler.”

There are some big benefits to the use of the nanocomposites. Recyclability is enhanced. A fraction (~3% volume) of the filler ordinarily used can do the job; less filler means recycling is comparatively simplified.

The parts can achieve the same stiffness with a fraction of the filler. The parts can be as much as 20% lighter (in the case of the step-up, the weight reduction is 7.5 to 8%). And they are less brittle in cold temperature than conventional filled TPOs.

No new equipment is necessary. Although “nanocomposites” sound exotic, there is no need for exotic tool-ing or molding machines to process parts. At the Blackhawk Automotive Plastics plant in Mason, Ohio, where the step-up is being molded, the same equipment is being used as had been for the traditional TPO part. Mark Bennett, technology manager for the company, says it was a “direct drop in.” He goes on to note that the change in material has resulted in some processing benefits. Cycle times are improved; slightly lower temperatures are needed; lower pressures are needed; the molds fill better. Over all, he says, the parts produced are better.

Importantly, these benefits are being achieved without a cost penalty. Taub says that today they are “cost neutral” on a part. It is anticipated that with more experience in engineering with the material and greater material use there will be further cost reduction.

Just imagine the amazing cars they must have on Vulcan.

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