Related: Automotive Materials
"My job is to develop future plastics for cars. We know that plastics come from petroleum currently, and that it is limited, and that it can become very expensive. Our job is to look for alternative materials and to start developing them now so that we have them available in the future," says Debbie Mielewski, Technical Leader of Plastics Research, at the Ford Motor Company.
Some of those alternatives are being deployed in Ford cars and trucks right now; they're not waiting for the future at Ford. And these alternatives are based on renewable resources, of which the supply isn't particularly limited. The latest in Ford's pursuit of material improvements takes the form of a polypropylene reinforced with 20% wheat straw. Yes, the stuff that's left over after wheat is harvested. Dr. Ellen Lee, a technical expert at Ford's Plastic Research, points out that the material has "no nutritional value. Sometimes it is used as filler for animal feed. Some of it is put back in fields as compost material. But the majority of the wheat straw is excess." In other words, this is not a material like corn, which opponents of ethanol production cite as being food being used for fuel.
As it turns out, the use of wheat straw is a consequence, in part, of where research on biomaterials was being done: at the University of Waterloo in Ontario, Canada, as part of the Ontario BioCar Initiative. Waterloo, Ontario, is about 74 miles west of Toronto, in a largely agricultural region. Which explains the availability of the wheat straw. In fact, there's approximately 30-million metric tons of the stuff available in the province.
The university researchers had been working with high-performance plastics supplier A. Schulman (aschulman.com; Akron, OH), on developing the wheat-straw reinforced materials.
Within about a year-and-a-half, the material went from a demonstration to a production application, the storage bins for the 2010 Ford Flex (which is built in the Ford Oakville, Ontario, Assembly Plant, approximately 56 miles away from Waterloo).
According to Lee, a part like the bin would ordinarily be produced with a talc-reinforced polypropylene, with the talc content ranging from 10 to 20%. "This part performs as well as one that is 20% talc reinforced, but it is 5% lighter, in addition to the environmental benefits."
When producing the material, the wheat straw, which comes in long strands, is chopped before compounding. "There is some aspect ratio to it," Lee says, adding, "but the fiber is very small." Still this is not unlike glass-reinforced plastics, Mielewski notes, as the glass fibers tend to get broken down to about 0.5-mm lengths. And, yes, this material can be recycled—"better than glass-reinforced," notes Lee.
They are investigating a number of materials, both plastic and other agri-cultural fibers. One of the reasons why the wheat straw works well with the poly-propylene is because the melt temperature of the plastic is sufficiently low so that it doesn't literally burn the straw. For example, Lee points out that nylon has a higher melt temperature, which would lead to "issues of thermal degradation and odor." So considerable attention is being paid to polyolefin materials.
As for reinforcing materials, Mielewski says that they're looking at a wide range of natural fibers, including sisal, Indian grass, and the fibers on the outside of a coconut shell. They're combining them with plastics and checking their mechanical properties.
One material that has been used for reinforcement is nanoclay, which is certainly a natural substance. Ford has looked at nanoclays, the researchers acknowledge, but while it is naturally occurring, it isn't particularly renewable (at least not in the scale of one's lifetime). In addition to which, they point out, nanoclay doesn't have the ability to sequester CO2, and wheat straw does as it grows. What's more, it is comparatively more expensive.
Mielewski is confident that there are plenty of opportunities for plastics with natural constituents in automotive applications. She says that the 2008 Ford Mustang is the first vehicle to use soy-based polyurethane foam for seats; subsequently, it is being used for the Expedition, F-150, Focus, Escape, Escape Hybrid, Mercury Mariner, Lincoln Navigator, and Lincoln MKS. This translates into about 1.5-million vehicles that are using the soy-based material, thereby reducing petroleum requirements. In addition to which, she points out that the 2010 Ford Escape and Mercury Mariner feature soy-foam headliners in place of traditional glass-mat headliners.
There are splash shield and radiator air deflector shields on Ford vehicles made from post-consumer recycled resins. The cylinder head covers for the Ford 3.0-liter Duratec engine started life as nylon carpeting.
But if you consider these applications, they are all not particularly cosmetic. Lee says of the wheat straw-reinforced plastic, "This material does grain well, and it could be a Class A material, depending on what you're looking for." That is, there is some read-through of the fibers in the matrix. As they're doing research on customer reaction to this, they're finding that the responses tend to be bi-modal: some like it; some don't. As Mielewski points out, this could be ideal as the material for "a radio bezel on a hybrid vehicle. The whole idea of 'Class A' could change with these materials." In other words, bio-based plastic reinforcements could actually be perceived as a beneficial feature, one people of an environmental inclination would prefer to the slick surfaces commonly characteristic of things like faux-wood trim.