A patent disclosure filed Oct. 27 by University of Delaware scientists describes a technique for using soybean oil--rather than petroleum-derived resins--to produce inexpensive, lightweight and potentially biodegradable composites for tractors, supercars, bridges and military vehicles.
Initially developed for Deere & Co., the world's leading farm equipment maker, the UD technique involves chemically modifying soy oil, a commodity that's 50 percent cheaper than the polyester, epoxy and vinyl ester resins commonly used in composite manufacturing processes, says Richard P. Wool, professor of chemical engineering and director of the ACRES (Affordable Composites from Renewable Sources) project at UD. Soy-based resin and reinforcing fibers such as glass may then be injected into a mold, where the liquid solidifies to form the composite, Wool explains.
Chuck Neff, manager of plastics applications and development at Deere & Co., predicts a $50 million market for farm equipment made from soy-based composites. The firm is currently gearing up for a nationwide test of the new materials. Composites based on soy resins will initially be used to make 50 or 60 tractor components, Neff says. These parts will be distributed to dealers and installed on farm equipment for field testing within a wide variety of climates and working conditions.
The UD scientists unveiled a door-sized sample of the environmentally friendly new material--manufactured by Contemporary Products Inc. of Milwaukee to serve as the side of a hay bailer--during the John Deere New Millennium Plastics Expo, which took place Sept. 16-17 in Moline, Ill. Featuring a foam core encased on both sides by a glass-reinforced, soy-based composite, the 8-by-3-foot prototype weighed just 25 pounds, making it up to four times lighter than a comparable metal bailer part. Though the prototype contained preservatives, Wool says, subsequent formulations could easily be made to biodegrade under certain conditions. Ultimately, he adds, natural straw or hay fibers might even replace the reinforcing glass matrix within the soy-based composite.
"This first test part would replace standard metal sheeting materials," Wool says. "It would not corrode or rust, and it was made using a low-energy procedure that is far more benign than metal casting systems. Moreover, it is structurally comparable to metal, but at lower cost, while its lower weight provides better fuel efficiency."
The use of soybeans in composite materials--an idea first proposed by auto maker Henry Ford some 60 years ago--has thus far been limited primarily to surface coatings such as varnish, "but none of these applications require any structural strength from the resulting material," Wool notes. By comparison, he says, the UD process strengthens soy oil by chemically modifying its structure, resulting in more highly cross-linked, and therefore inherently stronger molecules. More than a dozen different chemical reactions have been developed and are currently being patented by UD.
Sponsored by the United Soybean Board based in St. Louis, the UD researchers have achieved composite stiffness, strength and toughness comparable to that of commercial vinyl-ester based composites, says UD doctoral candidate Shrikant Khot. And, Wool says, genetically engineered soybeans now make it possible to produce a consistently reliable product , thereby avoiding problems such as seasonable variations in the chemical composition of the natural oil.
The ACRES project is an interdisciplinary research team established to create inexpensive and reliable, fiber-reinforced composite materials from renewable sources. Along with Wool and Khot, the UD research team included chemist Ralph Zhao, postdoctoral research associate; Selim Kusefoglu, visiting professor within UD's Center for Composite Materials; scientist Guiseppe Palmese; and Anne Boyd, industrial liaison.
"This work, conducted as part of the ACRES program, is ideally suited and sufficiently challenging for graduate as well as undergraduate research," Wool says. "It also promises significant new technologies to support various U.S. industrial sectors."