Researchers seem to have developed a tough-as-nails new form of plastic that is 50 percent renewable content.
It is a new form of ABS. In its conventional form, ABS (shorthand for acrylonitrile, butadiene and styrene) is a moldable polymer that makes up car bumpers and other materials, including protective headgear, kitchen appliances, Lego bricks and ventilation pipes. Currently, ABS is made with petroleum-derived chemicals.
A team at the U.S. Department of Energy's Oak Ridge National Laboratory in Tennessee replaced the styrene in ABS with lignin. The latter forms plants' woody cell walls, along with the material cellulose.
The result is a production process that is solvent-free and makes a pliable, meltable, moldable material that is actually ten times more tough than ABS. They've made a thermoplastic, and it is called ABL - for acrylonitrile, butadiene and lignin.
ABL is recyclable and can be melted three times while still performing well. Its production should result in many manufacturers having cleaner and cheaper raw materials on hand.
"The new ORNL thermoplastic has better performance than commodity plastics like ABS," noted main author Amit Naskar of ORNL, who has filed a patent application for the ABL-making process along with co-inventor Chau Tran. "We can call it a green product because 50 percent of its content is renewable, and technology to enable its commercial exploitation would reduce the need for petrochemicals."
There is potential for finding cheap ingredients by using biomass byproducts rich in lignin, from pulp and paper mills and biorefineries. As dropping natural gas and oil prices make renewable fuels weigh in as more expensive, biorefineries are looking for economically positive products to market. Among the byproducts of plants (including cellulose and hemicellulose), lignin is especially underused right now. The study at ORNL was focused on using lignin to make a renewable thermoplastic that could rival many properties of our contemporary petroleum-developed products.
In order to make a commercially viable product, the team needed to figure out a way to toughen the often-brittle polymer lignin. "We need to chemically combine soft matter with lignin. That soft matrix would be ductile so that it can be malleable or stretchable. Very rigid lignin segments would offer resistance to deformation and thus provide stiffness," Naskar said.
The scientists also needed to find a lignin that could remain stable when exposed to heat. They learned that lignin from hardwood is especially thermally stable. Also, certain types of lignins from softwood also were able to resist melting.
Ultimately, the team was able to combine the lignin with a type of rubber in order to make it less brittle.
"More renewable materials will probably be used in the future," Naskar said. "I'm glad that we could continue work in renewable materials, not only for automotive applications but even for commodity usage."
The findings were published in the journal Advanced Functional Materials.
