According to a report this past week by Phys.org online science magazine, Chicago, Ill, USA, your car's bumper is probably made of a moldable thermoplastic polymer called ABS, shorthand for its acrylonitrile, butadiene and styrene components. Light, strong and tough, it is also the stuff of ventilation pipes, protective headgear, kitchen appliances, Lego bricks, and many other consumer products. Useful as it is, one of its drawbacks is that it is made using chemicals derived from petroleum.

Now, researchers at the Department of Energy's Oak Ridge National Laboratory have made a better thermoplastic by replacing styrene with lignin, a brittle, rigid polymer that, with cellulose, forms the woody cell walls of plants. In doing so, they have invented a solvent-free production process that interconnects equal parts of nanoscale lignin dispersed in a synthetic rubber matrix to produce a meltable, moldable, ductile material that's at least 10 times tougher than ABS. The resulting thermoplastic—called ABL for acrylonitrile, butadiene, lignin—is recyclable, as it can be melted three times and still perform well. The results, published in the Advanced Functional Materials journal (Germany), may bring cleaner, cheaper raw materials to diverse manufacturers.

 

"The new ORNL thermoplastic has better performance than commodity plastics like ABS," said Senior Author Amit Naskar in ORNL's Materials Science and Technology Division, who along with Inventor Chau Tran has filed a patent application for the process to make the new material. "We can call it a green product because 50% of its content is renewable, and technology to enable its commercial exploitation would reduce the need for petrochemicals."

 

 

 

Equal parts lignin and synthetic nitrile rubber are heated, mixed, and extruded to yield a superior thermoplastic for cars and other consumer products. The technology could make use of the lignin-rich biomass byproduct stream from biorefineries and pulp and paper mills. With the prices of natural gas and oil dropping, renewable fuels can't compete with fossil fuels, so biorefineries are exploring options for developing other economically viable products. Among cellulose, hemicellulose, and lignin, the major structural constituents of plants, lignin is the most commercially underutilized. The ORNL study aimed to use it to produce, with an eye toward commercialization, a renewable thermoplastic with properties rivaling those of current petroleum-derived alternatives.

 

To produce an energy-efficient method of synthesizing and extruding high-performance thermoplastic elastomers based on lignin, the ORNL team needed to answer several questions: Can variations in lignin feedstocks be overcome to make a product with superior performance? Can lignin integrate into soft polymer matrices? Can the chemistry and physics of lignin-derived polymers be understood to enable better control of their properties? Can the process to produce lignin-derived polymers be engineered?

 

More information including answers to these questions are available in the full article online.