Plastic under Pressure

Professor Anne Mayes '86 and her colleagues in the Department of Materials Science and Engineering have developed a new process for molding plastic at room temperature that could allow plastics to be recycled many times and reduce the cost of plastic production.

The process involves squeezing certain combinations of polymers together, causing them to interact in such a way that they assume a moldable, liquidlike state-a goal manufacturers typically achieve by melting materials at about 200 C. The new process yields materials called baroplastics, which can be made from the same materials as traditional plastics. Mayes and her colleagues have known since 1998 that applying pressure could produce baroplastics, but they only recently discovered practical materials to squeeze.

When it comes to recycling, the new system offers a distinct advantage. "Polymeric materials don't handle the high temperatures of the [traditional] recycling process very well, so we typically end up with much lower-grade material than when we start," Mayes says. This means that traditional plastic can be recycled two times at most, while baroplastics remain strong and usable after many more recyclings. The system could also save manufacturers money by allowing them to make plastics of different consistencies-a milk jug and its cap, for example-out of the same basic elements.

Despite these advantages, Mayes says her system is far from commercial use because change is slow in the plastics industry, which relies on high-volume production at low profit margins.