Process to make a thermoset that can be reshaped and reused

A process to make a thermoset that can be reshaped and reused has been developed by researchers at Oak Ridge National Laboratory. The new plastic is a shape-memory polymer, so named because the material can “remember” its original shape and return to it after being deformed with heat or other forces. Orlando Rios from the Department of Energy's Oak Ridge National Laboratory and a team of researchers from Washington State University and the University of Idaho have developed a process to make a thermoset that can be reshaped and reused. The team's study is published in the journal Macromolecules. The new plastic is a shape-memory polymer, so named because the material can "remember" its original shape and return to it after being deformed with heat or other forces. The materials exhibit triple-shape memory behavior, meaning that the polymers can transform from one temporary shape to another temporary shape at one temperature, and then back to a permanent shape at another temperature. Rios explains that although researchers have been interested in making use of shape-memory polymers' intriguing characteristics, managing the shape-shifting behavior has been a struggle. "One big issue that has limited their use is controlling the transformation temperatures and their properties," he said. "We give a recipe where you can adjust the transformation temperature and shift the performance of the material." Changing the ratio of ingredients allows the researchers to control the overall properties of the material. The team's method also uses off-the-shelf chemicals that can be easily scaled up to manufacture the material in bulk. "We've taken it from somewhat of a scientific curiosity or fundamental research material to something that can be produced in larger volumes," Rios said. Mixing the shape-memory polymers with other materials could produce stronger and stiffer composite parts that can later be recycled or reprocessed. Recyclable carbon fiber and glass fiber composites, for instance, are in high demand in the automotive industry. "The ability to control the shape-memory behavior of the material provides great design flexibility," said Yuzhan Li of Washington State University. The material could also be used as binding glue for new types of rare earth-free magnets made from powders. The team is already experimenting with 3-D printing powder-based magnets with shape-memory polymers. "The applications for these materials are very broad, since the shape-shifting temperatures for these materials can be finely tuned by controlling the ratio of the chemicals used in their synthesis," said Michael Kessler of Washington State University. The team has filed for a patent on its method.