Scientists develop recyclable thermoset

Researchers from Washington State University and the University of Idaho have developed a process to make a thermoset plastic that can be reshaped and re-used.

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 behaviour, 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.

The study, authored by a team from the US Department of Energy’s Oak Ridge National Laboratory, has been published in the journal Macromolecules.

Researcher Orlando Rios explains that although scientists have been interested in making use of shape-memory polymers’ intriguing characteristics, managing the shape-shifting behaviour 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 fibre and glass fibre composites, for instance, are in high demand in the automotive industry.

“The ability to control the shape-memory behaviour of the material provides great design flexibility,” said one of the study’s co-authors, Yuzhan Li of Washington State University.