Swiss researchers make non-recyclable plastic recyclable

Swiss researchers have developed a new type of recyclable plastic. In the future, it could be installed in planes, cars or wind power plants, the Swiss Federal Laboratories for Materials Testing and Research announced on Tuesday.

“The production of carbon fibers requires a lot of energy and an enormous amount of CO2 is released,” explains research group leader Sabyasachi Gaan in the Empa press release. “If we could recycle them, their carbon footprint would be a lot bigger — and the price would be a lot lower.”

The Empa researchers have made the traditionally non-recyclable material epoxy resin recyclable. They recently presented the new material to experts in the Chemical Engineering Journal.

Epoxy resins belong to the so-called duromers, in which polymer chains are closely linked. These cross-links prevent the plastic from melting, which is necessary for recycling. So-called thermoplastics such as PET behave differently: here the polymer chains are close together, but they are not cross-linked.

This makes recycling easier, but also has other disadvantages. Due to the lack of crosslinking, their mechanical properties at elevated temperatures are generally not as advantageous as those of duromers, Empa said.

According to the researchers, the new epoxy resin combines these properties: it is actually a thermoset, but can melt like a thermoplastic. To do this, the scientists added a special molecule from the class of phosphonic acid esters to the epoxy resin. This creates bonds with the polymer chains, which can be broken again under certain conditions. This loosens the cross-linking of the polymer chains so that they can be melted and deformed.

According to Empa, the result is a recyclable material that is flame retardant and mechanically resistant.

(sda)