Scientists tackle thermoset polymers recycle challenge

London - Thermoset polymers such as rubber, polyurethane, bakelite, silicone and epoxy resin have long played an essential role in industrial processes but present a considerable obstacle to recycling.

Their strength and flexibility derives from the crosslinking polymer chains of molecules which puts such plastics in demand for composite materials, rubbers, paints and coatings. However, those same polymer chain crosslinks ensure the materials burn instead of melting, and are very difficult to break down and sustainably recycle.

But a group of scientists from Bath University and Surrey University, whose work was funded by the Engineering and Physical Sciences Research Council (EPSRC), report they have eased the challenge by introducing degradable bonds into polymers.

Dr Maciek Kope?, from the University of Bath’s Department of Chemistry, said: “Thermosets are used widely in the commercial sector, in materials like resins and adhesives.

“Being able to make bonds reversible in these materials will increase their applications as well as making them more recyclable.”

Writing in Polymer Chemistry, the researchers outlined how they created polymer gels with breakable bonds in various parts of the structure, testing to see how the properties altered when the gel was degraded and reformed.

They reported that gels with breakable bonds in the polymer chains retained their properties much better when reformed, compared with the polymers that were broken down via the cross-linked bonds. 

The hope is that the work will enabled the development of a ‘road map’ of the best locations for breakable bonds and to then develop other applications for various types of polymers but also ambitious projects such as adapting crosslinked polymers for controlled drug delivery systems.

Article by Process Engineering, an associate publication of European Rubber Journal.