Introducing degradable bonds into thermoplastics and thermosets for easier recycling

Researchers from the University of Bath and University of Surrey developed a way of introducing degradable bonds into difficult-to-recycle polymers, including thermoplastics and thermosets, to make the more easily recyclable.

Published in Polymer Chemistry, the word was funded by the Engineering and Physical Sciences Research Council (EPSRC).

Researchers developed a way to make polymer recycling easier.

Challenge to recycle polymers

Thermoplastics and thermosets are two types of plastics that both consist of long chains of molecules but behave differently when heated.

When heated to high temperatures, thermoplastics can subsequently be melted and reformed into other shapes. However, the material can break when stretched or stressed.

For thermoset plastics, they are cross-linked to form a network which makes them strong and flexible. However, the crosslinks mean that the material burn instead of melt when heated, making thermosets harder to break down and recycle.

Polymer gels with breakable bonds

The researchers made a series of polymer gels with breakable bonds incorporated into different parts of the structure, and tested whether the properties changed after the gel was degraded and reformed.

Gels with breakable bonds in the polymer chains (B) retained their properties much better when reformed, compared with the polymers that were broken down via the cross-linked bonds (A).

They found that while all gels can be degraded to some extent, gels with breakable bonds in the polymer chains retained their properties much better when reformed, compared with the polymers that are broken down via the cross-linked bonds.

The researchers hope that this model system can be applied to other types of polymers, including adhesives, sealants and elastomers.

“Being able to make bonds reversible in these materials will increase their applications as well as making them more recyclable,” explained Dr Maciek Kopeć from the University of Bath’s Department of Chemistry.

The researchers will also look at other applications of the work, including using cross-linked polymers as vehicles for controlled drug delivery systems.