Thermosets, or cross-linked polymers, are a class of materials with a permanent molecular architecture. One of the benefits of thermosets is that they can add additional stability, enhanced strengths, improved elasticity, and reduced creep compared to their linear counterparts. These properties are essential for a wide range of applications in insulators, adhesives, pipes, construction and transportation.
The thermoset industry has been growing dramatically with cross-linked polymers now constituting 15-20% of all polymers produced. However, the same thermomechanical properties responsible for their resistance and robustness prevent them from being recycled or reprocessed, and most thermosets are incinerated or landfilled. The lack of traditional waste management routes, coupled with the higher value potential applications, suggest that degradable cross-linked polymers could offer a more sustainable end-of-life solution.
Aliphatic polyesters have been some of the most widely studied compounds as potential degradable materials, yet cross-linking these systems is an under-explored tool that could control polymer fate in polyester resins. The decomposition of labile linkages would enable recovery of the starting compounds or release readily metabolised biodegradable products. For these novel materials to be commercially relevant, it is imperative they match or exceed the properties of their traditional counterparts. The majority of publicly reported degradable cross-linked polyesters are important precedent-setters, but their mechanical properties are often limited to low moduli and high elasticity.
While suitable for the biomedical field, the demanding requirements needed in construction or automotive fields remain elusive.
A team at the University of Manchester has developed a family of crosslinkers for the synthesis of hard, tough, and degradable polyester resins.
The key benefits of these resins are:
- Degradable: potential to recover monomer precursors and reinforcement agents – carbon fibre or other fillers
- Cheap and bio-based monomer sources
- Thermal and mechanical properties comparable to those of commercially available thermosets.