Spanish researchers have reported the discovery of a self-healing polymer which requires no external input. Previous self-healing materials have required specific light, heat, pressure or a catalyst to trigger the process, but this thermoset elastomer is the first example to heal spontaneously.
The researchers were led by Ibon Odriozola at the IK4-CIDETEC Center for Electrochemical Technologies in San Sebastian in Spain, a hotbed of innovative nanotechnology and advanced materials research.
In October 2012, IK4-CIDETEC announced that they would be taking part in a European project to develop commercial self-repairing materials, called SHINE - and they had considerable expertise in this area beforehand as well. Earlier that year, the team published an article in Chemical Communications reporting their development of a self-healing elastomer which used silver nanoparticles as a catalyst.
However, the silver nanoparticles were activated by an external pressure, so the regeneration was not completely spontaneous. The silver nanoparticles also raised the cost of the material, and Ibon and his team were keen to use commercial materials which are already proven to be compatible with industrial processes.
This new material is not essentially dissimilar to many industrial polymers in use today. The poly(urea-urethane) contains disulfide links which can reversibly exchange at room temperature, breaking and reforming links and giving the material the chance to flow.
This means that a sample of the polymer cut in two with a razor blade was able to reform in under two hours, and displayed 97% of its original strength - leading the researchers to dub it a "Terminator" polymer.
Whilst this initial research should be relatively easy to apply to similar materials currently in commercial use, it is limited to soft polymers. The group's next work will focus on trying to create the same functionality in harder materials.
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