Self-Healing Rubber by Harvard Engineers

Sep 18th, 2017

A group of scientists from Harvard College of Engineering and Applied Sciences (SEAS) have invented a material that helps to create a tire able to self-heal after a puncture. This is a new type of rubber which is as strong as natural and at the same time able to renovate the damage.

It is been times since the SEAS engineers have started working on self-healing rubber materials. They have already developed hydrogels, but it took them great effort to create dry materials. The bonds between polymers in rubber are permanent and covalent which makes rubber durable. However, once the bonds are broken, they are not able to reform.

Primarily, the scientists found reversible hydrogen bonds for connecting polymers, but they turned out to be are weaker than covalent ones.

Li-Heng Cai, a SEAS researcher, said that the scientists were challenged to create tough bonds able to reform after the damage. The research findings on a new type of rubber were published in Advanced Materials journal.  Li-Heng Cai, together with David A. Weitz, Canadian Professor of Applied Physics and Professor Jinrong Wu from Sichuan University,   created a hybrid rubber with reversible and covalent bonds. Comparing these types of bonds with water and oil, Li-Heng Ca explains that they are immiscible; however, theoretically, it is possible.

To do this, the scientists created a molecular rope or randomly branched polymers, which uniformly mixes these two bonds homogeneously. As a result, they received a tough, transparent, self-healing rubber.

When typical rubber is stretched, cracks appear; but they are connected by bundles of fibres that redistribute the stress and the material returns to its original form and the cracks heal.

SEAS filed a patent application for this technology. Researchers are looking for the ways to commercialize this new rubber type, assuring future producers and consumers that this type of rubber, in addition to car tires, has a wide application.