New self-healing plastic fixes its own cracks

Imagine if your broken cellphone could heal itself or that car scratch could fix on its own!
Researchers have developed new self-healing materials that can repair themselves rapidly and repeatedly after damage.
The novel polymer network self-heals at relatively low temperatures, researchers said.
Scientists of the Karlsruhe Institute of Technology and Evonik Industries in Germany developed a chemical cross-linking reaction that ensures good short-term healing properties of the material under mild heating.
The group headed by Christopher Barner-Kowollik uses the possibility of cross-linking functionalised fibres or small molecules by a reversible chemical reaction for the production of self-healing materials.
These so-called switchable networks can be decomposed into their initial constituents and reassembled again after the damage.

The advantage is that the self-healing mechanism can be initiated any time by heat, light or by the addition of a chemical substance.

"Our method does not need any catalyst, no additive is required," Barner-Kowollik said.
It took about four years of research for the working group of Barner-Kowollik to develop a novel polymer network.
At comparably low temperatures from 50 degrees Celsius to 120 degrees Celsius, the network exhibits excellent healing properties within a few minutes.
Reducing the time needed for healing and optimising the external conditions, under which the healing process takes place, are the major challenges of research relating to self-healing materials.

Using the healing cycle developed by them, researchers have found a large number of intermolecular compounds that close again within a very short term during cooling.
Mechanical tests, such as tensile and viscosity tests, confirmed that the original properties of the material can be restored completely.
"We succeeded in demonstrating that test specimens after first healing were bound even more strongly than before," Barner-Kowollik said.
The self-healing properties can be transferred to a large range of plastics known.
Apart from self-healing, the material is given another advantageous property: As flowability is enhanced at higher temperatures, the material can be molded well.

A potential field of application lies in the production of fibre-reinforced plastics components for automotive and aircraft industries.
The research was published in the Advanced Materials journal.