KIT and Evonik researchers develop novel polymer network that self heals rapidly and repeatedly at relatively low temperatures
Scientists of the Karlsruhe Institute of Technology and Evonik Industries have developed a chemical cross-linking reaction that ensures good short-term healing properties of a polymer material under mild heating. The research results have been published in the journal Advanced Materials.
The KIT group headed by Christopher Barner-Kowollik uses the possibility of cross-linking functionalized fibers or small molecules by a reversible chemical reaction for the production of self-healing materials. These “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. The method requires no catalyst or additive, said Professor Barner-Kowollik, Chair for Preparative Macromolecular Chemistry at KIT.
It took about four years of research for the working group of Barner-Kowollik, together with the Project House Composites of Creavis, the strategic innovation unit of Evonik, to develop a novel polymer network.
Reducing the time needed for healing and optimizing the external conditions, under which the healing process takes place, are major challenges for self-healing materials. At comparably low temperatures from 50°C to 120°C, the network exhibits excellent healing properties within a few minutes.
The KIT 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.
The self-healing properties can be transferred to a large range of known plastics. In addition to self-healing, flowability is enhanced at higher temperatures—i.e., the material can be molded well. A potential field of application lies in the production of fiber-reinforced plastics components for automotive and aircraft industries.
Oehlenschlaeger, K. K., Mueller, J. O., Brandt, J., Hilf, S., Lederer, A., Wilhelm, M., Graf, R., Coote, M. L., Schmidt, F. G. and Barner-Kowollik, C. (2014) “Adaptable Hetero Diels–Alder Networks for Fast Self-Healing under Mild Conditions,” Adv. Mater.. doi: 10.1002/adma.201306258