(427e) Development of Remendable Polymers with Thermally Reversible Bonds

Materials that can recover properties following mechanical failure are desirable, as they offer increased durability and safety. Mendable materials are particularly desirable for load-bearing applications in which material failure is costly and dangerous.

Inspiration for remendable materials comes from nature and there is a great interest in developing biomimetic processes by a number of functionalities can be applied to synthetic materials. Biomimicry in remendable materials has led to composites with vascular networks that “bleed” resin when a crack forms.

Epoxy-amine thermosets are high modulus materials that are used in composites for their mechanical strength. We report on the development of two healing systems for epoxy-amine thermosets based on the thermoreversible Diels-Alder reaction of furan and maleimide. In one, crack healing of a traditional epoxy-amine thermoset is induced by thermally reversible crosslinking of a secondary phase. In the other, furan functionalization of an epoxy-amine thermoset allows for in situ crack healing of this thermoset with a bismaleimide solution. Both phenomena occur at room temperature and minimal pressure and significant load recovery is possible multiple times in a given location.

Load recovery is postulated to be the result of both physical and chemical bonding across the crack surface. Physical bonding is caused by solvent-mediated swelling and subsequent interlocking of crack surfaces, while chemical bonding results from the Diels-Alder reaction of furan and maleimide. This form of the Diels-Alder reaction is reversible, forming a ring structure at room temperature and reforming the respective diene and dienophile between 60 and 90°C.