Autonomous self-healing in green epoxy thermosets for flexible functional coatings

In this study, self-healing in a plant-based bioepoxy resin has been reported by incorporating reversible ionic groups in the networks of epoxy resin using a simple blending process with ionic liquid. The interaction between the hydroxyl groups in epoxy resin and ionic groups in ionic liquids was reversible. Such material with reversible reactive bonds was expected to show instantaneous self-healing of minor cracks. To study the self-healing efficacy of the system, tensile and nanoindentation tests were performed. The tensile measurements reported the retention of mechanical properties after the reassembling of ionic clusters due to self-healing. It was observed that the self-healed samples retained ca. 42 % and 53 % of their tensile strength and elongation at break. Furthermore, nanoindentation repairing studies were carried out by making a nanoindentation mark on the prepared samples and measuring the needed time to undertake autonomous self-healing. Interestingly, the self-healing was initiated immediately (<3 sec) after the nanoindentation, although with scarring. The complete self-healing of the damage was observed after 48 h. Thus, the modified samples showed improved self-healing under nanoindentation test conditions. Further, studies were conducted to understand the thermal, morphological, and physical properties of the prepared blend. All these studies prove that the prepared blend is a promising material in application areas such as flexible indoor coatings.