MICROENCAPSULATION OF HEALING AGENT FOR USE IN POLYMER COATINGS

Abstract

Different healing agents, namely unsaturated polyester and epoxy were encapsulated in polystyrene by physical encapsulation technique. The effect of operating parameters on the microcapsule dimensions and morphology was established by SEM imaging. Thermal and structural properties of the microcapsules were determined by TGA and FTIR respectively. Core content of PS encapsulated microcapsules was found to be 45  3%. Epoxy and USP were encapsulated in urea-formaldehyde microcapsules by emulsion polymerisation process. The core content of the microcapsules was determined by solvent extraction method and was found to be 58 4%. Latent hardener (copper complex of 2-methyl imidazole) was synthesized by the reaction of copper chloride with 2 methyl imidazole. Self-healing composites are also prepared by dispersing varying amount of microcapsules (10-30% w/w) in the matrix. The impact strength was found to decrease with introduction of microcapsules in the composition. Latent hardener was used as a curing agent to effect self healing in epoxy compositions containing epoxy encapsulated in UF microcapsules. Self healing efficiency was determined as the ratio of impact strength of the samples before and after healing. ~67% efficiency could be achieved using copper complex as the latent hardener system. Self healing was also demonstrated in compositions containing unsaturated polyester encapsulated in UF microcapsules. Although USP underwent thermal self curing, the temperature required could be brought down significantly by using AIBN as the free radical initiator. Self healing efficiency of ~103% could be achieved using AIBN as the curing agent.