Effect of epoxy resin healing agent viscosity on the self-healing performance of capsules reinforced polymer composite

The structural integrity of micro and nano cracked polymer composites can be re-established without human intervention by employing biologically inspired capsule based self-healing system into the base material. In the present study, in order to evaluate the influence of core materials viscosity on the self-healing performance, two types of epoxy resins (LY556, CY230) of respective viscosities 10-12 Pa.s, 1.3-2 Pa.s and amine hardener (HY951) of viscosity 0.01–0.02 Pa.s were chosen and encapsulated in a thermoplastic poly methylmethacrylate (PMMA) shell. The mean capsule size of the developed LY556 epoxy,CY230 epoxy microcapsules and HY951 hardener microcapsules were measured as 61.58 µm, 67.64 µm and 63.31 µm respectively. Influence of core to shell(c/s) ratio on the preparation of epoxy capsules was investigated and 1:1 c/s ratio, 2:1 c/s ratios were recommended as an ideal ratios to prepare LY556, CY230 epoxy capsules respectively. Fourier Transform Infrared (FTIR), Nuclear magnetic resonance (NMR) and thermogravimetric(TGA) analysis were conducted. Tensile strength, fracture toughness and self-healing performance of the (LY556 + HY951) capsules, (CY230 + HY951) capsules reinforced epoxy composites were investigated. It was noticed that the tensile strength decreases and the fracture toughness increases with the increase in capsules concentration from 0wt% to 10wt%. In both the cases, it was found that the healing efficiency increased with the increase in capsules content. For both (LY556 + HY951) capsules reinforced, (CY230 + HY951) capsules reinforced epoxy composites an optimum capsules concentration was found to be at 7.5wt% and the respective measured healing efficiencies were noted as 66% and 72%.