Abstract
Mechanical properties of microcapsule shell have great influence on microcapsule suitability as a mechanical trigger in a self-healing composite. The elastic modulus and hardness of polymethyl methacrylate (PMMA) microcapsules containing epoxy prepolymer (EC 157) and pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) as healing agents were investigated using nanoindentation technique. The influence of the PMMA average molecular weight (MW), the kind of core material, and the mechanical mixing rate on the mechanical properties of the microcapsule shell were studied using the Taguchi experimental design approach. The results indicated that the most important factors which affect the elastic modulus and the hardness of microcapsules shell are the Mw of PMMA and the kind of core material. The average elastic modulus of PMMA shell of epoxy and mercaptan-loaded microcapsules was found between 2.386 and 3.495 GPa. The hardness of PMMA shell of healing agent microcapsules was obtained in the range of 0.064–0.219 GPa. This constitutes essential knowledge in order to design capsules with tailored properties for self-healing materials.
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