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Self-healing isocyanate microcapsules for efficient restoration of fracture damage of polyurethane and epoxy resins

He, Zhenglong, Jiang, Shuai, An, Na, Li, Xudong, Li, Qifeng, Wang, Junwei, Zhao, Yuhua, Kang, Maoqing
Journal of materials science 2019 v.54 no.11 pp. 8262-8275
composite polymers, crosslinking, epoxides, glass, polyurethanes, resins, scanning electron microscopy
Isophorone diisocyanate-loaded microcapsules were synthesized with controllable size for self-healing of structural polymer materials. The obtained microcapsules showed good compatibility with polymer resins, e.g., one-component epoxy and multi-component polyurethane/water glass structural materials. During the processing of composite self-healing materials, the highly cross-linked composite capsule wall ensured the integrity of microcapsules and prevented the leakage and degradation of reactive liquid isocyanates effectively. A relatively larger amount of self-healing agent could be released to the local cracks with the increasing size and content of microcapsules in polymer matrix which improved the self-healing efficiency of the composites. Based on the microcapsules with a diameter of ~96 μm, the healing efficiency of epoxy composites containing 15 wt% of capsules and polyurethane/water glass composites containing 20 wt% of capsules could reach to 105 and 101% recovery of fracture toughness, respectively. The crack-healing effect was further verified by scanning electron microscopy. Meanwhile, a possible self-healing mechanism of microcapsules to the cracks of composite polymer materials was proposed.