Preparation and mechanical properties of microcapsule made of self-repairing composite materials

To improve the healing performance and increase the service life of the polymer matrix composites, microcapsules with urea formaldehyde resin as wall material and dicyclopentadiene as core material were prepared by in-situ polymerization method. The effect of the dosage of urea, formaldehyde and emulsifier was investigated. By optimizing the conditions, the microcapsules with compact surface were dispersed well in an epoxy matrix for using in the self-healing system. The morphology and shell thickness of microcapsules were characterized using scanning electron microscopy, and the chemical structure of the microcapsules was confirmed by fourier transform infrared spectroscopy. Mechanical properties of the self-healing polymeric materials were measured by tensile test and finite element method analysis. The results show that the microcapsules had compact structure with proper molor ratio of urea to formaldehyde (1:2) and concentration of emulsifiers (0.5%). Healing was triggered by crack propagation through the microcapsules, which then initiated polymerization and healing of the crack inside the composites.