Magnetically gradient-distributed microcapsule/epoxy composites: Low capsule load and highly targeted self-healing performance

Abstract

One-component self-healing epoxy-matrix composites are needed urgently in the electronics industry because of their ability to repair surface damage autonomously. However, their practical applications are limited by unsuitable external stimuli and heavy microcapsule loads. Here, we report a magnetic-field and ultraviolet dual-responsive microcapsule to endow epoxy composites with a highly targeted self-healing capability under low microcapsule loads. Specifically, 5 wt% Fe3O4@SiO2 nanoparticles that were incorporated into the core material served as magnetic targets and helped the microcapsules to navigate to the near-surface region of a high-failure probability, to form magnetically gradient-distributed microcapsule/epoxy composites. This resulted in a more than fourfold increase in the local microcapsule concentration. The successful targeted self-healing with a microcapsule doping percentage as low as 4 wt% was confirmed by laser-scanning fluorescence confocal microscopy and scanning electron microscopy observations, and electrochemical testing. In addition, a kinetic model based on isothermal photo-differential scanning calorimetry measurements and a molecular-dynamics simulation model were both established to analyze the self-healing mechanism. Because of the facility and universality of this magnetic control method, these magnetic microcapsules could be guided to concentrate in vulnerable parts of other electrical insulators as desired, which highlights the good potential of this targeted self-healing method in energy fields.