Synthesis and self-healing properties of composite microcapsule based on sodium alginate/melamine-phenol–formaldehyde resin

In view of the inevitable microcracks and local damage of concrete materials, a new type of self-healing microcapsule material was proposed. The SA/MPF-E44 composite microcapsule material with sodium alginate/melamine phenolic resin as the shell and epoxy resin as the core was prepared by in situ polymerization. The surface morphology of the microcapsules was observed by optical microscope and scanning electron microscope. The particle size analysis was performed using a Malvern analyzer. By performing Fourier transform infrared spectrometry and a differential scanning calorimetry analysis, the functional group changes and thermal stability of the composite microcapsules were studied. The compression resistance and repair performance of cement mortar specimens with different dosage of microcapsules were tested by a uniaxial compression experiment. It can be concluded that the composite microcapsules have the characteristics of a small particle size, and the coverage rate has increased significantly. The average particle diameter is approximately 55.24 μm, and the coating ratio is 64.93%. When the microcapsule content is 4%, the microcapsule has the best compression and repair performance. The self-healing behavior of the epoxy resin and curing agent in cracks was studied by a molecular dynamics simulation. Finally, it is shown that SA/MPF composite microcapsules have certain advantages in cost and eco-efficiency, and have good self-healing ability for microcracks in concrete materials.