Preparation and characterization of novel melamine modified poly(urea–formaldehyde) self-repairing microcapsules

Microcapsules with adequate performance are required for self-healing materials. Novel self-repairing microcapsules with better heat resistance and water resistance were prepared by introducing melamine to urea–formaldehyde resin as wall material. The as-synthesized microcapsules were studied by various characterizations techniques, including scanning electron microscope (SEM), optical microscope (OM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and contact angle meter. Spherical poly(urea–formaldehyde) microcapsules (mean size: 96 μm) and melamine modified poly(urea–formaldehyde) microcapsules (mean size: 46 μm, wall thickness: ∼3 μm) were obtained when the amount of melamine was 6–8 wt% and the amount of core materials was 75 wt%. After modified by melamine, the water-resistance of microcapsule is improved and contact angle increases from 43° to 50°. The heat resistance, solvent resistance, acid resistance and alkali resistance are improved because of triazine ring in melamine, which resulting in long storage time for microcapsule at room temperature.