Novel waterproof bituminous coating using self-healing microcapsules containing ultraviolet light curing agent

Bituminous material is widely used in construction and building field, which often need excellent waterproof performance in the process of application. The aim of this work was to design a novel waterproof bituminous coating using self-healing microcapsules containing ultraviolet light curing agent. Core material of microcapsules was a compound of polyurethane acrylate (prepolymer 95 wt%) and 2-hydroxy-2-methyl-phenylacetone (initiator, 5 wt%). Morphology and chemical analysis showed that the cross-linked cured methylether-melamine–formaldehyde (HMMM) shell material protected core material under the condition of high temperature molding and avoid sunlight. The microcapsules had perfect spherical shape with a mean size of 20 μm and shell thickness of 2 μm. Microcapsules dispersed in bitumen homogeneously without agglomeration. No deboning was found in the interface between microcapsules and bitumen. Microcapsules resisted the temperature above 200 °C and remained the core material safety in shells. Through a man-made microcrack experiment, it proved that the bitumen sample with 3.0 wt% microcapsules completed a quick self-healing process with the help of ultraviolet light. Waterproof measurement also indicated that the microcrack in bituminous coating disappeared with the help of self-healing microcapsules under ultraviolet light. In other words, the rapid disappearance of microcracks can contribute to improving the waterproof performance of bituminous coating.