Anti-aging and self-healing SBS-modified bitumen waterproofing membrane based on montmorillonite and dynamic acylhydrazone bonds

The development of styrene-butadiene-styrene (SBS) block copolymer modified bitumen (SMB) waterproofing membrane with excellent anti-aging and crack self-healing properties is important to solve the persistent problems of building leakage. In this study, vinyltriethoxysilane modified montmorillonite (VTES-MMT) and acylhydrazone compound (AC) were synthesized and used to prepare a novel anti-aging and self-healing SMB. The structures of VTES-MMT and AC were characterized, and the effects of VTES-MMT and AC on the microstructure, physical properties, mechanical properties, self-healing properties and aging properties of SMB were systematically investigated. The results show that vinyl-functionalized VTES-MMT and AC with vinyl ends were successfully synthesized and they have good thermal stability. VTES-MMT and dynamic acylhydrazone bonds were introduced into SMB through the cross-linking reaction between vinyl and SBS. VTES-MMT and AC improved the dispersion stability, physical and mechanical properties of SMB and endowed it with excellent crack self-healing properties. Compared with SMB, the healing index (HI) and the impermeable pressure of VTES-MMT/AC/SMB increased by 52.86 % and 0.41 MPa. The introduction of VTES-MMT and dynamic acylhydrazone bonds effectively mitigated the oxidative condensation of bitumen and the chain-breaking degradation of SBS during the aging process. Compared with SMB, the low temperature flexibility increment, elongation at break retention rate and peel strength retention rate of VTES-MMT/AC/SMB were reduced by 6℃, 18.66 % and 21.76 % after UV aging, respectively. The cracks of VTES-MMT/AC/SMB could still be healed completely after aging, and its HI and impermeability pressure decreased by only 14.38 % and 0.08 MPa after UV aging, which implied that the synergistic effect of VTES-MMT and AC significantly improved the aging resistance of SMB, and VTES-MMT/AC/SMB still maintained a good crack self-healing ability after aging.