Preparation and properties of self-healing SBS modified bitumen with dynamic acylhydrazone bonds

Styrene-butadiene-styrene triblock copolymer (SBS) modified bitumen (SMB) with excellent self-healing performance not only saves resources, but is also important for the sustainable development of pavement and construction industry. In this paper, a self-healing agent (SHA) with acylhydrazone bond was synthesized, and the dynamic acylhydrazone bond was introduced into the SBS molecular chains to prepare the self-healing SMB (SHMB). The structure of SHA was characterized, and the physical properties, chemical structure, microstructure and self-healing performance of the SHMB were investigated. Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance spectra demonstrated that SHA was successfully synthesized. The physical performances of SMB were significantly improved by SHA and its optimal dosage was 0.6 %. FTIR indicated that the dynamic acylhydrazone bond was introduced into the SBS molecular chains, and formed hydrogen bonds in SHMB. The fluorescence microscope showed that SHMB had a denser network structure than SMB. The crack healing observation indicated that the crack healing speed of SHMB was much higher than that of SMB. The break tensile performance recovery showed that the recovery rate of elongation at break (Rε) of SMB and SHMB were 14.38 % and 58.27 % after self-healing at 25℃ for 32 h, and the Rε of SMB and SHMB was elevated to 50.12 % and 92.58 % after self-healing at 40℃ for 4 h, which indicated that the introduction of dynamic acylhydrazone bonds greatly enhanced the self-healing ability of SHMB.