Development of shape memory polyurethane/SBS compositely modified asphalt and synergistic modification mechanism

Abstract

To develop new shape memory polyurethane/styrene butadiene styrene (SMPU/SBS) compositely modified asphalt (PSA) with obvious shape memory property, and to reveal the synergistic modification mechanism and shape memory effect, the optimum blending ratio of different components in PSA and its preparation method were determined by orthogonal test and range analysis. Then the differential scanning calorimetry (DSC), shape memory property test, wide-angle X-ray diffraction (WXRD), Fourier transform infrared spectrometer (FTIR) and atomic force microscope (AFM) were used to study the phase transition temperature, shape memory property, chemical component compatibility, microphase separation and microscopic morphology of PSA samples. The results show that the developed PSA has better anti-deformation and anti-cracking properties, and the modifiers are compatible with matrix asphalt. The phase transition temperature of PSA is accommodative with the working temperature of asphalt pavement. Also, the shape recovery of SMPU can be stimulated by natural environment temperature, which improves the self-healing efficiency of damage or crack in PSA. The obvious microphase separation occurs between soft and hard segments in SMPU, so the shape memory property of PSA is better than that of SBS modified asphalt (SA). SMPU chemically modifies asphalt, which improves the orientation and arrangement of hard segments in SMPU, as well as the agglomeration, crystallization and precipitation of hard segments occur during the cooling. All these lead to the microphase separation between soft and hard segments, improving the shape memory properties of PSA. After the composite modification, the crystal size and spacing of hard segments in SMPU become smaller, as well as a continuous, stable and compact spatial network structure is formed in PSA. These increase the anti-deformation and shape recovery properties of PSA, as well as are conducive to improve the self-healing efficiency of damage or crack in PSA. This study reveals the synergistic modification mechanism of SMPU and SBS on asphalt, as well as the shape memory effect of PSA.