Study on Heat Response Recovery Characteristics and Shape Memory Mechanism of Shape Memory Polyurethane /Sbs/Cr Composite Modified Asphalt Sealant

Abstract

In normal road use, traffic loads as well as climate change lead to cracking, which is worsened by the lack of shape recovery properties when using normal asphalt as a crack sealant. In order to minimize further damage to the road caused by long-term accumulated deformation, SMPU (Shape memory polyurethanes)/ SBS (Styrene-butadiene-styrene copolymers)/ CR (rubber crumb) composite modified asphalt sealant (SMPUA) with excellent shape recovery ability, adhesion properties, and road performance was prepared. SMPU were first synthesized from polycarbonate diol (PCDL), diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO). The asphalt was subsequently modified by SMPU, SBS and CR. The shape memory behavior, high and low temperature rheological behavior, high temperature stability and adhesion properties of SMPUA were evaluated by shape memory performance test, dynamic shear rheology (DSR) test, bending beam rheology (BBR) test and thermogravimetric (TG) test to optimize the optimum dosage of SMPUA. The results show that SMPUA has good high and low temperature rheological properties, adhesive properties, and elastic properties. When the water bath temperature is 50 °C, the shape recovery rate (Rr) is up to 95%. And it is suitable for areas where the lowest temperature is below -16 °C. The shape recovery mechanism and modification mechanism of SMPUA were revealed by differential scanning calorimeter (DSC) test, fourier transform infrared spectroscopy (FT-IR) test and fluorescence microscope (FM) test. The stationary phase in SMPUA does not change state with temperature change and can memorize the shape of the material, while the reversible phase can change shape with temperature change. When SMPUA is heated again after its shape is changed by pressure, the stationary phase will drive the reversible phase to restore its original shape, which is macroscopically manifested as shape recovery. This study is of great significance to enhance the performance of the sealing material and prolong the service life of the material.

Keywords: Crack repair, Shape memory polyurethane, Shape memory effect, Compositely modified asphalt