Preparation and performance of microcapsules for asphalt pavements using interfacial polymerization

Abstract Microcapsules for asphalt pavement containing asphalt rejuvenator as the core material were prepared via interfacial polymerization using high-speed shearing. Isophorone di-isocyanate (IPDI) and distilled water were used as the reaction monomers of the oil and water phases, respectively. Polyvinyl alcohol (PVA) was used as an emulsifier. The preparation process was optimized based on the type and concentration of the emulsifier, shearing speed, shell-core ratio, and reaction temperature. The technical properties of the asphalt pavement microcapsules prepared via the optimal preparation process were evaluated by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), laser particle size analyzer, and Thermogravimetric analysis (TGA) from the aspects of micromorphology, particle size, shell thickness, and thermal stability. Results showed that PVA possesses satisfactory emulsifying and shell-forming properties, which made it a suitable emulsifier in the oil phase. The optimized conditions of the microcapsule preparation are as follows: the concentration of the emulsifier solution was 0.4%, the shearing speed was 5000 RPM, the shell-core ratio was 0.6, and the range of reaction temperature was 60–70 °C. The diameter of the optimal microcapsules was primarily distributed between 10 and 17 µm. Furthermore, the average particle size was 14.26 µm; the microcapsule shell thickness was relatively uniform (2–3 µm). The results of FT-IR and TGA demonstrated that the asphalt pavement microcapsules maintain good chemical and quality stability at high temperature, indicating that the microcapsules can withstand the high temperature during the asphalt-mixture production process. The results of salt tolerance test showed that microcapsules have certain salt tolerance. The mean elastic modulus and hardness of microcapsules were 466.86 MPa and 56.27 MPa, respectively obtained by nano indentation test.