Study on the Properties of Waterborne Epoxy Resin/Polyurethane Composite Modified Emulsified Asphalt

Waterborne epoxy resin emulsified asphalt (WEA) is often used as a preventive maintenance material for asphalt pavement due to its excellent mechanical properties and high-temperature stability. However, its relatively poor toughness and low-temperature crack resistance limit its broader application. To address this issue, a PPG-IPDI-based waterborne polyurethane/epoxy resin (WER/PU) emulsion was synthesized via the prepolymer dispersion method using polypropylene glycol (PPG), isophorone diisocyanate (IPDI), 2,2-bis(hydroxymethyl)propionic acid (DMPA), and epoxy resin (E-44) as the main raw materials. Fourier transform infrared (FT-IR) spectroscopy confirmed that flexible polyurethane segments were successfully grafted onto the epoxy resin. This WER/PU emulsion was then incorporated as a modifier into emulsified asphalt to prepare waterborne polyurethane/epoxy resin composite-modified emulsified asphalt (WER/PU-CMEA). A series of laboratory tests were conducted to compare the compatibility, conventional properties, mechanical performance, high temperature rheological properties, low-temperature crack resistance and aging resistance of ordinary emulsified asphalt (OEA), WEA, and WER/PU-CMEA. Scanning electron microscopy (SEM) was employed to analyze the modification mechanism of WEA by WPU. The results show that WER/PU exhibits good compatibility with emulsified asphalt, and the synergistic effect of WER/PU significantly enhances the overall performance of the emulsified asphalt. Compared with WEA, WER/PU-CMEA shows a slight decrease in tensile strength and high-temperature stability, but it notably improves material compatibility, flexibility, bond strength, elongation at break, high-temperature creep-recovery performance, and low-temperature crack resistance. This study provides a promising approach for developing high-performance emulsified asphalt materials, which have strong application potential in pavement maintenance, waterproof coatings, and tack coats.