Preparation and characterization of novel epoxy Vitrimer asphalt binders based on reversible covalent network

Although epoxy asphalt possesses excellent mechanical properties, good fatigue resistance, and high durability, it is not recyclable. The aim of this study is to apply the principle of renewable Vitrimer materials, using zinc acetate catalyst and multi-organic carboxylic acids for curing epoxy asphalt. Several epoxy asphalt materials are prepared including dynamic hydroxyl-ester covalent bond epoxy Vitrimer asphalt (DHVE-EVA), dynamic disulfide covalent bond epoxy Vitrimer asphalt (DTS-EVA), and double dynamic covalent bond epoxy Vitrimer asphalt (DTS-DHVE-EVA), and their physical and chemical properties are systematically investigated. Fourier transform infrared characterization studies reveal that zinc ions promote the participation of ester groups in the complexation reaction, thus facilitating the exchange reaction of the ester dynamic covalent bonds. The results of the thermogravimetric analysis show that DHVE-EVA has the best thermal stability, whereas DTS-EVA has inferior thermal stability due to the susceptibility of the S-S bond tends to break when undergoing heating. The thermal stability of DTS-DHVE-EVA is in between DHVE-EVA and DTS-EVA. Investigation into the mechanical properties shows that DHVE-EVA has better usability compared with DTS-EVA and DTS-DHVE-EVA. The tensile strength of DHVE-EVA can still be maintained at 3.0 MPa when its maximum tensile ratio reaches more than 300%. Scanning electron microscope images show that DHVE-EVA exhibits a plastic fracture morphology, while DTS-EVA specimens exhibit a brittle morphology. In addition, thermal regeneration tests show that DHVE-EVA can achieve self-healing at high temperatures and can recover more than 98% of its tensile strength by hot pressing after crushing. These results indicate that DHVE-EVA has good regenerative properties, which demonstrates its potential for engineering applications.