Preparation of a bio-based PU/EP IPN concrete adhesive with optimized performance and decent adhesion

An adhesive serves as a vital tool in construction, repair, and rehabilitation projects. Typically crafted from polymer materials such as epoxies or polyurethane latex, it facilitates the creation of resilient bonds between a variety of surfaces, ranging from concrete-concrete and metal-concrete to concrete-composites. However, employing epoxy or polyurethane individually as adhesives often demonstrate insufficient performance and weak interfacial adhesion during service. In this study, an adhesive combining polyurethane and epoxy was synthesized, featuring an interpenetrating polymer network (IPN) structure. This innovative agent was created using polyols sourced from soybean oil and a commercial epoxy resin. By tuning the infusion of polyurethane content, the resultant resin exhibited favorable flowability in civil applications, simultaneously improved strength and toughness due to the IPN structure, and outstanding thermal stability. Notably, the incorporation of 20 wt% polyurethane yielded a polymer with a remarkable tensile strength of 35.9 MPa. Additionally, the bonding adhesion of the prepared resins on concrete specimens was investigated through splitting tensile test and shear strength test. The study explored the influences of polyurethane content, concrete strength, and adhesive layer thickness on interfacial bonding strength. The introduction of an IPN structure within the PU-20 agent proved advantageous for enhancing the bonding adhesion of the concrete, resulting in remarkable interfacial tensile and shear strengths of 4.56 MPa and 21.73 MPa, respectively.