High-strength, flame-retardant, dielectric Si-functionalized biomass hybrid crosslinked non-isocyanate polyurethane-epoxy for general-purpose adhesive

The preparation of high-performance, multifunctional, eco-friendly non-isocyanate polyurethanes remains a challenging task. Herein, we designed a bio-based five-membered ring carbonate containing O-Si-O and constructed a poly(hydroxy)urea-epoxy hybrid polymer (SNIPU) through its hybrid cross-linking with epoxy resin. Hybrid cross-linking endows SNIPU with a lower curing energy requirement, facilitating the formation of the cross-linked network. SNIPU with a microphase-separated hybrid cross-linked network exhibits excellent mechanical properties, with tensile strength, strain, and notched impact strength reaching 112.78 MPa, 13.72 %, and 46.57 kJ/m 2 , respectively. The hybrid cross-linked network and abundant hydroxyl groups confer excellent cohesive strength and interfacial bonding drive to SNIPU, enabling it to exhibit outstanding bonding strength (lap-shear strength of 14.61 MPa) and bonding universality when used as an adhesive. The presence of O-Si-O confers excellent flame-retardant, dielectric, and hydrophobic properties to SNIPU, providing potential support of high-performance, multifunctional non-isocyanate polyurethanes for its application in adhesives. This study provides a new technical approach for the preparation.