Polyurethane-modified room-temperature curing epoxy super adhesive for artifact restoration and light emitting diode encapsulation

• A room temperature curing ultra-strong epoxy-based adhesive with a shear strength of up to 21 MPa. • Modified polyurethane and epoxy resin are co-crosslinked to achieve both high tensile strength (27.5 MPa) and high fracture toughness (2.8 MPa·m 1/2 ). • The unique crosslinking structure exhibits aggregation-induced emission effects and emits blue fluorescence. • The unique fluorescent properties of the adhesive have been successfully applied in the restoration of cultural relics and packaging of light-emitting diodes. Epoxy adhesives are widely used for their strong adhesion but face challenges due to high curing temperatures and brittleness, limiting their application in precision manufacturing and fine industries. In an innovative endeavor to address these limitations, we have synthesized a novel adhesive system by incorporating epoxy-functionalized polyurethane into the conventional bisphenol A-based epoxy resin. Upon subjecting the adhesive to a 24h curing period at ambient temperature, the resulting material exhibited remarkable mechanical properties. Specifically, the shear strength, tensile strength, and fracture toughness of the cured adhesive were 20.6 MPa, 36.7 MPa, and 2.87 MPa·m 1/2 , respectively, while the unmodified epoxy resin had values of only 1.9 MPa, 15.5 MPa, and 1.0 MPa·m 1/2 . Adhesive system unique crosslinked structure has been discovered to confer blue aggregation-induced emission fluorescent properties. We have successfully applied this interesting characteristic in the restoration of cultural relics and the encapsulation of light emitting diode. The research has yielded a groundbreaking adhesive formulation that not only overcomes the traditional limitations associated with epoxy materials but also introduces novel functionalities that extend its utility into diverse and sophisticated applications.