Study on novel rosin‐based polyurethane reactive hot melt adhesive

Abstract Chain extender is a major additive in polyurethane adhesive preparation, which has a great influence on its molecular weight, green strength, and thermal resistance. In this work, we first synthesized a novel rosin‐based chain extender to replace conventional petroleum derived ones due to rosin was a renewable and low cost natural material. Afterward, the as‐prepared rosin‐based chain extender reacted with the isocyanate‐terminated polyurethane prepolymer to prepare polyurethane reactive hot melt adhesive (PURHMA). Rosin contains rigid hydrophenanthrene ring, which may have good effect on the thermal and mechanical properties of PURHMA. Consequently, the characterization of the thermal and physical properties of sustainable PURHMA was made using differential scanning calorimetry, X‐ray diffraction, dynamic mechanical thermal analyzer, as well as thermogravimetric analysis. Eventually, the adhesion performance of PURHMA on wood substrates were investigated by adjusting the amount of rosin‐based chain extender in the adhesive system. It was found that with the increase of the chain extender content, the thermal resistance, mechanical property, and adhesion property of PURHMA were significantly improved. The tensile strength of adhesive joints increased from 4.15 to 15.53 MPa, and the ultimate lap shear strength increased from 5.76 to 8.92 MPa. More strikingly, the rosin‐based PURHMA exhibited excellent bonding strength even after aging in water (less than 18%).