Preparation and performance of urethane‐modified polytriazole adhesives

Abstract

AbstractPolytriazole adhesives are a new type of adhesives with excellent heat resistance, but the lap shear strength at room temperature is not ideal, which is about 15 MPa. In order to improve its adhesion performance at room temperature, a series of urethane‐modified polytriazole (UPTA) adhesives were successfully synthesized via 1, 3‐dipolar cycloaddition reaction between azides, and alkynes. Firstly, an alkynyl‐terminated urethane monomer di(but‐3‐yn‐1‐yl) (1,3‐phenylenebis(methylene)) dicarbamate (DBPMD) was synthesized and characterized. Then DBPMD was reacted with biphenyl dibenzyl azide (BPDBA) and N′,N′,N′,N′‐tetrapropargyl‐p,p′‐diaminodiphenyl methane (TPDDM) to prepare UPTA adhesives. Curing behavior, thermal properties, bonding performance, and resistance to damp heat aging of UPTA adhesives were studied. The results show that the introduction of urethane group has almost no effect on the curing behavior. The glass transition temperature (Tg) and the 5% thermal weight loss temperature (Td5) gradually decreased with the increased proportion of DBPMD added. Tg of UPTA adhesives ranged from 185 to 215°C and Td5 of UPTA adhesives were all above 300°C, which indicated its outstanding thermal stability. The lap shear strength at room temperature of UPTA adhesives increased first and then decreased with the increasing amount of DBPMD, which ranged from 13.9 to 19.9 MPa. The highest lap shear strength of UPTA adhesives can reach 19.9 MPa, which was 31.8% higher than PTA adhesive. The lap shear strength retention rate of UPTA adhesives at 180°C was all over 75%. Lap shear strength retention rate of UPTA adhesives under 168 h damp heat aging time was all over 80%. UPTA adhesives have good bonding performance, heat resistance, and damp heat aging resistance, which can meet many complex construction requirements.