UV-curable waterborne polyurethane with acrylate side groups for adhesive

To obtain a kind of UV-curable waterborne polyurethane adhesive with adjustable crosslinking degree and then regulate its properties, after polyurethane with carboxyl side groups was synthesized by a common method, glycidyl methacrylate (GMA) was grafted onto its side chain by the ring-opening reaction between carboxyl group and epoxy group, and then a kind of waterborne polyurethane with different acrylate group contents (WPUC) was conveniently prepared. The resulting WPUC can be cured to form the film with a three-dimensional crosslinked network structure (WPUC–C) under UV-light irradiation. The test results of gel fraction, volume swelling degree and crosslinking density show that the crosslinking degree of WPUC-C can be easily controlled by adjusting the GMA grafting content in WPUC. Furthermore, the relationships between the structure and properties of WPUC-C were researched. When the crosslinking degree of WPUC-C increases, its mechanical strength, adhesive property and thermal stability first increase and then decrease, the water resistance increases continuously and the light transmittance declines slightly. Among them, when the acrylate group content in WPUC is 0.4207 mmol g −1 , the resultant UV-cured WPUC-C has a tensile strength of 8.96 MPa and a shear strength of 1.67 MPa, good thermal stability and light transmittance (>95%), which exhibits the most optimal overall performance. Therefore, UV-curable waterborne polyurethane adhesive with excellent properties can easily be obtained by grafting GMA onto the side chain of waterborne polyurethane, which will have great application potential in the field of adhesive, particularly for bonding of heat-sensitive substrates and those requiring high transparency.