Enhancement of the adhesion strength of water-based ink binder based on waterborne polyurethane

Series of Waterborne Polyurethanes (WPUs) were synthesized by molecular structure design, using sodium 2-((2-aminoethyl) amino) ethanesulfonate (AAS) as the post-chain extender, and selecting poly-1,4-butanediol adipate (PBA) and isophorone diisocyanate (IPDI) as the soft segment and hard segment, respectively. The effects of changes in PBA molecular weight and AAS content on the properties of WPUs were investigated through analysis of adhesion, mechanical properties, and thermal properties. The result showed that the T-peel strength, shear strength, and adhesion of the film reached 7.75 ± 0.48 N/mm, 1.81 ± 0.08 MPa, and 1.45 ± 0.11 MPa, respectively, due to the higher hydrogen bond density in the molecular structure when the Mn of PBA was 2000 g/mol. Based on the selection, the introduction of sulfamate increased the urea bond content of the system, further increasing the intramolecular hydrogen bond density. When the content of AAS was 1.0 wt%, the T-peel strength, shear strength, and adhesion of the film were increased to the highest values of 10.63 ± 0.30 N/mm, 2.08 ± 0.09 MPa, and 2.41 ± 0.08 MPa, respectively. Therefore, WPU has a wide range of applications in the field of water-based ink binders due to its high adhesive strength.