Surface Properties and Adhesion of a Moisture-Cured Waterborne Polyurethane–Polyurea Semi-Interpenetrating Polymer Network (Semi-IPN)

Over the last 50 years, waterborne polyurethanes have been a class of polymers of growing interest to both industrial and research communities. This interest stems from increasingly stringent restrictions and new legislation relating to volatile organic compounds (VOCs) and human health problems caused by solvent-based systems. Waterborne polyurethanes show interesting properties, such as good adhesion to various substrates and mechanical properties, but poor water resistance. The aim of this paper is to characterize the surface properties and adhesion of a moisture-cured polyurethane using an isocyanate cross-linker. The adhesive used is a thermoplastic copolyester. Contact angle measurements and a T-peel test show that water resistance and adhesive strength can be improved simultaneously if an adequate semi-interpenetrating polymer network (semi-IPN) is formed. This simultaneous improvement in both properties is achieved without altering the mechanical properties, which is often the case and the aim when polymer networks are formed. These properties were investigated using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), optical profilometer, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The correlation of the results obtained from these various characterizations provides a deeper understanding of the structure-property relationship.