Optimization of adhesive performance of waterborne poly(urethane-urea)s for adhesion on high and low surface energy surfaces

Achieving adhesion to materials with a low surface energy is a challenge when designing new soft adhesives. With this question in mind, waterborne poly(urethane-urea) (WPUU) dispersions based on poly(ethylene oxide) (PEO) homopolymer and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) and poly (propylene oxide-b-ethylene oxide-b-propylene oxide) (PPO-b-PEO-b-PPO) triblock copolymers were prepared. Adhesives cast from the dispersions exhibited better adhesion on a low surface energy polypropylene (PP) probe than on a high surface energy steel probe. Moreover, with the aim of improving the adhesive performance of the WPUUs for pressure sensitive adhesive (PSA) applications, bilayer systems were designed. They were prepared using two WPUUs with differing viscoelastic behavior (one more solid-like and the other one, more liquid-like) to create a gradient in the viscoelastic properties. This strategy led to adhesive materials that exhibited fibrillation during probe tack measurements using a steel probe, which is typical of PSAs. Finally, prototype adhesive tapes were prepared from one of the bilayer systems. These adhesive tapes performed in a peel test in a similar way as a domestic commercial adhesive tape, making them interesting for that potential application.