Sustainable Design of Zwitterionic Polyurethane Acrylate Emulsions for Pressure‐Sensitive Adhesive Packaging

ABSTRACT Pressure‐Sensitive Adhesives (PSAs) are widely used in flexible packaging due to their rapid adhesion, excellent transparency, and mechanical flexibility. However, traditional solvent‐based PSAs pose environmental hazards; although waterborne alternatives are more eco‐friendly, they often suffer from limited adhesion, poor wetting on low‐energy surfaces, low mechanical strength, and inadequate microbial resistance without additional additives. To overcome these challenges, two hybrid polyurethane acrylate (PUA) systems were synthesized: a conventional PUA (prepolymer‐01) and a zwitterionic‐based PUA (ZPUA, prepolymer‐02). From these prepolymers, five PSA emulsions were formulated: one from acrylic monomers (PSA‐01), one from PUA (PSA‐02), and three from ZPUA (PSA‐03, PSA‐04, PSA‐05). The incorporation of zwitterionic segments into the PUA backbone was confirmed by FTIR spectroscopy. Thermogravimetric analysis (TGA) demonstrated the superior thermal stability of ZPUA over its non‐zwitterionic counterpart. ZPUA‐based emulsions exhibited excellent wettability on low‐energy surfaces, a key advantage for packaging applications. Moreover, tensile testing showed that zwitterionic PSA films (PSA‐03 to PSA‐05) outperformed their non‐zwitterionic counterparts (PSA‐01, PSA‐02) in both tensile strength and elongation at break. Improved adhesion was also observed on difficult‐to‐bond surfaces, confirming the benefit of zwitterion integration. Importantly, the ZPUA emulsions displayed intrinsic antimicrobial activity, potentially eliminating the need for formalin as a preservative.