Viscoelastic and Adhesion Properties of New Poly(Ether-Urethane) Pressure-Sensitive Adhesives

New thermoplastic poly(ether-urethane) (TPUs) pressure-sensitive adhesives (PSAs) have been synthesized with the prepolymer method by reacting methylene diisocyanate, different blends of polyether diols—poly(propyleneglycol) (PPG) and poly(tetramethylene ether glycol) (PTMEG)—and 1,4-butanediol chain extender; different NCO/OH ratios have been used. The properties of the TPU PSAs depended on both the NCO/OH ratio and the PTMEG content in the blend. The addition of PTMEG polyol produced semicrystalline regions in the soft segments of the TPUs and inhibited the mobility of the polymeric chains; this led to improved cohesion of the TPU PSAs; however, similar degrees of phase separation were obtained in all TPUs synthesized with different PTMEG contents. The increase of the PTMEG content in the polyols blend improved both the cohesion and the adhesion but decreased the tack of the TPU PSAs. The optimal balance between the adhesion and cohesion properties was found in the TPU PSA synthesized with 50 wt% PPG + 50 wt% PTMEG and an NCO/OH ratio of 1.20.