Compositional effect on the deformation behavior of polyurethane pressure-sensitive adhesive thin films

The careful selection of composition for thin films is a critical issue to deal with. A mere change in stoichiometry deforms the thin adhesive films brusquely. In this work, a series of thin films of polyurethane-based pressure-sensitive adhesives have been synthesized and the factors responsible for collapsing of the adhesive films have been investigated. The pressure-sensitive adhesives have been prepared by the use of polypropylene glycol and hydroxyl-terminated polybutadiene macrodiols along with isophorone diisocyanate. The 40 wt % of solid contents have been maintained with hard segment contents of 28–64 wt %. Thin films of 70–100 μm have been utilized for probe-tack analysis. The high storage modulus up to 1.83 MPa has been observed from dynamic mechanical analysis of PSA films. The adhesion properties evaluated by consideration of the ratio of the loss tangent to the storage modulus (tanδ/E′) for comparison resulted in the values from 0.03 to 0.45 MPa⁻¹. The glass-transition temperature is also appeared to be a decisive factor with variation from original values. The high-molecular weight of macrodiols resulted in the loss of adhesiveness.