Properties of Polyisoprene-Based Pressure Sensitive Adhesives Crosslinked by Electron Beam Irradiation

Many pressure sensitive adhesives are based on partially-crosslinked blends of an elastomer and a tackifying resin. In this work, a model pressure sensitive adhesive system was studied based on anionically-polymerized polyisoprenes. The effects of the initial molecular weight of the polyisoprene and the degree of crosslinking on the adhesive properties were investigated. The adhesives were crosslinked by electron beam irradiation to achieve particular levels of gel content. The dependence of gel content on dose and molecular weight is in good agreement with statistical crosslinking theory. The molecular weight of the soluble fraction was always dominated by that of the initial elastomer. With regard to creep resistance, it was observed that high gel content could compensate for low molecular weight. This was not true of the peel behavior.