Tack and viscoelastic properties of an acrylic block copolymer/tackifier system

The role of tackifier in a pressure sensitive adhesive tape was investigated. For this purpose, a model pressure sensitive adhesive was prepared using an acrylic block copolymer consisting of poly(methyl methacrylate) and poly(butyl acrylate) as base polymer and a tackifier. The poly(butyl acrylate) oligomer was also used as a diluent to compare the effect on the adhesion properties. Tack was measured using a rolling tack tester in wide temperature and rolling rate ranges, and the master curve was made in accordance with the time–temperature superposition law. The tack increased and the failure mode varied from cohesive failure to interfacial failure with an increase in the rolling rate. The tack was higher in the tackifier added system than in the oligomer added system. From a dynamic mechanical analysis, the modulus at high temperature decreased by the addition of both tackifier and oligomer, however, the glass transition temperature of poly(butyl acrylate) and the modulus at low temperature increased only by the addition of tackifier. The dynamic viscoelastic properties were measured in wide temperature and frequency ranges, and the master curve was also made. The viscoelastic properties varied in the order of viscosity, rubbery and glassy with an increase in the deformation rate. It was clarified that the tack value and the failure mode were strongly dependent upon the viscoelastic properties of adhesive. Both tackifier and oligomer improves the mobility of base polymer, whereas, only tackifier increases the cohesive strength of base polymer.