The effect of tackifier on phase structure and peel adhesion of a triblock copolymer pressure-sensitive adhesive

The role of tackifier on the adhesive properties of pressure-sensitive adhesive tape was investigated. For this purpose, a model system consisting of polystyrene-b-polyisoprene-b-polystyrene triblock copolymer and a tackifier was prepared. The hydrogenated cyclo-aliphatic resin, such as tackifier, which has poor compatibility with polystyrene increased the peel adhesion significantly. The increase became stronger above 40 wt% tackifier. Nanometer-sized agglomerates of tackifier were found in the polyisoprene matrix and these agglomerates increased in number with an increase in the tackifier content. The higher peel adhesion was obtained in the system with the larger amount of agglomerates of tackifier in the polyisoprene matrix. It was estimated that the tackifier dissolved with initial mixing at the molecular level in the polyisoprene matrix, enhancing the wettability of the adhesive, and separated out in the form of agglomerates over time, developing the cohesive strength. On the other hand, the rosin phenolic resin tackifier had good compatibility with polystyrene, and the peel adhesion increased effectively at the lower tackifier content. However, no significant additional increase at higher tackifier content was observed.