Sustainable terpene triblock copolymers with tuneable properties for pressure sensitive adhesive applications

A series of triblock copolymers in a hard-soft-hard block configuration with varying hard block alpha-pinene methacrylate content and molecular weight and butyl acrylate soft segment have been synthesised and investigated for viability in pressure sensitive adhesive (PSA) applications. The morphologies vary from pockets of hard phase distributed within a continuous soft matrix, through to lamellar with co-continuous phases, and finally continuous hard phase with pockets of soft phase dispersed. Uniaxial tensile properties, probe adhesion performance and cyclic adhesive behaviour are presented for seven compositions including four short chain and three long chain copolymers, alongside a commercial benchmark PSA. Structure-property relationships for the novel elastomers are evaluated, establishing that short chain materials with 20-25 wt% poly(alpha-pinene methacrylate) offer similar tensile and adhesion performance to the commercial elastomer. Raising the hard phase concentration has been observed to provide a considerable increase in ultimate tensile strength, stiffness and peak tack force, but at the expense of significant reductions in ultimate tensile strain, adhesive bond displacement and vibrational dissipation. The results suggest that the performance of these sustainable materials can be tuned to produce viable PSAs with a range of useful properties.