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.

Automated summary

A series of triblock copolymers with different hard block alpha-pinene methacrylate content and molecular weight and a butyl acrylate soft segment were synthesized and examined for their viability in pressure sensitive adhesive (PSA) applications. The morphologies of the copolymers varied, with some having pockets of hard phase dispersed within a continuous soft matrix and others having a lamellar with co-continuous phases structure. The evaluation of the structure-property relationship showed that short chain copolymers with 20-25 wt% poly(alpha-pinene methacrylate) exhibited similar tensile and adhesion performance to a commercial elastomer. Increasing the concentration of the hard phase led to increased ultimate tensile strength and stiffness, but also resulted in significant reductions in ultimate tensile strain, adhesive bond displacement, and vibrational dissipation. These sustainable materials can be tailored to produce PSAs with a range of useful properties.