Comparison of styrene with methyl methacrylate copolymers on the adhesive performance and peeling master curves of acrylate pressure sensitive adhesives

Styrene (S) and methyl methacrylate (MMA) copolymers were prepared with acrylates, such as butyl acrylate, 2-ethylhexyl acrylate and acrylic acid, for application as pressure sensitive adhesives (PSA). The copolymer compositions were designed to provide constant glass transition temperature. The PSA were tested using peel adhesion resistance, static shear resistance, loop tack and DMA. Time-temperature-superposition (TTS) was used to construct peel resistance master curves to compare copolymers containing S and MMA, and obtain a structural interpretation of the PSA performance. The TTS master curves were combined for related copolymer series to obtain composition super master curves. The super master curve construction demonstrated the comonomer composition dependence of the PSA performance and distinguished copolymers containing S from those containing MMA. Composition related performance was exhibited by static shear and loop tack, the latter in relation to the concentration shift factors. DMA results confirmed the adhesive performance interpretations. Composition super master curves suggested differences in the relative mobility of S and MMA copolymers. Chain branching and entanglements were more significant with MMA than with S copolymers. DMA and static shear resistance confirmed the peel resistance results. S copolymers decreased the loop tack consistent with their higher molecular weight and lower polydispersity, with fewer low molecular weight fractions contributing, to the tack. MMA copolymers dissipated more C, energy under high stress than S copolymers.