High-frequency rheology of three adhesive polymers

This paper reports linear shear-modulus rheological data for three adhesives. The data were obtained using a recently developed one-disk piezo-ceramic shear transducer that measures the complex shear modulus in a broad dynamical range, reaching frequencies up to 70 kHz [M. Mikkelsen et al., J. Rheol. 66, 983–1003 (2022)]. We first demonstrate consistency with data obtained by a standard rheometer. The paper proceeds to discuss new insights which the high-frequency data give rise to, with a focus on two questions important for applications: To which degree does time-temperature superposition apply? What is the temperature dependence of the high-frequency plateau shear modulus? For both questions, it is demonstrated that reliable predictions are much easier to arrive if high-frequency data are available. Thus, we show that the commonly used master-curve construction may lead to erroneous conclusions if based only on standard rheometer data. Finally, the data for the high-frequency plateau modulus are used to investigate the shoving-model prediction for the non-Arrhenius temperature dependence of the average relaxation time, which is found to apply to a reasonable approximation for all three samples.