Combining oscillatory shear rheometry and dynamic mechanical analysis to obtain wide-frequency master curves
Ábris Dávid Virág, Zsolt Juhász, Attila Kossa, Kolos Molnár
Abstract
The frequency-dependent rheological behaviour of polymers provides much information about their molecular structure and their mechanical behaviour under dynamic loading conditions. Due to the viscoelastic nature of polymers and the limited frequency measurement range of instruments, wide-frequency range characterisation is a complex task. Several methods are available to construct wide-frequency master curves, but most need a niche or custom-built equipment. In this paper, we present a novel approach combining widely available techniques, oscillatory shear rheometry and dynamic mechanical analysis to obtain wide-frequency master curves. Using polystyrene, a thermorheologically simple thermoplastic, we showed that continuous master curves can be generated from melt-state torsion and solid-state shear tests. The effects of specimen thickness and Poisson's ratio on the modulus were also considered via finite element analysis. The results can facilitate the characterisation of polymers from viscous to elastic state, and the development of test methods that use more accurate calculations. In this paper, we present a novel approach combining widely available techniques, oscillatory shear rheometry and dynamic mechanical analysis to obtain wide-frequency range master curves. We carried out finite element analysis to investigate the influence of the specimen thickness and Poisson's ratio on the moduli measured with a shear sandwich clamp in solid-state. We demonstrated that the thickness/height ratio of the specimen greatly influences its shear stress state. Using polystyrene, which is a thermorheologically simple thermoplastic, we showed that continuous master curves can be generated from melt-state torsion and solid-state shear tests. Our results can facilitate the characterisation of polymers from viscous to elastic state and the development of test methods that use more accurate calculations.