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Dynamic Rheometry (DR)

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Dynamic rheometry or small angle oscillatory shear viscometry is a technique for studying the viscoelastic behaviour of materials. It is most suited for studying liquids, gels, and soft rubbers. For materials having a higher stiffness, DMA is more suitable. In Dynamic rheometry (DR) a sample is placed between two plates, small sinusoidal displacement is applied to the upper plate, and the torque needed for this is measured. The measured oscillatory shear stress and strain permit the calculation of the viscoelastic response, characterized by the storage shear modulus, loss shear modulus and the loss angle. DR is a very sensitive technique for studying rheological changes due to polymerization reactions, changing physical interactions,... .

Keywords: chemorheology, visco-elastic behaviour, rheological properties, dynamic rheometry, small angle oscillatory shear viscometry

Our TA Instruments AR-G2 equipped with a liquid nitrogen cooling and electrically heated plates (both upper and lower) can be used for measurements from subambient temperatures to 600°C at heating and cooling rates between 0.1 and 20 K/min using frequencies from 0.01 Hz to 200 Hz. Using the time-temperature-superposition principle, the frequency range can be further extended to lower and higher frequencies.

Measurements can be done using prallel plates, cone-and-plate, or other geometry options. In addition to isothermal and non-isothermal experiments and frequency sweep experiments, stress relaxation and creep measurements can be performed.

For the determination of the visco-elastic properties of solids and stiff rubbers, dynamic mechanical analysis can be used.