Rheometer, oscillatory

The shear modulus of a material can be determined by a static torsion test or by a dynamic test employing a torsional pendulum or an oscillatory rheometer. The maximum short-term shear stress (strength) of a material can also be determined from a punch shear test. 

Torsion property As noted, the shear modulus is usually obtained by using pendulum and oscillatory rheometer techniques. The torsional pendulum (ASTM D 2236 Dynamic Mechanical Properties of Plastics by Means of a Torsional Pendulum Test Procedure) is a popular test, since it is applicable to virtually all plastics and uses a simple specimen readily fabricated by all commercial processes or easily cut from fabricated products. 

ISO 6721-8 1997 Plastics - Determination of dynamic mechanical properties - Part 8 Longitudinal and shear vibration - Wave-propagation method ISO 6721-10 1999 Plastics - Determination of dynamic mechanical properties - Part 10 Complex shear viscosity using a parallel-plate oscillatory rheometer ISO 9311-2 2002 Adhesives for thermoplastic piping systems - Part 2 Determination of shear strength... 

The mechanical properties of actin filament networks depend on the manner in which actin monomer is prepared and stored, as well as how they are polymerized conditions. Differences in mechanical properties are not the consequence of using two different types of forced oscillatory rheometers. Xu et aid found that filaments assembled in EGTA and Mg from fresh, gel-filtered ATP-actin monomer (1 mg/mL) have an elastic storage... 

Dynamic or oscillatory rheometers measure viscous and elastic modulus in shear or tension. Energy dissipation produces a phase difference, so stress, strain, and phase angle can be used to characterize complex viscosity behavior. 

When using small deformation rheology there are several useful parameters that may be obtained to describe a material the complex modulus (G ), storage modulus (G ), loss modulus (G") and the tangent of the phase shift or phase angle (tan 5). These values must be taken from within the LVR, and are obtained using a dynamic oscillatory rheometer (Rao 1999). Outside the LVR, important information may be obtained such as the yield stress and yield strain. 

A commercial instrument for extensional viscosity measurements is currently offered by the Thermo Electron Corporation [40], The device uses capillary breakup techniques and is called the Haake CaBER . Vilastic Scientific, Inc. also offers an orifice attachment to their oscillatory rheometer for extensional viscosity determinations [41,42], The principle of operation of the rheometer is oscillatory tube flow [43,44], Dynamic mechanical properties can be determined... 

Mezger TG. The Rheology Handbook For Users of Rotational and Oscillatory Rheometers. 2nd ed. Haimover Vincentz Network GmbH Co KG 2006. 

The effect of temperature on the mechanical properties of a liquid can be investigated using a special type of dynamic mechanical analyser called an oscillatory rheometer. In this instrument the sample is contained as a thin film between two parallel plates. One of the plates is fixed while the other rotates back and forth so as to subject the liquid to a shearing motion. It is possible to calculate the shear modulus from the amplitude of the rotation and the resistance of the sample to deformation. Because the test is performed in oscillation, it is possible to separate the shear modulus (G) into storage (G ) and loss modulus (G") by measuring the phase lag between the applied strain and measured stress. Other geometries such as concentric cylinders or cone and plate are often used depending on the viscosity of the sample. 

Shear modulus can be determined by a static torsion test or by a dynamic test using primarily a torsional pendulum (ASTM D 2236). Also used is an oscillatory rheometer test. The torsional pendulum is applicable to virtually all plastics and uses a simple specimen readily fabricated by all commercial fabricating processes or easily cut from fabricated part. The moduli of elasticity, G for shear and E for tension, are ratios of stress to strain as measured within the proportional limits of the material. Thus the modulus is really a measure of the rigidity for shear of a material or its stifihess in tension and compression. For shear or torsion, the modulus analogous to that for tension is called the shear modulus or the modulus of rigidity, or sometimes the transverse modulus. 

Many oscillatory rheometers can also perform creep experiments. Essentially, these protocols will place the sample under a constant stress for a fixed amount... 

ISO 6721 1999 Plastics — Determination of dynamic mechanical properties — Part 10 Complex shear viscosity using a parallel-plate oscillatory rheometer. 

Mezger TG (2006) The rheology handbook for users of rotational and oscillatory rheometers. Vincentz Network, Hannover... 

Plastics—Determination of Dynamic Mechanical Properties. Part 10 Complex Shear Viscosity Using a Parallel Plate Oscillatory Rheometer Plastics—Determination of Tensile-Impact Strength... 

T. G. Mezger, The Rheology Handbook, Vincentz Verlag, Hannover, 2002. An excellent resource for users and potential purchasers of rotational and oscillatory rheometers. 

Sheriff M, Warburton B. 1974. Measurement of dynamic rheological properties using the principle of externally shifted and restored resonance. Polymer 15 253-254. Sheriff M, Warburton B. 1975. The theory of a universal oscillatory rheometer for the study of linear viscoelastic materials using the principle of normalized resonance. In Theoretical Rheology. London Applied Science Publishers, pp 299-316. Shinoda K, Yoneyama T, Tsutsumi H. 1980. Evaluation of emulsifier blending./Disper Sci Technol 1(1) 1-12. 

An oscillatory rheometer (RMS 800) was used with a plate-plate fixture at 250 °C. Dynamic moduli and complex viscosity were measured by a frequency sweep from 0.1 to 100 rad/s. All samples used for the measurements were prepared with the same thermal history. In the case of the modified samples, a time sweep at a constant frequency (10 rad/sec) was carried out to confirm the absence of unreacted modifier in the sample before each frequency sweep. 

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