Torsion pendulum method

ISO 4663 1986 Rubber - Determination of dynamic behaviour of vulcanizates at low frequencies - Torsion pendulum method... 

Torsion pendulum method for determining crystallinity and void content of tetrafluoroethylene resins. ASTM Bull. No. 242, 80—82 (1959c). 

One of most popular techniques for dynamic mechanical analysis is the torsion pendulum method. In a modification of this method designed to follow curing processes, a torsion bar is manufactured from a braid of fibers impregnated with the composition to be studied this is the so-called torsional braid analysis (TBA) method.61 62,148 The forced harmonic oscillation method has been also used and has proven to be valuable. This method employs various types of rheogoniometers and vibroreometers,1 9,150 which measure the absolute values of the viscoelastic properties of the system under study these properties can be measured at any stage of the process. The use of computers further contributes to improvements in dynamic mechanical analysis methods for rheokinetic measurements. As will be seen below, new possibilities are opened up by applying computer methods to results of dynamic measurements. 

Part 1 General guidance Part 2 Torsion pendulum methods... 

G Torsion pendulum method (Nielsen, 1962) (measurement of frequency of oscillations and rate of damping, at different temperatures) Measurement of speed of shear wave (Schuyer et al., 1954, Hartmann, 1980) G = pu2sh... 

The viscosity of the melts of the KF-K2M0O4-B2O3 system has been measured by Silny et al. (1995) using the computerized torsion pendulum method. The viscosity of... 

One of the most used and also most suitable methods of viscosity measurement of molten salts is the torsional pendulum method, which could be developed by the introduction of automatic and computational methods. The pendulum is realized in general by an arbitrary rotational body suspended from a torsional wire. However, the exact... 

Generally, the operative frequency range for the torsional pendulum method is 0.01 to 50 Hz, the upper limit of the frequency defined by the dimensions of the oscillatory frequency relative to the dimensions of the sample. At higher investigative temperatures, the polymeric materials may undergo extensional deformation (creep) due to the weight of the inertia bar. Under such circumstances, a modified torsion pendulum apparatus may be used in which an inertia disk is attached directly onto the end of the sample (12). In addition, this method is frequently employed to measure the torsion modulus at low frequencies. 

Previously, the major drawback to the simple torsion pendulum method was that it could not be used while the hber is immersed in liquids because of the damping effect of the liquid. However, Wolfram and Albrecht [83] have devised an ingenius scheme to overcome this obstacle by inserting the hber into a small glass capillary tube, thus permitting the torsional properties of hair hbers (and other hbers) to be measured in both air and liquids. Other methods are available [79,80,84] for measurement of the rigidity of hbers immersed in liquids. For additional details, see the references indicated and the texts by Meredith and Hearle [84] and Morton and Hearle [76]. 

High polymers behave—cum crano sails—elastically at very low temperatures. But no deformation of materials is free from internal friction and damping processes. By means of the sensitive torsion pendulum method, the mechanical loss was determined. In Fig. 10, tan 6 has been plotted versus temperature, where is the mechanical loss angle. These are the results ... 

The torsion pendulum method was used for the viscosity measurement The platinum cylinder with the diameter of 15 mm and the height 20 mm was used as the measuring body. The oscillation of the pendulum system were followed by means of two phototransistors, placed in the path of a light beam reflected from a mirror attached... 

A. Torsion Pendulum Method (Damped Free Vibration) for Solid Polymers... 

The dynamic shear modulus G (in Pascals) depends on the shape of the specimen and can be obtained by using the torsion pendulum method and the relation... 

ISO 6721 Plastics-Determination of Dynamic Mechanical Properties consists of 7 parts. Part 1 General principles. Part 2 Torsion-pendulum method. Part 3 Flexural vibration (Resonance-curve method). Part 4 Tensile vibration (Nonresonance method). Part 5 Flexural vibration (Non-resonance method). Part 6 Shear vibration (Non-resonance method), and Part 7 Torsional vibration (Non-resonance method). 

Like any other experimental method, the torsion pendulum method has its advantages and disadvantages. While the method has the advantage of making it possible to carry out studies under pure stress conditions, it has a limitation due to the nonuniformity of the stress in the gap between the pendulum and the cuvette. 

---