Mechanical attachment rheology

Rheology. The rheological properties of the blends and their components were determined on a Rheometrics Mechanical Spectrometer (RMS 800). Three kinds of dynamic oscillatory measurements (i.e. temperature, time, and frequency sweeps) were carried out. All experiments were done by using a parallel plate attachment with a radius of 12.5 mm and a gap setting from 1.2 to 1.8 mm. There was no significant dependence of the experimental results on the gap setting. 

Two liquid crystalline copolyesters of 60 mole % PHB/PET and 80 mole % PHB/PET were used in this study. These samples were supplied by Tennessee Eastman and the properties are given elsewhere. Rheological properties were measured under various conditions of shear and thermal history using a 0.1 radian cone and plate attachment of a Rheometrics Mechanical Spectrometer (RMS). Various types of flow histories were used in this study and these are listed below ... 

The rheological compatibility of PPBC with EPDM was also investigated. Melt blends of PPBC and EPDM (1,2,5, and 10 wt%) were prepared in a twin shaft roller mixer attached to Brabender Plasticorder. The mixing temperature (230°C), screw speed (80 rpm), and mixing time (5 min) were kept constant. Dynamic mechanical properties of the individual pol3rmers and blends were measured using RDS - 7700 (Rheometrics Inc.) in the parallel plate mode, with gap, 2 -I- 0.1 mm, and at temperature 230 + 1°C. 

It is now well established that most colloidal systems in aqueous media remain stable because of the cooperative effect between electric charges attached to the suspended particles and the counter-ions in the immediate environment around them. A suitable description of this electrical picture,therefore, must be included in the foundation for any thermodynamic or statistical mechanical analysis of such colloidal systems. One should also point out,however, that many problems of practical interest are concerned with irreversible processes taking place in the colloid, i.e. coagulation or flocculation, rheology, and electro-kinetic behavior. An understanding of these processes cannot be derived from equilibrium phenomena. Moreover, even a complete treatment of colloid equilibrium should not be based exclusively on electrostatic considerations but should also allow for short range forces, such as van der Waals attraction. 

Abstract The structure and mechanics of very thin hquid crystal films depend on the intermolecular interactions in confined dimensions. The rheology of such films has been investigated by a shear force apparatus constructed as an attachment to the surface forces apparatus. The novelty of this method is that the rheological parameters are extracted from the amplitude and the phase of the output signal as a function of the resonance frequency. The apparent viscosity of the liquid crystal film is calculated from the damping coefficient by using a simple theoretical model. The viscosity of nanometer thin films of 4-cyano-4-... 

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