Rheometer measurement, automated

The Rheo-Tex rheometer is an inexpensive, automated instmment using load cell technology to measure indentation and creep. Available software calculates hardness/softness, brittleness, plasticity, and tensile strength. This instmment is particularly valuable for measurements on foods and personal care products. 

The capillary rheometer is a valuable tool for predicting the processability of thermoplastic resins. This is done by measuring melt viscosities at shear rates and temperatures commonly encountered in extrusion and injection molding. This procedure is difficult and time consuming due to the complex nature of rheological measurements and analyses. An automated system for acquisition and analyses of capillary rheometer data has been developed to speed up and simplify this important analytical technique. 

GBC Scientific Equipment offers a Micro Fourier Rheometer, MFR 2100. The rheometer applies a squeezing motion to the sample, performing analyses on sample volumes less than 100 p.1. An automated sample injection system is included in the instrument design. The rheometer is capable of handling low-viscosity fluids, 1 mPas, with storage modulus measurement down to 10-4 Pa. Using a different measurement technique, both benchtop and in-line, the real-time ultrasonic rheometer and fluid characterization device uses spatially resolved ultrasonic... 

A versatile interfacial and film rheometer has been developed in our laboratory (7—10). In this technique, a curved, spherical cap-shaped fluid interface or liquid film is formed at a capillary tip and the interfacial tension (IFT) of the single interface or the film tension of the film can be determined by measuring the capillary pressure of the interface or film (Fig. 1). The IFT or film tension is related to the capillary pressure and the radius of the interface or film curvature by the Young-Laplace equation. The IFT and film tension can be measured not only in equilibrium, but also in dynamic conditions as well. The automated apparatus makes it possible to change the interfacial or film area in virtually any mode (expansion or contraction) at various rates (Fig. 2). This instrument is now made available through our laboratory. 

Traditional measurements reported by various investigators have been made on extrudates either with a micrometer or by weight per unit length. The Monsanto Industrial Chemicals Co. (Akron, OH) has introduced an automated capillary rheometer (the Monsanto Processability Tester) which employs an extrudate swell detector based on interaction with a scanning laser beam positioned immediately below the capillary die exit. This enables measurement of the running die swell. 

Measurement of processability and rheological behaviour of raw (unvulcanised) elastomers at variable shear rates and temperatures (viscosity and elasticity) THS Rheometer BS EN ISO 9001 [39] Negretti Automation ... 

Figure 18.52 Characterisation of polymer flow behaviour with TMS rheometer showing (A) viscosity at very low shear rates, the stress measured is a function of viscosity, (B) transient flow-step changes from low to high shear rates generate a peak stress value which is a product of the thixotropic and structural features of the sample, (C) elasticity - high shear rates produce results that represent elastic behaviour. Source Negretti Automation, Aylesbury, UK)...

This chapter covers some of the methods and instruments used to determine the mechanical properties of polymers. Examples of instrument designs and typical data generated in these measurements will be introduced. In particular, automated axial tensiometers (to find elastic modulus, yield stress, and ultimate stress), dynamic mechanical analyzers (to determine storage and loss moduli), and rheometers (to measure flow viscosity) will be introduced. This chapter considers the principles behind the devices used to establish and measure the properties of viscometric flows. One of the common techniques used to determine viscous flow properties, PoisueiUe (laminar) flow in cylindrical tubes, is also important in technical applications, as polymer melts and solutions are often transported and processed in this manner. The time-temperature superposition principle is also covered as a way to predict polymer behavior over long timescales by testing materials across a range of temperatures. 

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