Rheological testing

The testing of plastics and rubber can be divided into several areas. 

---

The fluids which are used in the hydraulic fracturing process can be quite complex. Laboratory research and development on these fluids require many hours of rheology testing to discover suitable compositions and systems. To speed this process, an automated stimulation fluid rheology laboratory was constructed. In this paper, we describe the types of instruments which are used in this laboratory, the computer system, and how t.vr cal experiments are set up, run, and results stored and analyzed. In the accompanying paper (Part II), the focus is on the automation of one of the more complex Instruments in this laboratory. 

M. Flanagan, Mechanical and rheological testing. In B.J. Hunt and M.I. James (Eds.), Polymer Characterisation, Blackie Academic and Professional, Glasgow, 1993, pp. 261-296 Chapter 9. 

The pulse mode experiments were conducted by placing the sample between the quartz plates and exposing it to 30 second bursts of UV radiation. Dynamic rheological tests were then applied to the sample and this process was repeated until the sample had passed its gel point and became highly cross-linked. 

Activation Energy. The gel times, determined by dynamic rheological tests, can also be utilized to calculate an apparent activation energy. We can obtain the gel times over the temperature range of interest and if the extent of reaction at these temperatures are constant, an apparent activation energy can be determined. First, the polymerization reaction can be represented by a generalized kinetic expression of the type (24)... 

Capillary rheology tests, 19 578 Capillary separations, 4 602-647 sample preparation, 4 609-610 Capillary viscometers, 21 726-731 commercial, 21 729 uses of, 21 727... 

Quality Control. In controlling the quality of production propellants, it is necessary to conduct various rheological tests on propellant samples in the laboratory. 

EAI. see Emulsifying activity index El. see Electron impact ionization Elasticity, gel rheology tests, see also Viscoelasticity... 

Since sensory and mechanical properties of a food depend on its microstructure, the knowledge of microstructure must precede any operation aimed to the attainment of a specific texture (Ding and Gunasekaran, 1998). The instrumental measurements of mechanical and rheological properties represent the food responses to the forces acting on the food structure and, for this reason, are affected by the way in which these analyses are performed. Furthermore, mechanical and rheological tests are always destructive and make impossible the execution of other analyses. 

Example 6.14 Squeezing Flow between Two Parallel Disks This flow characterizes compression molding it is used in certain hydrodynamic lubricating systems and in rheological testing of asphalt, rubber, and other very viscous liquids.14 We solve the flow problem for a Power Law model fluid as suggested by Scott (48) and presented by Leider and Bird (49). We assume a quasi-steady-state slow flow15 and invoke the lubrication approximation. We use a cylindrical coordinate system placed at the center and midway between the plates as shown in Fig. E6.14a. 

The Williams Plastometer, which is based on this geometry, has been used in the rubber industry for many years. [I. Williams, Plasticity and its Measurement, Ind. Eng. Chem., 16, 362-364 (1931).] More recently, Leider and Bird (49) pointed out the advantage of this simple geometry for transient nonviscometric rheological testing of polymeric melts. 

Large Deformation Rheological Testing of Milk Fat and Butter... 

For a plastic fat, the yield stress was defined as the stress at the limit of linearity in a small deformation rheological test. Agreement between theory and experiment was found to be good. 

Cheeses range from very soft to semi-solid to very hard, and display a very wide spectrum of rheological behavior. Consequently, virtually the whole gamut of rheological test methods already described, and many empirical tests, are applied to cheeses (Gunasekaran and Ak, 2002). 

For estimation of the processability of a moulding polymer melt, the pressure to fill a standard mould has to be measured. Furches and Kachin (1989) have compared the results of several rheological tests often used to evaluate injection moulding polymer melts. 

A variety of rheological tests can be used to evaluate the nature and properties of different network structures in foods. The strength of bonds in a fat crystal network can be evaluated by stress relaxation and by the decrease in elastic recovery in creep tests as a function of loading time (deMan et al. 1985). Van Kleef et al. (1978) have reported on the determination of the number of crosslinks in a protein gel from its mechanical and swelling properties. Oakenfull (1984) used shear modulus measurements to estimate the size and thermodynamic stability of junction zones in noncovalently cross-linked gels. 

---