Rheology pseudoplastic

Xanthan, used in EOR trials in the USA, and still being considered elsewhere, has found a niche in drilling fluids, which, together with other oilfield uses, accounts for some 2000 tons per year. Xanthan solutions have several useful properties they display a highly pseudoplastic rheology, are tolerant to salt, and have good thermal stability. There was we felt, however, some scope for improvement. 

Shellflo-S, succinoglycan is an interesting new polymer for use in the oilfield, in many ways complementary to xanthan. It is particularly appropriate for use in well completion fluids at moderate temperatures, where a more pseudoplastic rheology than that provided by HEC, and a more rapidly breaking polymer than xanthan is required. 

Ben-Kerrour L, Duchene D, Puisieux F, Carstensen JT. Temperature-and concentration-dependence in pseudoplastic rheological equations for gum guar solutions. Int Pharm 1980 5 59-65. 

Thixotropy of casting slips is characterized by the time dependence of both viscosity and yield point. This phenomenon is caused by reversible sol-gel transition in the clay component, which can be affected by mechanical means (stirring, vibration). The effect is much more distinct with enamel slips than with ceramic casting slips. A more marked yield point is required with the former, while ceramic casting suspensions are usually characterized by a pseudoplastic rheological behaviour without a distinct yield point. 

For the most part, PFDs exhibit shear-thinning (pseudoplastic) rheological behavior that is either time-independent or time-dependent (thixotropic). In addition, many PFDs also exhibit yield stresses. The time-independent flow curves are illustrated in Figure 1. The shear-thinning behavior appears to be the result of breakdown of relatively weak structures and it may have important relationship to mouthfeel of the dispersions. Because the viscosity of non-Newtonian foods is not constant but depends on the shear rate, one must deal with apparent viscosity defined as ... 

The viscous fermentation broth used in this project exhibited pseudoplastic rheology that is modeled quite well over a wide range of shear rates by the power law model. Consequently, the power law was used to model fluid rheology in this study for at 10, 15, 20% solids concentration. The upper and lower limits for n in this study were obtained from experiments with fermentation broth (Z mobilis cultures) and ranged from 0.46 to 0.97 during the portion batch fermentation. 

The presence of liquid-crystalline material at the emulsion interface has been shown by electron microscopy using the freeze-etching technique 18). Typical liquid-crystalline structures are shown in Figure 16. These liquid-crystalline compositions are viscous, and the lamellar phase displays pseudoplastic rheology. The lamellar phase is the most important of all liquid-crystalline phases for emulsion stability. The presence of a liquid-crystalline phase causes a reduction of the available London-van der Waals forces for coalescence 16). As a consequence of the reduction of the influence of these dispersion forces and the high viscosity of the liquid-crystal layer, the time for coalescence is increased dramatically. 

Uses Rheology modifier for coatings, spray and thick film applies. Features Highly pseudoplastic rheology solvent-free used with Acrysol RM-2020NPR for exc. flow/sag/syneresis balance Properties Vise. 2800-4000 cps nonionic 19% solids in water Acrysol RM-825 [Rohm Haas]... 

Two separate theoretical analyses of polymer molecular behavior in solution have been carried out by Bueche (12) and Graessley (13). Both analyses predict a pseudoplastic rheology for polymer solutions in simple shear. However, Bueche s explanation is based on the response of independent polymer molecules to a shearing flow field and Graessley s explanation is based on the response of entangled molecules when placed in a shearing flow field. 

Rheology The study of material flow. Used in the ceramic industry to describe the reaction of a fluid to an applied stress. While some slips may increase in viscosity upon stirring (dilatent rheology), others will decrease in viscosity (pseudoplastic rheology). The third major rheological category, Newtonian, describes a fluid whose viscosity does not change with applied shear stress. 

Special Comments Excellent stability in the presence of acids and salts and at low pH. Excellent pseudoplastic rheology. Anionic polysaccharide Supplier Calgon, TIC Gums, Rhone-Poulenc, Vanderbilt... 

Pseudoplastic rheology was extensively discussed in Chapter 3, Section 3.4 2. Examples of pseudoplastics are listed in Table 3-10. 

The SSF products exhibit unique pseudoplastic rheology. Figure 3 shows the general behavior of Diuron SSF system. At zero or very low shear rates the system has a very high viscosity. This high viscosity contributes to the high physical stability of SSF products with no settling of the suspended solids. After die yield stress is reached the structure of the system breaks and the viscosity quickly decreases to very low values. This low viscosity allows die SSF product... 

A behaviour of the dense fine grained slurries in laminar flow regime can be described by Bingham fluid model or the yield pseudoplastic rheological model, respectively... 

Uses Surfactant, thickener for facial cleansers, body washes, baby shampoo, specialty shampoo, skin cleansers, personal washes, traditional shampoo Features Highly pseudoplastic rheology compat. with a wide range of ingredients ... 

Polyacrylates Unsupported, heavier weight gloves Polyacrylates are often supplied as an emulsion, becoming effective on raising their pH. They usually give a pseudoplastic rheology. 

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