Shear temperature

Many different combinations of surfactant and protective coUoid are used in emulsion polymerizations of vinyl acetate as stabilizers. The properties of the emulsion and the polymeric film depend to a large extent on the identity and quantity of the stabilizers. The choice of stabilizer affects the mean and distribution of particle size which affects the rheology and film formation. The stabilizer system also impacts the stabiUty of the emulsion to mechanical shear, temperature change, and compounding. Characteristics of the coalesced resin affected by the stabilizer include tack, smoothness, opacity, water resistance, and film strength (41,42). 

To subject test fluids to the full range of shear, temperature and time conditions which may be encountered 1n a typical fracturing treatment, different Instruments may be coupled together. For... 

This is a theoretical equation that was derived from free volume theory. If extruding materials at lower than normal temperatures, the higher sensitivity of the viscosity to temperature is an issue that needs to be considered. The engineering-based viscosity equation developed by Adams and Campbell [18] has been shown to hold for all nominal processing temperatures, from within a few degrees of Tg [26, 27] to conventional extruder melt temperatures. The Adams-Campbell model limiting shear temperature dependence is ... 

Weir (1963) defined the mouldability index, aSTv (the index STV stands for shear-temperature-viscosity), as follows ... 

The open-cell vinyl foams produced by mechanical frothing, is used to produce sheets, such as flooring underlay, wall coverings, and other applications requiring relatively close thickness tolerances. Plastisol is mixed with a given amount of air in a high-shear, temperature-... 

In rubber systems containing carbon black, flocculation may cause substantial changes in mechanical properties. Flocculation in these systems counteracts filler dispersion. Carbon black flocculation occurs in filled rubber stock during storage or during vulcanization in the absence of shear. " Temperature is the important kinetic factor which affects the flocculation rate (Figure 5.19). In addition to temperature and time, flocculation depends on the type of carbon black and its concentration. 

The foregoing mastication pattern is characteristic of the several fully formed thermoplastic polyurethane elastomer compositions we have examined. An obvious question the pattern raises is why mastication reduces already formed polymer to such essentially constant low viscosity level under a given set of shear/temperature/time conditions while the same conditions raise the viscosity of the same composition of forming polymer to a much higher and growing or constant viscosity level, (e.g., Polymer 5, Figure 3). 

This is achieved by heating the starch above the glass transition temperature (Tg) and the melting temperatures (Tm) of its components, until they undergo endothermic transitions under shear, temperature and pressure for a time sufficient to destroy also the granular sttucture. As already stated, the water volume fraction required has to be below 0.45 and preferably below 0.28 [27]. 

A generalized analysis that combines the effects of shear, temperature and pressure on the rheological parameters, may lead to an expression of a so-called effective viscosity, p, for a power-law liquid in a limited operational range. 

Patterns, i.e. regular spatiotemporal structures, can easily be generated in liquid crystals via a large variety of external stresses, e.g., by mechanical shear, temperature or pressure gradients, electric or magnetic fields, etc. representative examples can be found in Buka and Kramer. Here we concentrate on patterns induced by electric fields in nematics and in particular on the implications of flexoelectricity. 

Similar observations were obtained in studies of iPP processed with a heteronuclear dimetal complex of lanthanum and calcium with some specific ligands used as the nucleating agent. Lamellar thickness was dependent on the shear temperature and shear rate. ... 

Figure 4.5. The 2D-SAXS patterns of the iPP sample containing 0.2 vrt% nucleating agent (heteronuclear dimetal complex of lanthanum and calcium) as a function of shear rate and shear temperature of (a) 200, (b) 180, and 160°C. The numbers at the bottom of the pictures represent the shear rate. The shear direction is vertical. [Adapted, by permission, from Zhang, C Wang, B Yang, J Ding, D Yan, X Zheng,, Dai, K Liu, C Guo, Z, Polymer, 60, 40-9, 2015.]...

Figure 21. Shear line scheme and near-shear temperature distribution.

Mixing mode, shear, temperature, rate, ratio... 

Assay Purity Solubility Temp Stability API/polymer solubUity Stability due to shear/temperature API vs polymer solubility in the wash Stabihty Stability... 

Extrusion is an energy eflftcient system able to break down the starch granule structure through a combination of high shear, temperature and pressure and can successfully melt starch. T3 ical single or double screw extruders, in general form consists of a hopper, barrel, feed screw, thermocouples, and dies. 

Reactive blending or extrusion in the presence of a free-radical initiator or reactive monomer have a better chance. Combining shear-temperature effect in the... 

A new type of test methodology for characterizing engineering plastics has been developed. These techniques simulate the extrusion and molding process to show what a polymer would undergo in terms of shear, temperature, pressure, and residence-time deformation. The behavior of a compound can be accurately predicted prior to processing. An online-type rheometer continuously measures the viscosity of the polymer from the die on a real-time basis, and the data is used to make screw speed adjustment to keep the viscosity consistent (10). 

A continuous highly oriented fiber may be grown from dilute polyethylene solution subjected to shear flow in a Couette apparatus [70,74]. This device consists of a pair of coaxial cylinders, the inner one of which can be rotated rapidly. A dilute polyethylene solution introduced into the gap between the cylinders is subjected to shear flow. When the appropriate conditions of shear, temperature, and concentration are met, the polymer will crystallize on to a seed fiber held in the flow field. As the extended polyethylene fiber grows, it is wound up at a rate equal to its extensional growth rate, the tip of the growing fiber thus remaining at a fixed position. The resulting fiber consists of a bundle of shish... 

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