Viscosity behaviour

Pectins with Dilliefent Viscosity Behaviour due to Different... 

H. U. Khan, J. Handoo, K. M. Agrawal, and G. C. Joshi. Determination of wax separation temperature of crude oils from their viscosity behaviour. Erdol Erdgas Kohle, 107(l) 21-22, January 1991. 

Leibler, L., E. Pezron, and P.A. Pincus, Viscosity behaviour of polymer solutions in the presence of complexing ions. Polymer, 1988.29 p. 1105-1109. 

It is expected that around 500,000 tons mPE will be manufactured in 2000 in Western Europe. Resins from high-pressure- as well as from low-pressure processes suffer more difficult processability. Their narrow molecular-weight distribution results in an unfavourable viscosity behaviour [8], As with linear low-density polyethylene (LLDPE), the viscosity of mPE is independent of the shear-rate over a wide range and reduces only at high shear-rates (Fig. 9.5-11). Therefore, energy consumption is high when mPE is processed with extruders which are designed for LDPE. 

Figure 9.5-11. Viscosity behaviour of various polyethylene resins. Solid line, mPE dashed line, LDPE dotted line, LLDPE.

In addition, the viscosity behaviour of many polymers follows the power law. In many cases, the power law index n is only constant over a few decades in the shear rate and in general, decreases with increasing shear rate. Table 15.9 gives this extreme decrease in n-values for some typical polymers. 

This effect may be responsible for the popular belief that the extensional viscosity of polymer melts increases with increasing rate of deformation. Obviously, this statement is too simplistic, as one more parameter is needed to describe the relationship between extensional viscosity and rate of deformation. The situation is even more complicated. It is certain that the correlation of Fig. 15.22 has no universal validity, but depends on the nature of the polymer. Therefore, at this moment it is not possible to predict the extensional viscosity behaviour of an arbitrary polymer. 

No differences have been found between the 3,4 - and 4,4 -dicarboxy diphenyl ether substituted poly(pheny1-1,4-phenylene terephthalate) with regards to the steady shear viscosity behaviour, but a dramatic increase in viscosity was observed as the degree of substitution was high enough to result in a isotropic melt. 

Fig. 1.28 Typical viscosity behaviour of different liquid classes. Left flow curves, right viscosity curves.

Fig. 1. 33 Material functions of polymer solutions from Fig. 1.31, upper plot, which exhibit a viscoelastic viscosity behaviour from [195],... 

Kivelson and Tarjus (1998) have considered the attractive possibility of invoking the concept of "structural frustration" in supercooled liquids, to account for the observed liquid viscosity behaviour. Around the melting temperature, T (7>1.37 g), most melts behave normally in the sense of exhibiting an Arrhenius temperature... 

Here at low concentration (c < c ) the chain dimension, r is unaffected by its neighbours, but at higher concentrations (c > c ) the chain dimension is reduced. Eventually, at very high concentrations (c > C++), the polymers are well entangled and no further reduction in spacing can occur. Also, as shown in Figure 2.4, the viscosity behaviour becomes different above a critical concentration times molecular weight (cM ). 

Utility The excellent thickening ability of OCRs has led to their extensive use in engine oils, both diesel and gasoline. However, the relatively poor low-shear, low-temperature viscosity behaviour of OCRs together with difficulty of achieving the necessary lower molecular weights (better shear stability) have precluded significant use in most other speciality lubricants. 

The viscosity is defined as the shear force per unit area necessary to achieve a velocity gradient of unity. Equation 5.2 applies to the majority of fluids, and they are generally known as Newtonian fluids, or fluids that display Newtonian behaviour. There are exceptions, and some fluids (usually liquids) do not conform to Equation 5.2, and these are generally classified as non-Newtonian fluids although within this grouping there is a sub classification with distinctly different "viscosity" behaviour for the fluids within the different groups. 

The difference between single and twin-bore capillary rheometers (Fig. 9) cannot be dealt with in this contribution. Basically this is a matter of being able to make the so-called Bagley correction with less effort and fewer errors. Likewise, no reference can be made here as to how dilatant respectively structural viscose behaviour (Rabinowitsch correction) and the strain properties of ceramic bodies or wall slipping effects (according to the Mooney method) can be determined with the capillary rheometer. 

The presence of surfactants, besides altering the latex particle surface, can also interact with the water-soluble polymer. For instance, poly(ethylene oxide) homopolymer and block copolymers interact with sodium dodecyl sulfate surfactant [109], and hence alter the latex viscosity behaviour [110]. Other water-soluble polymers are also capable of interacting with specifle surfactants [111]. When pigmented latex dispersions are thickened with associative thickeners one must consider the interactions with some of the pigment stabilizers [112] and other additives, like coalescing aids [113]. 

Where a fluid is not spinnable the various orifice flow techniques, which involve pressure drop measinements across a contraction [Binding, 1988, 1993], can provide a means of estimating the extensional-viscosity behaviour of shear-thinning polymer solutions. 

If flocculation occurs slowly, the viscosity, measured at low rates of shear, increases with time during the rest period after an efficient shearing. When this happens the paint is said to be thixotropic. If there is no dependence on time or on the previous treatment of the paint and if the viscosity decreases as the rate of shear increases, then the paint is said to be pseudo-plastic. If there is a minimum stress required before any flow can occur at all, the viscosity behaviour is said to be plastic. All these types of behaviour are, of course, contrary to Newton s equation and are grouped together under the heading of non-Newtonian viscosity. 

The coacervates, which have been investigated as regards their viscosity behaviour, behave as Newtonian liquids. See note 3 on page 245. 

PAAm/AAcNa) which are prepared by polymer analogous reactions and therefore have the same degree of polymerization and chain length distribution. Figure 5 shows the viscosity behaviour at zero-concentration for co-polymer compositions between 0 and... 

Nasr-EI-Din, H., B. F. Hawkins and K. A. Green, Viscosity Behaviour of Alkaline, Surfactant and Polyacrylamide Solutions Used for Enhanced Oil Recovery, SPE 21028, presented at the SPE Int. Symposium on Oilfield Chemistry, Anaheim, California, USA, Feb. 20-22 (1991). 

Usually, the viscosity of a latex is not appropriate for its intended end use, and must be increased by the incorporation of a water-soluble viscosity modifier. Particle-particle interaction in latexes strongly affects viscosity behaviour (147). At higher solids contents, the viscosity rapidly inaeases. Alternatively, smaller particles (at the same solids content) have less distance between particles, and as a result, a higher latex viscosity. Latex viscosity is also a function of the particle size distribution, such that high solids latexes may be produced as polydisperse or bimodal distribution latexes, in which smaller particles fill the interstices between the larger ones. The formation of... 

Pingping et al. examined the viscosity behaviour in PCL/PVC blends (50 50 w/w) in dilute solutions (<0.02 g cm" ) in several solvents - 1,2-dichloroethane (DCE), N,N-dimethyl formamide (DMF) and tetrahydrofuran (THF) [97]. In each case the intrinsic viscosity (the limiting values of r p c at zero concentration) of the PCL used was about 0.2 dl g and values of r]gp/c varied Httle with concentration. Intrinsic viscosities of PVC in DCE, THF and DMF were 1.7,1.0 and 0.76 dl g respectively in THF and DMF values of rj p/c increased with PVC concentration but in DCE decreased with increasing polymer concentration. In the three solvents the blends had intermediate viscosity behaviour variations of 77sp/c with concentration were slight and in DCE the dependence was non-linear. The authors defined ideal solution behaviour for a binary mixture of polymers A and B as one for which the relation... 

The effect of added electrolytes (sodium and potassium halides of progressively increasing molecular volume) in the concentration range 0.125—3 M on the viscosity behaviour of an aqueous sucrose solution (292 mM) between 25 and 40 °C has been investigated. Conductance data on the interaction of the sodium salts of several low-carbon aliphatic acids with sucrose in water and in formamide solutions have been reported and interpreted in terms of the effects that hydrocarbon chains have on hydrogen bonding in saturated solutions of sucrose. Conductance data have also been reported for the interaction of sucrose with symmetrical tetra-alkylammonium halides in formamide and in water in the temperature range 25—70°C. 

A novel characterization of the time evolution of the shear viscosity behaviour for xanthan and puUulan fermentation has been reported. ... 

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