Direct viscosity enhancement

The direct viscosity enhancement of CO2 would also improve its performance as a fracturing fluid in low permeability formations. A more viscous fluid would be able to transport the proppant particles into the fracture more effectively. These proppants hold the high permeability fracture open, increasing the rate of fluid recovery from the well. 

Finally, practical suspension formulations may contain a number of other additives that are included to provide features, not all of which are directly related to suspension stability. Viscosity-enhancing additives are an obvious example, but other formulation agents may relate to the preservation of suspension stabilizing agent, such as antimicrobial agents (e.g. benzoic acid, aldehydes and phenolics) and antioxidants (reducing agents). 

A typical dimensionless plot [25] of Q versus A for k = 0.5 and different values of n is shown in Fig. 11 based on Eq. (32). Note that the discharge rate in the axial direction is enhanced for non-Newtonian fluids by the shearing imposed in the tangential direction because the additional shearing leads to a decrease in the viscosity in accordance with Eqs. (28) and (29). 

In this chapter we examine the flow behavior of bulk polymers in the liquid state. Such substances are characterized by very high viscosities, a property which is directly traceable to the chain structure of the molecules. All substances are viscous, even low molecular weight gases. The enhancement of this property due to the molecular structure of polymers is one of the most striking features of these materials. 

Solutions in organic solvents may, with certain reservations, be used directly, provided that the viscosity of the solution is not very different from that of an aqueous solution. The important consideration is that the solvent should not lead to any disturbance of the flame an extreme example of this is carbon tetrachloride, which may extinguish an air-acetylene flame. In many cases, suitable organic solvents [e.g. 4-methylpentan-2-one (methyl isobutyl ketone) and the hydrocarbon mixture sold as white spirit ] give enhanced production of ground-state gaseous atoms and lead to about three times the sensitivity... 

In most cases polymer solutions are not ideally dilute. In fact they exhibit pronounced intermolecular interactions. First approaches dealing with this phenomenon date back to Bueche [35]. Proceeding from the fundamental work of Debye [36] he was able to show that below a critical molar mass Mw the zero-shear viscosity is directly proportional to Mw whereas above this critical value r 0 is found to be proportional to (Mw3,4) [37,38]. This enhanced drag has been attributed to intermolecular couplings. Ferry and co-workers [39] reported that the dynamic behaviour of polymeric liquids is strongly influenced by coupling points. 

In summary, there are at least four ways in which residual moisture in the amorphous state can impact on chemical reactivity. First, as a direct interaction with the drug, for example, in various hydrolytic reactions. Second, water can influence reactivity as a by-product of the reaction, by inhibiting the rate of the forward reaction, for example, in various condensation reactions, such as the Maillard reaction. Third, water acting locally as a solvent or medium facilitating a reaction, without direct participation. Finally, by virtue of its high free volume and low Tg, water can act as a plasticiser, reducing viscosity and enhancing diffusivity [28]. 

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