Internal Viscosity Effects

If there is particle—particle interaction, as is the case for flocculated systems, the viscosity is higher than in the absence of flocculation. Furthermore, a flocculated dispersion is shear thinning and possibly thixotropic because the floccules break down to the individual particles when shear stress is appHed. Considered in terms of the Mooney equation, at low shear rates in a flocculated system some continuous phase is trapped between the particles in the floccules. This effectively increases the internal phase volume and hence the viscosity of the system. Under sufficiently high stress, the floccules break up, reducing the effective internal phase volume and the viscosity. If, as is commonly the case, the extent of floccule separation increases with shearing time, the system is thixotropic as well as shear thinning. 

The surface viscosity effect on terminal velocity results in a calculated drag curve that is closer to the one for rigid spheres (K5). The deep dip exhibited by the drag curve for drops in pure liquid fields is replaced by a smooth transition without a deep valley. The damping of internal circulation reduces the rate of mass transfer. Even a few parts per million of the surfactant are sometimes sufficient to cause a very radical change. 

It has often been remarked from experimental data that the internal viscosity effect appears to be approximately proportional to the solvent viscosity [102,103]. This suggests that the molecular mechanism of the rotational rearrangements may be considered as an example of Kramer s... 

The application of atomic spectroscopy methods to the analysis of petroleum products is important to the oil industry. All oil samples must be prepared in solution form and be at a concentration so as to be detected to quantify all metals of interest with accuracy and precision. Solutions containing petroleum products in organic solvents may be measured directly or with the use of internal standards to correct for viscosity effects. It is important that the selected solvent dissolves the oil and products and does not cause erratic flickering of the plasma, or quenches it. It is also important that the same solvent can be used to prepare calibration standards. The following methods are common sample preparation methods for metal analysis of crude and lubricating oils. 

Studies on local viscosity effects can be carried out using a free probe molecule, such as naphthacene, in polymer solution. Thus poly(styrene) in benzene solution has been studied with this probe at a concentration of 10 mole S,. Two stepwise increases In local viscosity at polymer concentrations of 20 to 30% and 60 to 70% were taken as indications of internal structure in the polymer solution at these concentrations (4). Similar studies were carried out on melts of n-paraffin homologues and poly(ethylene) at 150°C. The local viscosity increased with increasing molecular weight in the low molecular-weight range, but reached a plateau at around MW 2000. 

In the previous discussion, it was stated that internal pha.se content is the most important parameter in terms of viscosity and rheological behavior. Anything that slightly modifies the effective internal phase fraction produces a steep change of viscosity (remember the exponential dependency of t), with [Pg.590]

Vienna Convention for the Protection of the Ozone Layer (1985). Created a framework for international cooperation and monitoring. It was agreed in principle to tackle a global environmental problem before its effects were felt (or scientific certainty obtained), viscosity. The internal resistance to flow of a fluid mathematically defined as the ratio of shear stress to shear rate. 

In order to study the viscosity effect on the quenching of triplet excited state of (53) by TEMPO, chemically induced dynamic electron polarization and transient absorption spectra have been measured in ethylene glycol, 1,2-propanol and their mixtures. The results indicate that the quenching rate constant is viscosity-dependent and decreases linearly with the increase in solvent viscosity. The spectroscopy and dynamics of near-threshold excited states of the isolated chloranil radical anion have been studied using photoelectron imaging taken at 480 nm, which clearly indicates resonance-enhanced photodetachment via a bound electronic excited state. Time-resolved photoelectron imaging reveals that the excited state rapidly decays on a timescale of 130 fs via internal conversion. ... 

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