Viscosity enhancement

Figure 2.15 Log of viscosity enhancement factor versus parameter measuring branch length for polyisoprene, [Data from W. W. Graessley, T. Masuda, J. E. I. Roovers, and N. Hadjichristidis, Afacromo/ecu/ej 9 127 (1976).]...

Low Solids/Nondispersed. Fresh water, clay, and polymers for viscosity enhancement and filtration control make up low sohd/nondispersed muds. Low soflds muds are maintained using minimal amounts of clay and require removal of all but modest quantities of drill soflds. These are called nondispersed systems because no additives are used to further disperse or deflocculate the viscosity building clays. Most water-based muds are considered dispersed because deflocculating additives are used to control the flow properties. 

In addition to chemical and spectral sensitizers, several other classes of chemical compounds are added to emulsions before coating. Additives are used to facihtate coating operations, eg, surfactants (qv) and viscosity enhancers to reduce spontaneous development ia unexposed regions, eg, tetraazaiadenes and mercaptotetrazoles and to reduce abrasion and permit high temperature processing, eg, aldehydes (qv). 

To prepare stable emulsions ia this way gelation of the continuous medium is necessary. The appearance of a Hquid emulsion may be retained by choosing a polymer for the continuous phase, giving a thixotropic solution with short breakdown and buildup times. The polymers used for this purpose are natural gums (qv) or synthetic polymers. Clay particles also act as viscosity enhancers. The members of the bentonite family derived from... 

On homogenization, the lysate may drastically increase in viscosity due to DNA release. This can be ameliorated to some extent using multiple passes to reduce the viscosity. Alternatively, precipitants or nucleic acid digesting enzymes can be used to remove these viscosity-enhancing contaminants. 

Being compared to conventional Reynolds equations, /12 can be regarded as a modification coefficient of the micropolar effects on viscosity, and its effects are shown in Fig. 8. This shows that the microstructure and microrotation will add an increase in lubricant viscosity. When the ratio hH increases, the viscosity enhancement decreases further increasing the ratio, the modiflcation approaches unit. Because I is related to the molecular size, and h is the film gap, this means that if the problem scale is much larger than the molecular dimension, microrotation and the microstructure of particles will contribute msignrhcantly to the macroscopic properties. The larger N is, the more the increase is, as also evidenced by Fig. 8. 

The effective viscosity is also affected by the microrotation of the rigid particles. If the gap is much larger than the molecular dimensions, the boundary walls will have little influence on the microrotation motion. This means that if the gap between the solid walls is sufficiently large, the micropolarity can be reasonably taken out of consideration without losing precision. The microrotation in thin film lubrication will result in viscosity-enhancements and consequently higher film thicknesses, which contribute to a better performance of lubrication. 

Fig. 7—Viscosity enhancement of confined iiquid (a) effective viscosity of dodecane measured on SFA [18] (b) effective viscosity of hexadecane measured on interferometer [19],...

In 1988, Terry and coworkers attempted to homopolymerize ethylene, 1-octene, and 1-decene in supercritical C02 [87], The purpose of their work was to increase the viscosity of supercritical C02 for enhanced oil recovery applications. They utilized the free radical initiators benzoyl peroxide and fert-butyl-peroctoate and conducted polymerization for 24-48 h at 100-130 bar and 71 °C. In these experiments, the resulting polymers were not well studied, but solubility studies on the products confirmed that they were relatively insoluble in the continuous phase and thus were not effective as viscosity enhancing agents. In addition, a-olefins are known not to yield high polymer using free radical methods due to extensive chain transfer to monomer. 

Ross and Miles foam heights with amide fatty acid amides, 2 456t viscosity enhancement, 2 455t Sodium lauryl sulfate, 24 145 cosmetic surfactant, 7 834t effect of coconut diethanolamide on foaming, 2 453t... 

Figure 14.5 Effect of a commercial solid-stating accelerator (Irgamod 1425) on the rate of intrinsic viscosity enhancement of PET (data obtained from Ciba Specialty Chemicals)...

The mixing of solvents in various ratios tinned out to be a powerful optimization tool in nonaqueous CE, since a favorable ratio of mixture dielectric constant to its viscosity enhances separation efficiency and analysis speed. 

LMC is used in underwater concrete for both new construction and repair. The important requirements to obtain antiwashout capability, such as segregation resistance, flowability, self-leveling characteristics and lower bleeding are provided by the addition of viscosity-enhancing polymeric admixtures at polymer-cement ratios of 0.2-2.0%. These admixtures are water-soluble polymers, and classified under two groups, viz., cellulose types such as methyl cellulose and hydroxy ethyl cellulose and polyacrylamide types such as polyacrylamide and polyacrylamide-sodium acrylate [101]. 

In the area of tidal concreting for sea defense work, e.g. between tides, the concrete is required to develop strength rapidly even under winter conditions. The advent of viscosity-enhancing admixtures (VEAs) which... 

The ability to consistently produce HFSCC has been made possible by the development of a new type of VEA. Most viscosity-enhancing admixtures (VEA) are readily adsorbed on cement grains and often form bridges between the cement particles. Consequently, they strongly affect... 

Fig. 7.45 Adsorption of the superplasticizer and viscosity-enhancing adnnixture molecules on the cement particles (Yammuro etal. [73]).

Fig. 7.46 Effect of interaction between superplasticizer and viscosity-enhancing admixture on flow value (Yammuro et ai. [73]).

Furthermore, dispersions of a-lactalbumin nanotubes could have promising industrial application as viscosity enhancing agents or gelling agents. 

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