Surface active transfer agents

The formulations of emulsion pol3mierization may include a wide variety of ingredients chain transfer agents are added to a latex formulation to help regulate the molar mass and molar mass distribution of the latex polymer. The mercaptans are the most common fppe of chain transfer agents. The surface active transfer agents, "transurjs", are also used in... 

A disperse dye suspension responds somewhat differently when a surface-active solubilising agent is added. At low concentrations of this type of additive the saturation solubility of the dye remains relatively little changed, but when the critical micelle concentration of the surfactant is reached a sudden marked increase in dye solubility is observed [57]. When micelles of the surfactant begin to form in the solution, these provide a more amenable environment into which the dye molecules or dimers can transfer. Above the critical micelle concentration the increase in solubility of the dye is directly proportional to the concentration of surfactant present [1,56]. 

Polymerization occurs at active sites formed by interaction of the metal alkyl with metal chloride on the surface of the metal chloride crystals. Monomer is chemisorbed at the site, thus accounting for its orientation when added to the chain, and propagation occurs by insertion of the chemisorbed monomer into the metal—chain bond at the active site. The chain thus grows out from the surface (31). Hydrogen is used as a chain-transfer agent. Chain transfer with the metal alkyl also occurs. 

Interfacial Phenomena These can significantly affect overall mass transfer. In fermentation reactors, small quantities of surface-active agents (especially antifoaming agents) can drastically reduce overall oxygen transfer (Aiba et al., op. cit., pp. 153, 154), and in aerobic... 

Volatilization — Volatilization is a physico-chemical phenomenon of particular interest to environmental managers as well as safety managers. It is the tendency of a material to transfer from a liquid phase (either pure or dissolved as in aqueous systems) to a gaseous phase (commonly air). The volatilization, or evaporation as it is more commonly called, is controlled by a number of factors, the most important of which are the vapor pressure of the material, temperature (vapor pressure increases with temperature), and air/material interfacial surface area, and the action of active mass transfer agents such as wind. 

The mechanisms by which this interaction occurs may be divided into two distinct groups (S4) first, the hydrodynamic behavior of a multiphase system can be changed by the addition of surface-active agents, and, as a result, the rate of mass transfer is altered secondly, surface contaminants can interfere directly with the transport of matter across a phase boundary by some mechanism of molecular blocking. 

Experimental observations (S3) indicate that a stagnant cap is formed over the rear of the droplet as surface-active agents are added, and that this cap tends to enlarge with increasing concentrations until the entire droplet is enveloped. Thus, circulation may occur only in the front portion of the bubble. In contrast to this mechanism, Thorsen and Terjesen (T3) and Gamer (Gil) concluded that most of the mass transfer takes place at the rear of the bubble. 

Certain hydrodynamical problems, as well as mass-transfer problems in the presence of surface-active agents, have been investigated theoretically under steady-state conditions (L3, L4, L10, R9). However, if we take into account the fact that in gas-liquid dispersions, the nonstationary term must appear in the equation of mass- or heat-transfer, it becomes apparent that an exact analysis is possible if a mixing-contacting mechanism is adopted instead of a theoretical streamline flow around a single bubble sphere. 

Stirred-slurry operation, 120-123 holdup, axial dispersion, 122-123 mass transfer, 120-122 reactors, 80 Subcooling, 236-238 inlet, 261 Subreactors, 363 Sulfite-oxidation, 300-301 Summerfield, combustion equation, 44-43 Surface-active agents, 327-333 experiment, 327-329 theory, 329-333... 

The crude pigment provides only limited tinctorial strength. This necessitates the following aftertreatment dissolution as a sodium salt, precipitation with mineral acid, possibly in the presence of surface active agents, followed by drying or flushing in order to transfer the material from the aqueous to the oily phase (mineral oil, linseed oil). 

The possible existence of an interface resistance in mass transfer has been examined by Raimondi and Toor(12) who absorbed carbon dioxide into a laminar jet of water with a flat velocity profile, using contact times down to 1 ms. They found that the rate of absorption was not more than 4 per cent less than that predicted on the assumption of instantaneous saturation of the surface layers of liquid. Thus, the effects of interfacial resistance could not have been significant. When the jet was formed at the outlet of a long capillary tube so that a parabolic velocity profile was established, absorption rates were lower than predicted because of the reduced surface velocity. The presence of surface-active agents appeared to cause an interfacial resistance, although this effect is probably attributable to a modification of the hydrodynamic pattern. 

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