Particle size dependence polymer concentration

Figure 9.6 Dependence of the particle size on polymer concentration in the solvent stream. The group dp/yf has been plotted to account for the influence of hydrodynamics. Acetone (or THF when specified) as solvent, W/S volumetric ratio = 1 particles measured after production and quench (quench volumetric ratio = 0.2) in CIJM-dl.

Figure 1. Critical hydroxyethyt)cellulose concentration for latex particles flocculation, Dependence of both polymer molecular weight and latex median particle size on thickener concentration is illustrated. Reproduced with permission from reference 5. Copyright 1984 Academic Press.)...

The possibility of preparing colloidal particles of Pt between 50 - 60 A in diameter by photoreduction of K2PtCl4 inserted into polymer bubbles [49] was demonstrated. It was, moreover, found that the catalyst activity in during C2H4 hydrogenation increases with a decrease in Pt particle size. The dispersity of colloidal particles size depended on the concentration of the solvent used for K2PtCl4. 

Fig. 14. Dependence of particles size (curve 1), concentration of precipitated polymer (curve 2), turbidity (curve 3) of PA-3 on pH of the solution. Cp=0.1 g dL" ...

Metal/polymer nanocomposites were prepared by Chen and co-workers (55) using dispersion of metal chlorides in polyurethane. Both pol5nirethane and metal salts were dissolved in iV,A( -dimethylacetamide, followed by film casting and reduction of the metal salts by sodium borohydrate. The metal particle size depended on the type of metal salt used and on its concentration. 

Where Tj and t are the viscosities of the suspension and the solvent, respectively, R is a coefficient depending on particle size, shape and concentration, and 3> is the effective volume concentration. K can be determined in pure solvent without polymer being added and then used to determine the change in O resulting from addition of polymer. 

Figures 9.5 and 9.6 show that the power law dependence of particle size on polymer initial concentration may be significantly different for different polymers (see Table 9.2) PHDCA shows a stronger dependence than the other model polymers considered, and this value is also largely affected by the solvent used (compare for this polymer the curve for acetone and THE).

Experimentally, tire hard-sphere phase transition was observed using non-aqueous polymer lattices [79, 80]. Samples are prepared, brought into the fluid state by tumbling and tlien left to stand. Depending on particle size and concentration, colloidal crystals tlien fonn on a time scale from minutes to days. Experimentally, tliere is always some uncertainty in the actual volume fraction. Often tire concentrations are tlierefore rescaled so freezing occurs at ( )p = 0.49. The widtli of tire coexistence region agrees well witli simulations [Jd, 80]. 

The sample concentration also should be kept as low as possible, particularly in analyses of polymers on columns packed with small particle size resins. The maximum sample concentration to achieve maximum resolution decreases as the sample molecular weight becomes higher and the resin particle size becomes smaller. It is usually in the range of 0.05-5 mg/ml, depending on the sample molecular weight and resin particle size. 

Models for emulsion polymerization reactors vary greatly in their complexity. The level of sophistication needed depends upon the intended use of the model. One could distinguish between two levels of complexity. The first type of model simply involves reactor material and energy balances, and is used to predict the temperature, pressure and monomer concentrations in the reactor. Second level models cannot only predict the above quantities but also polymer properties such as particle size, molecular weight distribution (MWD) and branching frequency. In latex reactor systems, the level one balances are strongly coupled with the particle population balances, thereby making approximate level one models of limited value (1). 

PVA and TaM -for the 88%-hydrolyzed PVA. The same dependence was found for the adsorbed layer thickness measured by viscosity and photon correlation spectroscopy. Extension of the adsorption isotherms to higher concentrations gave a second rise in surface concentration, which was attributed to multilayer adsorption and incipient phase separation at the interface. The latex particle size had no effect on the adsorption density however, the thickness of the adsorbed layer increased with increasing particle size, which was attributed to changes in the configuration of the adsorbed polymer molecules. The electrolyte stability of the bare and PVA-covered particles showed that the bare particles coagulated in the primary minimum and the PVA-covered particles flocculated in the secondary minimum and the larger particles were less stable than the smaller particles. 

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