Surface area growth, particle

Figure 11. Particle surface area growth ((--------------) total emulsifier (------) total...

The rate of crystal growth is determined by two effects mass transfer toward the crystal surface, and in-building of ions in the crystal lattice. The first process is first order at low concentrations, the second process is proportional to Ac to a power between 1 and 2. Both processes are in principle proportional to the particle surface area, however, the rate of in-building may be different for different crystal planes. 

In emulsion polymerization, the monomer-swoUen polymer particle-water interfacial area is continuously generated during the particle nucleation and growth stages. What is the significance of the expanding total particle surface area with the progress of polymerization ... 

Chern and Chen [30] studied the effect of the reactive surfactant, sodium dodecyl allyl sulfosuccinate, on the semibatch emulsion polymerization of n-butyl acrylate initiated by sodium persulfate. Sodium dodecyl allyl sulfosuccinate plays a similar role in the particle nucleation and growth stages to the conventional sodium dodecyl sulfate. The final number of latex particles per unit volume of water is proportional to the concentration of sodium dodecyl allyl sulfosuccinate in the initial reactor charge (the most important parameter with regard to particle nucleation) to the 0.72-0.80 power. The saturated particle surface area occupied by one molecule of sodium dodecyl allyl sulfosuccinate is 0.36 nm for the poly (n-butyl acrylate) particles prepared by the... 

An expression for the number of particles formed during Stage I was developed, assuming micellar entry as the formation mechanism (13), where k is a constant varying from 0.37 to 0.53 depending on the relative rates of radical adsorption in micelles and polymer particles, r is the rate of radical generation, m is the rate of particle growth, is the surface area covered by one surfactant molecule, and S is the total concentration of soap molecules. 

Purely physical laws mainly control the behaviour of very large particles. Further down the particle size range, however, specific surface area, i.e. surface area per unit mass, increases rapidly. Chemical effects then become important, as in the nucleation and growth of crystals. Thus, a study of particulate systems within this size range of interest has become very much within the ambit of chemical engineering, physical chemistry and materials science. 

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