Coagulum mechanism

The quahty of the water used in emulsion polymerization has long been known to affect the manufacture of ESBR. Water hardness and other ionic content can direcdy affect the chemical and mechanical stabiUty of the polymer emulsion (latex). Poor latex stabiUty results in the formation of coagulum in the polymerization stage as well as other parts of the latex handling system. 

The usual description of these different polymerization processes suggests that all produce stable latexes and various hypotheses have been advanced to explain the stability of these latexes to such factors as added electrolyte, mechanical shear and freezing and thawing. In the literature, there is little mention of the fact that many of these polymerizations produce varying amounts of coagulum, i.e., polymer recovered in a form other than that of a stable latex. This coagulum is produced in all sizes of polymerization reactors, ranging from the smallest laboratory... 

Despite these generalizations, the reduction or elimination of coagulum is usually best accomplished by a "systems approach", i.e., a consideration of latex properties to be achieved in the emulsion polymerization, the economics of the polymerization process, and the deliberate design of the reactor system for that particular polymerization system. Each polymerization system must be considered as a separate system and treated as such. The most effective approach to reduce or eliminate the formation of coagulum is to determine the mechanism by which it is formed and... 

Solubility Latex Coagulum Particle panicles surface mechanical electrolyte... 

In batch experiments, the solids were varied from 35 to 75% [10]. The primary surfactant was Aerosol A103 (disodium ethoxylated nonyl phenol half ester of sulfosuccinic acid) with HD as the cosurfactant. These were used in concentrations of 1 and 4 wt% on monomer, respectively. Two KPS concentrations, 1 and 2 wt% on water, were tried. The miniemulsions were produced by ultra-sonification. Parallel conventional emulsion polymerizations were conducted for comparison to the miniemulsion polymerizations (75 °Q. Coagulum-free latexes resulted from miniemulsion polymerizations up to 60% solids, while only 50% solids could be achieved for the cxmventional process. These differences were attributed to the resulting particle size distributions where the miniemulsion polymerizations produced latexes with larger particles, broader distributions and lower viscosities than their conventional counterparts. As in other studies, this difference in PSDs was explained by differing nucleation mechanisms. However, as in other studies, it was not possible to determine whether the nucleation in the miniemulsion systems was predominantly by radical entry into chxjplets. 

B. Rai, G. Kumar, R.K. Diwan, and R.K.Khandal, Study on effect of euphorbia coagulum on physic-mechanical and fire retardant properties of polyester-banana fiber composite. Ind. 

Polymer Areas Emulsion polymerization. Effective in styrene-butadiene, poly(vinyl chloride), poly(vinyl acetate), acrylic, and styrene-acrylic latexes. Imparts excellent mechanical, thermal and electrolyte stability, low coagulum and small particle latexes. 

Coagulum is formed in many emulsion polymerizations, from the smallest laboratory size to the largest production reactors. It is observed in many forms, from a single lump of polymer with little or no fluid latex to tiny sand-like grains suspended in an otherwise stable latex. Usually, it is found as lumps in the latex or deposited on the reactor surfaces. The type and amount of coagulum formed depends upon the polymer system and the polymerization recipe and technique. Two mechanisms are proposed for the formation of coagulum (i) a failure of the stability of the latex, giving rise... 

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