Polymer agglomeration

Butyl slurry at 25—35 wt % mbber continuously overflows from the reactor through a transferline to an agitated flash dmm operating at 140—160 kPa (1.4—1.6 atm) and 55—70°C. Steam and hot water are mixed with the slurry in a nozzle as it enters the dmm to vaporize methyl chloride and unreacted monomers that pass overhead to a recovery system. The vapor stream is compressed, dried over alumina, and fractionated to yield a recycle stream of methyl chloride and isobutylene. Pure methyl chloride is recovered for the coinitiator (AlCl ) preparation. In the flash dmm, the polymer agglomerates as a coarse cmmb in water. Metal stearate, eg, aluminum, calcium, or zinc stearate, is added to control the cmmb size. Other additives, such as antioxidants, can also be introduced at this point. The polymer cmmb at 8—12 wt % in water flows from the flash dmm to a stripping vessel operated under high vacuum to... 

The individual macromolecular chains of conducting polymers agglomerate into more complicated structures, usually fibrous. The electronic conductivity of this system is a superposition of the conductivity of the individual fibres (chains) and that due to electron hopping between these domains. The latter is usually much lower, i.e. it controls the total conductivity of the system. 

The probability of the formation of polymer agglomerates is appreciably increased by electrostatic interactions. This phenomenon is, inter alia, also known in the handling of polymer powders. Owing to the fact that the polymer particles are not electrically conductive, electrostatic charging occurs in pneumatic transport systems in an... 

It was found that complete solvation of both polymers was not obtained when the apparent viscosity plateau was used as the sole criterion for solvation. A more definitive standard for determining polymer solvation should also include tests that would assure that partially dissolved polymer agglomerations could not be removed from the fluid during its application. In the work described here, viscosity measurements were supplemented by filtration testing and particle settling experiments. 

Finishing. The halogenated rubber solution then passes into a vertical drum where the solvent is flashed and stripped by steam and hot water. Calcium stearate is added to the slurry in this drum to prevent polymer agglomeration. A second vessel in series provides additional residence time for the solvent to diffuse from the ruhher and be vaporized. The final solvent content and the steam usage for solvent removal depend on the conditions in each vessel. Typically, the lead flash drum is operated at 105-120°C and 200-300 kPa (29-43.5 psi). Conditions in the final stripping stage are 101°C and 105 kPa (15 psi). The hexane can be reduced to 0.5-1.0 wt% with a steam usage of 2.0-2.5 kg/kg rubber. 

The spontaneous formation of Au particles at room temperature in air-saturated aqueous solutions of poly(ethylene glycol)s was investigated using optical, potentiometric and conductivity techniques. The kinetic information is consistent with a mechanism in which Au(III) complexes bind through ion-pairs to pseudocrown ether structures of the polymers. Reduction of the metal centers follows through their reactions with the oxyethylene groups that form these cavities. The particle size of the metal crystallites is controlled by the molar mass of the polymers. Agglomerates of small Au particles are formed as final products when polymers of low molar mass are used in the synthesis. 

Powder suspension in photosensitive organic monomer Forming, layer by layer, of powder-polymer agglomerations of a shape determined by exposure to laser beam 3D ... 

Since polymer swelling is poor and the aqueous solubiUty of acrylonitrile is relatively high, the tendency for radical capture is limited. Consequentiy, the rate of particle nucleation is high throughout the course of the polymerization, and particle growth occurs predominantiy by a process of agglomeration of primary particles. Unlike emulsion particles of a readily swollen polymer, such as polystyrene, the acrylonitrile aqueous dispersion polymer particles are massive agglomerates of primary particles which are approximately 100 nm in diameter. 

Phase Inversion (Solution Precipitation). Phase inversion, also known as solution precipitation or polymer precipitation, is the most important asymmetric membrane preparation method. In this process, a clear polymer solution is precipitated into two phases a soHd polymer-rich phase that forms the matrix of the membrane, and a Hquid polymer-poor phase that forms the membrane pores. If precipitation is rapid, the pore-forming Hquid droplets tend to be small and the membranes formed are markedly asymmetric. If precipitation is slow, the pore-forming Hquid droplets tend to agglomerate while the casting solution is stiU fluid, so that the final pores are relatively large and the membrane stmcture is more symmetrical. Polymer precipitation from a solution can be achieved in several ways, such as cooling, solvent evaporation, precipitation by immersion in water, or imbibition of... 

The most widely used pitch control method is the addition of pitch dispersants, which can be either organic, ie, typically anionic polymers such as naphthalene sulfonates, ligninsulfonates, and polyacrylates (33,34), or inorganic, ie, typically clay or talc. The polymers maintain the pitch as a fine dispersion in the pulp, preventing agglomeration and potential deposition on the paper machine or the sheet. When talc, clay, or other adsorbent fillers are added to the furnish, moderate amounts of pitch can adsorb on these materials, producing a nontacky soHd that can be retained in the sheet. 

Suspensions of oil in water (32), such as lanolin in wool (qv) scouring effluents, are stabilized with emulsifiers to prevent the oil phase from adsorbing onto the membrane. Polymer latices and electrophoretic paint dispersions are stabilized using surface-active agents to reduce particle agglomeration in the gel-polarization layer. 

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