Granular polymerization

In mass polymerization bulk monomer is converted to polymers. In solution polymerization the reaction is completed in the presence of a solvent. In suspension, dispersed mass, pearl or granular polymerization the monomer, containing dissolved initiator, is polymerized while dispersed in the form of fine droplets in a second non-reactive liquid (usually water). In emulsion polymerization an aqueous emulsion of the monomer in the presence of a water-soluble initiator Is converted to a polymer latex (colloidal dispersion of polymer in water). 

Precipitation polymerization. In precipitation polymerization, monomer is polymerized either in bulk or in solution (aqueous or organic), however, the polymer formed is insoluble in the reaction media. As such, the forming polymer precipitates and the viscosity of the medium does not change appreciably. This pol5mierization is often referred to as powder or granular polymerization because of the forms in which the polymers are produced. Solution polymerization of acrylonitrile in water, and bulk polymerization of vinyl chloride are examples of precipitation polymerization. 

Solution polymerization is used for the manufacture of polyethylene, polypropylene, and polystyrene, but by far the most widely used process for polystyrene and PVC is suspension polymerization. In the latter process (also known as bead, pearl, or granular polymerization because of the form in which the final products may be obtained), the monomer is dispersed as droplets (0.01-0.05 cm in diameter) in water by mechanical agitation. Various types of stabilizers, which include water-soluble organic polymers, electrolytes, and water-insoluble inorganic compounds, are added to prevent agglomeration of the monomer droplets. Each monomer droplet in the suspension constitutes a small bulk polymerization system and is transformed finally into a solid bead. Heat of polymerization is quickly dissipated by continuously stirring the suspension medium, which makes temperature control relatively easy. 

EFFICIENCY OF DRYING OF CERTAIN GRANULAR POLYMERIC MATERIALS IN A COMBINED DRIER. 

EFFICIENCY OF DRYING OF CERTAIN GRANULAR POLYMERIC MATERIALS IN A COMBINED DRIER. //ENGLISH TRANSLATION OF ZH. PRIKL. KHIM. 41 /9/ 1987-92,1968.//... 

Granular polymerization n. A polymerization process in which the monomer, or mixture of monomers, is dispersed by mechanical agitation in a liquid phase, usually water, in which the monomer droplets are polymerized while they are dispersed by continuous agitation. Odian GC (2004) Principles of polymerization. John Wiley and Sons Inc., New York. 

Pearl polymerization See granular polymerization and suspension and bead polymerization. 

Plug flow generally does not happen in polymer melts, except in the case of wall slip (PVC). However, it does occur with granular polymeric solids. The solids conveying theory of single screw extruders is based on the assumption of plug flow of the solid polymer. 

Superficially, the free radical polymerization of TFE to form PTFE seems to be a relatively simple process. One starts with an autoclave partly full of water containing a very small amount of an initiator and, perhaps, some surface active agent. The mixture is heated at a moderate temperature, very pure TPE monomer is introduced into the kettle under pressure, and the polymer forms as white, relatively coarse particles in granular polymerization and as a milky-looking suspensoid in the other type. When the desired amount of polymer is obtained, the batch is cooled and the polymer is isolated. All of these operations must be done by remote control of the well-barricaded autoclaves. 

Granular Polymerization n A polymerization process in which the monomer, or mixture of monomers, is dispersed by mechanical agitation in a liquid phase, usually... 

Pearl Polymerization See Granular Polymerization and Suspension and Bead Polymerization. 

Copolymers of vinyl chloride with vinyl acetate (VAC) prepared by granular polymerization are the most important. As crystallinity of the PVC is almost certainly eliminated by copolymerization, a typical copolymer with 13% VAC has a lower Tg and much improved flow properties, compared with the homopolymer. 

In a precipitation polymerization, the system initially is in a homogeneous phase, because monomer and initiator are completely soluble in the initial reaction medium, but, upon initiation, the formed polymer precipitates as soon as it forms. After precipitation, the polymerization proceeds by absorption of monomer and initiator into the polymer particles. Bulk polymerization of vinyl chloride and solution polymerization of acrylonitrile in water are examples of precipitation polymerization. Precipitation polymerizations are often referred to as powder or granular polymerizations because of the forms in which the final polymer products are obtained. 

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