Polyvinyl chloride emulsion polymerization

Emulsion polymerization is widely used to produce polymers in the form of emulsions, such as paints and floor polishes. It also used to polymerize many water insoluble vinyl monomers, such as styrene and vinyl chloride. In emulsion polymerization, an agent emulsifies the monomers. Emulsifying agents should have a finite solubility. They are either ionic, as in the case of alkylbenzene sulfonates, or nonionic, like polyvinyl alcohol. 

Why are suspension and emulsion polymerization processes the primary methods by which polyvinyl chloride is manufactured How are these processes carried out ... 

Similar grafting experiments by the emulsion technique were described (34) in the system vinyl chloride/copolymer butyl methacrylate-methacrylic acid and in the reverse system, and also in the system styrene/polyvinyl chloride. In this last case again as in homogenous medium, the inverse process failed (vinyl chloride on polystyrene). Grafted acrylonitrile copolymers were also prepared in order to improve their dyeability, by polymerizing acrylonitrile in emulsion in the presence of many different polymers as polyvinyl alcohol, polymethacrylamide and polyvinylpyrrolidone (119, 120, 121), polyvinyl acetate and polyacrylic acid (115), wool (224,225), proteins (136), etc. 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

Polyvinyl chloride is produced by the free-radical polymerization of vinyl chloride. Bulk, emulsion, solution, and suspension polymerization processes have been used. 

A similar situation occurs with vinyl chloride (VC) for a very different reason. Vinyl chloride is very soluble in water, but polyvinyl chloride (PVC) is not soluble in its own monomer. VC does swell PVC, and for that reason, there is a driving force for VC transport across the aqueous phase in macroemulsion polymerization. This transport is aided by the fact that VS is very soluble in water. However, this is one macro emulsion system that might greatly benefit from the miniemulsion synthesis route. 

Molecular Weight of Polyvinyl Chloride Produced by Radiation Induced Emulsion Polymerization at 25°C... 

In vinyl compound polymerization of vinyl acetate, alcohol, bromide, chloride, or carbonate, ascorbic acid can be a component of the polymerization mixture (733-749). Activators for the polymerization have been acriflavine (734), other photosensitive dye compounds (737,738), hydrogen peroxides (740,741,742), potassium peroxydisulfate (743), ferrous sulfate, and acyl sulfonyl peroxides (747). Nagabhooshanam and Santappa (748) reported on dye sensitized photopolymerization of vinyl monomers in the presence of ascorbic acid-sodium hydrogen orthophosphate complex. Another combination is vinyl chloride with cyclo-hexanesulfonyl acetyl peroxide with ascorbic acid, iron sulfate, and an alcohol (749). Use of low temperature conditions in emulsion polymerization, with ascorbic acid, is mentioned (750,751). Clarity of color is important and impact-resistant, clear, moldable polyvinyl chloride can be prepared with ascorbic acid as an acid catalyst (752) in the formulation. 

Emulsion Polymerization Emulsions have particles of 0.05- to 5.0-pm diameter. The product is a stable latex, rather than a filterable suspension. Some latexes are usable directly, as in paints, or they may be coagulated by various means to produce very nigh-molecular-weight polymers. Examples are polyvinyl chloride and butadiene-styrene rubber. 

Used as a plasticizer for vinyl resins and for applications involving co-polymerization with polyvinyl chloride and vinyl acetates in emulsion paints and adhesives. Provides elasticity and flexibility. 

The polymerization of the gaseous monomer (bp, 13.9°C) can be performed in solutionv in emulsion, and in suspenrion the polymer is obtmned in the form of a fine powder. It is only difficulty soluble, and elevated temperatures and special solvents such as chloronaphthalene, dibutyl phthalate, tricresyl phosphate, and benzyl benzoate must be ployed. In order to achieve better solubility in a larger number of solvents, the polymers are often subjected to finther treatment, which consists in an afterchlorination, a treatment with acids, or milling. Increased solubility of the polymer is also attained by solution polymerization at high pressures and temperatures. Polyvinyl chloride is insoluble in its own monomer. 

When a mixture of water, monomer, surfectants, initiator, and property control agents forms microdroplets of monomer in water with dimensions of 1 pm, an emulsion has been formed (8). If polymerization occurs in the 1 pm droplets by migration of an initiator active site from the aqueous phase to the microdroplet to completely react the droplet, the process is emulsion polymerization. A major problem in emulsion polymerization is developing a mixture which remains a stable emulsion throughout the polymerization. Polymerization kinetics is controlled by the number of microdroplets in the reaction mixture and the polymerization rate of the monomer. Polymer can be recovered as fine particles fiom the completed reaction but is most often used as the emulsion of polymerized product. Emulsion polymerization is commonly used to synthesize two polymer types covered in this book, polyvinyl chloride... 

When solid polymer precipitates fiom bulk, solution, suspension, or emulsion polymerizations by a chain mechanism, the kinetics of the reaction and properties of the product may change sharply. If the solid phase is not swollen by the reaction mixture, the active site of the polymerization is isolated from possible termination reactions and may produce pronounced auto acceleration and increases in molecular weight of polymer formed. This behavior was quantified for one chain reaction polymer, polyvinyl chloride, covered in this book. Micldey (9) showed that polyvinyl chloride synthesis in bulk followed a two term kinetics equation with the second term representing incremental increases in polymerization rate due to accelerated polymerization in precipitated particles of polymer. 

We consider a mathematical model of polymerization which in the language of chemistry is called emulsion polymerization. This type of polymerization takes place in an aqueous medium in the presence of appropriate auxiliary substances. The well-known polymer polyvinyl chloride (PVC) can be produced in this way starting from the monomer vinyl chloride. 

It is well known that polymer miscibility is not only important in the case of simple mixture, but it also determines the physical nature of block and graft copolymers. Multi-layer structures have been studied in recent years as a means for improving physical and mechanical properties of the polymer composition. It is possible to obtain a number of functional properties by means of the multi-stage sequential emulsion polymerization. As concerns this multi -layer structure, we have already reported some interesting results in a study of the processing aid for polyvinyl-chloride, 5 which amazingly improved the processability for polyvinylchloride due to its multi-stage polymer composition produced by sequential emulsion polymerization. 

Polyvinyl chloride is one of the cheapest plastics in use today. It is prepared by the polymerization of vinyl chloride (VCM) (CH2=CHC1, B.P.—14°C) as a suspension or emulsion in a pressure reactor. The polymer is unstable at high temperamres and liberates HCl at T > 200°C. It can be injection molded or formed into a hard and brittle material. It can be readily softened by the addition of plasticizers such as diethylhexylphthalate to the extent of 30%. Plasticized PVC is used as an upholstery substitute for leather. Since the plasticizer is volatile to a small extent, it slowly leaves the vinyl which eventually becomes hard, brittle, and then cracks. This can be restored by replacing the plasticizer by repeated conditioning of the vinyl surface. 

ABS) and polyvinyl chloride (PVC). In the emulsion polymerization, reactive surfactants can be used as inisurfs when they can replace both the initiator and the surfactants, as transurfs when they may be used to control the molecular weight, and finally as surfmers when they are used as comonomers which are polymerizable. 

Polyvinyl chloride (PVC) is a homopolymer of vinyl chloride. Eighty percent of commercial PVC in packaging is produced by chain-reaction polymerization using a suspension method. Other methods are emulsion and solution polymerization. Chain-reaction polymerization requires initiators to produce free radicals, then the reaction proceeds until the chain is terminated. The predominant configuration of the monomer in the polymer chain follows a head-to-tail alignment to yield a syndiotactic polymer. 

Uses Surfactant for emulsion polymerization incl. styrene and acrylic systems, styrene butadiene rubber, polyvinyl acetate, and polyvinyl chloride food-pkg. adhesives defoamer in food-contact paper/paperboard in food-contact rubber articles Features High purity... 

The densities of most polymer dispersions are close to 1 g cm as the corresponding polymers (with the exception of polyvinyl chloride and poly(vinylidene chloride)) have densities in the range 1.0 to 1.2 g cm [2]. Since the densities of the polymer particles almost match the density of the aqueous phase, sedimentation is usually only a problem in emulsion polymers if they contain very coarse particles. Density measurements have been used in the past to follow the course of emulsion polymerization reactions, because the density of the monomer is usually lower than that of the polymer (densitometry [1]). Densities can, for instance, be determined quite simply with a pycnometer (see ISO 2811). Very high precision density measurements ( 5 X 10 g cm" ) are possible with a vibrating-tube densimeter [3]. In this method, the change in the resonant frequency of the tube, which depends on its total mass, is measured when the dispersion is placed in it. It is essential that the sample is wholly free of gas bubbles. 

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