Vinylacetate polymerization

Comparison of published tota on vinylacetate polymerization kinetics, for which a steady-state period is typical (13), to the kinetics of variation of the number of particles which decreases during the process up to a factor of 40 (14), permits us to conclude that there is no correlatlonbetween the rate and the number of particles. This conclusion was supported by Medvedev et al. ( ) in the case of emulsion polymerization of methylm hacrylate. We deduce from the above data that the emulsifier concentration itself does not determine either the total surface of the disperse phase or the mmber of particles during polymerization of polar monomers. 

Vinylacetate polymerization 49, 59 Vinylic groups 49 N-Vinylpyrrolidone copolymers 8... 

A series of tests [15] were conducted to compare three types of polymeric modifiers for PVC Du Ponf s Elva-loy 741, a copolymer of ethylene, vinylacetate, and carbon monoxide Goodyear s Chemigum P83, a copolymer of butadiene and acrylonitrile and 566TPU from our lab, a polyester-based TPU. Some of the results are provided in Tables 5 and 6. 

This photoinitiating system is also used for the polymerization of other vinyl monomers such as styrene (St), acrylonitrile (AN), and vinylacetate (VA). The efficiency of photoinitiation by this system follows the order ... 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Vinyl-type addition polymerization. Many olefins and diolefins polymerize under the influence of heat and light or in the presence of catalysts, such as free radicals, carbomum ions or carbamons. Free radicals are particularly efficient in starting polymerization of such important monomers as styrene, vinylchloride, vinylacetate, methylacrylate or acrylonitrile. The first step of this process—the so-called initiation step—consists in the thermal or photochemical dissociation of the catalyst, and results in the formation of two free radicals-. 

Poly (benzyl ether) [G-2]-TEMPO, [G-3]-TEMPO, and [G-4]-TEMPO compounds have been synthesized and used as additives in the benzoyl peroxide initiated polymerization of styrene [127] (see Scheme 15c). After an induction period, chain growth is observed. However, the MWD is larger than in a dendrim-er-free TEMPO modulated system (Mw/Mn 2). The expectation that the den-drimer would isolate the growing chain end and prevent side reactions is not borne out. Polymerizations of methylmethacrylate, vinylacetate, and n-buty-lacrylate with the same initiator/TEMPO recipe are disappointing. 

Membrane-reservoir systems based on solution-diffusion mechanism have been utilized in different forms for the controlled delivery of therapeutic agents. These systems including membrane devices, microcapsules, liposomes, and hollow fibres have been applied to a number of areas ranging from birth control, transdermal delivery, to cancer therapy. Various polymeric materials including silicone rubber, ethylene vinylacetate copolymers, polyurethanes, and hydrogels have been employed in the fabrication of such membrane-reservoir systems (13). 

Internal plasticizers are synthesized by copolymerization of suitable monomers. Polymeric non-extractable plasticizers, mostly copolymers having substantially lower glass transition temperatures due to the presence of plasticizing ( soft ) segments such as poly(ethylene-co-vinyl acetate) with approximately 45 % vinylacetate content, ethylene-vinyl acetate-carbon monooxide terpolymer, or chlorinated PE, are available for rather special applications in medicinal articles (Meier, 1990). In this case, the performance of the internally plasticized polymers is the principal advantage. However, copolymerization may account for worse mechanical properties. A combination with external plasticizers may provide an optimal balance of properties. For example, food contact products made from poly(vinylidene chloride) should have at most a citrate or sebacate ester based plasticizers content of 5 % and at most 10 % polymeric plasticizers. 

Since the initiation by y-irradiation is unsatisfactory for AAm-TAA system, the suspension polymerization procedure is adopted using isopropanol as solvent and AIBN as initiator to obtain a resin having a capacity of 0.63 meq/g. When vinylacetate (26 % by weight based on AAm) is used as a third monomer, the capacity is improved from 0.63 to 0.9 meq/g. For the MAAm-TAA system the chemical initiation is not preferred since the yields of the resins obtained by this method are lower than those obtained by y-irradiation. 

It has been attempted to perform template polymer syntheses without using biological sources. Concepts focus on the formation of a complex between monomer molecules and a present macromolecule [4,480], This way the monomer will get preorganized and the polymerization is supposed to follow a zip mechanism controlled by the length and the configuration of the template polymer, offering replication of the molecular weight and control of the stereo structure. Polymerization of acrylic acid in the presence of poly(ethyleneimine), N-vinylimidazole/ poly(methacrylic acid) or acrylonitrile with poly(vinylacetate) have been described [469,470,471,472,473]. Recently the preparation of solid polyelectrolyte complexes from chitosan and sodium-styrenesulfonate has been reported [481]. 

Table 6. Various transfer constants for the polymerization of dienes and vinylacetate initiated by thermally decomposed hydrogen peroxide...

The carbanionic character of 2 is shown from UV and HNMR spectra. The method is not of synthetic significance, since cisjtrans mixtures of 4 arise trans strongly predominate), and 4 is usually accompanied by dimers, polymers, vinylacetic acids (from uncyclized 2) and other byproducts. Stereochemical information in 1 is lost because allylmagnesium halides 2 are subject to fast EjZ isomerization. Heating of 2, neat or in solution, does not lead to 3, and gives polymeric products. ... 

Primary steam reforming Secondary steam reforming Carbon monoxide conversion Carbon monoxide methanation Ammonia synthesis Sulfuric acid synthesis Methanol synthesis Oxo synthesis Ethylene oxide Ethylene dichloride Vinylacetate Butadiene Maleic anhydride Phthalic anhydride Cyclohexane Styrene Hydrodealkylation Catalytic reforming Isomerization Polymerization (Hydro)desulfurization Hydrocracking... 

To solve the presented problem as study object well investigated vinylacetate (VA) polymerization system initiated by AIBN photodecomposition has been choiced.At first let us discuss some literature data concerning AIBN decomposition. According to [1]... 

Traditionally, polymers have been named by attaching the prefix poly to the name of the CRU, real or assumed monomer, the source from which it is derived. Thus PS is the polymer made from styrene. When the name of the monomer consists of two or more words, parentheses should be used, but for common polymers such as polyvinylchloride, poly vinylacetate, etc., it is customary to omit them. Different types of polymerization can take place with many monomers, and there are different ways for obtaining a polymer. 

Ethylene-vinylacetate blends with PVC have been widely used in Europe as permanent polymeric plasticizers for PVC. Low cost and good weatherability of these blends permitted their use in window profiles, cable jacketing and other outdoor applications. Ethylene vinylacetate copolymer with 65-75% vinyl acetate content is quite miscible with PVC exhibiting a single T for the blend [Hammer, 1971 Ranby, 1975 Rellick and Runt, 1985]. Two phases are apparent when the vinylacetate is < 45%. Vinylchloride grafted ethylene-vinyl acetate copolymers have also been used for blending with PVC. 

In a thesis, M.B. Urquiola at Lehigh [26, 27] compares the behaviour in vinylacetate (VA) emulsion polymerization of a commercial surfmer sodium... 

Vinyl polymerization using metallocomplexes commonly proceeds by a radical pathway and rarely involves an ionic mechanism. For instance, metal chelates in combination with promoters (usually halogenated hydrocarbons) are known as initiators of homo- and copolymerization of vinylacetate. Similar polymer-bound systems are also known [3]. The polymerization mechanism is not well understood, but it is believed to be not exclusively radical or cationic (as polymerization proceeds in water). The macrochelate of Cu with a polymeric ether of acetoacetic acid effectively catalyzes acrylonitrile polymerization. Meanwhile, this monomer is used as an indicator for the radical mechanism of polymerization. Mixed-ligand manganese complexes bound to carboxylated (co)polymers have been used for emulsion polymerization of a series of vinyl monomers. Macromolecular complexes of Cu(N03)2 and Fe(N03)3 with diaminocellulose in combination with CCI4 are active in polymerization of MMA, etc. 

Write down the mechanism for the free-radical polymerization of vinylacetate initiated by 2,2 -azobis(2,4-dimethylpentanenitrile) (Vazo 52) in ethyl acetate including (a) initiation, (b) propagation, and (c) termination by disproportionation. 

Classification Polyvinylpyrrolidone-vinylacetate copolymer Definition Copolymer obtained by free-radical polymerization of 6 parts of vinylpyrrolidone and 4 parts vinyl acetate in I PA Formula (C6H,N0) (C,H602) ... 

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