Vinylidene chloride copolymer monomer

Equations to Calculate Monomer Composition of Vinyl Chloride-Vinylidene Chloride Copolymers from 13C NMR Areas... 

The data shown in Tables HI and TV show that the 13C nmr spectra of vinyl chloride-vinylidene chloride copolymers have a redundancy of structural relationships. By analyzing a range of compositions, this system has been found to yield a reasonable description of both monomer composition and monomer sequence distribution. The data also show that this copolymer is a good example of a system best described by first order Markovian statistics as compared to Bernoullian statistics. 

See a/so Vinylidene chloride copolymer Vinylidene chloride monomer... 

VCAfAC. See Vinyl chlorlde/vinyl acetate copolymer VDC. See Vinylidene chloride monomer VdC. See Vinylidene chloride copolymer Vegetable carbon. See Carbon black... 

VDC. See Vinylidene chloride monomer VdC. See Vinylidene chloride copolymer VDF. See Vinylidene fluoride VE 225, VE 317 Black. See Vinyl ester resin VEB-500, VEB-IOOa, VEB-350a, VEB-10,00a, VEB-20,000, VEB-60,00a, VEB-165,000. See Dimethicone, vinyidimethyl-terminated VEctomer VE 4010. See Bis (4-vinyl oxy butyl) isophthalate... 

Vinylidene chloride copolymers may be prepared by bulk, solution, suspension and emulsion processes suspension polymerization is the preferred industrial method. The procedure used is essentially that described for the preparation of poly(vinyl chloride) (Section 4.2.3.2.) The polymerization rate for vinylidene chloride/vinyl chloride mixtures is markedly less than for either monomer alone so somewhat higher temperatures and initiator levels are used together with longer reaction times. Molecular weights are generally relatively low (Mn 20 000-50 000). 

Laser Raman spectroscopy has been proposed as a useful technique for probing the microstructure of copolymers. Good correlations were found between the concentrations of some isolated, dyad, triad and tetrad comonomer sequences in vinyl chloride/vinylidene chloride copolymers and certain scattering intensities [99]. The positions and intensities of particular absorption bands have also been correlated with chain microstructure in an infrared study of ethylene/vinyl chloride copolymers, previously characterised by C-NMR analysis [100]. More recently, FTIR spectra have been analysed for monad, dyad and triad monomer sequence-distribution dependencies in random styrene/acrylonitrile copolymers [101]. Changes in peak intensities from normalised spectra were correlated with microstructure probabilities assignments were given if there existed a linear relationship between peak intensity and the number fraction of a microstructure. 

Chang Yu Wang and Smith used pyrolysis - gas chromatography to elucidate the composition of and carry out structural studies on vinyl chloride-vinylidene chloride copolymers. The number average sequence length, which reflects monomer arrangement in the copolymer, were calculated using formulae that incorporate pure trimer and hybrid trimer peak intensities. 

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used eommercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be proeessed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

Copolymers of acrylonitrile and vinylidene chloride have been used for many years to produce films of low gas permeability, often as a coating on another material. Styrene-acrylonitrile with styrene as the predominant free monomer (SAN polymers) has also been available for a long time. In the 1970s materials were produced which aimed to provide a compromise between the very low gas permeability of poly(vinylidene chloride) and poly(acrylonitrile) with the processability of polystyrene or SAN polymers (discussed more fully in Chapter 16). These became known as nitrile resins. 

The polymer may be prepared readily in bulk, emulsion and suspension, the latter technique apparently being preferred on an industrial scale. The monomer must be free from oxygen and metallic impurities. Peroxide such as benzoyl peroxide are used in suspension polymerisations which may be carried out at room temperature or at slightly elevated temperatures. Persulphate initiators and the conventional emulsifying soaps may be used in emulsion polymerisation. The polymerisation rate for vinylidene chloride-vinyl chloride copolymers is markedly less than for either monomer polymerised alone. 

Up to this point we ve discussed only homopolymers—polymers that are made up of identical repeating units, in practice, however, copolymers are more important commercially. Copolymers are obtained when two or more different monomers are allowed to polymerize together. For example, copolymerization of vinyl chloride with vinylidene chloride (1,1-dichloroethylene) in a 1 4 ratio leads to the polymer Saran. 

The program will be demonstrated with poly(vinyl alcohol) for tacticity analysis and with copolymer vinylidene chloride isobutylene for monomer sequence analysis. Peak assignments in C-13 spectra were obtained independently by two-dimensional NMR techniques. In some cases, assignments have been extended to longer sequences and confirmed via simulation of the experimental data. Experimental and "best-fit" simulated spectra will be compared. 

Acrylic fibers. Acrylic fibers are polymers of acrylonitrile and another chemical. When acrylonitrile is 85% or more of the polymer, the fiber is called acrylic. If there s more copolymer so the percentage of acrylonitrile decreases to 35-85%, the fiber is called modacrylic. Some of the popular monomers used as copolymers are methyl acrylate and methacrylate, acrylamide, vinyl acetate, vinylidene chloride, and vinyl chloride, Dynel is 40% acrylo and 60% vinyl chloride. 

Uses. Production of copolymers of high vinylidene chloride content, the other major monomer usually being vinyl chloride such as Saran and VELON for films and coatings... 

Vinylidene chloride is used principally in copolymers with vinyl chloride, acrylonitrile and other monomers for packaging materials, adhesives and synthetic fibres (Lewis, 1993). 

The conformational entropies of copolymer chains are calculated through utilization of semiempirical potential energy functions and adoption of the RIS model of polymers. It is assumed that the glass transition temperature, Tg, is inversely related to the intramolecular, equilibrium flexibility of a copolymer chain as manifested by its conformational entropy. This approach is applied to the vinyl copolymers of vinyl chloride and vinylidene chloride with methyl acrylate, where the stereoregularity of each copolymer is explicitly considered, and correctly predicts the observed deviations from the Fox relation when they occur. It therefore appears that the sequence distribution - Tg effects observed in many copolymers may have an intramolecular origin in the form of specific molecular interactions between adjacent monomer units, which can be characterized by estimating the resultant conformational entropy. 

Recently Kargin, Usmanov and Aikhodzhayev [7] prepared a grafted copolymer of nitrocellulose with vinyl chloride or vinylidene chloride. The method roughly consists in the formation of free macro-radicals of nitrocellulose (through y-irra-diation or — more effectively — ozonization of nitrocellulose). After that, the monomer of vinyl chloride or vinylidene chloride is reacted with the macro-radical in the presence of a redox catalyst. This eventually gives a copolymer of the following diagrammatic structure ... 

Reinhardt (17) and later Kargin and Markova (18) refer to some copolymers of vinylidene chloride with vinyl monomers here crystallinity is observed for contents up to about 30% of the latter components. 

POLYVINYLIDENE CHLORIDE. [CAS 9002-86-2J. A stereoregular, thermoplastic polymer is produced by the free-radical chain polymerization of vinylidene chloride (H>C=CCIi) using suspension or emulsion techniques. The monomer lias a bp of 31.6°C and was first synthesized in 1838 by Regnault. who dehydrochlorinated 1,1.2-trichloroethane which he obtained by the chlorination of ethylene. The copolymer product has been produced under various names, including Saran. As shown by the following equation, the product, in production since the late 1930s, is produced by a reaction similar to that used by Regnault nearly a century earlier ... 

Copolymerization. Vinyl chloride can be copolymerized with a variety of monomers. Vinyl acetate, the most important commercial comonomer, is used to reduce crystallinity, winch aids fusion and allows lower processing temperatures. Copolymers are used in flooring and coatings. This copolymer sometimes contains maleic add or vinyl alcohol (hydrolyzed from the poly(vinyl acetate ) to improve the coating s adhesion to other materials, including metals, Copolymers with vinylidene chloride are used as barrier films and coatings. Copolymers of vinyl chlonde with acrylic esters in latex from are used as film formers in paint, nonwoven fabric binders, adhesives, and coatings. Copolymers with olefins improve thermal stability and melt flow, but at some loss of heat-deflection temperature,... 

VINYLIDENE CHLORIDE MONOMER AND POLYMERS. Vinyli dene chloride copolymers most valuable property is low permeability to a wide range of gases and vapors. From the beginning in 1939, the word Saran has been used for polymers with high vinylidene chloride content, and it is still a trademark of The Dow Chemical Company in some countries. Sometimes Saran and poly(vinylidene chloride) are used interchangeably in the literature. 

In this paper we would like to describe a new design, based on gas chromatographic analysis of the monomer mixture, for production of constant composition copolymers and its application to emulsion copolymerization. This design was already shortly described and applied to solution copolymerization (3) of methylmethacrylate and vinylidene chloride. Since then, the apparatus was made more simple, more reliable and more accurate. It is actually monitored by an analogic computering system which keeps the ratio of the monomers constant by controlling the addition of one of them. The process based on it can be called corrected batch process because the initial value of this ratio is kept up to the end. 

Carbon-13 nuclear magnetic resonance was used to determine the molecular structure of four copolymers of vinyl chloride and vinylidene chloride. The spectra were used to determine both monomer composition and sequence distribution. Good agreement was found between the chlorine analysis determined from wet analysis and the chlorine analysis determined by the C nmr method. The number average sequence length for vinylidene chloride measured from the spectra fit first order Markovian statistics rather than Bernoullian. The chemical shifts in these copolymers as well as their changes in areas as a function of monomer composition enable these copolymers to serve as model... 

Vinylidene chloride copolymerizes randomly with methyl acrylate and nearly so with other acrylates. Very severe composition drift occurs, however, in copolymerizations with vinyl chloride or methacrylates. Several methods have been developed to produce homogeneous copolymers regardless of the reactivity ratio (43). These methods are applicable mainly to emulsion and suspension processes where adequate stirring can be maintained. Copolymerization rates of VDC with small amounts of a second monomer are normally lower than its rate of homopolymerization. The kinetics of the copolymerization of VDC and VC have been studied (45—48). 

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