ETHYLENE-VINYL CHLORIDE

Based on the IR spectra of PVC and its model compounds and the IR spectrum of 4-chlorooctane, it would be expected that all three V-centred E-V triad structures (EVE, EVV, VVV) contributed intensity to the S h and C-Cl vibrations at 606-614 and 665-693 cm , respectively. On the other hand, only the WV and the racemic EW[EW(r)] triads should have Shh C-Cl vibrations in the frequency range 627-638 cm (see Table 7.5). Knowledge of the E-V triad distributions should permit an analysis of the C-Cl stretching region of the IR spectra of E-V copolymers. 

Tonelli and Bowmer [65] studied the C-H stretching vibrations in the IR spectra of ethylene-vinyl chloride copolymers and investigated the correlation between conformations, microstructure, conformation possibilities and IR intensities (Table 7.5). 

Reprinted with permission from A.E. Tonelli and T.N. Bowmer, Journal of  

Polymer Science Polymer Physics Edition, 1987, 25, 5, 1153. 1987, John  

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Ethylene Vinyl chloride Propene trans 1 Chloropropene... 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

The monomer is produced from trichloroethane by dehydrochlorination Figure 17.2). This may be effected by pyrolysis at 400°C, by heating with lime or treatment with caustic soda. The trichlorethane itself may be obtained from ethylene, vinyl chloride or acetylene. 

Bowmer and Tonelli [161] have also studied the thermal characteristics of the whole range of ethylene-vinyl chloride copolymers prepared by partial reductive dechlorination of PVC using tri-n-butyltin-hydride. Naqvi [162] has substantiated further his explanations for the thermal stability characteristics of ethylene-vinyl chloride copolymers reported by Braun et al. [159] using the results of Bowmer and Tonelli [161] as a basis. 

The initiator can be a radical, an acid, or a base. Historically, as we saw in Section 7.10, radical polymerization was the most common method because it can be carried out with practically any vinyl monomer. Acid-catalyzed (cationic) polymerization, by contrast, is effective only with vinyl monomers that contain an electron-donating group (EDG) capable of stabilizing the chain-carrying carbocation intermediate. Thus, isobutylene (2-methyl-propene) polymerizes rapidly under cationic conditions, but ethylene, vinyl chloride, and acrylonitrile do not. Isobutylene polymerization is carried out commercially at -80 °C, using BF3 and a small amount of water to generate BF3OH- H+ catalyst. The product is used in the manufacture of truck and bicycle inner tubes. 

Other commercially relevant monomers have also been modeled in this study, including acrylates, styrene, and vinyl chloride.55 Symmetrical a,dienes substituted with the appropriate pendant functional group are polymerized via ADMET and utilized to model ethylene-styrene, ethylene-vinyl chloride, and ethylene-methyl acrylate copolymers. Since these models have perfect microstructure repeat units, they are a useful tool to study the effects of the functionality on the physical properties of these industrially important materials. The polymers produced have molecular weights in the range of 20,000-60,000, well within the range necessary to possess similar properties to commercial high-molecular-weight material. 

Uses. In the production of ethylene, vinyl chloride, and chlorinated hydrocarbons as a component of bottled fuel gas... 

PVC production, on the other hand, is carried out by first high severity steam cracking of gas oil to produce ethylene. Vinyl chloride monomer (VCM) is then... 

Depending on the monomer, one needs to adjust the components of the system as well as reaction conditions so that radical concentrations are sufficiently low to effectively suppress normal termination. The less reactive monomers, such as ethylene, vinyl chloride, and vinyl acetate, have not been polymerized by ATRP. Acidic monomers such as acrylic acid are not polymerized because they interfere with the initiator by protonation of the ligands. The car-boxylate salts of acidic monomers are polymerized without difficulty. New ATRP initiators and catalysts together with modification of reaction conditions may broaden the range of polymerizable monomers in the future. 

RIS theory is used to calculate mean-square unperturbed dimensions 0 and dipole moments

of ethylene-vinyl chloride copolymers as a function of chemical composition, chemical sequence distribution, and stereochemical composition of the vinyl chloride sequences. As was previously found for several other copolymeric chains, is much more sensitive to chemical composition and chemical sequence distribution than is 0. The present calculations also indicate that both and are most strongly dependent on chemicel sequence distribution for ethylene-vinyl chloride chains having vinyl chloride sequences which are significantly syndiotactlc in structure. 

Copolymers. Vinyl acetate copolymenzes easily with a few monomers, e g, ethylene, vinyl chloride, and vinyl neodecanoate, which have reactivity ratios close to its own. Block copolymers of vinyl acetate with methyl methacrylate, acrylic acid, acrylonitrile, and vinyl pyrrolidinone have been prepared by copolymerization in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical,... 

It has been shown that tensile shear and peel strength for several latex polymers (ethylene vinyl acetate, polyvinyl alcohol, ethylene vinyl chloride, polyvinyl chloride, and acrylic) can be significantly increased by the addition of 10 percent by weight of an epoxy emulsion cured with a tertiary amine curing agent.17 The epoxy modification improves the bond strength in all cases. The degree of improvement is dependent on the selection of the latex type and the chemistry of the latex polymer. 

The tetraalkylammonium cation is not reduced. The solvent is decomposed on the cathode, yielding H2, ethylene, vinyl chloride, and car-banions. Similar processes also occur in the cathode space with the electrolyte R4N + C104. HC104 is formed around the anode and the monomer is polymerized in the anode space so far it is not known whether this is only by the effect of HC104 or whether cations from the supporting electrolyte are also involved. 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

A paper coating is based on an ethylene - vinyl chloride -MAM copolymer, pigmented with TiO and clay. (32) Similar terC. polymers, prepared with delayed adaition of vinyl chloride and NMAM, are applied to nonwoven fabrics. Drying at 119° produces a textile of good strength, handle and drape. (33)... 

AIR PRODUCTS AND CHEMICALS, INC. AIRFLEX Ethylene-Vinyl Chloride(EVCL) ... 

AIRFLEX Ethylene-Vinyl Chloride Copolymers(Continued) AIRFLEX TL-68 ... 

Ethylene-vinyl acetate polymer Ethylene-vinyl chloride Ethylene-vinyl chloride copolymer Fatty acid amide Fatty acid amides Fatty acid amine and silicone blend... 

Another type of branching occurs in some free-radical polymerizations of monomers like ethylene, vinyl chloride, and vinyl acetate in which the macroradicals are very reactive. So-called self-branching can occur in such polymerizations because of atom transfer reactions between such radicals and polymer molecules. These reactions, which are inherent in the particular polymerization process, are described in Chapter 6. 

The advantage of the small molar volume of VBr is shared by monomers like ethylene, vinyl chloride or vinyl iodide. But, the first two do not have a labile bond which could give radicals before main chain scission takes place (see Table 2). Vinyl iodide, on the other hand, has too labile a bond (C-I 221 kJ/mol, Egger and Cocks ), which probably would not even survive spinning operations. 

Table III. Reactivity Ratios and Q and e Values for Ethylene-Vinyl Chloride and Ethylene-Vinyl Acetate Copolymerizations...

Some data recently obtained on high pressure ethylene copolymerizations illustrate the quantitative aspects of an ethylene-based Q-e scheme (6). In Figures 3 and 4 copolymer composition curves for the ethylene-vinyl chloride and the ethylene-vinyl acetate copolymerizations are given. The monomer reactivity ratios for these two systems are tabulated in Table III along with Q values and e values for vinyl chloride and vinyl acetate calculated using ethylene as the standard (Q = 1.0 and g = 0). These Q and e values may be compared with those obtained using styrene as the standard. 

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