Polymer poly + chlorinated

VINYL CHLORIDE POLYMERS. Poly(vinyl chloride) (PVC), commanding large and broad uses in commerce, is second in volume only to polyethylene, having a volume sales in North America in 1995 of 6.2 x 109 kg(13.7 x 109 lb). Vinyl compounds usually contain dose to 50% chlorine, which not only provides no fuel, but acts to inhibit combustion in the gas phase, thus supplying the vinyl with a high level of combustion resistance, useful in many building as well as electrical housings and electrical insulation applications. 

In practice, highly conductive particles do not make good ER fluids, in part because of excessive conduction in the resulting suspension. An acceptable conductivity of the particles seems to be around 10 f2 m (Block et al. 1990), at least for particles of the polymer poly(acenequinone) in chlorinated oil. These ER fluids show a yield stress of about 1 kPa at E = 1 kV/mm, roughly equal to the predicted maximum possible value for this electric field. As expected, even higher yield stresses exceeding 10 kPa are possible when E exceeds 3 kV/mm. 

I. Organic carbochain polymers and copolymers of poly-4-methylpentene-l [4] PMMA or methyl methacrylate (MMA) copolymers with other alkyl-(meth)acrylates (AMA) [1-3, 5] poly(vinyl acetate) vinyl acetate copolymer with ethylene [4, 6-8] polymers of chlorine-containing olefins [9]. 

Chlorination of poly(vinyl chloride) destroys the regularity of the tacticity. Dor-restijn et al. [123] executed chlorination in two different ways. First, pol>tvinyl chloride) was chlorinated in solution so that no preference existed for the kind of hydrogen atom which was replaced by chlorine atoms the tacticity of the polymer molecules is destroyed more or less completely. Second, the polymer was chlorinated in powder form in this case there is a large preference for the amorphous parts, whereas the crystalline parts are mudi less available for chlorination and remain more or less intact Even if the polymer is attacked prrferentially at the isotactic sequences, the tendency to form gels will decrease, as the [nresence of an even number of isotactic sequences in between syndiotactic sequences causes an enormous increase in the crystallinity of polyfviny chloride) [82,84]. Dorrestijn et al. showed that chlorination had a dramatic influence on the tendency to form gels in the case of solution chlorination, whereas powder chlorination had only a minor effect despite much higher chlorine contents. 

It is often desirable to perform some kind of chemical modification to polymers once they have formed. Acetylation of cellulose, for example, represents the chemical modification of a naturally occurring polymer (see chapter 3) to give the technologically useful cellulose diacetate and triacetate polymers. Poly(vinyl alcohol) (PVA) is a well-known example of a polymer that can only be formed by chemical modification since vinyl alcohol monomer does not exist (except as its keto form, acetaldehyde). Instead, PVA is formed by hydrolysis of poly(vinyl acetate) (PVAc). Partly hydrolysed PVAc is, of course, simply a copolymer of VA and VAc. As another example, ethylene/vinyl chloride copolymers can be prepared by reductive elimination of chlorine from poly (vinyl chloride) (PVC). The driving force here is that, although ethylene and vinyl chloride can be copolymerised directly, the normal routes to these polymers give insufficient control over composition and sequence distribution. 

Tohoku National Industrial Research Institute is studying poly-chlorinated bi-phenyls and waste polymers. Kumamoto University is studying sewage sludge treatment and University of Tokyo the kinetics of SCWO of phenol. 

The latest more extensive work on the chlorination of PVC was part of an overall study of the chlorination of polyalkenamers. The chlorinated butadiene polymer (poly-butenamer) was found to be crystalline or at least had crystalline chain segments a unit cell for chlorination products of trans-1,4-polybutadiene was determined and for the crystalline material a structure of a diisotactic poly(erythro-l,2-dichlorobutadiene) was proposed. This proposal required the assumption that the addition of chlorine is stereospecific. It was also mentioned that the number of ordered units of about ten is sufficient to display crystallinity, sufficient to allow the determination of the structure by x-ray analysis. 

In 1991, another class of sulfiir-nitrogen-phosphorus polymers, poly-thionylphosphazenes, were reported (96,97). These materials, which possess four-coordinate sulfuifVI) atoms in the backbone, possess improved stability and were prepared by a thermal ROP of cyclic thionylphosphazenes (30), with either chlorine or fluorine at the sulfuifVI) center, at 165-180°C (eq. 27) (98). An... 

A copolymer of methyl methacrylate and vinyl chloride containing labelled chlorine ( "Cl) has been examined using thermovolatilization analysis and radiochemical assay. The yields of methyl chloride and hydrogen chloride agree with predictions made from sequence distribution calculations. The thermal degradation of a number of chlorine-containing polymers, poly(vinyl chloride), chlorinated polyethylene, chlorosulphonated polyethylene, polychloroprene, poly-epichlorhydrin, and co- and ter-polymers of epichlorhydrin has been compared and structural effects elucidated. ... 

Figure 7.6 shows the electronic spectra of poly(52-3). While this showed one peak due to the Amax In an aqueous solution of the salt form, a film cast from an acid form solution indicated that the polymer was in a well doped-state. Since chlorine anions, sodium cations and iron cations were completely removed from the solution, self-doping took place in the polymer. Poly(52-3) had an of about 1 x 10, which was sufficient for a flexible free-standing film to be cast. Cast films were deep greenish-brown and had a conductivity of 0.1 Scm without adding any external dopants. Cyclic voltammometry... 

Fig. 19. The conductivities at 293 K of poly(A/ -vinylcarbazoles) (PNVCs) containing cation radical XII at mole fractions x. Characteristics of samites o and from PNVCs of molecular weights 1.6 X 10 and 1.25 x 10 respectively from a PNVC, 75% mono-substititted with chlorine and molecular weight 9.5 x 10 a similar polymer < 90% chlorinated and molecular we t 10 a physical mixture of an oxidised sample with PNVC...

The molecular weight of a polymer can be controlled through the use of a chain-transfer agent, as well as by initiator concentration and type, monomer concentration, and solvent type and temperature. Chlorinated aUphatic compounds and thiols are particularly effective chain-transfer agents used for regulating the molecular weight of acryUc polymers (94). Chain-transfer constants (C at 60°C) for some typical agents for poly(methyl acrylate) are as follows (87) ... 

Poly(vinyl chloride). PVC is a hard, brittle polymer that is self-extinguishing. In order to make PVC useful and more pHable, plasticizers (qv) are added. More often than not the plasticizers are flammable and make the formulation less flame resistant. Flammability increases as the plasticizer is increased and the relative amount of chlorine decreased, as shown in Table 7. The flame resistance of the poly(vinyl chloride) can be increased by the addition of an inorganic flame-retardant synergist. 

Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometaUic compounds. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinyhdene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. Without the use of heat stabilizers, PVC could not be the widely used polymer that it is, with worldwide production of nearly 16 million metric tons in 1991 alone (see Vinyl polymers). 

The most innovative photohalogenation technology developed in the latter twentieth century is that for purposes of photochlorination of poly(vinyl chloride) (PVC). More highly chlorinated products of improved thermal stabiUty, fire resistance, and rigidity are obtained. In production, the stepwise chlorination may be effected in Hquid chlorine which serves both as solvent for the polymer and reagent (46). A soHd-state process has also been devised in which a bed of microparticulate PVC is fluidized with CI2 gas and simultaneously irradiated (47). In both cases the reaction proceeds, counterintuitively, to introduce Cl exclusively at unchlorinated carbon atoms on the polymer backbone. 

Trilialophenols can be converted to poly(dihaloph.enylene oxide)s by a reaction that resembles radical-initiated displacement polymerization. In one procedure, either a copper or silver complex of the phenol is heated to produce a branched product (50). In another procedure, a catalytic quantity of an oxidizing agent and the dry sodium salt in dimethyl sulfoxide produces linear poly(2,6-dichloro-l,4-polyphenylene oxide) (51). The polymer can also be prepared by direct oxidation with a copper—amine catalyst, although branching in the ortho positions is indicated by chlorine analyses (52). 

Solubility. Poly(ethylene oxide) is completely soluble in water at room temperature. However, at elevated temperatures (>98° C) the solubiUty decreases. It is also soluble in several organic solvents, particularly chlorinated hydrocarbons (see Water-SOLUBLE polymers). Aromatic hydrocarbons are better solvents for poly(ethylene oxide) at elevated temperatures. SolubiUty characteristics are Hsted in Table 1. 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

The 1,1-disubstitution of chlorine atoms causes steric interactions in the polymer, as is evident from the heat of polymeri2ation (see Table 1) (24). When corrected for the heat of fusion, it is significantly less than the theoretical value of —83.7 kJ/mol (—20 kcal/mol) for the process of converting a double bond to two single bonds. The steric strain apparentiy is not important in the addition step, because VDC polymeri2es easily. Nor is it sufficient to favor depolymeri2ation the estimated ceiling temperature for poly (vinyhdene chloride) (PVDC) is about 400°C. 

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