Dehydrochlorinated polyvinyl chloride

Measurements of birefringence An, and the UV or visible dichroic ratio D were made on films cast from tetrahydrofuran solution as a function of extension (up to 200%) at 80 C. At this temperature the polymer behaves as a rubberlike material, effectively cross-linked by the 

Also consistent with theoretical predictions was the observation that the ratio An/fp was essentially constant, independent of extension and reaction time. Here = (/)—l)/(Z)-l-2) is the polyene segment orientation function which follows from eqn. (11), noting that the absorbance is a maximum in the direction of the segment axis and that the small perpendicular component of absorbance is negligible. Assuming that the constant vklue A /f0 = may also be applied to the pure PVC, we may write. 

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Polyvinyl chloride has been modified by photochemical reactions in order to either produce a conductive polymer or to improve its light-stability. In the first case, the PVC plate was extensively photochlorinated and then degraded by UV exposure in N2. Total dehydrochlorination was achieved by a short Ar+ laser irradiation at 488 nm that leads to a purely carbon polymer which was shown to exhibit an electrical conductivity. In the second case, an epoxy-acrylate resin was coated onto a transparent PVC sheet and crosslinked by UV irradiation in the presence of both a photoinitiator and a UV absorber. This superficial treatment was found to greatly improve the photostability of PVC as well as its surface properties. 

Dehydrochlorination of poly vinylidene chloride and chlorinated polyvinyl chloride was carried out. High chlorine content in the polymers (more than 60%) provides the formation of chlorinated conjugated polymers, polychlorovinylenes. The reactivity of chlorinated polyvinylenes contributes to the sp carbon material formation during heat treatment. Synthesis of porous carbon has been carried out in three stages low-temperature dehydrohalogenation of the polymer precursor by strong bases, carbonization in the inert atmosphere at 400-600°C and activation up to 950°C. 

The initial halogenated polymeric materials were obtained from the polyvinyl chloride-polyvinylidene chloride, PVC-PVDC (Rovil fiber) and chlorinated polyvinyl chloride, PVC. Dehydrochlorination was performed in the presence of a base solution in a polar organic solvent (dimethylsulfoxide, acetone or tetrahydro-furane). The products were filtered and extracted with water in a Soxhlet apparatus until all chloride ions were removed. Thermal treatment was performed in a tubular furnace in CO flow at 10 cm min". ... 

Fig. 4.3 Data of Raman spectroscopy (He-Ne laser, A,=632,8 nm) for the following samples 1 - polyvinyl chloride-polyvinylidene chloride composition after chemical dehydrochlorination (80°C, KOH in dimethyl sulfoxide -propan-2-ol 1 1, w/w) 2 - chemically dehydrochlorinated polymer carbonized in CO at 350°C 3 - carbonized product activated in CO at 950°C...

Carbon materials were obtained from polymeric precursors produced by chemical dehydrochlorination of polyvinyl chloride-polyvinyUdene chloride and chlorinated polyvinyl chloride in the presence of a strong base, followed by subsequent thermal treatment under relatively mild conditions. The sorbents obtained have three types of pores ultra-micropores, miaopores, and mesopores. hi this respect, they differ substantially from microporous activated carbons such as Saran, conventionally prepared from chlorinated polymers by thermal treatment without chemical dehydrochlorination. 

Polyvinyl Chloride. It is well-known how various attempts have been made to stabilise PVC against dehydrochlorination by salts, usually of divalent metal ions - as long chain alkylcarboxylates of Cd(II), Ba(U), Zn(II) [96]. Biswas and Moitra [102] recently established that the 3d metal ions incorporated in PVC-DMG-complex enhance the thermal stability of PVC in the order. 

The radical copolymeiization of N-vinyl-4,5,6,7-tetrahydroindole with vinyl chloride was accompanied by dehydrochlorination of polyvinyl chloride blocks (Equation (56)) (08MI315). 

The delay in dehydrochlorination is particularly marked in this system and a-methylstyrene production is initiated earlier than in polyvinyl-chloride-polymethylmethacrylate mixtures. 

Radiation-induced dehydrochlorination of polyvinyl chloride (PVC) and poly(vinylidene chloride (PVDC) and concomitant doping of polyaniline (PANI)-base with released HCL (From Guven, O., Radiation-induced conductivity control in polyaniline blends/composites. Radiation Physics and Chemistry 2007,76,1302-1307. With permission.)... 

PVC heat stabilizers are used to protect polyvinyl chloride against thermal dehydrochlorination during processing and during use above room temperature. Similar additives are sometimes useful in other halogenated systems as well. 

PTFE increases the decomposition temperature of cadmium oxalate trihy-drate. Moreover, the products of cadmium complex degradation, in turn, increase the temperature at which an intensive degradation of PTFE begins. The thermal decomposition of the highly dispersed copper formate leads to the formation of a metal-polymer composition (20-34% Cu). The maximum on the nanoparticles granulometric composition curve corresponds to 4nm. No chemical interaction between the components was observed. The decomposition of a fine dispersion of palladium hydroxide in polyvinyl chloride (PVC) results in spatial structures with highly dispersed Pd particles (S = 26 m g ) in the nodes. This process increases in the temperature required for complete dehydrochlorination of PVC. The thermolysis of cobalt acetate in the presence of PS, PAA, and poly(methyl vinyl ketone) proceeds... 

The dehydrochlorination of polyvinyl chloride (PVC) can be carried out by chemical, photochemical, or thermal reactions. 

From the literature devoted to the study of the decomposition of polyvinyl chloride under the influence of heat, various types of radiations, oxygen, and ozone, it is known that the basic routes of decomposition are dehydrochlorination, oxidation, destruction, and structuring. 

Fig. 86. Influence of the molecular weight (M) on the rate of dehydrochlorination of polyvinyl chloride at various temperatures in a stream of nitrogen, x is the fraction of chlorine split out of the total amount in the polymer.

Some peculiarities of the thermal and thermooxidative decomposition of polyvinyl chloride depend on the conditions of its production. Thus, it is known that samples of the polymer produced by initiating the polymerization of vinyl chloride with ultraviolet irradiation possess higher stability in comparison with samples produced in polymerization under the action of chemical agents [26, 27]. Reversibility of the process of dehydrochlorination in the decomposition of samples of polyvinyl chloride produced by the latex method is noted, while in the process of decomposition of suspension polymer, the phenomenon of reversibilily is not observed [21]. It has been shown that the rate of dehydrochlorination of the latex polymer is significantly higher than that of the suspension polymer under the same conditions [21]. It has been established that the polymerization of vinyl chloride in the presence of oxygen leads to the formation of unstable peroxide groups, which can initiate decomposition of the polymer [28, 29]. It is noted that an extremely substantial influence on the stability of polyvinyl chloride is exerted by the purity of the monomer, as well as the presence of impurities of metals of variable valence [28]. 

After irradiation, the polymer becomes less thermally stable (Figs. 90 and 91). This aftereffect phenomenon can be explained by the formation of free radicals capable of initiating thermal and thermooxidative decomposition during the process of irradiation. Table 12 presents the values of the rate of dehydrochlorination of polyvinyl chloride in the case... 

For samples of polyvinyl chloride irradiated by Co in a dose of 8 Mrad, the rate of variation of the free-radical concentration and the rate of dehydrochlorination at 80°C have been investigated. It has been found that three types of free radicals, the half-lives of which are equal to 6500, 345, and 28 min, are formed in the y-irradiation of polyvinyl chloride. The results of a simultaneous measurement of the free-radical concentration in the sample and the rate of dehydrochlorination at 80°C are cited in Fig. 93. A comparison of the intensity of the color of the sample, determined by means of a spectrometer, with the variation of the free-radical concentration showed that when the irradiated polymer is exposed at 80°C for 900-3000 min, only long-lived radicals are present in it, the concentration of which is inversely proportional to the color intensity [51]. 

Copolymersof vinyl chloride with vinylidine chloride, produced by the suspension method, are more stable than the latex copolymers. The rates of thermal decomposition of polyvinyl chloride and the copolymer of vinyl chloride with vinylidine chloride, produced by the latex method, are practically the same for the latex copolymer, just as for the latex homopolymer, reversibility of the process of dehydrochlorination is observed [21]. In an investigation of the stability of copolymers of vinyl chloride with vinyl acetate, vinylidine chloride, and with vinylisobutyl ether in nucleophilic substitution reactions, it was found that the copolymer with vinyl acetate is the least stable to the action of alcoholic alkali the copolymers with vinylidine chloride and vinylisobutyl ether proved more stable [56]. The stability of the copolymer of vinyl chloride witii methyl acrylate is substantially increased when the degree of homogeneity of the copolymer with respect to composition is increased, and when monomers with a smaller content of impurities are used, as well as when the copolymerization is conducted in the presence of chain carriers [57, 58]. 

There are data on the basis of which we can conclude that the metals contained in the salts participate in the decomposition reactions of polyvinyl chloride according to a radical mechanism. Metals salts of stearic acid, depending on the position of the metal in the period system, temperature, and concentration, can accelerate or decelerate dehydrochlorination. The greatest influence on the rate of dehydrochlorination is exerted by salts of those metals in which the d-layer of the electron shell following the outer shell is filled, namely salts of lead, cadmium, and zinc. A relatively weak influence on the rate of dehydrochlorination is exerted by the stearates of calcium and barium, which contain no d-elec-trons in the shell following the outer shell [73]. The observed phenomenon agrees with the representations of the catal3d ic action of metals of... 

Lead, cadmium, and zinc are not typical metals of variable valence however, they do have a d-layer filled with electrons in the shell following the outer shell in those cases when the d-electrons take part in the formation of a bond with the activated molecule, they can act like transition metals [83], This can explain the relatively weak influence of salts of calcium and barium on the rate of dehydrochlorination of polyvinyl chloride [73]. 

In an investigation of the stabilizing action of alkojgr, mercapto, and acid derivatives of dibutyltin, it was shown that they are decelerators of dehydrochlorination when polyvinyl chloride is heated. The activity of... 

TABLE 13, Dependence of the Effectiveness of the Stabilizing Action of Polyvinylacetylene and the Product of Total Dehydrochlorination of Polyvinyl Chloride on the Concentration and Temperature... 

Figure 95 shows the kinetic curves of the splitting out of hydrogen chloride from polyvinyl chloride at 175°C in a stream of air in the presence of lead silicate, dibutyltin maleate, diphenylolpropane, and polypheny lace tylene. These curves show the high effectiveness of the inhibiting action of polyphenylacetylene. Table 13 presents data characterizing the influence of polyphenylacetylene and the complete dehydrochlorination product of polyvinyl chloride, corresponding in composition to the formula (-CH=CH-CH =... 

In a study of the interrelationship between the ability of stabilizers to slow down dehydrochlorination and prevent the formation of crosslinks during heating of polyvinyl chloride, it was established that stabilizers - acceptors of hydrogen chloride, which do not inhibit dehydro-... 

The synergic action of three types of mixtures of polyvinyl chloride stabilizers mixtures of two decelerators of thermal dehydrochlorination that do not bond hydrogen chloride, mixtures of two stabilizers that are hydrogen chloride acceptors, and mixtures of hydrogen chloride acceptors with decelerators of dehydrochlorination, possessing no acceptor properties, was investigated in [54, 73, 86]. 

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