Polyvinylchloride decomposition

Fig. 4.22 Apparent specific surface A(app) of carbons obtained from the decomposition of polymers, plotted against the carbonization temperature, (a) Polyfurfuryl carbons (b) dibenzanthrone carbons (c) polyvinylchloride carbons. O, A(app) estimated from CO2 isotherm at 195 K (a fCOj) = 17-0 A ) A. /f(app) estimated from N2 isotherm at 77 K = 16-2 A ). (Courtesy Marsh and Wynne Jones.)...

Several purely organic polymers like pyrolized polyacrylonitrile Sl polyamino-quinones 52>, vulcanized aniline black or ordinary aniline black 53>S4) and pyrolized chlorinated polyvinylchloride ss> were shown to be active for H2Oa decomposition. pH dependence was found in some cases, but mostly no correaltions were found with paramagnetism or semiconductivity. It has been shown S6> for the case of pyrolized polyacrylonitrile, that this polymer actually behaves as a polyquinone, capable of reversible electron transfer ... 

Although it is well known that when polyvinylchloride (PVC) is irradiated with UV light, discoloration, dehydrochlorination, decomposition and crosslinking occur, few ESR studies on PVC irradiated with UV light have been reported. Nishijima et al. (86) observed an ESR spectrum after UV irradiation of a polyvinylchloride film with light of 185 nm at —196° C under vacuum. The sample was heated at various temperatures for 10 min after UV irradiation at —196° C. The changes in a spectral shape, radical concentration, A Hmsl and A H are shown in Figs. 9 and 10. It is apparent that a broad component decays out at about —100° C and a narrow component at about 80° C. The former could be attributed to some kinds of alkyl radicals and the latter to... 

The structure —CHC1—CH2—CO—CH2 — was found by Kwei [99] in polyvinylchloride after photo-oxidation. Such j3 chloroketones decompose by the Norrish type I mechanism without loss of chlorine atoms. Hydrogen chloride is obtained only when polyvinylchloride is photo-oxidized above 30°C [98]. It seems that zipper dehydrochlorination plays little role in the reaction occurring on exposure to ultraviolet light at temperatures below 150°C in the presence of air [97], and that hydrogen chloride is mainly a product of thermal decomposition rather than photolysis [98], The following mechanism can be proposed which takes into account the experimental results namely, that chain scission and crosslinking occur simultaneously on irradiation at 253.7 nm [100] and that carbon dioxide is evolved, while an absorption band at 1775 cm-1 (ascribed to peracids) is detected in the infrared spectrum [98]. 

Individual polychloroalkanes were used as model compounds in studies of thermal decomposition of polyvinylchloride [51]. 

Figure 16.10 TGA thermal curves showing the decomposition temperatures of some common polymers PVC, polyvinylchloride PMMA, pol3miethylmethacrylate HOPE, high-density polyethylene PIPE, polytetrafluoroethylene PI, polyimide. (Courtesy of TA Instmments, New Castle, DE, www.tainst.com.)...

Free radicals may be generated by the chemical decomposition of azo and peroxide compounds thermally and by y-irradiation. In the polymerization reactions (4)—(7), vinyl chloride monomer and free-radical initiator are involved, resulting in polyvinylchloride (PVC) by free-radical polymerization. 

Figure 7 Constant heat rate decomposition method. PVC = polyvinylchloride PMMA = poly(methyl methacrylate) HPPE high-pressure polyethylene PTFE PTFE = polytetrafluoroethylene PI = polyimide. 

Hydrogen Chloride - 200-800 93-426 - G — — HCI resulting from the decomposition of all types of wire insulation, m eluding polyvinylchloride-cooling water spray. 

Polyvinylchloride (PVC) is much less crystalline than the polyolefins. The base polymer is very hard and for most applications it has to be plasticised to make it flexible enough for use. There are many plasticisers available for PVC. Food contact applications, of course, impose their own requirements of intrinsic safety and low migration rate of the plasticiser. Due to the nearness of its decomposition and processing temperatures, PVC has to be stabilised against heat by the addition of 1-2% of heat stabiliser and this, in turn, has food contact implications. 

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