Vinyl polymers pyrolysis

Deschant [15] has discussed in detail the IR spectra of 35 polymers and Hippe and Kerste [16] developed an algorithm for the IR identification of vinyl polymers. Pyrolysis followed by IR spectroscopy is a particularly useful technique for application to polymers that are rendered opaque or completely non-transparent by the presence of pigments or fillers. Leukoth [17] used this technique to determine the chemical composition of plastics and rubbers containing high proportions of pigments or fillers. 

Z. Czegeny and M. Blazso, Effect of phosphorous flame retardants on the thermal decomposition of vinyl polymers and copolymers, J. Anal. Appl. Pyrolysis, 81(2) 218-224, March 2008. 

Recently the pyrolysis of polymer mixtures has become a focus of interest due to the increasing role of plastics recycling. Many researchers have investigated the thermal decomposition of various polymers in the presence of PVC. Kniimann and Bockhom [25] have studied the decomposition of common polymers and concluded that a separation of plastic mixtures by temperature-controlled pyrolysis in recycling processes is possible. Czegfny et al. [31] observed that the dehydrochlorination of PVC is promoted by the presence of polyamides and polyacrylonitrile however, other vinyl polymers or polyolefins have no effect on the dehydrochlorination. PVC generally affects the decomposition of other polymers due to the catalytic effect of HCI released. Even a few per cent PVC has an effect on the decomposition of polyethylene (PE) [32], HCI appears to promote the initial chain scission of PE. Day et al. [33] reported that PVC can influence the extent of degradation and the pyrolysis product distribution of plastics used in the... 

Another group of synthetic polymers have a linear structure. Poly(furfuryl alcohol), already mentioned in connection with Fig. 31 [377], belongs to this group, as of course do the vinyl polymers, e.g., PVC. Schuster has described the admixture of active carbon powder to overcome the agglutination of the thermoplastic polymers upon heating [400, 401]. The pyrolysis temperatures were rather low 40 ( ) to... 

The polyene chain further decomposes under the influence of heat, generating aromatic hydrocarbons such as benzene, styrene, naphthalene, etc. This type of reaction can be the source of some polycyclic aromatic hydrocarbons found in traces during the pyrolysis of certain vinyl polymers. The elimination of a HX molecule from a vinyl type polymer is favored by the presence of a p-double bond in a compound of the form -CH2-CHX-CH=CH-. For this reason the side reaction for vinyl polymers is slower for the intact polymer and accelerates as the polymer tends to decompose. 

Starch thiols can have the SH group directly on the pyranose ring or in a side chain. There are several methods of synthesizing starch thiols of the first type. One of them is based on the pyrolysis of starch xanthates (32), but the reaction proceeds in two parallel routes one producing thionates (35) and the other producing thiols (37).2675,2677 Reduction of starch xanthates with NaBPU in alkali is another approach to thiols. Thiols prepared in this manner were subjected to graft polymerization with vinyl polymers. Nucleophilic substitution of the chlorine... 

Earlier work (9) indicated that the addition of 1 mg of zinc dust exerted a catalytic effect upon the decomposition of vinyl polymers. One sample in Table I, G, was investigated extensively over the temperature range from 300° to 600°G. Addition of zinc dust lowers the temperature necessary to achieve pyrolysis of the polybutadiene. Zinc-catalyzed results obtained at 300°G compare favorably with uncatalyzed results achieved at 450°C. Normally 300°G does not give sufficient pyrolysis of polybutadiene to permit identification of products by IR spectroscopy. It is possible, of course, that the effect of the zinc was merely better conduction of heat to the sample and that no genuine catalytic effect was observed. However, zinc has a long history as a catalyst for the degradation of natural products and a single experiment with aluminum showed no such effect. 

The thermal elimination process can be applied to most substituted groups in vinyl polymers by controlled pyrolysis at 600-700°C, producing polyvinylene compounds, for example, by the splitting off of acetic acid from poly(vinyl... 

Marcilla, A. and Beltran, M., Thermogravimetric kinetic study of poly(vinyl-chloride) pyrolysis, Polym. Deg. Stab., 48, 219, 1995. 

The thermal elimination process can be applied to most substituted groups in vinyl polymers by controlled pyrolysis at 600 to TOO C, producing poly vinylene compoimds, e.g., by the splitting off of acetic acid from poly(vinyl acetate). By careful temperature control, one can achieve bifunctional reactions and/or intramolecular cyclizations. This has been developed commercially at relatively high temperatures, in the case of the polymerization of methacrylamide above 65°C, to yield a polymer with a substantial proportion of imide groups ... 

This procedure provides poor reproducibility, because the pyrolysis products depend strongly on the experimental conditions, but provides a useful analytical tool in the identification of acrylic and vinylic polymers or monomer units from polyester, polyurethane, and phenolic and polyacrylate resins. 

After brief discussion of the state-of-the-art of modern Py-GC/MS, some most recent applications for stixictural and compositional chai acterization of polymeric materials are described in detail. These include microstixictural studies on sequence distributions of copolymers, stereoregularity and end group chai acterization for various vinyl-type polymers such as polystyrene and polymethyl methacrylate by use of conventional analytical pyrolysis. 

The color of the polymer can also be affected by inappropriate reaction conditions in the polymerization process, such as temperature, residence time, deposits of degraded polymer or the presence of oxygen. Degradation of polyesters and the generation of chromophores are thermally effected [29b, 29c, 39], The mechanism of thermal decomposition is based on the pyrolysis of esters and the formation of unsaturated compounds, which can then polymerize into colored products. It can be assumed that the discoloration takes place via polymerization of the vinyl ester end groups or by further reaction of AA to polyene aldehydes. 

Polyvinyl fluoride and PVDF are more stable to elevated temperatures than the corresponding chloride polymers. The decomposition temperatures of polytrifluoroethylene and polytetrafluoroethylene (ptfe) are progressively higher than polymers of vinyl fluoride or vinylidene fluoride. The pyrolysis of PAN and polymethacrylonitrile yields polycyclic ladder polymers. 

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