Polyvinylchloride thermal degradation

M. Brebu, T. Bhaskar, K. Murai, A. Muto, Y. Sakata, and M.A. Uddin, The individual and cumulative effect of brominated flame retardant and polyvinylchloride (pvc) on thermal degradation of acrylonitrile-butadiene-styrene (ABS) copolymer, Chemosphere, 56(5) 433 440, August 2004. 

Anthony, G. M. Kinetic and chemical studies of polymer cross-linking using thermal gravimetry and hyphenated methods. Degradation of polyvinylchloride. Polymer Degradation and Stability 1999 64 353. 

Fig. 47. Absorption spectrum of thermally degraded polyvinylchloride (Vestolit SK 55), polyvinylbromide and a copolymer vinyl chloride—isobutene in tetrahydrofuran. The absorption maxima correspond to polyene sequences with n = 4, 5, 6, etc. [ 184 ].

The thermal degradation of polyvinylalcohol has been studied by several workers [201—204]. The main products of degradation have been shown to be water from an elimination reaction similar to that observed with polyvinylacetate, and acetaldehyde from depolymerization. Small amounts of aldehydes and ketones of the general formula OCH-(CH=CH) -CH3 and CH3-CO-(CH=CH) -CH3 were also detected by Tsuchiya and Sumi [204]. Water is formed by a mechanism similar to that for hydrogen chloride production from polyvinylchloride, and acetic acid from polyvinylacetate, leaving a conjugated polyene... 

The rates of production of volatile material from polyvinylacetate, polyvinylchloride and vinylacetate vinylchloride copolymers, covering the entire composition range, have been compared by thermal volatilization analysis. It has been found that, at both extremes of the composition range, incorporation of the comonomer unit induces de-stabilization. Minimum stability occurs for composition of approximately 40—50 mole % vinylacetate. The rate of volatilization as a function of the composition of the copolymers is given in Fig. 74. The results were confirmed by a study of the thermal degradation in tritolylphosphate solution. The stability of the copolymers is a minimum at 30—40 mole % vinylacetate. HC1 and acetic acid catalyse the degradation of the... 

Figure 28 shows that substituted cinnamic acid derivatives have a relatively low absorption in the 310—320 nm region, so that they are relatively ineffective ultraviolet absorbers. Their main advantage is that they have no phenolic hydroxyl group which could be sensitive to alkali or heavy metal ions. The alkali sensitivity is a severe shortcoming for textile applications. On the other hand, with polyoxymethylene for instance, the thermal degradation can be catalysed by phenols, and with polyvinylchloride, side reactions can occur with metal stabilizers. 

Montaudo, G. and Puglisi, C., Evolution of Aromatics in the Thermal Degradation of Polyvinylchloride A Mechanicistic Study, Polym. Deg. Stab., 33, 229, 1991. 

The method of production has been found to have a striking influence on the thermal stability of polyvinylchloride (PVC) over a temperature range up to 340 °C [1, 2]. Thus, PVC obtained as a result of y-irradiation and benzoyl peroxide (BP) initiation has approximately the same stability, while PCV obtained by initiation with azobisisobutyronitrile (AZBN) is noticeably less thermally stable over the temperature range of 220-270 °C. However, stabilisation towards further thermal degradation of all PVC samples tested is observed at about 60% weight loss, possibly due to the considerable dehydrochlorination of the polymer to form polyene and crosslinked structures. 

Other polymers that have been examined by EGA include polyvinylchloride (PVC) [17-19], polystyrene [20-23], styrene-acrylonitrile copolymers [24-26], PE and PP [27-32], polyacrylates and their copolymers [33-36], and polyethylene terephthalate, polyphenylenes, and polyphenylene oxides and sulfides [36-41]. Studies involving the use of chromatography include the thermal degradation of PVC [42], vinyl plastics [43] and polysulfone [44],... 

Figure 3.26 Thermal degradation of polyvinylchloride. This example describes the thermal degradation of PVC. The TGA mass loss curve exhibits two clear steps. The IR spectrum (above left) measured at the maximum of the peak at 310°C corresponds to HCI formed through the reaction (CH2—CHCI) (CH =... 

Evolved gas analysis, particularly in the form of TGA-DTA-MS, has obvious synthetic polymer applications. It has been applied to study the thermal behavior of homopolymers, copolymers, polymeric blends, composites, residual polymers, solvents, additives, and toxic degradation polymers. In the latter context, hydrogen chloride evolution from heated polyvinylchloride materials is readily quantified by TGA-DTA-MS and such data are of major significance in... 

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