Polyvinylchloride 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. 

Elements Ge, Sn, and Pb form many interesting varieties of organometallic compounds, some of which are important commercial products. For example, EuPb is an anti-knock agent, and organotin compounds are employed as polyvinylchloride (PVC) stabilizers against degradation by light and heat. Some examples and advances are discussed in the present section. 

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. 

Figure 5 Percent degradation of Dacarbazine intravenous solution and increase of Diazo-IC in unprotected polyvinylchloride infusion containers and protected by Amberset A90, exposed to indirect sunlight (-300 micro W cm UV light intensity at 365 nm) ( ) protected, ( ) unprotected. Source. From Ref. 43.

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... 

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 ].

Fig. 48. Frequency of polyene sequences for a polyvinylchloride sample degraded at 170 C in nitrogen and a polyvinylbromide sample degraded at 100°C in nitrogen [184] conversion x 0.16 x 10 2.

The values calculated according to this model for the yield of HC1, and concentration and distribution of polyene sequences are in agreement with the experimental results that Tvidos et al. obtained for the degradation of polyvinylchloride. 

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... 

All the observed features of the interaction of polymethylmethacrylate and polyvinylchloride, when degraded as a blend, are explained by two simultaneous reactions [322, 323]. 

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. 

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