Degradation of polyethylene

The chemical and physical properties of the polymers obtained by these alternate methods are identical, except insofar as they are affected by differences in molecular weight. In order to avoid the confusion which would result if classification of the products were to be based on the method of synthesis actually employed in each case, it has been proposed that the substance be referred to as a condensation polymer in such instances, irrespective of whether a condensation or an addition polymerization process was used in its preparation. The cyclic compound is after all a condensation product of one or more bifunctional compounds, and in this sense the linear polymer obtained from the cyclic intermediate can be regarded as the polymeric derivative of the bifunctional monomer(s). Furthermore, each of the polymers listed in Table III may be degraded to bifunctional monomers differing in composition from the structural unit, although such degradation of polyethylene oxide and the polythioether may be difficult. Apart from the demands of any particular definition, it is clearly desirable to include all of these substances among the condensation... 

Schink B, M Stieb (1983) Fermentative degradation of polyethylene glycol by a strictly anaerobic, Gram-negative, nonsporeforming bacterium, Pelobacter venetianus sp. noy.Appl Environ Microbiol 45 1905-1913. 

Figure 71 compares the 2,000-1,000 cm-1 FTIR spectral region for the heat seal layers of the "good" and "bad" films, and the center opaque polyethylene layer for the "bad" film. Of particular interest is the carbonyl region between approximately 1,800 and 1,650 cm-1. The two heat seal surface spectra show mainly the vinyl acetate ester carbonyl band at 1,740 cm-1. For the middle polyethylene layer of the "bad" film, the shape and position of the carbonyl band is consistent with oxidative degradation of polyethylene. The peak maximum at... 

In summary, practical experience with predicting the hydrolytic degradation of polyethylene terephthalate is an example of the use of Arrhenius extrapolation, a demonstration of the problems encountered when there are changes in the state of the polymer as the temperature is raised, and an example of the large variability in prediction of lifetime due to the logarithmic scale. 

Schaaf, E. and Zimmermann, H., Thermogravimetric investigation on the thermal and thermooxydative degradation of polyethylene terephthalate, Faserforschung Textiltechnik, 25, 434-440 (1974). 

As already described, the mechanochemical degradation of polyethylene terephthalate takes place mainly at the heteroatomic links (the weakest), while the breaking of —C—C— links is less pronounced. In wet media there is also a mechanochemically activated hydrolysis. 

Oxidative degradation of polyethylene (PE) and polypropylene (PP) can occur at all stages of their lifecycle (polymerisation, storage, processing, fabrication and in-service). The auto-oxidation process of polyolefins is best described by the classical free-radical-initiated chain reaction outlined in Scheme 1 [1]. Impurities initially present in the polymers during polymerisation or melt processing, exert profound effects on the behaviour of the final polymer article in service. 

Since the environmental degradation of polyethylene starts with abiotic oxidation, the determination of abiotic oxidation products is an important step towards establishing the environmental degradation mechanisms and environmental impact of the material. In a secondary process, microorganisms may utilise these abiotic degradation products and the low molecular weight... 

Jens G (1996) Degradation of polyethylene glycol. A study of the reaction mechanism in a model molecule Tetraethylene glycol. Polym Degrad Stabil 52(3) 217-222... 

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