Oxidative degradation weight loss

In general, the degradation of PET is characterized by a loss in molecular weight, a loss in weight in the case of thermal and thermal oxidative degradation, and an increase in the carboxyl end groups. This is usually accompanied by the material first turning yellow, then brown and finally black [17]. 

PET requires special flame-retardant chemistry since the antimony oxide synergist that is normally used in combination with brominated flame retardants causes de-esterification of the PET chain and concomitant molecular weight loss. In place of antimony oxide, PET requires a sodium antimonate synergist. Another problem with antimony trioxide is that it decreases the thermal stability of the brominated flame retardant which then produces hydrobromic acid which degrades the PET. 

Electrolytic or anodic oxidation is fast, uniform and best suited to mass production. This process is most widely used for treatment of commercial carbon fibers. The oxidation mechanism of most carbon fibers is characterized by simultaneous formation of CO2 and degradation products that are dissolved in the electrolyte of alkaline solution or adhere onto the carbon fiber surface in nitric acid. Only minor changes in the surface topography and the surface area of the fiber are obtained with a small weight loss, say, normally less than 2%. 

Milled rigid sheets of poly (vinyl chloride) on heating at 185°C. lose weight at a rate which increases with time. By polymer fractionation procedures, it was shown the rate of hydrogen chloride loss increases as the content of tetrahydro-furan-insoluble resin increases. The insoluble resin content accumulates at a rate which depends, in part, on the additive present. This insolubilization reaction is catalyzed by cadmium compounds. The increased dehydrochlorination rate of the insoluble crosslinked resins may result from the susceptibility of the crosslinked structures to oxidation and from the subsequent thermal degradation of the oxidation products. The effects of various common additives on the rates of insolubilization and weight loss are described. 

The work described here supports the view that the chemical combination of metal ions with organic molecules leads to coordination complexes and polymers with enhanced stability with respect to weight loss, thermal degradation, or oxidation. Bis(8-hydroxyquinoline) derivatives were used to prepare a series of coordination polymers containing first-row transition metals, and the thermal stabilities of the polymers were evaluated. The influence of the structure of the organic molecule and the role of the metal are discussed. 

Other studies have shown that in the thermal treatment of cellulose at temperatures below 300 °C, the rate of weight loss can be accelerated by oxidation reactions such as the degradation of cellulose by atmospheric oxygen. When cotton cellulose was heated at 190 °C for 50 h, carboxyl and carbonyl groups formed at a linear rate. When rates of glycosidic bond scission at 170 °C in nitrogen and in air were compared, the rate in nitrogen was close to one-half of the rate in air (30). 

Fig. 1. Isothermal oxidative degradation studies of NVCFP and PNVCFP. (O) increase in capacity of NVCFP ( ) increase in capacity of PNVCFP (O) weight loss of NVCFP ( ) weight loss of PNVCFP...

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