Degradation phenomena

Deterioration. The causes of degradation phenomena in textiles (155—158, 164) are many and include pollution, bleaches, acids, alkaUes, and, of course, wear. The single most important effect, however, is that of photodegradation. Both ceUulosic and proteinaceous fibers are highly photosensitive. The natural sensitivity of the fibers are enhanced by impurities, remainders of finishing processes, and mordants for dyes. Depolymerization and oxidation lead to decreased fiber strength and to embrittlement. 

Similarly to PTFEP, phosphazene fluoroelastomers proved to be rather stable to thermal treatments up to 175 °C [560,561], while for temperatures above this value degradation phenomena start to be relevant. 

Chu, C. C., Degradation phenomena of two linear aliphatic polyester fibers used in medicine and surgery. Polymer. 26,... 

Degradation phenomena in small-molecule organic light-emitting devices H. Aziz, Z.D. Popovic Chemistry of Materials, 16 4522-4532... 

The instrument should be in a well-ventilated area, especially at experiments done above room temperature as the polymer or the additives may be subject to decomposition/degradation phenomena. 

REVIEW OF PEM FUEL CELL DEGRADATION PHENOMENA AND MECHANISMS... 

It is noteworthy that when the voltage is close to the electrochemical decomposition voltage there is an acceleration of the degradation phenomena, especially in the higher temperature domain. 

More, K., Borup, R., and Reeves, K., Identifying contributing degradation phenomena in PEM fuel cell membrane electride assemblies via electron microscopy, ECS Trans., 3, 717, 2006. 

EPTMs are suffidently reactive toward firee radicals (see previous Section), even when they contain low amounts of conjugated unsaturation (0.1 M or less). Thus degradation phenomena are practically avoided during their radical curing. We have verified the po ibility of codicumyl peroxide-based formulations. Figure 13 shows that with 0 J—1.5 % peroxide... 

Halogenation of saturated hydrocarbon polymers can hardly be controlled and is frequently assodated with chain degradation phenomena In contrast, the presence of randomly distributed olefinic unsaturations, allows selective halogenation reactions by adopting appropriate conditions. For instance, butyl rubber can be chiorinated or brominated in allylic positions and chloro-butyl or bromo-butyl rubber results The latter polymers are very interesting since they exhibit fast curing rates when sulfur and ZnO are introduced in the formulations. 

The specifics of the degradation phenomena define the electrode pretreatment. In the case of mechanical treatment, the surface composition can vary due to heating [60], and this can be avoided by polishing in nonaqueous solutions [47] or by slowly cutting the surface layer while it is out of contact with air. Chemical treatment [60,61] will be discussed below in the context of the HTSC etching problem. 

Attention is usually focused on degradation phenomena that are caused by interaction with water (including atmospheric moisture) and carbon dioxide. Regarding interactions with water, YBCO and its substituted derivatives are the most active [457-460]. Their hydrolysis leads to the formation of a number of ions, including unstable aquacomplexes of Cu which react with water evolving oxygen. In a small volume of water or a moist atmosphere solid products are accumulated, and the process as a whole is usually represented as... 

Park, J.M. and Lee, J.Y., The intrinsic degradation phenomena of LaNi5 and LaNi47Alo,3 by temperature induced hydrogen absorption-desorption cycling. Materials Research Bulletin, 1987, 22(4) p. 455 65. 

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