Nonoxidative degradation

Bhakdi S, Torzewski M, Klouche M, et al. (1999) Complement and atherogenesis binding of CRP to degraded, nonoxidized LDL enhances complement activation. Arterioscler Thromb Vase Biol 19 2348-2354... 

Klouche M, Rose-John S, Schmiedt W, et al. (2000) Enzymatically degraded, nonoxidized LDL induces human vascular smooth muscle cell activation, foam cell transformation, and proliferation. Circulation 101 1799-1805... 

Refractory fibers are most often used in applications above 1000°C. Table 1 shows the maximum long-term use temperatures in both oxidising and nonoxidizing atmospheres. For short exposures, however, some of these fibers can be used with Htde degradation at temperatures within 100°C of their melting points. 

Like ldpe, polybutadienes are resistant to most nonoxidizing acids, alkalis, and salts. However, because they are unsaturated, the polyalkadienes are attacked by hydrochloric, hydrobromic, and hydrofluoric acids, as well as by hydrogen and chlorine. The reaction products, which are thermoplastic, have been used as commercial nonelastomcric plastics. NR and other diene elastomers are also attacked by peroxides and ozone. In the absence of an tioxidants and carbon black filler, these unsaturated elastomers are degraded in the sunlight. 

The flexural modulus and heat deflection temperature of these aryl polyesters are increased by the incorporation of reinforcing fillers. PET and related aryl polyesters are resistant to nonoxidizing acids, alkalis, and salts, as well as to polar and nonpolar solvents at room temperature. (Above room temperature some alkalis and acids begin to degrade polyesters.)... 

Si Improves oxidation, nitriding, sulfidation and carburizing resistance. Detrimental to nonoxidizing chlorination resistance Synergistically acts with chromium to improve high-temperature degradation... 

In its simplest definition pyrolysis is the degradation of polymers at high temperatures under nonoxidative conditions to yield valuable products (e.g. fuels and oils). Pyrolysis is also referred to as polymer cracking and its main advantages are that it can deal with plastic waste which is otherwise difficult to recycle and it creates reusable products with unlimited market acceptance. 

The final step in the synthesis must be carried out imder nonoxidative conditions because of the very facile oxidation of L-ascorbic acid to dehydro-irascorbic acid followed by further degradation. 

Initial degradation is often simileir in air and under inert conditions consistent with initial degradation being nonoxidative. Subsequent degradation is dissimilar and consistent with oxidatively degradation occurring in air. 

Histidine ammonia-lyase is the first enzyme in the degradation pathway of L-histidine and catalyzes the nonoxidative deamination of histidine (12) to form w r-urocanic acid (13) plus ammonia (Equation (3)). Histidine ammonia-lyase is present in several bacteria and in animals. The mechanism for the reaction that is catalyzed by histidine ammonia-lyase is presumed to be similar to that described above for phenylalanine ammonia-lyase (see Scheme 3). 

Mechanism of Nonoxidative Thermal Dehydrochlorination. This subject is still very controversial, with various workers being in favor of radical, ionic, or molecular (concerted) paths. Recent evidence for a radical mechanism has been provided by studies of decomposition energetics (52), the degradation behavior of PVC-polystyrene (53) or PVC-polypropylene (54) mixtures, and the effects of radical traps (54). Evidence for an ionic mechanism comes from solvent effects (55) and studies of the solution decomposition behavior of a model allylic chloride (56). Theoretical considerations (57,58) also suggest that an ionic (El) path is not unreasonable. Other model compound decompositions have been interpreted in terms of a concerted process (59), but differences in solvent effects led the authors to conclude that PVC degrades via a different route (59). 

Tt is known that the principal pathway for nonoxidative thermal - degradation of poly (vinyl chloride) (PVC) involves the evolution of HC1 and the accumulation of unsaturation in the polymer chains (1,2,3,4), as shown in Equation 1 ... 

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