Oxidation and Ageing

The deactivating influence of the chlorine atom attached to the double bond, besides effectively preventing conventional sulphur vulcanization, also results in better heat and oxidation resistance than shown by the diene hydrocarbon rubbers. Such thermal stability can be improved further by the use of suitable antioxidants. Johnson (1976) comments that variations in compounding formulation and 

The oxidation of chloroprene polymers is complex since it is accompanied by dehydrochlorination. Thus at temperatures up to ISO C hydrochloric acid is eliminated at a rate closely related to oxygen uptake and is autocatalytic (Gardner and McNeill, 1971). 

The main oxidation reaction is proposed (Bailey, 1967) to involve peroxy radical attack on the a-methylene hydrogen followed by rearrangement  

Subsequent reactions, similar to the Bevilacqua proposals for natural rubber, (see Sections 8.2 and 8.2.1.) involve intramolecular peroxidation and the formation of /3-alkoxy peroxide radicals which then decompose to carbonyl compounds by the following reaction  

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C2. Cao, G., and Cutler, R. G., Protein oxidation and aging. I. Difficulties in measuring reactive protein carbonyls in tissues using 2,4-dinitrophenylhydrazine. Arch. Biochem. Biophys. 320, 106-114 (1995). 

Theories and instrumentation of Fourier transform IR spectroscopy and electron spectroscopy for chemical analysis are briefly reviewed. The possibility of using these techniques in detection and analysis of acid impurities distributed at surfaces of paper documents produced during the period from 1790 to 1983 is demonstrated. Results show that all of the papers tested contained carboxylic groups. The carboxylic acids found in the paper of 1790 are the results of oxidation and aging. Acids in other papers are due to fiber oxidation as well as the presence of rosin acids. These techniques show promise as nondestructive methods for elucidating chemical characteristics of surfaces of paper documents. 

Stadtman ER, Van Remmen H, Richardson A, Wehr NB, Levine RL (2005) Methionine oxidation and aging. Biochim Biophys Acta Proteins Proteomics 1703 135... 

Aviation oils The bulk of aviation lubricant demand is for both military and civilian gas turbine lubricants. Hydrocarbon oils cannot meet the requirements placed on jet engine oils, primarily lubrication, oxidation and ageing stability. Type 1, the first generation of oils were diesters but over the last 30 years have lost ground to the more expensive polyol esters. Type 2. Some diesters are still used in less demanding applications such as for small private aircraft and turbo-prop engines. Type 2 aviation gas turbine lubricants are produced to a viscosity of 5 cSt at lOO C but for some military applications where low-temperature operability is vital, this is reduced to 3 cSt. 

As mentioned above extra stabilization is needed in some POs, particularly PP, to prevent induced oxidation and aging from sterilization treatments. Radiation-stabilized materials require a carefiil mix of primary and secondary antioxidants for optimum stabilization. However, given the multiple factors affecting sterilization degradation and the compoimds specialized nature, suppliers often conceal their stabilization formulations as proprietary information. 

Creep Behavior of Non-Oxide Fibers and Effects of Heat Treatment, Oxidation, and Aging... 

Oxidation or ageing of the bitumen affects the mechanical behaviour of the bitumen and usually reduces the pavement s service life. The changes that occur are as follows reduction of penetration, increase of softening point, reduction of elasticity and adhesion ability and increase of friability. Oxidation and ageing can be decelerated with the use of chemical additives. 

Different types of primary and secondary antioxidants, or the same types of antioxidants with different molecular structures, have different functions and application effects and both have their own strengths. A composite antioxidant is compounded with two or more different types of antioxidants or with different varieties of the same type that are mutually complementary, thereby achieving optimum antithermal oxidation and aging effects with minimal amount of antioxidants and lowest cost. 

CK Haywood. Oxidation and aging. In A Renfrew, P Morgan, eds. Polythene The Technology and Uses of Ethylene Polymers, 2nd ed. London Iliffe Sons Ltd., Interscience, 1960, p 131. 

Pandey, K. B. Mishra, N. Rizvi, S. I. Protein oxidation biomaikers in plasma of type 2 diabetic patients. Clinical Biochemistry. 2010,43, (4-5), 508-511, March. Stadtman, E. R. Protein oxidation and aging Free Radic. Res. 2006,40,1250-1258. Rosenfeld, M. A. Leonova, V. B. Konstantinova, M. L. Razumovskii, S. D. Mechanism of enzymatic cross-linking of fibrinogen molecules. Izv. Ros. Akad Nauk, Biol. Ser. 2008, 6, 578-584. 

Yu et al. reported RCCM could be employed in the apple juice production [51]. The contents of methamidophos and parathion-methyl in the juice treated by RCCM decreased 58.76% and 71.92%. Furthermore, RCCM was used to clarification for beer by the ways of a column [52]. RCCM could hydrolyze sensitive protein and increase contents of free amino acid in the beer. Therefore, the beer treated by RCCM could stay oxidation and aging procedure due to some metal ions being absorbed by RCCM. 

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