Oxidative stabilization of dimethyl silicone fluids with iron between 70 and 370°C
| Autor: | J. M. Nielsen |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Polymer Science: Polymer Symposia. 40:189-197 |
| ISSN: | 1936-0959 0360-8905 |
| DOI: | 10.1002/polc.5070400124 |
| Popis: | Long term oxidation tests below 150°C on dimethyl silicone (DMS) fluids with controlled iron content, in conjunction with previous work, have provided a broad concept of the processes of oxidation in DMS fluids between 70 and 370°C. A nonfree radical, iron-catalyzed oxidation of DMS fluid occurs both below and above 150°C. A diverging, free radical chain reaction which is inhibited by iron is initiated by direct attack of oxygen on the methyl groups of DMS above 150°C. It is believed that a ferric iron complex is the key mechanistic species both in the catalyzed oxidation and in the free radical reaction inhibition. When temperature, iron dispersion, and aeration are held constant, the oxidation rate of a DMS fluid below 150°C varies directly with its iron level. Above 150°C the oxidation rate is still dependent on iron level, but an ‘optimum iron level’ for a minimum oxidation rate exists for each temperature of oxidation. This optimum iron level increases with the temperature. A conceptual diagram has been developed to unify and summarize these effects over the temperature range 70–370°C, providing a basis for the most effective use of iron to stabilize DMS fluids. |
| Databáze: | OpenAIRE |
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