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Continuous distribution kinetics for microwave-assisted oxidative degradation of poly(alkyl methacrylates)

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Abstract

The microwave-assisted oxidative degradation of poly(alkyl methacrylates) namely poly(methyl methacrylate), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) was investigated. The kinetic parameters were compared to that obtained by thermal oxidative degradation. The molecular weight distributions (MWDs) were simulated using continuous distribution kinetic models. The MWD of polymer was expressed as a γ-distribution, and the mathematical solutions were developed in terms of γ-distribution parameters. The MWD of degradation mixture approaches an exponential distribution under both oxidative thermal degradation and microwave-assisted oxidative degradation of poly(alkyl methacrylates), indicating random chain scission. The degradation of PEMA was investigated in the presence of three different oxidizers. The hydrogen abstraction from polymer and the oxidative random chain scission of polymer radicals were found to be the important steps in the overall mechanism of microwave-assisted oxidative degradation of poly(alkyl methacrylates). The model developed can be used to predict degradation rate of the polymer in the presence of any oxidizers by knowing only the dissociation rate constant of the oxidizer. © 2008 American Institute of Chemical Engineers AIChE J, 2008

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