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Effects of Weak Linkages on the Thermal and Oxidative Degradation of Poly(Methyl Methacrylates).


pdf icon Effects of Weak Linkages on the Thermal and Oxidative Degradation of Poly(Methyl Methacrylates). (5510 K)
Kashiwagi, T.; Inaba, A.; Brown, J. E.; Hatada, K.; Kitayama, T.; Masuda, E.

Macromolecules, Vol. 19, No. 8, 2160-2168, 1986.

Keywords:

polymethyl methacrylate; free radicals; thermal degradation; weight loss

Abstract:

The thermal and oxidative degradation mechanisms of poly(methyl methacrylate) (PMMA) were studied in atmospheres of nitrogen and air by thermogravimetry using various specially polymerized samples. Thermal degradation of PMMA polymerized with a free radical method proceeds in three steps of weight loss: the least stable step is initiated by scissions of head-to-head linkages, the second step by scissions at the chain-end initiation from vinylidene ends, and the most stable step by random scission within the polymer chain. There are no significant differences seen in the thermal or oxidative degradation of PMMA polymerized with the free radical method between azobis(isobutyronitrile) and benzoyl peroxide as the initiators. Gas-phase oxygen traps radicals resulting from chain scissions at head-to-head linkages. No weight loss is observed from this step in air. Similarly, oxygen traps radicals generated by end initiation, but it is not as effective as for the case of head-to-head linkages. Possible mechanisms for end initiation and oxidative termination of radicals initiated from scission at the head-to-head linkages are discussed.