Effects of Weak Linkages on the Thermal and Oxidative Degradation of Poly(Methyl Methacrylates).
Effects of Weak Linkages on the Thermal and Oxidative
Degradation of Poly(Methyl Methacrylates).
Kashiwagi, T.; Inaba, A.; Brown, J. E.; Hatada, K.;
Kitayama, T.; Masuda, E.
Macromolecules, Vol. 19, No. 8, 2160-2168, 1986.
polymethyl methacrylate; free radicals; thermal
degradation; weight loss
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