Thermal and photo-chemical oxidation of nylon 6,6: Some aspects of the importance of α,β-unsaturated carbonyl groups and hydroperoxides

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Abstract

The thermal and photochemical oxidation of nylon 6,6 film (50 μm thick) has been studied using second-order derivative uv spectroscopy, hydroperoxide analysis and viscometry. During oven ageing the growth and decay of hydroperoxide follows the same pattern as in polyolefins. Subsequent photo-oxidation of the oven aged films results in an initial increase in viscosity due to cross-linking, followed by a rapid decrease due to chain scission. Films of nylon polymer with high initial concentrations of hydroperoxide show little or no initial cross-linking but rapid chain scission, indicating that the latter is induced by hydroperoxides resulting in β-bond scission to give a free macroalkyl radical and carbonyl group. Using second-order derivative uv spectroscopy, a new intense absorption band is observed at 230 nm. The thermal and photo-chemical behaviour of this band matches that known to be present at 290 nm, confirming the presence of α,β-unsaturated carbonyl impurity groups in the polymer.

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