Degradation mechanism of poly(ether-urethane) Estane® induced by high-energy radiation. II. Oxidation effects

To predict long-term polymer behavior during a nuclear waste storage time, radiation effects on a segmented aromatic poly(ether-urethane) induced by high-energy radiation under oxygen atmosphere were investigated. To obtain a predictive model of polymer radio-oxidation during several centuries, the first step consists to elaborate the elementary degradation mechanisms. Thus, electron paramagnetic resonance (EPR), Fourier transform infra-red spectroscopy (FT-IR), electrospray ionisation-mass spectrometry (ESI-MS), and gas mass spectrometry were carried out to identify radicals, chemical modifications, and gases to reach the radio-oxidative mechanism at doses inferior than 1000 kGy. Degradation mainly occurs at urethane bonds and in polyether soft segments that produces stable oxidative products as formates, alcohols, carboxylic acids and H₂, CO₂ and CO gases. Predominant degradation occurred at polyether soft segments and crosslinking is in competition with scission. On the basis of the results, a mechanism of degradation for aromatic poly(ether-urethane) is proposed.