Ageing of EPDM - 2. Role of hydroperoxides in photo- and thermo-oxidation

The first stages of pho to - and thermo-oxidation of ethylene-propylene-diene monomer (EPDM) based on 5-ethylidene-2-norbornene (ENB) were studied and compared with the photolysis and thermolysis of hydroperoxidized EPDM (EPDM-OOH), which were described in our first paper. Nitric oxide derivatizations of oxidized EPDM revealed an unexpectedly strong contribution of secondary hydroperoxides while sulfur tetrafluoride and ammonia treatments showed the presence of saturated and unsaturated carboxylic acids and ketones. Saturation reactions of the residual ENB double bond are more efficient in thermal oxidation, as they were in thermolysis of EPDM-OOH. Photo-oxidation and thermal oxidation of EPDM (ENB) are compared with those of EPDM-OOH, EPDM based on dicyclopentadiene (DCPD) and EPDM based on 1,4-hexadiene (HD). The inductive effect of hydroperoxide as well as the lower stability of ENB sites compared with DCPD and HD are revealed. (C) 1998 Elsevier Science Limited. All rights reserved.