AGING OF EPDM - 2 - ROLE OF HYDROPEROXIDES IN PHOTOOXIDATION AND THERMOOXIDATION

The first stages of pho to - and thermo-oxidation of ethylene-propylen e-diene monomer (EPDM) based on 5-ethylidene-2-norbornene (ENB) were s tudied and compared with the photolysis and thermolysis of hydroperoxi dized EPDM (EPDM-OOH), which were described in our first paper. Nitric oxide derivatizations of oxidized EPDM revealed an unexpectedly stron g contribution of secondary hydroperoxides while sulfur tetrafluoride and ammonia treatments showed the presence of saturated and unsaturate d carboxylic acids and ketones. Saturation reactions of the residual E NB double bond are more efficient in thermal oxidation, as they were i n thermolysis of EPDM-OOH. Photo-oxidation and thermal oxidation of EP DM (ENB) are compared with those of EPDM-OOH, EPDM based on dicyclopen tadiene (DCPD) and EPDM based on 1,4-hexadiene (HD). The inductive eff ect of hydroperoxide as well as the lower stability of ENB sites compa red with DCPD and HD are revealed. (C) 1998 Elsevier Science Limited. All rights reserved.