A CRITICAL COMPARISON OF METHODS FOR HYDROPEROXIDE MEASUREMENT IN OXIDIZED POLYOLEFINS

Hydroperoxide products in solid oxidized polyolefins have been measured by iodometry, Fe2+ reaction and by derivatization infrared spectroscopy methods. Polyethylene, polypropylene and elastomers were oxidized by photo, thermal and gamma-initiation. The traditional iodometric method appears to be highly reliable within certain constraints of reaction time imposed by sample crosslinking. The Fe2+ reaction was found to give values consistently one order of magnitude below the true level because of failure of the reagents to penetrate into the oxidized polymers even after a prior swelling step. Derivatization of hydroperoxides by reaction with nitric oxide produced nitrates which could be measured by infrared spectroscopy with high sensitivity. Total nitrate yields agreed well with iodometric determination of hydroperoxide for reaction conditions under which the nitrates were stable. Different nitrates, and hence hydroperoxides, could be identified and quantified by this method.