Analysis of hydroperoxides in solid polyethylene by MAS C-13 NMR and EPR

C-13-enriched polyethylene was subjected to gamma-irradiation in the presen ce of air at. 25 and 80 degrees C for total doses ranging from 71 to 355 kG y. Significant quantities of hydroperoxides were detected in the 25 degrees C irradiated sample by C-13 magic angle spinning NMR spectroscopy. This me thod of detection was performed on the solid polymer and required no chemic al derivatization or addition of solvent. The chemical stability and subseq uent products of the hydroperoxide species were studied by annealing the ir radiated samples in air at temperatures ranging from 22 to 110 degrees C. A time-temperature superposition analysis provided an activation energy of 1 08 kJ/mol for the hydroperoxide decomposition process. The primary products of hydroperoxide decomposition were ketones and secondary alcohols with le sser amounts of acids and caters. EPR measurements suggest that the reactiv e hydroperoxide species reside in the amorphous phase of polyethylene, cons istent with degradation occurring in the amorphous phase.