KINETICS OF FREE-RADICAL DECAY REACTIONS IN LACTIC-ACID HOMOPOLYMERS AND COPOLYMERS IRRADIATED TO STERILIZATION DOSE

The kinetics of flee radical decay reactions of poly(L-Lactic acid), p oly(DL-Lactic acid) and random copolymer of lactic and glycolic acid h ave been investigated for decays taking place in air and in vacuum. Th e change in ESR lines of gamma-irradiated polymers have been followed over a long time period. The decay has been found to follow neither si mple first-order nor second-order kinetics. Various kinetic approaches including composite first or second-order mechanisms and diffusion-co ntrolled first or second-order equations were determined to be also un satisfactory. The decay of radicals in bulk irradiated lactic acid hom o and copolymers was found to be best described when the second-order non-classical equation with time dependent rate constant approach was used.