IRRADIATION OF POLY-D,L-LACTIDE

Compression-moulded samples of poly-D,L-lactide have been gamma-irradiated in air to give received doses up to 10 Mrad. Molecular weight and mechanical property changes have been established and are consistent with a random scission process. Substantial embrittlement occurs at the higher dose levels. The radiochemical yield for scission G(s) has been calculated to be 2.9 over the dose range examined. The properties of irradiated materials have been monitored over a 504-day period and show no evidence of post-irradiation aging. Moisture uptake has been measured by immersion in pH 7.4 buffer at 37-degrees-C and indicates that the irradiated material absorbs water at a slightly slower rate than the unirradiated material. The primary effect of irradiation on hydrolytic degradation is associated with the initial reduction of molecular weight and there are no subsequent changes in degradation mechanism.