[Degradation of polyurethanes in aqueous environment].

The effect of in vitro exposure to aqueous environments on the change of properties of polyurethanes was studied as a model experiment for understanding the in vivo degradation of polyurethanes. Films of three commercially available medical polyurethanes consisting of diphenylmethane diisocyanate (MDI) (Biomer, Cardiothane and TM-3) and an experimental segmented polyurethane based on hydrogenated MDI (HMDI) were immersed in phosphate buffer or HEPES buffer containing lithium chloride at pH 7.4 at 70 degrees C for up to one year. Samples were subjected to ATR-FTIR measurement, tensile testing and viscosity measurement. Stability to hydrolytic degradation increased in the order: HMDI, TM-3, Biomer and Cardiothane. This ranking was consistent with that obtained in vivo. The results suggest that an in vitro model experiment is helpful for understanding and predicting degradation performance of polyurethanes in vivo.