Abstract
To improve the performance of dialysis membranes, it is important to relate diffusive and convective permeabilities with asymmetrical structure of the membranes. We evaluated the asymmetrical structure of three polysulfone dialysis membranes (PS-400, PS-UW, APS) by observation with SEM, comparison of sorption rates, BET method and DSC method. The membranes were found to consist of the skin layer near the inner surface and the supporting layer at interior region and the outer surface of the membranes by the observation with SEM. The sorption rate curves of inside to outside and outside to inside were different for PS-400 and PS-UW, and were the same for APS, suggesting that the differences in the sorption rate curve were attributed to the difference in the structure of the skin layer and the supporting layer. The pore size distributions of the membranes determined by BET method could not be evaluated for larger pore that almost comprise the supporting layer. The pore size distributions of the membranes determined by DSC method, representing those of the supporting layer, were similar. In conclusions, the polysulfone dialysis membranes consist of the skin layer and the supporting layer, and have the difference in structure of skin layer.
