New polymethylmethacrylate-polyurethane (PMMA-PU) membranes for hemodialysis applications

PMMA has been introduced recently in dialysis procedures as a hollow fiber device. In order to improve efficiency, hemocompatibility and mechanical properties, new flat membranes have been made by spraying PMMA-PU mixtures over a cylindrical rotating mandrel using a combined spraying and phase inversion technique (4). Three different mixtures have been evaluated, namely : PMMA(70)-PU(30), PMMA(SO)-PU(SO), PMMA(20)-PU(80). Mechanical testing showed that adding PU results in a substantial toughness increase, especially for PU content above 20%. Hemocompatility characterization was carried out according to the protocol for blood material interaction proposed in a n NIH publication (6). No significant differences from the basal value for any performed test were found. Transport property measurements with water, NaCl, Vit.B12 were performed in a dialysis apparatus of new design. Such new membranes showed higher permeability to small solutes and middle molecules in comparison with Cuprophane® and polyacrylonitrile (PAN) particularly in convective diffusion. The resulting hydraulic permeability was about one order of magnitude higher than PAN. Our preliminary results show an improvement in mechanical behaviour, hemocompatibility, and in molecular sieving capacity with respect to PMMA. The high hydraulic permeability also makes these formulations interesting for hemofiltration.