Dispersion-casting thin and ultrathin fabric-reinforced silicone rubber membrane for use in the membrane lung

Pinholes in thin silicone rubber membrane have previously been traced to undispersed silica filer aggregates within the silicone rubber. This was overcome by centrifuging the dispersion to remove the aggregates prior to membrane fabrication. Thin (less than 75 mu) and ultra-thin (less than 25 mum) membrane could then be dispersion-cast. To facilitate handling and to increase mixing of blood in the membrane lung, it is often desirable to reinforce the silicone rubber membrane with fabric. Unfortunately, this process frequently introduces pinholes of its own. We have found than pinhole-free fabric-reinforced silicone rubber membrane can consistently be produced by the double-layer casting technique. First, the dispersion is cast onto aluminum foil, solvent evaporated, and partially cured. A second layer is next cast on top of it, followed by fabric. After solvent evaporation, final cure is under nitrogen using organic peroxide catalysts. This technique has permitted us to consistently cast strong pinhole-free membranes as thin as 9 mu.