Study on multi-layer composite hollow fiber membranes for gas separation

Novel multi-layer composite hollow fiber membranes were prepared using silicone rubber, poly(4-vinylpyridine) and polysulfone as sealing layer, selective layer and support layer, respectively. The resultant composite membranes possess a different structural configuration from the conventional multilayer composite membranes, i.e. (sealing layer)/(selective layer)/(support layer) versus (selective layer)/(gutter layer)/(support layer). The new membrane structure lead to high performance membranes for gas separation applications. For example, the polysulfone hollow fiber membrane coated from a 3 wt% silicone rubber solution and a 0.2 wt% poly(4-vinylpyridine) solution had an O₂ permeance of 6.69 x 10^-6 cm³(STP)/cm² s cmHg with O₂/N₂ selectivity of 7.26. From the permeation results of polysulfone hollow fibers coated with poly(4-vinylpyridine) and SEM photo micrographs, it was concluded that the surface of poly(4-vinylpyridine) layer was defective and the high membrane performance was rendered only after coating with a silicone rubber layer. The analysis by a resistance model suggested that the poly(4-vinylpyridine) layer comprised most of the resistance(99%) and provided the separation performance. The surface porosity of the polysulfone support layer and the permeability of poly(4-vinylpyridine) can also be roughly calculated by applying the resistance model.