ULTRAFILTRATION MEMBRANES MADE OF VINYL-CHLORIDE VINYL-ACETATE COPOLYMER

This paper presents the results of investigations concerning the formation, structure and transport properties of tubular ultrafiltration membranes made of copolymer vinyl chloride-vinyl acetate (Winicet, Poland). A method of tubular membrane formation by the phase-inversion method has been worked out. To prepare the casting solution, dimethylformamid was used as the solvent, and water as the nonsolvent. The compactness of the membranes can be controlled by changing the concentration of polymer in the casting solution, the gelation temperature and by using polyethylene glycol as an additive to the casting solution. The porosity of the membranes was determined by means of electron microscopy, the bubble-point method and nitrogen adsorption/desorption method. The obtained membranes are asymmetrical and the macroporous sublayer has a finger-like structure. The pore size distribution of the skin has a rather narrow character. The transport-separation properties of the membranes were determined by measuring the water flux and retention coefficient of water soluble macromolecules and colloids.