Studies on syntheses and permeabilities of special polymer membranes: 24. Permeation characteristics of poly(vinylidene fluoride) membranes

The permeation characteristics of poly(vinylidene fluoride) membranes were investigated by changing the preparation conditions of the membranes, the composition of the casting solution, membrane thickness, time of heat treatment and temperature, etc.; and by changing the permeation conditions, operating temperature, the feed concentration, and the feed solute, etc. Aqueous solutions of poly(vinyl alcohol) and poly(ethylene glycol) were used as feed. The permeation characteristics were influenced significantly by the change of the above conditions and were dependent on the structure of resulting membrane, the viscosity of feed, the form of polymer molecules in aqueous solution, and the concentration polarization of polymer solute molecules onto the membrane surface. The permeation through very swollen membranes (ca. 85% in water content) followed the viscous flow.