CHARACTERIZATION OF GRAFT-MODIFIED POROUS POLYMER MEMBRANES

Porous poly(vinylidene fluoride) membranes were graft modified with ac rylic acid by radiation-induced grafting utilizing electron beam. When the grafted membranes were characterized by the measurements of conve ctive permeability, diffusion, and ion exchange properties, the membra nes showed properties of variable permeability membranes with respect to the permeability of solvent and the ionic semipermeability. The per meability for the studied membranes (extent of grafting varied from 0 to 93 wt %) can be controlled by the ionic strength and pH of the perm eate. The more grafted the membranes are the greater are the changes i n the permeability; e.g., for the extent of grafting of 85 wt % the pe rmeability increases ca. 4 orders of magnitude when the electrolyte co ncentration is increased from 10 mM to 1 M. The membranes with the ext ent of grafting of ca. 10 wt % or more appeared to have equal charge d ensity on the pore walls resulting in the same cation transference num ber.