Surface modification of polypropylene membranes by gamma-ray induced graftcopolymerization and their solute permeation characteristics

Porous hydrophobic polypropylene (PP) membranes were subjected to the surfa ce modification by the gamma -ray induced graft copolymerization with hydro philic 2-hydroxyethyl methacrylate (HEMA). The structural changes and surfa ce morphologies of the modified PP membranes were characterized by a Fourie r transform infrared spectroscopy (FT-IR), elemental analysis (EA) and fiel d emission scanning electron microscopy (FE-SEM). Peroxides produced from g amma -ray irradiation were determined by a 1,1-diphenyl-2-picryl hydrazyl ( DPPH) method and the surface hydrophilicities of membranes were measured by a static contact angle measurement. The contact angle of the modified memb ranes reduced with the degree of grafting (DG) of HEMA onto the membrane su rface., and it decreased up to about half of that before modification. The permeation behaviors of all membranes were investigated by a bovine serum a lbumin (BSA) filtration experiment. As a result, the DG of the modified mem brane increased with the reaction time. However. in the case of irradiation dosage it showed the maximum value at 20 kGy. Also, the modified membrane showed a higher solution flux, lower BSA adsorption, and the better flux re covery after cleaning than that of the unmodified membrane. Particularly, 4 0.6% grafted membrane showed a two-fold increase in a BSA solution flux, 62 % reduction in total fouling and three-fold increase in flux recovery after chemical cleaning. (C) 2001 Elsevier Science B.V. All rights reserved.