Surface modification of polypropylene membrane by low-temperature plasma treatment

Microporous polypropylene membranes were low temperature plasma treated wit h acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Exce ss power damaged the membrane surface and excess monomer flow rate increase d the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with th e increase of plasma treatment time. Deposition of the plasma polymer on th e membrane surface was confirmed by FTIR/ATR spectra of the treated surface . In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BS A (bovine serum albumin) solution test confirmed that fouling was greatly r educed after the plasma treatment. The BSA solution flux through the plasma -treated membranes depended on pH, whereas pH variation had no serious effe cts on the untreated membrane. Modification of the surface charge by the pl asma treatment should exert a substantial influence on the adsorption and r emoval of BSA. (C) 2001 John Wiley & Sons, Inc.