Preparation, Structure, and Transport Properties of Ultrafiltration Membranes of Poly(vinyl chloride) (PVC), Carboxylated Poly(vinyl chloride) (CPVC), and PVC/CPVC Blends P. RAMESH BABU, V. G. GAIKAR Department of Chemical Technology, University of Mumbai, Nathalal Parikh Marg, Matunga, Mumbai 400019, India Received 21 September 1997; accepted 10 November 1998 ABSTRACT: Ultrafiltration (UF) membranes were prepared from poly(vinyl chloride) (PVC), carboxylated poly(vinyl chloride) (CPVC), and PVC/CPVC blends by the phase- inversion method. The physical structure of the membranes was characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The fouling characteristics of all the three membranes and acrylamide (AA)-grafted PVC mem- branes were characterized by ultrafiltration of bovine serum albumin (BSA) solution over a range of pH and of salt concentrations. Maximum adsorption of the protein on the membrane occurred near the isoelectric point of BSA and in the presence of the salts. The charge on BSA appears to be a dominant factor in determining the fouling. The UF results are explained in terms of nature of the membrane polymer, and effect of different ionic environments on the conformational changes of the protein. The ultrafiltration fluxes are correlated by a model based on the membrane resistance and the time-dependent resistance of the concentration polarization layer of the protein. The values of a mass transfer coefficient and concentration polarization were deter- mined. Zeta potential of the membranes were also determined before and after the UF. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1117–1130, 1999 Key words: ultrafiltration membranes; poly(vinyl chloride) (PVC); carboxylated poly- (vinyl chloride) (CPVC); PVC/CPVC blend; DSC; SEM analysis; AFM analysis; BSA; zeta potential INTRODUCTION The feasibility of a membrane separation process depends mainly on the characteristics of the membrane. If a polymer of desired properties is not available, then two or more different polymers can be combined to obtain blends with desirable features. Over the years, numerous membrane materials, based on the chemical combinations of monomers in graft or block or by copolymeriza- tion, have been developed. 1,2 Blends of similar cellulose esters have been known as membrane materials since 1969, 3 but the first real blends of different polymers were reported by Cabasso et al. 4,5 followed by several other workers. 6–8 The most common and practically important miscible polymers owe their miscibility to specific interac- tions, for example, hydrogen bonding, electro- static interactions, etc., between different groups on the polymeric structure of the components. For example, a weak hydrogen bond is postulated be- Correspondence to: V. G. Gaikar. Contract grant sponsor: U.S. Department of Commerce (INDO–US Collaborative Research Project). Journal of Applied Polymer Science, Vol. 73, 1117–1130 (1999) © 1999 John Wiley & Sons, Inc. CCC 0021-8995/99/071117-14 1117