XPS and contact angle characterization of surface modified cellulose acetate membranes by mixtures of PMHS/PDMS

A mixture of polymethylhydrosiloxane (PMHS) and polydimethylsiloxnae (PDMS) is used for modifying the surface of reverse osmosis and nanofiltration membranes. The porous substructure made of cellulose acetate (CA) was obtained by a phase separation process from acetone/formamide (2/1 wt/wt) casting solutions. Two polymer concentrations (22 and 25 wt.%) were used with a heat post-treatment temperature (80 degrees C) in order to produce membranes with pore sizes responding to nanofiltration and reverse osmosis needs. Overcoating the CA substructure with a PMHS-PDMS thin layer gave rise to the composite membranes. Surface characterization with X-ray Photoelectron Spectroscopy (XPS) indicates the success of modifying the CA membrane surface with PMHS-PDMS. Contact angle measurements showed an increase in hydrophilicity of the modified membrane surface. Tensile strength measurements indicate that modification by a mixture of PMHS-PDMS has an insignificant decrease in Young's modulus. The pure water flux measurements reveal that layer modification by PMHS-PDMS show an improvement in water permeability which is in agreement with contact angle results. (C) 2012 Elsevier B.V. All rights reserved.