Effect of coating method on gas separation by PDMS/PES membrane

Abstract

In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO2, CH4, and N2 were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO2 was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO2 permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO2/N2 and CO2/CH4 selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers

Enhanced gas separation performance of PSF membrane after modification to PSF/PDMS composite membrane in CO2/CH4 separation

“…The peak at 1405.82 cm 21 also attributes to the stretching vibration of aromatics in PSF while the peak at 1151.13 cm 21 is assigned to the symmetrical vibrations of sulfone group. 16 The stretching vibration of aromatic benzenes indicates the presence of sulfone group, thus confirming that membrane is PSF based. 33 The aromatic CAH bending is attributed by a peak at 837.84 cm 21 .…”

“…13,14 It can be concluded from permeation results that modification of PSF membrane to PSF/PDMS composite membrane enhanced the separation performance of PSF membrane. PDMS coating time also plays a significant role in defining the gas permeation performance, 16 as the selectivity in the composite membrane with coating time of 30 min was 55% and 10% higher than the selectivity of the composite membrane with coating time of 10 and 20 min, respectively. This is due to the complete phase transition and appropriate crosslinking between polymer chains due to larger coating time.…”

“…Asymmetric PSF membrane was dip coated with PDMS solution by the method reported by Madaeni et al 16 PDMS solution was prepared with n-hexane as a solvent. Based on the literature, 18 tetraethyl orthosilicate was used as a crosslinker in PDMS solution to aid the crosslinking between PDMS and PSF chains.…”

“…Due to excellent thermal and chemical stability, PDMS can be a good candidate to be used in aggressive feed conditions. 16,17 PDMS is also known to remove surface defects from base asymmetric membranes. 22 The combination of PSF and PDMS into a composite membrane would result in a high-performance membrane.…”

“…It was reported that higher concentration of PES with higher PDMS coating resulted in the decrement of CO 2 permeance with the increase in CO 2 /CH 4 selectivity. Madaeni et al 16 developed PDMS/PES membrane using dip coating and film casting technique and investigated the gas permeation of CO 2 , CH 4 , and N 2 for prepared membranes. Selectivity of dip-coated membranes was higher than the film cast membranes due to the complete crosslinking between PDMS and PES.…”