Improvement of the water selectivity of ULTEM poly(ether imide) pervaporation films by an allylamine‐plasma‐polymerized layer

Abstract

ABSTRACT:The wettability and surface energy of extruded ULTEM poly(ether imide) films strongly increased (the water contact angle varied from 75 to 38°and the surface energy varied from 45.3 to 59.5 mJ m Ϫ2 , respectively) with the deposition of an allylamine-plasma-polymerized layer and were characterized with X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy according to the experimental parameters. Pervaporation tests for dehydrating the water/ethanol azeotropic mixture were performed at 40°C with nontreated and plasma-treated ULTEM films for 15, 30, 60, and 120 min. No significant difference was noticed in the total flow (ca. 2.5 g/m 2 h) among the various films. However, for the 30-min duration, a great increase in the water selectivity from 850 to 10,850 was measured, and it was related to the higher N/C ratio and the presence of amide groups on the surface.

Time-dependence of pervaporation performance for the separation of ethanol/water mixtures through poly(vinyl alcohol) membrane

“…For instance, the surface modification of poly(dimethylsiloxane) (PDMS) membranes with no change in their inner structure can control the selectivity of the solution process without changing the diffusion process [31]. The allylamine-plasma surface-modified PEI membrane was shown to exhibit a higher separation factor, but there was no significant difference in permeate flux between untreated and treated PEI membranes [12]. Therefore, our results that the flux with operating time shows a similar changing trend no matter what side is in contact with the feed are readily understood because there is no change in their inner structures.…”

“…For example, H 2 O wt% in the permeation through poly(vinyl alcohol) (PVA) membrane treated with allyl alcohol plasma first increased, and finally attained equilibrium as the pervaporation process proceeded [8]. When the poly(ether imide) (PEI) membrane deposed an allylamineplasma-polymerized layer employed to dehydrate the water/ethanol azeotropic mixture, its selectivity toward water increased from 2000 to 10,850, while the total flux decreased from 3 to 2.6 g/m 2 h after about 30 h of operation [12]. The reason for such time-dependent properties of pervaporation performance was debatable.…”

“…However, some investigations have revealed that the separation performance of the membrane had significant time dependence [8,[11][12][13][14][15]. For example, H 2 O wt% in the permeation through poly(vinyl alcohol) (PVA) membrane treated with allyl alcohol plasma first increased, and finally attained equilibrium as the pervaporation process proceeded [8].…”

Diamine modification of P84 polyimide membranes for pervaporation dehydration of isopropanol

“…Additionally, the apparent N 1s peak ( Figure 3) is broadened and shifted from a higher binding energy (attributed to NOCAO groups, about 400 eV) to a lower binding energy (attributed to CON groups, about 399 eV), which implies the formation of amide. 13 On the basis of FTIR and XPS results, a reaction mechanism is proposed in Figure 4, which is similar to the crosslinking of 6FDA-polyimde 17 and Matrimid ® . 18 XRD spectra as shown in Figure 5 reveal that the peaks gradually shift to the right after crosslinking, indicating the d-space decreases significantly.…”

“…Plasma treatment is another way to modify the properties of polyimide. Kaba et al 13 found that the wettability of polyetherimide (PEI) dense films and the selectivity of the membrane can be significantly improved by the anallylamineplasma polymerized layer for the dehydration of ethanol. Crosslinking modification of polyimide has been extensively studied in the preparation of gas separation membranes; however, the crosslinking modification of polyimide is seldom used for pervaporation dehydration.…”