Poly(acrylic acid)-poly(vinyl alcohol) semi- and interpenetrating polymer network pervaporation membranes

A series of poly(acrylic acid) (PAA)-poly(vinyl alcohol) (PVA) semiinterpenetrating (SIPN) and interpenetrating (IPN) polymer network membranes were prepared by crosslinking PVA alone or by crosslinking both PVA and PAA. Glutaraldehyde and ethylene glycol were used as crosslinking agents for the PVA and PAA networks, respectively. The presence of PAA increases the permeability of the membranes while the presence of PVA improves their mechanical and film-forming properties. The mechanical properties of the membranes were investigated via tensile testing. These hydrophilic membranes are permselective to water from ethanol-water mixtures and to ethanol from ethanol-benzene mixtures. The IPN membranes were employed for the former mixtures and the SIPN membranes for the latter, because the IPN ones provided too low permeation rates. The permeation rates and separation factors were determined as functions of the IPN or SIPN composition, feed composition, and temperature. For the azeotropic ethanol-water mixture (95wt% ethanol), the separation factor and permeation rate at 50°C of the PAA-PVA IPN membrane, containing 50 wt% PAA, were 50 and 260 g/m2 h, respectively. For the ethanol-benzene mixture, the PAA-PVA SIPN membranes had separation factors between 1.4 and 1200 and permeation rates between 6 and 550 g/m2 h, respectively, depending on the feed composition and temperature.