Experimental investigation of the effects of crosslinking processes on the swelling and hygroscopic performances of a poly(vinyl alcohol) membrane

ABSTRACT Poly(vinyl alcohol) (PVA) membranes crosslinked with L‐malic acid were prepared, and the effects of the heat‐treatment temperature and crosslinker concentration on their swelling and hygroscopic performances were investigated. Both the swelling and hygroscopic performances of the PVA membranes decreased with increasing heat‐treatment temperature; while the former decreased, the latter increased with increasing crosslinker concentration. The PVA membranes were characterized with differential scanning calorimetry (DSC), acid–base titration, and Fourier transform infrared spectrometry. The DSC results indicated that there was freezing and nonfreezing water in the swollen membranes, whereas there was only nonfreezing water in the moistened membranes. In addition, acid–base titration analysis revealed that both increased heat‐treatment temperature and increased crosslinker concentration increased the bilateral ester group levels (crosslinking degree) and decreased the content of freezing water. By contrast, the content of hydrophilic groups decreased and increased with increasing heat‐treatment temperature and crosslinker concentration, respectively; this resulted in decreased and increased levels of nonfreezing water, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44481.