Crosslinking of polyvinyl alcohol with di, tri, and tetracarboxylic acids: an experimental investigation

In this study, three polycarboxylic acids with varying numbers of carboxyl groups were employed to crosslink polyvinyl alcohol (PVA): malonic acid as a diacid (MA), citric acid as a triacid (CA), and 1,2,3,4-butane tetracarboxylic acid as a tetraacid (BTCA). The crosslinking abilities of these acids were compared using physical, chemical, mechanical, morphological, thermal, and swelling measurements to assess their impact on the physicochemical properties of the resulting films. Based on the degree of crosslinking, mechanical strength, and thermal stability, tetra acid demonstrated superior crosslinking performance compared to di and tri acids. The highest strength was observed in the tetra acid crosslinked film, which exhibited a 127% increase over neat PVA. Regarding thermal stability, the decomposition temperature followed the order of tetraacid (450 °C) > triacid (378 °C) > diacid (350 °C). However, in terms of swelling behavior, triacid-crosslinked film, i.e., P-CA, exhibited the highest swelling. Further, the tetra acid-crosslinked film exhibited the lowest crystallinity and a higher contact angle (104.9°) than diacid and triacid crosslinked films. Additionally, the crosslinked films displayed enhanced elasticity compared to pure PVA, with the elasticity order being diacid > triacid > tetraacid, possibly due to differences in available crosslinking sites among the crosslinkers.