Although PVA has good mechanical properties in the
dry state, its application is limited by its water-soluble
nature. Because of the inherent hydrophilic properties of
PVA, researchers have attempted to introduce hydropho-
bic character into PVA via heat treatment, radiation, or by
using crosslinking agents for removal of the OH groups
of PVA. The crosslinking agents include hexamethylene or
hexaethylene diisocyanate, glyoxal, boric acid, dialdehy-
des, dicarboxylic acids, dianhydrides