Water absorption and states of water in thermosets from ethylene-vinyl alcohol copolymers and dianhydrides

The crosslinking reaction of two ethylene-vinyl alcohol copolymers (EVOH) with 3,3′,4,4′-tetracarboxybenzophenone dianhydride, pyromellitic carboxylic acid anhydride and 7-methyl-5-(tetrahydro-2,5-dioxo-3-furyl)-3a,4,5,7-tetrahydroisobenzofuran- 1,3-dione (Epiclon B-4400) as hardeners was carried out in solution. Different degrees of crosslinking were obtained. The crosslinked products were characterized by spectroscopic techniques and thermal methods. The water absorption of these crosslinked materials was determined gravimetrically as a function of time at room temperature. Differential scanning calorimetry was used to estimate the contents of three possibles types of water absorbed by hydrophilic materials: free water, bound and freezable water and bound but non-freezable water.