High strength biobased films prepared from xylan/chitosan polyelectrolyte complexes in the presence of ethanol.

The effect of different ethanol concentrations (0; 3; 9; 12 and 16 wt%) on the degree of ionization of xylan and chitosan, the characteristics of polyelectrolyte complex (PEC) suspensions, and the derived films, were exhaustively analyzed through several analytical techniques. Results indicate that the degree of ionization of both polyelectrolytes was reduced, whereas particle sizes and z-potential values of PEC suspensions were remarkably modified. As ethanol concentration was increased up to 12 wt%, the crystallinity of films decreased. Furthermore, the stress at break increased from 45 to 75 MPa. Wet stress-strain results were promising (up to 5.0 MPa, 55%) for all films. Although water vapor permeability was not modified, the swelling capacity was favorably reduced (12%). Results reveal that, for preparing films, it might not be necessary to remove all the ethanol used for xylan precipitation and purification.