Elastic behavior of chitosan films

The thermoelastic behavior and equilibrium stress–strain properties of chitosan films lightly crosslinked with gluteraldehyde and swollen with water were studied. Precautions were taken to preclude changes in the swelling ratio of swollen sample films during the experiment. The results indicate that at relatively low extensions the elastic behavior of the biopolymer is entropic in origin. The equilibrium stress–strain isotherms of chitosan did not obey Mooney–Rivlin equation because of sharp increases in stress with extension ratio at high extensions. This is attributed mainly to interchain hydrogen-bonded interactions, but a possible contribution due to strain–induced crystallization cannot be ruled out. © 1997 John Wiley & Sons, Inc.