Biodegradable fish gelatin/chitosan composite films: homogeneous and bi-layer structures

Fish gelatin and chitosan were used to develop composite biodegradable films using two strategies: (i) the mixture of both polymers to obtain homogeneous polymer matrixes and (ii) the formation of two layers. The films produced were characterized in terms of water absorption, solubility, water vapour permeability and mechanical properties. Both strategies revealed to produce films with a high strain at break (60-70%), and a quite significant solubility in water and in acetic acid 1.7% (around 40%). Little differences were observed between homogeneous and bi-layer films. On the other hand, homogenous films revealed to have a lower water sorption capacity, compared to pure gelatin and bi-layer films. The results have shown that, under the conditions tested, there was no advantage on using the bi-layer technique. A high affinity towards liquid water was observed in all films tested, even though a crosslinking agent (poly(ethyelene glycol) diglycidyl ether) was added to the film formulations. This fact may be due to a low crosslinking degree, added to the hydrophilic nature of the crosslinking agent itself.