Preparation of biopolymer films by aqueous tape casting processing

Abstract

Biopolymer films have been prepared by continuous aqueous tape casting, using dextran–water solutions. The effect of dextran concentration and solution temperature on the flow behavior was studied by steady and dynamic rheological measurements. Rheological measurements revealed that increasing dextran concentration strongly increased viscosity, while increasing temperature reduced the viscosity marginally, limiting the film processing techniques to tape casting. Elastic effects were also seen in the biopolymer rheology studies, and no changes in the fluid internal microstructure were detected in the rheological measurements. The effect of casting speeds on the biopolymer film thickness was experimentally determined and compared with a pseudoplastic fluid model. Mechanical properties of the biopolymer films presented an isotropic behavior. Adding sorbitol as an external plasticizer produced more elastic films but induced an anisotropic response on the elongation at break.