Cellulose acetate/sodium caseinate based films

MARIANA PEREDA; GUILLERMINA AMICA; ILONA RÁCZ; NORMA E. MARCOVICH

Lyon

Simposio; 2nd International Symposium Frontiers in Polymer Science; 2011

Nowadays, there is a growing tendency to utilize environmental friendly materials with the intention of substituting non-degradable materials, thus reducing the environmental pollution resulting from waste accumulation. One of the approaches is to use renewable biopolymers such as polysaccharides, proteins, lipids and their complexes, derived from animals and plants. In particular, sodium caseinate, obtained by acid precipitation of casein, easily forms aqueous solutions due to their random- coil nature and ability to form extensive intermolecular hydrogen bonds. On the other hand, cellulose is the most abundant source of complex carbohydrates in the world. Water-soluble cellulose derivatives are used for packaging because of their edibility and biodegradability. At the same time they offer good barrier properties, being non-toxic, non-polluting and having low cost. The aim of this work is to improve glycerol/sodium caseinate-based film properties by reinforcing it with cellulose acetate. Films were prepared by casting and solvent evaporation. The effects of CA concentration (0, 1, 2 and 3 %wt.) on the properties of the films were analyzed. Clearly, sodium caseinate films become less transparent with the addition of CA. The increase in film opacity arises from the light scattering produced by the cellulose particles thoroughly distributed in the protein network that constitutes the film, reducing the overall light transmitted through it. In composite films, tensile strength and elastic modulus increased significantly with increasing cellulose concentration, indicating that the filler is properly dispersed in the matrix structure. On the other hand, the deformation at break decreased as cellulose concentration increases due to the rigid nature of the filler. Contact angle measurements (using ethylene-glycol as solvent) show that cellulose acetate addition causes an increase in the superficial hydrophilicity of sodium caseinate samples, and contact angle values decreased with cellulose concentration. This effect is due to the polar character of this carbohydrate.