INVESTIGADORES
MARCOVICH norma Esther
congresos y reuniones científicas
Título:
BIODEGRADABLE NANOREINFORCED FILMS
Autor/es:
MARIANA PEREDA; NORMA E. MARCOVICH; MIRTA I. ARANGUREN; ALAIN DUFRESNE
Lugar:
Pretoria, SOUTH AFRICA
Reunión:
Conferencia; 11th International Conference on Frontiers of Polymers and Advanced Materials; 2011
Institución organizadora:
University of Pretoria, South Africa
Resumen:
In this work, nano-reinforced films aimed for food packaging applications, made from chitosan and/or sodium caseinate, using glycerol as plasticizer, were prepared by casting from aqueous suspensions. To maintain the desirable matrix properties (i. e. relatively high elongation at break and transparency) and to keep the bio-degradability and potential edibility of the material, very low concentrations (up to 3 wt%) of nano-cellulose crystals prepared from acid hydrolysis of microcrystalline cellulose were selected as the reinforcing phase. FSEM observations performed on the surface of the samples allowed confirming the homogeneity of filler dispersion in all cases. Dynamic mechanical analysis performed on chitosan-based films revealed that their thermal transitions are almost not affected by the addition of nano-cellulose. Chitosan is a semicrystalline polymer, and the presence of crystalline portions could avoid that the amorphous part of the matrix got in contact with the nanofibers. Nevertheless, when chitosan-caseinate hybrid is used as matrix, the addition of only 0.5 % of nanocellulose results in a shift of the α-transition towards higher temperatures (from -54ºC to -41ºC). While chitosan is a semicrystalline polymer, chitosan-caseinate hybrid is an amorphous one, which facilitates its interaction with nanofibers. By increasing nanofiber concentration above 0.5%, Tg values decreased again. This last effect is due to fibers aggregation and led to a reduced contact surface to interact with the matrix. In the same way, the storage modulus of composites based on chitosan was always higher than the corresponding to chitosan-caseinate hybrids, with almost no differences related to cellulose concentration. In the second case (hybrid films) the storage modulus of composites was higher than that of the neat matrix, without a clear trend with nano-filler content.