Amido e sericina na produção de filmes biodegradáveis

Abstract

The using of plastic materials for oil sources generates environmental nuisances. In this context, researches about biodegradable materials have been performed. Biodegradable films of cassava starch and poly (Butylene Adipate co-Terephthalate), plasticized with glycerol, were produced by extrusion-blowing in two steps (90-120-120-120-120°C and 100 rpm; 90-120-120-130-130°C and 40 rpm) using sericin as the reinforcing agent in different concentrations (0.5; 1.0 and 1.5% m/m). The thickness, the transverse stretching and the apparent opacity of the films ranged from 180 to 248µm, 310 to 343% and from 0.24 to 0.31%.µm-1, respectively. Since the film with 1.0% (m/m) of sericin showed greater thickness, and lower transverse stretching and apparent opacity. For the analysis of mechanical properties, the films were conditioned at different equilibrium relative humidities (RH) (33, 53 and 75%). In general, the tensile strength and Young’s modulus of the films increased as the concentration of sericin was increased. On the other hand, the elongation values were reduced with the increasing concentration of sericin. However, due to the plasticizing action of water, the films conditioned at 75% of RH were more flexible. The water vapor permeability of the films ranged from 5.94 to 7.55 x10-11 (g.(m.s.Pa)-1), and to this variable the lowest value was found for the film with 1.5% of sericin, which presented a more homogenous and compact structure verified by fracture micrographs obtained by SEM with increase of 1600x. The FT-IR analysis demonstrated, by the reduction in the intensity of the peak related to hydrogen bonding between hydroxyl groups, in the region of 3000-3500 cm-1, that there is an interaction between the polymeric chains of starch and sericin.