Uso de enzinas na extração de polihidroxialcanoatos sintetizados por Cupriavidus necator

Abstract

Materials prepared from biodegradable polymers can be an alternative for reducing the environmental problems provoked by petroleum derived polymers used to produce packages. Starches from different sources have been considered as a technically viable raw material for producing biodegradable films at low cost. Moreover, starches are from renewable sources, which allow applying environmental politics for controlling the carbon cycle. Starch based films dot not resist to the mechanical stress they are submitted when used in commercial packages, and have high water vapor permeability (WVP). Incorporation of nanoclay and cellulose fibers have been reported as a viable alternative for reinforcing these films. The objective of this work was to investigate the influence of the incorporation of nanoclay and cellulose fibers on the properties of starch bases films. The work was performed in two steps. In the first step, films were prepared with different formulations and different processes of nanoclays incorporation their mechanical properties and WVP were determined. In the second step, the addition of nanoclay and cellulose fibers was investigated. For that, starch films, starch-nanoclay films and starch-nanoclay-cellulose fibers composites-films were prepared. The starch-nanoclay composites-films showed WVP one-fold lower that the values found for starch films. These composites were seven-fold more rigid than starch films, but with the same tensile strength of starch films, indicating that the added nanoclay did not reinforce the starch films. On the other hand, the incorporation of fibers and nanoclay increased the films tensile strength in 8.5 times and their rigidity (Young modulus) in 14 times. The composites diffractograms indicated intercalation between the clay lamellas and the starch chains. The WVP of composites-films were lower than the values found for starch films, and increased with the air relative humidity. The results reported in this work indicate that the incorporation of nanoclay and fibers to starch films is a viable alternative for reinforcing mechanically these films, and for reducing their WVP.