Mechanical Analysis of Biodegradable Films from Native and Chemically Modified Potato Starches

The production of biodegradable films has been studied to be a substitute of conventional plastics. The use of starch in biodegradable films are of great interest and starch modification improves an increase to the mechanical properties the film. The mechanical properties were evaluated by Dynamic Mechanical Analysis (DMA). The aim of this study is to determine the mechanical properties of biodegradable films produced from native and chemically modified potato starch. The starch was extracted and subjected to chemical modification by oxidation in different concentrations of active chlorine. The biodegradable films were prepared with starch and glycerol as plasticizer, and were observed with an optical microscope to evaluate the morphology and their relationship with the strength. The tensile tests were performed at 80oC to evaluate the mechanical properties by means of stress-strain curves. The morphology of biodegradable potato starch films shows that the starch granules were partially gelatinized during the film formation. As the elastic modulus is a property which determines the stiffness of the material, by means of he DMA analysis it can be seen that oxidation results in beneficial changes in the mechanical properties of the films, because the modulus increased from 346.70 MPa for the native starch to 651.75 MPa to oxidized starch with 1.5% of active chlorine, respectively.