INVESTIGATIONS ON HIGH AMYLOSE CORN STARCH FILMS .3. STRESS-STRAIN BEHAVIOR

By autoclaving a watery high amylose corn starch suspension, homogenous and isotrope films were obtained with different processing parameters. The films were used for investigations on the stress strain behavior. A systematical dependence on the water content and the relationship between native lipids and the starch chains was observed. Especially for films obtained from defatted corn starch, a clear transition was obtained, depending on the water content, from a brittle behavior far below the glass transition temperature T-G with a very high Youngsmodulus to a ductile failure behavior above T-G. The results led to a microscopical model for the native high amylose corn starch films, which in addition outlines the very interesting possibility of controlling in detail changes of the macroscopic stress strain behavior through variations on a molecular scale.