Rheological Behavior of Some Starch - Based Bioplastics

The recent interest in the field of bioplastics is to obtain packaging material from pure starch without synthetic polymers. The rheological behaviour represents one of the most important feature of such materials. Samples with different ratio of starch, glycerol and water were prepared and investigate regarding their rheological behaviour. After the samples reaches their limit of swelling and were completely decomposed viscosity was measured with a Brookfield DV-III Ultra rheometer at different temperatures and share rates. The data were analyzed with Kaleidagraph software. For a given sample our measurements show that the viscosity is dependent on share rate and switches from a non-Newtonian to a Newtonian behaviour in function of temperature and sample composition. We used the power law model to describe this dependence and for a given set of data there is only one output for the fit parameters. We consider the best fit of the experimental data when the curve traced by the computer passes almost through all experimental points. In the present research work we establish a particular algorithm of mathematical analysis of experimental data which allows a separation of the contribution of each variable to the viscosity.