Preparation of thermoplastic starch

Abstract

Native starch and WX-starch, i.e., native starch enriched with amylopectin, were mixed with plasticizers and thermomechanically treated in a twin screw mixer in order to obtain thermoplastic starch. Ethylene glycol, propane tricl (glycerine) or poly(ethylene glycol) with a molar mass less than 1000 g/mol were used as plasticizers. Transformation to thermoplastic starch was only successful when glycerine or ethylene glycol were used as the plasticizers, the temperature of the thermomechanical treatment being dependent on the plasticizer and starch used. Rheological properties of the obtained thermoplastic starch were determined using a mechanical spectrometer. As a result of these measurements, the complex viscosity (η*), shear moćulus of stored (G') and of lost energy (G'') were obtained as a function of frequency at constant temperature. The measurements were performed at three temperatures: 140, 170 and 210°C. The results obtained showed that the thermoplastic starch behaved like a typical thermoplastic polymer.