Urea and ethanolamine as a mixed plasticizer for thermoplastic starch

Mixtures of urea and ethanolamine were used as plasticizers for preparing thermoplastic starch (TPS) in a single-screw extruder. The interaction between urea/ethanolamine and starch was investigated using Fourier Transform Infrared (FT-IR). Glass transition temperature of TPS was tested by Differential scanning calorimetry (DSC). Both FT-IR and DSC proved that the mixture of urea and ethanolamine could form more stable and strong hydrogen bonds with starch molecules than the conventional plasticizer, glycerol. By Scanning Electron Microscope (SEM) native starch granules were proved to transfer to a continuous phase. The thermal stability, mechanical properties and starch retrogradation behavior were also studied by TG (Thermal Gross), tensile testing and X-ray Diffraction (XRD), respectively. TPS plasticized by urea (15 wt/wt%) and ethanolamine (15 wt/wt%) showed a better thermal stability and mechanical properties than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and Energy Break, respectively, reached 9.00 MPa, 34.4% and 1.34 N m. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch and urea.