Preparation and properties of ethylenebisformamide plasticized potato starch (EPTPS)

Ethylenebisformamide plasticized potato starch (EPTPS) was prepared by extrusion. Starch was blended with ethylenebisformamide at 25, 30, and 35% (W/W) and extruded in a single-screw extruder. The samples were extruded at 135–140–135–135 °C from feed zone to die. FT-IR expressed that the microcosmic chemical environments of the group in EPTPS compared to the native potato starch, which indicated that, the strong and stable hydrogen bond had been formed between ethylenebisformamide and starch. By Scanning Electron Microscope (SEM) native potato starch granules were proved to transfer to a continuous phase. After being stored for 1 week at RH=33%, the mechanical properties of ethylenebisformamide plasticized thermoplastic starch (EPTPS) was also studied and the elongation reached to 140% utmost with a decrease of the tensile strength. X-ray diffraction (XRD) showed that the typical B-style crystallinity in the native potato starch has been destructed. On the other hand, water resistance of EPTPS was better than glycerol plasticized potato starch (GPTPS). It decreased from 50.2% for the glycerol plasticized potato starch down to 35.3% for the ethylenebisformamide plasticized sample at RH 100%. EPTPSs proved to be having good thermal stability by thermogravimetric analysis (TGA). Tg (detected by differential scanning calorimetry (DSC)) of EPTPS was higher than that GPTPS.