Comparative study of plasticizing effect of corn starch using formamide and urea

Formamide and urea were used as plasticizers for corn starch to prepare formamide plasticized-thermoplastic starch (FPTPS) and urea plasticized-thermoplastic starch (UPTPS), respectively. The properties of thermoplastic starch (TPS) were tested by scanning electron microscope (SEM), x-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and mechanical testing machine. Scanning electron microscope result shows that both formamide and urea can make corn starch plasticized form uniform continuous phase, but plasticizing effect of formamide was better than that of urea. X-ray diffraction exhibits that the crystallization peaks of FPTPS were disappeared, and a reduction minish for UPTPS, the crystallinity of FPTPS was smaller than UPTPS. The gelatinization temperature of two kinds of thermoplastic starches was basically the same, but the gelatinization enthalpy of FPTPS was much less than UPTPS. Formamide was better plasticized than urea for corn starch, which made the TGA inflection temperature and residual quantity of FPTPS was lower than UPTPS. FPTPS tensile strength was lower than UPTPS, but the elongation at break was much bigger than UPTPS.