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Keywords:

  • Retrogradation;
  • TPS;
  • Ethylenebisformamide;
  • Sorbitol

Abstract

Several thermoplastic starches (TPSs), i.e. ethylenebisformamide, sorbitol and ethylene-sorbitol plasticized (EPTPS, SPTPS and ESPTPS) were prepared and their retrogradation was investigated by X-ray diffraction, Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). These studies revealed that the mixture of ethylenebisformamide (E) and sorbitol (S) was a good plasticizer for corn starch, restraining the retrogradation of the TPSs. The mechanical properties were also investigated of the TPSs after conditioning for 150 days at ambient atmosphere. It indicated that TPS produced by mixed plasticizer possessed better mechanical properties than TPS produced using a single plasticizer (ethylenebisformamide or sorbitol). From the analysis of X-ray, FT-IR and SEM data it was hypothesized that some interaction between ethylenebisformamide and sorbitol occurred, which could prevent the plasticizer form separating out of the TPS matrix. As a result, the retrogradation of ESPTPS was limited, resulting in better mechanical properties compared with those of EPTPS and SPTPS.