The plastcizers containing amide groups for thermoplastic starch

Including formamide, acetamide and urea, several plasticizers containing amide groups for thermoplastic starch (TPS) were studied with the reference of glycerol in this paper. The effects of water contents on mechanical properties of TPS showed that formamide-plasticized TPS (FPTPS) had a good flexibility at the wide scope of water contents, and the strain of UPTPS increased up to 65% at high water content (42%). Fourier Transform infrared (FT-IR) spectroscopy showed that a small percent of urea could react with starch at the given TPS processing conditions. The other plasticizers could not react with starch. The order of the hydrogen bond-forming abilities with starch was urea>formamide>acetamide>polyols, confirmed by B3LYP chemical computation. The hydrogen-bonding interaction in 1:1 complexes formed between plasticizers (urea, formamide, acetamide or glycerol) and starch were respectively 14.167, 13.795, 13.698 and 12.939 kcal/mol. Glycerol-plasticized TPS, FPTPS, acetamamide-plasticized TPS and urea-plasticized TPS were tested at three typical humidities using X-ray diffractometry. Urea and formamide could effectively restrain the retrogradation of TPS, and acetamide could not increase re-crystalline of original APTPS. The properties of TPS mainly relied on the hydrogen bond-forming abilities between plasticizers and starch molecules.