| Much effort has recently been made to develop biodegradable materials becauseof the worldwide environment and resources problems resulted from petroleum-derived plastics. Starch, a natural renewable polysaccharide obtained from a greatvariety of crops, is one of the promising raw materials for the production ofbiodegradable plastics. Thermoplastic Starch (TPS) plasticized with glycerol, aconventional TPS, was thought to tend to retrogradation after being stored for a periodof time, and this retrogradation embrittled TPS. Several plasticizers containing amidegroups were chosen to restrain starch retrogradation and ameliorate the otherproperties of TPS. Hydrogen bond between plasticizers and starch and its effects onproperties of TPS were also studied. Its significance meant to enlarge TPS applicationand solve the problems of the environment and resource. Such as formamide, acetamide and urea, several plasticizers containing amidegroups for TPS were studied with the reference of glycerol. Thermal stability,rheology, mechanical properties, retrogradation and water absorption among theseTPSs were compared. By Scanning Electron Microscope (SEM) native cornstarchgranules were proved to transfer to a continuous phase with the destruct of allcrystallinity. By rheology tests, it was shown that formamide, acetamide and ureamade TPS less sensitive to the temperatures than glycerol during the processingtemperature range from 110℃ to 150℃. At three typical environments of RH=0,50% and 100%, formamide or urea could effectively restrain starch retrogradation,because they could form more stable hydrogen bonds with starch hydroxy group thanglycerol. Mechanical testing showed that FPTPS had a good strain but poor stress,while UPTPS had a good stress but poor strain. Comparing with water resistance ofGPTPS, FPTPS and APTPS were poor, but UPTPS was good. Formamide and urea (10%/20% weight based on starch) were used as a mixedplasticizer to prepare formamide and urea-plasticized TPS (FUPTPS) with the goodmechanical properties to overcome the facile retrogradation of GPTPS. After beingstored for one week at RH=33%, the tensile strength, elongation and energy break ofthis TPS respectively reached 4.83 MPa,104.6 % 和 2.17 N?m. Both the thermalstability and water resistance of FUPTPS was better than ones of TPS plasticized byeach single plasticizer (including glycerol). The properties of TPS composites firstly prepared with urea and formamide asthe mixed plasticizer and micro-fibrils as reinforcement were studied. SEMmicrograph showed the dispersion of micro-fibrils in TPS and good adhesion betweenstarch and micro-fibrils. When micro-fibrils were introduced into the matrix ofFUPTPS, FUPTPS could still restrain the starch retrogradation. The reinforced TPSameliorated tensile strength, Youngs Modulus, thermal stability and water resistance. The hydrogen bond interaction between starch and plasticizers in TPS was testedby FT-IR spectroscopy, which revealed that the oxygen of C-O-C group participatedin the hydrogen bond with plasticizers, and the hydrogen of C-O-H group in starchformed the hydrogen bond with plasticizers rather than the oxygen of C-O-H group.The excessive plasticizers would form hydrogen bond within each other and weakenthe interaction between plasticizers and starch. The hydrogen bonding of 1:1 complexs formed between plasticizers molecularand structural unit of starch were investigated using B3LYP method to determine thereasonable geometries, hydrogen-bonding energy and vibrational frequencies of thecomplexs. The order of hydrogen-bonding energy between plasticizer and starch wasurea-starch > formamide-starch > glycerol-starch, and the hydrogen-bonding energywere respectively 14.167 Kcal/mol,13.795 Kcal/mol and 12.939 Kcal/mol. Thehydrogen bonding of 1:1 complexs formed between plasticizers molecular andstructural unit of starch all contained two couples. One was the hydrogen bondingbetween hydrogen ato...
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