科研之友
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摘要
The main disadvantages of thermoplastic starch ( TPS) are their retrogradation and unsatisfactory mechanical properties particularly under wet or dry environments. Formamide was used as an individual plasticizer to prepare thermoplastic starch ( TPS) to overcome the facile retrogradation of polyols-plasticized TPS with good mechanical properties or the poor mechanical properties of urea-plasticized TPS with good retrogradation resistance. By using scanning electron microscope (SEM) the native cornstarch granules were proved to transfer to a continuous phase with out crystallinity after plasticization with formamide. By rheology tests, it was shown that formamide made TPS less temperature sensitive than glycerol did in the processing temperature range of formamide-plasticized TPS (FPTPS) from 110degreesC to 150degreesC. Thermal analysis reveals that glycerol-plasticized TPS (GPTPS) exhibits better thermal stability and FPTPS has a slightly lower glass transition temperature. The effect of water contents on the mechanical properties of FPTPS and GPTPS was also studied, and FPTPS showed good ductility at water contents of 13% similar to 35%. The maximal failure stress and strain were 3.9 MPa and 95%, respectively. At three typical environment conditions of RH = 0,50 % and 100 % the influence of formamide and glycerol on the retrogradation of TPS was studied using X-ray diffractometry. It was found that compared to glycerol, formamide could effectively restrain the retrogradation at various humidities. The property improvement of TPS by using formamide was ascribed to the formation of more stable hydrogen bonds between plasticizer molecules and the hydroxy groups of the starch.
- 出版日期2004-4
- 单位天津大学
