The effects of citric acid on the properties of glycerol-plasticized thermoplastic starch (GPTPS) were studied. In the presence of citric acid and glycerol, native cornstarch granules are transferred to a continuous phase as shown by scanning electron microscopy (SEM). As shown by thermogravimetric analysis (TGA), the improvement in thermal stability confirms that the adhesion between citric acid, glycerol, water and starch in TPS was enhanced with the addition of citric acid. It was proven by Fourier transform infrared (FTIR) spectroscopy that citric acid can form stronger hydrogen-bond interactions with starch than glycerol. Both FTIR spectroscopy and X-ray diffractometry of citric acid-modified GPTPS (CATPS) revealed that citric acid can effectively inhibit starch re-crystallization (i.e. retrogradation), because of the strong hydrogen-bond interaction between citric acid and starch. Rheology studies revealed that citric acid can obviously decrease the shear viscosity and improve the fluidity of TPS. Citric acid can also improve the elongation of GPTPS and ameliorate the water resistance of GPTPS at high relative humidities, but decreased the tensile stress.

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柠檬酸对甘油增塑热塑性淀粉性能的影响

研究了柠檬酸对甘油增塑热塑性淀粉（GPTPS）性能的影响。如扫描电子显微镜 (SEM) 所示，在柠檬酸和甘油存在的情况下，天然玉米淀粉颗粒被转移到连续相中。如热重分析 (TGA) 所示，热稳定性的改善证实了柠檬酸、甘油、水和淀粉在 TPS 中的附着力随着柠檬酸的添加而增强。傅里叶变换红外（FTIR）光谱证明柠檬酸与淀粉的氢键相互作用比甘油强。柠檬酸改性 GPTPS (CATPS) 的 FTIR 光谱和 X 射线衍射表明，柠檬酸可以有效抑制淀粉重结晶（即回生），因为柠檬酸和淀粉之间有很强的氢键相互作用。流变学研究表明，柠檬酸能明显降低TPS的剪切粘度，提高流动性。柠檬酸还可以提高GPTPS的伸长率，改善GPTPS在高相对湿度下的耐水性，但降低了拉伸应力。