不同取代度乙酰化淀粉的制备、表征及热塑性分析

Preparation,Characterization and Thermoplastic Analysis of Acetylated Starch with Different Substitution Degree

为了使淀粉作为高分子材料更好地应用在材料行业,需要将淀粉进行改性,本研究以木薯淀粉为原料,依次对其进行预处理和无水介质的乙酰化处理,通过控制反应时间的变化,制备了不同取代度乙酰化淀粉。并且通过X射线衍射、偏光显微镜、扫描电子显微镜、接触角测量、差示扫描量热分析等表征手段探究了预处理对乙酰化淀粉颗粒理化性质的影响、高取代度淀粉与低取代度淀粉理化性质的差异。结果表明:预处理可缩短原淀粉乙酰化所需时间,高取代度乙酰化淀粉晶体衍射峰消失,偏光十字消失,形貌由圆形变为多孔状,可以在丙酮等有机溶剂中溶解,预处理淀粉乙酰化反应0.5 h其疏水接触角就可达69.006°±0.520°,淀粉熔融温度降到155℃,分解温度由280℃增加到340℃,使淀粉热稳定性增强,具有热塑性。该研究可在半小时内制备出取代度为2.5的乙酰化淀粉,可以溶解在有机溶剂中,为淀粉在材料行业的应用提供了新思路。

In order to better apply starch as a polymer material in the material industry,it is necessary to modify starch.In this study,cassava starch was used as raw material,and it was pretreated and acetylated in an anhydrous medium.By controlling the change in reaction time,acetylated starch with different degrees of substitution was prepared.And the effects of pretreatment on the physicochemical properties of acetylated starch particles,as well as the differences in physicochemical properties between high degree of substitution starch and low degree of substitution starch,were investigated through characterization methods such as X-ray diffraction,polarizing microscope,scanning electron microscope,contact angle measurement,and differential scanning calorimetry analysis.The results showed that pretreatment could shorten the time required for acetylation of raw starch.The crystal diffraction peak of high degree of substitution acetylated starch disappeared,the polarized cross disappeared,and the morphology changed from circular to porous.It could be dissolved in organic solvents such as acetone.After 0.5 hours of acetylation reaction,the hydrophobic contact angle of pretreated starch could reach 69.006°±0.520°,the starch melting temperature decreased to 155℃,and the decomposition temperature increased from 280℃to 340℃,enhanced the thermal stability of starch and possessed thermoplastic properties.This study can prepare acetylated starch with a degree of substitution of 2.5 within half an hour,which can be dissolved in organic solvents,providing new ideas for accelerating the application of starch in the material industry.