高取代度淀粉苯甲酸酯的水相法制备及其性质

Preparation and Properties of Highly Substituted Starch Benzoate

以玉米淀粉为原料,苯甲酰氯(BC)为酯化剂,在水相中制备了淀粉苯甲酸酯(SB),并对其理化性质进行了系统研究.实验结果表明,最佳的反应条件为:BC与AGU摩尔比为3. 0,NaOH与BC摩尔比为1. 95,反应时间1 h,反应温度24℃,此时,取代度(DS)可达到0. 66. FTIR分析表明淀粉分子上成功接入了苯甲酰基团,羟基峰随取代度增大不断减弱; SEM测试显示淀粉苯甲酸酯基本保留原有的颗粒型态,颗粒表面形貌遭到了一定程度的破坏; XRD测试表明淀粉苯甲酸酯的结晶结构被破坏,微晶区已经完全消失,亚微晶区相对完整;接触角的变化表明淀粉苯甲酸酯与原淀粉相比具有更强的疏水性;同时淀粉苯甲酸酯具有优良的乳化性能且当取代度为0. 30时性能最佳;热重分析表明淀粉苯甲酸酯的持水力比原淀粉弱,耐温性较差.

Starch benzoate(SB)was prepared from native corn starch in aqueous phase and characterized by FTIR,SEM,X-ray diffraction,contact angle measurement and emulsifying ability measurement.The optimal conditions are as follows:the molar ratio of benzoyl chloride to native starch is 3.0,the molar ratio of sodium hydroxide to benzoyl chloride is 1.95,reaction temperature,24℃,and reaction time,1h.According to FTIR,the benzoyl group has grafted onto native starch chain unit while hydroxyl groups gradually disappeared with the increase of DS.SEM showed morphology of granules was retained but became rough and cracked after the modification.X-ray diffraction pattern indicated that crystalline regions of SB were damaged while sub crystalline regions remained relatively complete.The results of contact angle measurement and emulsifying ability measurement proved that SB possesses much better hydrophobicity and emulsifiability than native starch.The TG curves suggest that SB has poorer ability to retain water and to stand temperature in comparison with native starch.