论文部分内容阅读
以魔芋葡甘聚糖(KGM)为原料,浓硫酸为催化剂,乙酸酐为改性剂,制备了KGM醋酸酯.研究了反应条件对KGM醋酸酯取代度(DS)的影响,KGM醋酸酯制备的最佳反应条件是乙醇∶水量比5∶5,反应时间2h,反应温度75℃,催化剂浓硫酸的浓度0.1mol/L,KGM与乙酸酐的量比5∶40(g/mL),取代度高达2.93,其分子量与KGM相比,则明显降低.运用傅立叶红外光谱仪(FTIR)、X射线衍射仪(XRD)、扫描电镜(SEM)、热重分析仪(TGA)、示差扫描量热仪(DSC)和旋转流变仪对KGM和高取代度KGM醋酸酯进行了表征.结果表明,KGM醋酸酯的羰基(CO)特征吸收峰较KGM明显增强,其表观形貌大部分为疏松絮状,KGM及其醋酸酯均为非晶态结构.与KGM相比,KGM醋酸酯的热稳定性下降,分解温度(Td)由KGM的261.10℃降低至KGM醋酸酯的204.56℃,KGM醋酸酯出现了明显的玻璃化转变,其玻璃化转变温度(Tg)为128.49℃.KGM醋酸酯是典型的黏弹性材料,其弹性比率占21.27%,其剪切黏度η对温度变化非常敏感,可通过温度的改变来调节KGM醋酸酯的加工流动性.KGM醋酸酯具有较好的热塑性.
The KGM acetate was prepared by using konjac glucomannan (KGM) as raw material, concentrated sulfuric acid as catalyst and acetic anhydride as modifier.The effect of reaction conditions on the degree of substitution (DS) of KGM acetate was studied, and the preparation of KGM acetate The optimal reaction conditions were ethanol: water ratio 5: 5, reaction time 2h, reaction temperature 75 ℃, concentration of catalyst concentrated sulfuric acid 0.1mol / L, molar ratio of KGM to acetic anhydride 5:40 (g / mL) Degree of 2.93, the molecular weight of KGM was significantly lower than that of KGM.Using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), differential scanning calorimeter (DSC) and rotary rheometer were used to characterize KGM and highly substituted KGM acetate.The results showed that the carbonyl (CO) characteristic absorption peak of KGM acetate was obviously enhanced compared with that of KGM, and the apparent morphology of KGM acetate was mostly loose pulp KGM and acetate were amorphous.Compared with KGM, the thermal stability of KGM acetate decreased, the decomposition temperature (Td) decreased from 261.10 ℃ of KGM to 204.56 ℃ of KGM acetate, and KGM acetate A significant glass transition occurred with a glass transition temperature (Tg) of 128.49 ° C. KGM acetate is a typical viscoelastic material with an elastic modulus Accounting for 21.27%, the shear viscosity η is very sensitive to temperature changes, the processing flow may be adjusted .KGM acetate KGM acetate has better by changing the temperature of the thermoplastic.