超临界CO_(2)/乙醇共溶剂处理对醋酸纤维素结构的影响

Effect of Supercritical CO_(2) and Ethanol as a Cosolvent Treatment on the Structure of Cellulose Acetate

为提供醋酸纤维素(CA)加工增塑的新思路,以超临界二氧化碳(ScCO_(2))/乙醇作为共溶剂体系,采用傅立叶红外光谱仪、X射线衍射仪、差示扫描量热仪、热失重分析仪及核磁共振谱仪测试了不同乙醇摩尔分数下CA的结构与热性能。结果表明,ScCO_(2)完善了CA的晶体结构,结晶度由未处理时的30.41%提升至41.94%。加入乙醇(摩尔分数2%,4%,6%)后,晶体结构变差,结晶度可降低至23.12%(乙醇摩尔分数6%)。CA的热稳定性随乙醇摩尔分数的升高而变差,初始分解温度(T0)和最大热失重速率处的温度(Tmax)在乙醇摩尔分数6%时降至最低。乙醇摩尔分数的升高会减小CA中1H-13C残余偶极相互作用。乙醇摩尔分数不改变CA的化学结构,但对氢键影响显著。

To provide a new idea for the plasticization of cellulose acetate(CA),supercritical carbon dioxide(ScCO_(2))and ethanol were used as a cosolvent system in the treatment of CA.Fourier infrared spectrometer, X-ray diffractometer, differential scanning calorimeter, thermogravimetric analyzer and nuclear magnetic resonance(NMR)spectrometer were used to investigate the structure and thermal properties of CA under various ethanol contents.The results show that ScCO_(2)improves the crystal structure of CA and increases the crystallinity from 30.41%to 41.94%.After adding ethanol(mole fraction 2%,4%,6%),the crystal structure becomes worse and the crystallinity is reduced to 23.12%(mole fraction 6%).The thermal stability of CA deteriorates with the increase of ethanol content, and both the initial decomposition temperature(T0)and fastest thermal decomposition temperature(Tmax)decrease to the lowest at 6%ethanol.The increase of ethanol content can weaken the residual dipole-dipole interaction of 1H-13C in CA.Ethanol contents do not change the chemical structure of CA,but have a significant effect on hydrogen bonding.