乙醇再生微晶纤维素的分级及其结构表征

Structure and properties of regenerated microcrystalline cellulose from ethanol grading

摘要:

摘要：在微晶纤维素（MCC）的NaOH/尿素溶液中加入不同质量的无水乙醇进行分级沉降，得到分级再生微晶纤维素。通过粘度法测定了再生微晶纤维素的聚合度，通过FTIR、XRD、XPS、TG和SEM对再生微晶纤维素的结构、结晶度、热稳定性和形貌等进行了表征。结果表明，随着分级次数的增加，再生微晶纤维素的聚合度逐渐降低，从203降至77；SEM结果表明，微晶纤维素形貌由表面由光滑的棒状纤维结构变为粗糙多孔的结构；FTIR和XRD结果表明，再生微晶纤维素的晶型由Ⅰ型转变为Ⅱ型，三次分级后微晶纤维素的结晶度由65.58%降至32.05%。XPS结果表明，分级再生微晶纤维素的自由羟基增加，参与成键的羟基减少；TG结果表明，再生微晶纤维素的热稳定性随着分级次数的增加而降低，三次分级后初始分解温度由310 °C降至257 °C。

Abstract:

Graded regeneration microcrystalline cellulose (MCC) were obtained by adding anhydrous ethanol with various weight in NaOH/ urea solution of MCC. The degree of polymerization of the regenerated MCC was determined by viscometer method. The structure, crystallinity, thermal stability and morphology of regenerated MCC were characterized by FTIR, XRD, XPS, TGA and SEM respectively.The results showed that the degree of polymerization of regenerated MCC decreased from 203 to 77 with the increasing grading times with ethanol. The SEM results showed that morphology of MCC changed from smooth rod fiber structure to rough and porous structure after regeneration. FTIR and XRD results indicated that the crystallization phase of regenerated MCC changed from typeⅠto type Ⅱ, and the amorphous region increased. After the third time grading by ethanol, the crystallinity of MCC decreased from 64.4% to 31.9%. XPS results showed that in regenerated MCC the binding energy and relative content of free hydroxyl group increased, resulting in the decreasing trend of crystallinity. TG results showed that the thermal stability of regenerated MCC decreased with the increasing grading times, and the initial decomposition temperature decreased from 310 °C to 257 °C after the third-time regeneration.