纤维素的酸处理及醋酸酯化表面改性研究

分别用HCl和H2SO4处理从棉纤维中提取的纤维素,100℃下回流水解30～60 min得到微晶纤维素(MCC),并对其进行醋酸酯化表面改性.采用X-射线衍射(XRD)、热重分析(TG)、红外光谱(IR)技术研究酸处理对MCC的聚合度、结晶度和热稳定性的影响,探讨了改性方法对产物性能的影响.结果表明,纤维素微晶化后仍保持原来的晶型以及晶区和非晶区共存的微细结构,结晶度不能达到100%.扫描电子显微镜(SEM)测试结果表明,不同酸处理后所得产物的形态和热性能有所不同,MCC的最高适用温度不宜超过270℃.适宜的醋酸酯化改性条件为:硫酸和水体积比1∶8、温度60～70℃、改性处理3～5 h.改性后微晶纤维素的内部结晶区结构没有变化,在有机溶剂中的分散性得到良好的改善.

Study on Treating with Acid and Surface Modification by Acetic Anhydride for Cellulose

Microcrystalline cellulose (MCC) was prepared from cotton stalks bleached pulps using hydrochloric and sulfuric acid as hydrolysis agent at 100℃ for 30～60 min. The sample properties, such as degree of polymerization (DP), crystallinity index, and thermal stability were studied by means of XRD, TG and IR. In order to improve the disperisibility of MCC, the modified reaction with acetylation was introduced to modify the MCC surface. XRD results showed that the original crystalline type and biphase system still remained in the micronized cellulose, but the crystallinity could not attain to 100%. SEM and TG analysis indicated that the morphology and decomposition temperature of the products treated with hydrochloric and sulfuric acid were different due to the degree of crystallinity, the use temperature could not exceed 270℃. The appropriate condition by acetic anhydride modification was at 60～70℃ for 3～5 h with the volume ratio of sulfuric acid to water of 1∶8. After surface modification, the crystallinity of MCC remained constant. The dispersibility of the resulting products was improved in the proper solvents to form stable suspensions.