内切纤维素酶预处理对TEMPO氧化制备纳米纤维的影响

发布时间：2018-05-27 05:25

本文选题：纳米纤维 + 内切型纤维素酶　；参考：《南京林业大学》2015年硕士论文

【摘要】：纤维素是自然界最丰富的天然高分子材料,利用纤维素制备纳米纤维是当今研究的热点。纳米纤维主要利用木材、棉花、禾草类茎秆等植物,通过机械、化学、生物和人工合成等方法得到。纳米纤维因具有较高的结晶度,巨大的比表面积、高纯度、高杨氏模量、良好的生物可降解性和生物相容性等特点,在生物制药、食品加工、功能材料和造纸领域具有独特的应用价值。现有制备纳米纤维的方法中,分别存在产品得率低、设备要求高、能量消耗高、工艺复杂、制得的纳米纤维粒径和尺寸分布不合理等缺陷。因此,纳米纤维的制备方法有待继续研究。本研究利用内切型纤维素酶(EG1)预处理全漂硫酸盐针叶浆,再经过超声波协助TEMPO氧化制备纳米纤维。研究中,利用氧化还原滴定和电导滴定监测TEMPO氧化过程中残余有效氯和纤维中的羧基含量;利用纤维粒度分析仪、毛细管粘度计和透射电镜等仪器,分析制备样品的流动性能、尺寸分布以及纤维形貌,研究了EG1预处理对超声波协同TEMPO氧化制备纳米纤维的影响,研究结果表明:1.EG1预处理增加了超声波协同TEMPO催化氧化后纤维中的羧基含量。超声波协同TEMPO氧化8h后羧基含量为2.05mmol/g,EG1预处理12h、24h和48h后相同的超声波协同TEMPO氧化条件下羧基含量分别增加到2.35mmol/g、3.03mmol/g和3.13mmol/g;与对照相比,经EG1预处理再TEMPO氧化制备样品的透明度增加,纤维宽度减小,流经毛细管粘度计的时间增加。2.原料通过氢氧化钠润胀或者打浆处理后再经过EG1处理制备的纳米纤维,和未经过EG1处理的相比,羧基含量增加,透明度增加,粒径分布向细小方向移动,流经毛细管粘度计的时间增加。3.纤维原料随EG1预处理时间增加得率下降,但都保持在93%以上。EG1预处理后纤维聚合度下降,EG1处理时间18h-48h后纤维素聚合度分别由原来的1478降至986-948。4.经纤维素酶预处理24h以上的纤维原料可以通过高压均质机制备纳米纤维,制备的纳米纤维呈现短棒状。
[Abstract]:Cellulose is one of the most abundant natural polymer materials. Nanofibers are obtained by mechanical, chemical, biological and synthetic methods, mainly using wood, cotton, grass stalks and other plants. Because of its high crystallinity, large specific surface area, high purity, high Young's modulus, good biodegradability and biocompatibility, nanofibers are widely used in biopharmaceutical and food processing. Functional materials and paper making have unique application value. Among the existing methods of preparing nanofibers, there are some defects such as low yield of products, high requirement of equipment, high energy consumption, complex process, unreasonable size distribution and so on. Therefore, the preparation methods of nanofibers need to be further studied. In this study, the endo-cellulase (EG1) was used to pretreat the fully bleached Kraft needle pulp, and then the nanofibers were prepared by ultrasonic assisted TEMPO oxidation. In the study, redox titration and conductometric titration were used to monitor the residual available chlorine and carboxyl content in fiber during TEMPO oxidation, and the fluidity of the prepared samples was analyzed by means of fiber particle size analyzer, capillary viscometer and transmission electron microscope. The effects of EG1 pretreatment on the synthesis of nanofibers by ultrasonic and TEMPO oxidation were studied. The results showed that the pretreatment of EG1 increased the carboxyl content of the fibers after ultrasonic and TEMPO catalytic oxidation. The carboxyl content of the sample prepared by EG1 pretreatment and TEMPO oxidation increased to 2.35 mmol / g 3.03 mmol / g and 3.13 mmol / g respectively under the same ultrasonic and TEMPO oxidation conditions after pretreatment of 2.05 mmol / g EG1 for 12 h and 48 h after 8 h of ultrasound combined with TEMPO oxidation. Compared with the control, the transparency of the samples prepared by EG1 pretreatment and TEMPO oxidation was increased. The width of the fiber decreased and the time of flowing through the capillary viscometer increased by. 2. 2. Compared with those without EG1 treatment, the content of carboxyl group increased, the transparency increased, and the particle size distribution moved to the fine direction, compared with the nanofibers prepared by sodium-hydroxide swelling or beating treatment and then treated with EG1. Increase the time of flowing through capillary viscometer. The yield of fiber raw materials decreased with the increase of EG1 pretreatment time, but the degree of fiber polymerization decreased after pretreatment with EG1 and 18h-48h from 1478 to 986-948.4 respectively. After pretreatment with cellulase for more than 24 hours, nanofibers can be prepared by high pressure homogenizer.
【学位授予单位】：南京林业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ352;TB383.1

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