酶促麦草纤维素微纤丝制备、结构及性能的研究

发布时间：2018-03-23 07:53

本文选题：漂白麦草纤维　切入点：纤维素微纤丝　出处：《陕西科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：纤维素微纤丝(cellulose microfibril,简称CMF)作为一种可再生、性能优良的新型纳米生物质材料,具有广泛的应用价值和市场前景。然而,在CMF的制备过程中需要消耗大量的机械能量对纤维细胞壁结构进行解离,并且机械解离作用也会对CMF产品的结构和性能产生极大的影响。因此,本课题以漂白麦草纤维为原料,采用酶预处理结合高压均质法制备CMF。通过研究三种不同种类纤维素酶(复合纤维素酶、内切葡聚糖酶和外切葡聚糖酶)对纤维细胞壁表面形貌和孔隙结构的影响,以阐明酶预处理作用机理;在此基础上,探讨不同酶预处理对高压均质的作用效果以及处理条件对CMF结构和性能的影响;将上述CMF用于薄膜制备,并进一步研究CMF薄膜相关性能,以期实现CMF高效制备及产品应用开发。研究不同纤维素酶对纤维细胞壁表面形貌和孔隙结构的影响。结果表明:经三种纤维素酶处理后,纤维表面变得粗糙,细胞壁外层逐渐脱落,出现横向沟槽和纵向裂隙,甚至切断,其原因是由于酶分子从细胞壁外层逐渐作用于内层,细胞壁结构遭到破坏。同时,当酶用量较小时,含有较多孔隙的细小纤维组分会优先被酶水解,使三种酶水解后纤维总孔容和平均孔径均减小;随着三种纤维素酶用量的增加,酶水解向纤维细胞壁内部的进一步深入作用,产生新孔隙和破坏孔隙这两方面的共同作用使纤维平均孔径等参数有所变化,但整体上表现出增大的趋势。将经上述三种纤维素酶水解后的纤维样品(纤维得率均为75%)再经高压均质处理30次制备出CMF。结果表明:CMF仍具有天然纤维素的基本化学结构和结晶结构;与纤维原料相比,CMF悬浮液具有良好的分散稳定性,其热稳定性有一定程度的提高;与未经酶预处理所制备的CMF相比,经酶预处理所制备的CMF平均直径由64.2nm显著下降到28.5nm附近,长度达几微米到十个微米间,长径比明显增加,经酶预处理制备的CMF结晶度增加约18%,平均聚合度降低约48%,阳离子需求量增加约22%,保水值增加约37%;与其他两种酶相比,由于复合纤维素酶预处理后纤维具有更大的平均孔径等参数,经高压均质更容易解离,所制备的CMF具有更高的结晶度和聚合度等,且成本相对低。因此,酶预处理可以显著改善后续均质处理效果,且复合纤维素酶的作用效果较好。采用复合纤维素酶对纤维进行预处理,考察均质次数对CMF结构和性能的影响。结果表明:随着均质次数的增加,解离出来的微纤丝变得更细更均匀,平均聚合度逐渐减小,阳离子需求量逐渐增加,悬浮液的稳定性逐渐提高,而结晶度表现出先增加后逐渐减小的趋势;当均质次数超过20次后,CMF直径和平均聚合度下降趋势变缓,而阳离子需求量增大趋势也变缓,再增加均质次数并不能达到显著改善CMF性能的效果,反而增加机械能耗。对于不同的酶用量预处理,增加均质次数会发生相似的变化趋势。因此,酶预处理后再均质20次能够达到很好的作用效果。将上述不同CMF制备出一系列CMF薄膜,考察酶预处理及均质处理对CMF薄膜力学性能和光学性能的影响。结果表明:随着酶用量或均质次数的增加,CMF薄膜的拉伸强度和断裂伸长率表现出先增加后减小的趋势,透光率表现出持续增加的趋势。在酶用量为15 FPU/g,均质次数为20次时,CMF薄膜(厚度54μm)的拉伸强度和断裂伸长率达到最大值30.65MPa和1.61%,且透光率可达到约70%。
[Abstract]:The cellulose microfibrils (cellulose microfibril, referred to as CMF) as a kind of renewable, the excellent performance of the new nano biological material, has wide application value and market prospect. However, during the preparation of CMF need to consume a large amount of energy to mechanical dissociation of fiber cell wall structure, and mechanical dissociation will produce great the influence on the structure and properties of the CMF products. Therefore, the bleaching of wheat straw fiber as raw material, using the enzyme pretreatment combined with high pressure homogenization preparation of CMF. through the research of three kinds of cellulase (complex cellulase, endoglucanase and exoglucanase) effect on fiber cell wall surface morphology and pore structure, to clarify enzyme pretreatment mechanism; on this basis, to explore the influence of different enzyme pretreatment effect of high pressure homogenization and processing conditions on the structure and performance of CMF; The CMF is used for film preparation, and further study the related properties of CMF thin films, preparation and application of product development in order to achieve efficient CMF system. To study the effect of different cellulase on the fiber cell wall surface morphology and pore structure. The results show that the three kinds of cellulase treatment, the fiber surface roughness and the outer wall is gradually falling off there, the lateral grooves and longitudinal cracks, even cut off, the reason is because the enzyme molecules from the outer wall to the inner wall of the cell gradually, the destruction of the structure. At the same time, when the enzyme dosage is small, fine fibers containing more pore components is preferentially hydrolyzed to three kinds of fiber volume after enzyme hydrolysis and total pore the average pore size decreases with the increase of three; the amount of cellulase, the further effect of enzyme hydrolysis to fiber cell wall inside the common new pore and pore damage of these two aspects of the The average fiber diameter and other parameters change, but overall showed a tendency to increase. By the above three after hydrolysis of cellulose fiber samples (fiber yield were 75%) by high pressure homogenization treatment 30 times to prepare CMF. results show that the basic chemical structure and crystal structure of CMF still has natural cellulose; comparison with fiber materials, CMF suspension has good dispersion stability, to a certain extent improve its thermal stability; compared with untreated enzyme pretreatment prepared by enzyme pretreatment of CMF, the average diameter of the CMF prepared by 64.2nm was significantly decreased to near 28.5nm, the length of several microns to ten microns. The ratio of length to diameter increased significantly after enzyme pretreatment of CMF crystallization preparation degree increased by about 18%, the average degree of polymerization decreased by about 48%, the cationic demand increased by about 22%, the water retention value increased by about 37%; compared with the other two enzymes, because of complex cellulase pretreatment After the fiber has larger average pore size and other parameters by high-pressure homogenization to dissociate more easily, the prepared CMF has higher crystallinity and degree of polymerization, and the cost is relatively low. Therefore, enzyme pretreatment can significantly improve the subsequent homogenization effect, and the effect of compound cellulase cellulase were used for better. The pretreatment of fiber, the effects of homogenization times on the structure and performance of CMF. The results showed that with the increase of the number of homogeneous, microfibril dissociation became finer and more uniform, the average degree of polymerization decreases, the cationic demand gradually increased, the stability of suspensions increased gradually, while the crystallinity showed first increased gradually after decreased; when the homogeneous number more than 20 times, CMF diameter and average degree of polymerization decreased slowly, while the cationic demand increases trend is slow, and then increase the number of homogeneous and can not achieve significant To improve the performance of CMF, but increased the mechanical energy. For the different dosage of enzyme pretreatment, increased the number of homogeneous change trend similar. Therefore, enzyme pretreatment can reach 20 after homogenizing effect is very good. The different CMF prepared a series of CMF thin film, the effects of enzyme pretreatment and homogenization treatment on the mechanical and optical properties of CMF films. The results showed that with the increase of the amount of enzyme or the number of homogeneous CMF films, tensile strength and elongation showed first increased and then decreased, the transmittance showed increasing trend. The enzyme dosage was 15 FPU/g, the number of homogeneous 20, CMF thin films (thickness 54 m) tensile strength and elongation at maximum 30.65MPa and 1.61%, and the transmission rate can reach about 70%.

【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ352.79

【参考文献】