秸秆微晶纤维素用作片剂崩解剂的初步评价

对实验室自制秸秆微晶纤维素用作片剂崩解剂进行了初步评价。参照《中国药典》(2010版)中微晶纤维素的有关规定,评估自制秸秆微晶纤维素的质量;以阿司匹林为模型药物,以市售微晶纤维素(PH-101)为对照,测定秸秆微晶纤维素的溶胀性、崩解性。结果表明,自制的秸秆微晶纤维素质量符合《中国药典》有关规定,且溶胀性和崩解性优于市售微晶纤维素(PH-101),可用作片剂崩解剂。在秸秆微晶纤维素含量为20%时,崩解速度最快。     

微晶纤维素对聚乙烯醇薄膜性能的影响

用稻秆制得的微晶纤维素对聚乙烯醇薄膜进行改性。考察了微晶纤维素添加量对微晶纤维素/聚乙烯醇复合膜性能的影响。结果表明,随着微晶纤维素含量的增加,复合膜的拉伸强度和断裂伸长率呈现先增加后降低的趋势,当微晶纤维素质量分数为5%时,这两种力学性能达到最好。同时微晶纤维素的加入,也可以明显提高聚乙烯醇薄膜的热稳定性。     

乙醇再生微晶纤维素的分级及其结构表征

在微晶纤维素（MCC）的Na OH/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。通过黏度法测定了再生微晶纤维素的聚合度，采用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，3次分级后微晶纤维素的聚合度由MCC的203降至77；微晶纤维素形貌由表面光滑的棒状纤维结构变为粗糙多孔的结构；再生微晶纤维素的晶型由MCC的Ⅰ型转变为Ⅱ型，3次分级后微晶纤维素的结晶度由MCC的65.58%降至32.05%。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；再生微晶纤维素的热稳定性随着分级次数的增加而降低，3次分级后初始分解温度由MCC的310℃降至257℃。     

微晶纤维素的制取

微晶纤维素用途广泛,一般用做电焊条的辅料,粘合剂及试剂等。制取微晶纤维素的方法因原料不同而异,利用针织物的下脚料、稻草、木屑、竹粉等制取微晶纤维素,不但来源方便而且产品价格低廉。用针织物下脚料制取微晶纤维素每吨0.3～0.35万元,用木屑制取的微晶纤维素每吨仅300元,而且总纤维素含量差20%左右。 用旧棉花、稻草粉、木屑、竹粉等原料制取微晶纤维素的方法如下:     

离子液体对稻草和微晶纤维素溶解性能的研究

研究了离子液体对稻草和微晶纤维素的溶解情况。升高温度、延长时间都可以使离子液体对纤维素的溶解能力提高,但应控制适宜的温度和时间,以免纤维素发生炭化。将稻草溶解再生产物的红外谱图与微晶纤维素的红外谱图比较,结果表明,稻草在离子液体中的溶解产物主要是纤维素：将从离子液体中析出的再生微晶纤维素进行红外光谱分析,结果表明微晶纤维素溶解前后的FT—IR谱图是相同的,说明离子液体是微晶纤维素的直接溶剂。     

离子液体对稻草和微品纤维素溶解性能的研究

研究了离子液体对稻草和微晶纤维素的溶解情况.升高温度、延长时间都可以使离子液体对纤维素的溶解能力提高,但应控制适宜的温度和时间,以免纤维素发生炭化.将稻草溶解再生产物的红外谱图与微晶纤维素的红外谱图比较,结果表明,稻草在离子液体中的溶解产物主要是纤维素;将从离子液体中析出的再生微晶纤维素进行红外光谱分析,结果表明微晶纤维素溶解前后的FT-IR谱图是相同的,说明离子液体是微晶纤维素的直接溶剂.     

微晶纤维素增强热塑性淀粉塑料薄膜的研究进展

纤维素和淀粉均为自然界中储量较丰富的天然高分子聚合物,微晶纤维素可作为增强相添加到热塑性淀粉基材制备塑料薄膜,因其具有良好的生物相容性、可生物降解特性而广泛应用在包装材料领域。文章简述了热塑性淀粉和微晶纤维素的特点,以及热塑性淀粉/微晶纤维素的制备机理。分析热塑性淀粉/微晶纤维素颗粒中常见两种增塑剂,对比热塑性淀粉/微晶纤维素塑料薄膜的四种制备工艺的特点,归纳不同类型热塑性淀粉/微晶纤维素塑料薄膜的研究进展,为研发绿色包装材料提供参考。     

微晶纤维素的性质与应用

微晶纤维素是一种新兴的纤维素功能材料。微晶纤维素的独特性质使它在医药、食品、日用化学品等领域获得广泛的应用。本文从应用角度阐述了微晶纤维素的理化性质和形态结构，介绍了微晶纤维素的工业产品的主要应用途径。     

纳米微晶纤维素热稳定性的研究进展

纳米微晶纤维素来自天然高分子聚合物,具有成本低、强度高、轻便等特点,并可循环利用或者生物降解。纳米微晶纤维素研究倍受关注,但纳米微晶纤维素存在一些实用方面的困难。制备过程复杂、热稳定性差等是限制纳米微晶纤维素大规模商业化应用的主要的因素。本文综述了纳米微晶纤维素的热降解机理及其热稳定性影响因素,探讨了提高其热稳定性的途径。     

甘蔗渣微晶纤维素特性及其对可得然胶溶液流变特性的影响

为丰富甘蔗渣的综合利用,提高综合产业价值,采用酸解法制备甘蔗渣微晶纤维素,分析甘蔗渣微晶纤维素理化性质及结构,构建甘蔗渣微晶纤维素/可得然胶混合液体系,研究甘蔗渣微晶纤维素对可得然胶溶液流变特性的影响。结果表明,甘蔗渣微晶纤维素聚合度为143,持水力7.55,直径约为10μm,熔融温度为169.5℃,FTIR、XRD分析表明其保留了纤维素基本化学结构。甘蔗渣微晶纤维素能增强可得然胶溶液,在扫描范围内,G′>G″,其流变表现为典型的弱凝胶特性,表明甘蔗渣微晶纤维素在可得然胶溶液中分散性良好,有助于增强溶液体系网络结构,溶液稳定性良好。     

Electrospinning of ultrafine cellulose fibers and fabrication of poly(butylene succinate) biocomposites reinforced by them

In this study, electrospinning conditions for ultrafine cellulose fibers was systematically studied and poly(butylene succinate) biocomposites reinforced by the ultrafine cellulose fibers (cellulose/PBS biocomposite) were fabricated. The ultrafine cellulose fibers were electrospun from cellulose (DP = 700) solutions in N‐methylmorpholine‐N‐oxide hydrate (85/15 w/w) at 100°C. The optimal electrospinning concentration of the cellulose solutions was determined to be 7 wt % and the average diameter of the resulting cellulose fibers was 560 nm. The cellulose I structure of the native cellulose was converted to the cellulose II structure after electrospinning. The ultrafine cellulose fibers showed a reinforcing effect in the cellulose/PBS biocomposite, suggesting that they have potential applications as reinforcement fibers for biocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystalline Structure of Microbial Cellulose Compared with Native and Regenerated Cellulose

Microbial cellulose is a chemically pure form of plant cellulose with an ultrafine reticulated structure. In this study, microbial cellulose was biosynthesized in a static condition by acetobacter xylinium (Gluconacetobacter xylinus) of three different mono- and disaccharides, and its crystallinity structure was investigated and compared with each other and also with the crystalline structure of cellulose existing in cotton and ordinary viscose rayon fibers. According to the results, the cellulose production efficiency of monosaccharide (glucose) was higher than that of disaccharides (lactose and sucrose). The crystalline structures of all biosynthesized cellulose were cell I and their dominant allomorphs were I(alpha), contrary to native cellulose, which was I(beta). The crystallinity amount of microbial cellulose was less than 10-15% of cotton and greater than 9% of viscose.     

Behavior of cellulose grafted with poly(methyl methacrylate) and polyacrylonitrile toward some direct and reactive dyes

Viscose rayon fibers modified with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were dyed with some direct and reactive dyes. Exhaustion rate of the dye onto fibers was governed by the amount and nature of the polymer grafted. In general, the dye affinity for cellulose and dye exhaustion onto fibers decreased as the graft yield increased. Dye affinity for the PAN–cellulose graft copolymers was greater than that found with PMMA–cellulose graft copolymers. Except in a few cases, the tendency of cellulose graft copolymers of ca. 13% graft to accept direct dyes was more than that of the untreated cellulose, whereas the affinity of reactive dyes for cellulose graft copolymers of up to ca. 43% polymer was more than that of untreated cellulose. The dye fixation, based on the weight of cellulose component, increased as the graft yield increased. The dyeability of cellulose oxidized with ceric ammonium nitrate was also examined. Oxidation of cellulose prior to dyeing reduced the affinity of the dye for cellulose.     

聚丙烯腈/棉纤维素薄膜的制备与性能研究

以N,N二甲基乙酰胺/无水氯化锂（DMAc/LiCl）为溶剂配置聚丙烯腈（PAN）和棉纤维素溶液,采用旋涂法制备不同比例的PAN/棉纤维素薄膜。通过旋转黏度计对PAN/棉纤维素共混溶液的表观黏度进行研究,采用X射线衍射仪、傅里叶红外光谱仪、电子万能试验机以及吸水性能测试对PAN/棉纤维素薄膜的结构和性能进行了研究。结果表明,共混溶液的表观黏度随着纤维素含量的增加逐渐增大;DMAc/LiCl溶剂对PAN和棉纤维素的溶解为直接溶解,没有发生衍生化反应;PAN和棉纤维素均保持各自结晶结构不变;当棉纤维素含量为2.0 %（质量分数,下同）时,复合薄膜的拉伸强度和断裂伸长率达到最大值;棉纤维素含量越高,复合薄膜的吸水性越好。     

Extraction and structural characterization of cellulose from milkweed floss

The aim of this study was to investigate the utilization of milkweed fruit floss residues as a source for the isolation of cellulose. Cellulose was extracted by acidified sodium chlorite and sodium hydroxide treatments. Characterization of the pristine milkweed floss and extracted cellulose was performed by chemical composition analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The extracted cellulose had mainly α-cellulose as the other components hemicellulose and lignin were significantly removed during cellulose extraction process. The FTIR spectra also indicated that the chemical treatments extensively removed hemicellulose and lignin from the pristine milkweed floss. SEM technique was used to investigate the surface morphology of the pristine milkweed floss and extracted cellulose. The intensity of the crystalline peak in the X-ray diffractograms of the extracted cellulose was higher than that of pristine milkweed. Further, the XRD results indicated a structural transformation of cellulose I (pristine milkweed) to cellulose II (extracted cellulose) because of the chemical treatments. The extracted cellulose, which is a high biomass, had better thermal stability than the pristine milkweed floss owing to removal of non-cellulosic components.     

The preparation and characteristics of low-density polyethylene composites containing cellulose treated with cellulase

Low-density polyethylene (LDPE) composites containing untreated cellulose, cellulose treated with cellulase, and cellulose treated with cellulase after pretreating with NaOH were prepared. The purpose of the cellulase treatment of cellulose is to enhance the interfacial adhesion between the cellulose and the matrix. The effect of this treatment was studied by viscometry and X-ray diffraction. Maleic anhydrideg-polythylene (MAH-PE) was also added to the composite to enhance interfacial interactions between the cellulose and the matrix and to increase the dispersibility and the wettability of cellulose. The increased adhesion in composites containing the treated cellulose and MAH-PE was studied by FTIR. In addition, the thermal, dynamic mechanical, and tensile properties of the composites were investigated. When MAH-PE was added to the composite, it was found that the reaction between MAH-PE and treated cellulose occurred more easily.     

DSC study on regioselectively substituted cellulose heteroesters

Six kinds of regioselectively substituted cellulose heteroesters (cellulose propanoate diacetate, cellulose butanoate diacetate, cellulose acetate dipropanoate, cellulose butanoate dipropanoate, cellulose acetate dibutanoate, and cellulose propanoate dibutanoate) and three kinds of cellulose triesters (cellulose triacetate, cellulose tripropanoate, and cellulose tributanoate) were prepared from a microcrystalline cellulose, and their melting points were measured by differential scanning calorimetry. Based on the results of strong correlationship between the melting point and the length of the acyl groups at the secondary hydroxyl groups at C2 and C3 positions, the latter was identified as playing a decisive role in the thermal properties of the cellulose fatty acid heteroesters. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1511–1515, 1997     

Flow birefringence and viscosity of cellulose solutions in semi-dilute regime

An attempt was made to study the flow birefringence and the viscosity of the systems of cellulose in aqueous sodium hydroxide and cadoxen solutions. For this purpose alkali-soluble cellulose samples with crystal form I (simply denoted as cellulose I sample), prepared from conifer wood pulp by the steam-explosion method, and alkali-soluble cellulose samples with crystal form of cellulose II (cellulose II sample), regenerated from cuprammonium cellulose solution under specific conditions, were used. The extinction angle χ of aqueous alkali solutions of the cellulose I sample is significantly less shear rate (γ) dependent as compared with that of the cellulose II sample. In the latter system the χ versus γ relations for a given cellulose sample shifted to the higher γ side with decrease in the average molecular weight. The viscosity of the cellulose II sample in aqueous sodium hydroxide solutions is approximately twice that of the cellulose I sample in the same solvent if compared at the same molecular weight, same concentration, and same temperature. The latter solution showed a non-Newtonian property at relatively smaller γ than the former solution did. Spin-lattice relaxation time T₁ (by ¹³C-NMR) of cellulose in cadoxen solution was smaller in cellulose I, suggesting the existence of intra- and intermolecular hydrogen bondings at the C₆ position of cellulose molecules in cellulose I solution. A dynamic light scattering study on cellulose in cadoxen showed that in a 5 wt % solution of cellulose I cellulose particles are dispersed with time into smaller particles and the larger particles could be excluded by ultracentrifuge and in cellulose II solutions the cellulose particles had almost the same size during storage. The above findings indicate that in 5 wt% cellulose I solutions in aqueous alkali or in cadoxen, cellulose I is not dissolved molecularly, but a supra-molecular structure of the solid is at least partly reserved in the above solutions.     

纤维素在离子液体AmimCl中的均相苯甲酰化反应

酱油渣中可以提取到纤维素等生物资源,但由于纤维素不溶于水和一般溶剂,难以进行衍生化应用,因此常常遭到浪费。而离子液体对纤维素呈现出较好的溶解性,可作为纤维素衍生化的良好溶剂。本文利用提取过油脂和半纤维素的酱油渣为原料进一步提取纤维素,并对以离子液体为溶剂,无催化剂条件下纤维素的均相苯甲酰化进行了研究。重点考察了离子液体种类对均相苯甲酰化的产率和取代率的影响,反应温度、时间、苯甲酰氯与葡萄糖单元摩尔比对均相苯甲酰化的取代率的影响。研究结果发现以离子液体AminCl（1-烯丙基-3甲基咪唑氯盐）为溶剂时有最优的产率。在最优反应条件为温度80℃、时间90min、苯甲酰氯与葡萄糖单元摩尔比4：1时,可得到最高取代率0.72。     

Preparation,structure, and properties of montmorillonite/cellulose II/natural rubber nanocomposites

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co‐coagulating NR latex, montmorillonite aqueous suspension and cellulose xanthate. The clay was previously exfoliated in water, and the resulting suspension was then added to the mixture of NR latex with cellulose xanthate. Morphological, rheometric, mechanical, and dynamic mechanical properties were evaluated, and an increase in these properties was observed upon the addition of cellulose and clay nanomaterials to the rubber matrix. The results show the advantage in using cellulose as a nanopolymer as well as MMT as nanofiller. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011