一锅法合成氨基化纳米纤维素及其性能表征

为实现纳米纤维素衍生物的绿色高效制备,以过硫酸铵为氧化剂,基于机械力化学作用,在微波-水热条件下氧化降解竹浆粕得到羧基化纳米纤维素(CNC),然后与二乙烯三胺发生缩合反应,实现水相中氨基化纳米纤维素(ACNC)的一锅法合成,并对其性能进行研究。结果表明:ACNC呈棒状,直径为10~40 nm,长度为50~300 nm, 氨基的接枝率为6.29%;ACNC的晶型并未发生改变,仍为纤维素Ⅰ型,结晶度由竹浆粕的59%增加到79%;ACNC的热稳定性较竹浆粕并未显著下降,但较CNC显著提高,说明CNC表面接枝氨基后热稳定性能得到改善;该制备方法绿色高效,得到的纤维素衍生物有望在生物固化和物理性能增强方面发挥作用。     

纤维素的研究进展

纤维素是自然界最丰富的有机高分子,具有可再生、绿色和生物相容性,不仅在制浆造纸产品中得到大宗应用,也是化学化工的重要基础原材料。本文主要对纤维素的溶解、化学改性、纳米纤维素制备和纤维素/纳米纤维素新材料等方面的研究进展进行了综述。     

Industrialization Progress of Nanocellulose in China

Nanocellulose, a kind of cellulose with nanometer sizes, has drawn great interest in the pulp and paper industry due to its unique structure and excellent performance. It can be divided into five categories: nanocrystalline cellulose (NCC), nanofibrillated cellulose (NFC), bacterial cellulose (BC), electrospun cellulose nanofibers (ESC), and precipitation regenerated cellulose nanofibers (PRC). In this paper, we reviewed the industrialization progress of nanocellulose in China. Furthermore, we proposed that efficient and environmentally friendly preparation methods and high value utilization would be the focus of nanocellulose development.     

Simultaneous Extraction of Carboxylated Cellulose Nanocrystals and Nanofibrils via Citric Acid Hydrolysis—Sustainable Route

In this study, cellulose nanocrystals (CNC) with surface carboxylic groups were prepared from bleached softwood pulp by hydrolysis with concentrated citric acid at concentrations of 60 wt%~80 wt%. The solid residues from acid hydrolysis were collected for producing cellulose nanofibrils (CNF) via post high-pressure homogenization. Citric acid could be easily recovered after hydrolysis reactions through crystallization due to its low water solubility or through precipitation as a calcium salt followed by acidification. Several important properties of CNC and CNF, such as dimension, crystallinity, surface chemistry, thermal stability, were evaluated. Results showed that the obtained CNC and CNF surfaces contained carboxylic acid groups that facilitated functionalization and dispersion in aqueous processing. The recyclability of citric acid and the carboxylated CNC/CNF give the renewable cellulose nanomaterial huge potential for a wide range of industrial applications. Furthermore, the resultant CNC and CNF were used as reinforcing agents to make sodium carboxymethyl cellulose (CMC) films. Both CNC and CNF showed reinforcing effects in CMC composite films. The tensile strength of CMC films increased by 54.3% and 85.7% with 10 wt% inclusion of CNC and CNF, respectively. This study provides detailed information on carboxylated nanocellulose prepared by critic acid hydrolysis; a sustainable approach for the preparation of CNC/CNF is of significant importance for their various uses.     

超声辅助硫酸水解法制备银杏果壳纳米纤维素及其特性表征

为充分利用银杏的工业生产副产物,以银杏果壳为原料,采用超声辅助硫酸水解法制备银杏果壳纳米纤维素（nanocrystalline cellulose isolated from ginkgo nut shell,NCC-GNS）。通过单因素实验研究了硫酸质量分数、反应温度和反应时间3个因素对NCC-GNS得率的影响,并应用正交试验进行优化,获得NCC-GNS的最佳制备条件。以常规硫酸水解法（未加超声辅助）制备的纳米纤维素（nanocrystalline cellulose,NCC）为对照,通过扫描电镜（scanning electron microscopy,SEM）、透射电镜（transmission electron microscopy,TEM）、Zeta电位和动态光散射（dynamic light scattering,DLS）、X-射线衍射（x-ray diffraction,XRD）、傅里叶变换红外光谱（fourier transform infrared spectroscopy,FT-IR）、热重（thermogravimetric analysis,TGA）等分析超声辅助处理对NCC-GNS的影响。结果表明:超声功率120 W时,制备NCC-GNS的最佳条件为硫酸质量分数48%、反应温度60 ℃、反应时间25 min,最优条件下NCC-GNS得率为37.01%;超声辅助和常规硫酸水解法制备的NCC-GNS均为长棒型,尺寸无明显差异,超声辅助制备的NCC-GNS长度和直径的分布范围相对集中,长度80～180 nm、直径3.5～5.5 nm;超声辅助制备的NCC-GNS结晶度为88%,高于常规硫酸水解的75%;两种方法制备的NCC-GNS均具有较低的Zeta电位和有良好的热稳定性。综上,超声辅助硫酸水解法制备的NCC-GNS得率较高,获得的NCC-GNS结晶度高、热稳定性好,在生物质复合材料领域表现出良好的应用前景。     

纳米纤维素晶体的性能研究

竹子溶解浆经植物粉碎机预处理,再用硫酸水解制备纳米纤维素晶体(NCC)。利用马尔文激光粒度仪、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、红外光谱(FTIR)、热重分析仪(TGA)对原料及纳米纤维素晶体的尺寸、形貌、晶体特性、结构和热性能进行表征。结果表明:NCC的Z均粒径为128.7nm;竹浆经机械粉碎部分纤维长链被切断;由TEM图观察可知NCC为棒状,直径5~10nm,长度100~200nm;竹浆及NCC属于纤维素Ⅰ型,结晶度由竹浆的64.27%提高到72.04%;FTIR图谱表明竹浆与NCC化学结构基本一致;TGA分析表明NCC的热稳定性低于竹浆,但NCC的降解速率较竹浆缓慢,并且NCC的热解残余率增大。     

Nanocellulose-based fibres derived from palm oil by-products and their in vitro biocompatibility analysis

Abstract

Fibres with nanocellulose isolated from oil palm empty fruit bunches (OPEFBs) were produced. Nanocellulose and PVA-nanocellulose fibres were prepared by wet spinning in an acetone coagulation bath without drawing. The addition of nanocellulose was varied from 10% to 30%, to reveal the beneficial effects of nanocellulose content on the properties of produced spun-fibres. Higher concentration of nanocellulose increased the stiffness of spun-fibres. PVA and PVA-bacterial cellulose fibres were also produced as a control and for comparison, respectively. The nanocellulose fibre formed a compact structure, while PVA fibres had hollow structures. The effect of the produced spun-fibres on the biocompatibility of calf pulmonary artery endothelial cells was assayed by an MTT test. Based on the MTT assay the addition of nanocellulose increased the percentage of cell viability of the obtained spun-fibres slightly. These results point towards the use of sustainable sources of nanocellulose as a beneficial and biocompatible fibre material.     

硅烷偶联剂改性纳米纤维素气凝胶的制备及其表征

为研究硅烷偶联剂含量对纳米纤维素气凝胶性能的影响,选用氨丙基三乙氧基硅烷(KH-550)和甲基三甲氧基硅烷(MTMS)2种硅烷偶联剂对纳米纤维素(CNF)气凝胶进行修饰。通过扫描电子显微镜、热重分析仪、万能强力机和热常数分析仪进行测试与表征。结果表明:硅烷偶联剂的添加使改性气凝胶红外光谱图上出现了含硅峰值,但并未改变气凝胶的组分;改性后气凝胶的孔洞明显增多;MTMS与CNF的质量比为1∶2时,改性气凝胶的压缩回弹性最好(7.25 kPa);MTMS的添加使改性气凝胶具有良好的疏水性,接触角为156°;随着KH-550的添加,气凝胶导热系数先降低后升高;随着MTMS的添加,气凝胶导热系数逐渐降低。     

纳米零价铁-微纤化纤维素复合材料的制备及在造纸废水深度处理中的应用

以微纤化纤维素作为天然高分子载体,通过原位液相化学还原反应负载零价铁制备得到了纳米零价铁-微纤化纤维素(NZVI-MFC)复合材料。通过红外光谱(FT-IR)、透射电镜(TEM)、X射线衍射(XRD)和热重分析仪(TGA)来表征NZVI-MFC复合材料并研究其耐热性能,同时,将NZVI-MFC复合材料应用于造纸废水深度处理,探讨了NZVI-MFC复合材料添加量和废水初始pH值对废水处理效果的影响。结果表明,NZVI通过原位化学反应均匀负载到MFC基材上,在废水深度处理最佳条件下,造纸废水的COD_Cr和色度总去除率分别达到78.4%和90.7%。     

利用甘蔗渣制备羟甲基纤维素的工艺研究

本文采用甘蔗渣为原料，经单一态氧漂白，在乙醇溶剂中与氢氧化钠、氯乙酸反应，制备了羟甲基纤维素。讨论了反应温度、时间及物料配比对产品性能的影响。确定了最佳反应条件。