竹纤维素纳米晶须的结构与性质

利用酸水解制备竹纤维纳米晶须(CNW),借助原子力显微镜(AFM)和核磁共振,研究了酸水解不同时间对制备的竹纤维纳米晶须形貌和结构的影响。结果表明:硫酸水解15 min之前NCW的形貌呈棒状结构,超过15 min转变为较细的针状结构;在酸水解时间为20 min时长径比最大,结晶度最高,次晶含量最低,晶粒尺寸最大。通过偏光显微镜观察CNW悬乳液,其具有形成手性向列相液晶指纹状结构的性质。CNW质量分数为1%时,浓度太低晶须之间不能相互作用,当CNW质量分数达到2.5%(2.5%～7.5%),随着CNW悬乳液浓度增加,形成的手性向列相液晶的指纹间距减小。     

NaOH浓度对纳米Fe3O4/纤维素复合膜结构和性能的影响

以N-甲基吗啉-N-氧化物（NMMO）天然纤维素膜为基材,NaOH为沉淀剂,利用原位共沉淀法制备出纳米Fe₃O₄/纤维素复合膜,通过X射线衍射光谱（XRD）、傅里叶变换红外光谱（FT-IR）、扫描电镜（SEM）、热重分析（TGA）仪和振动样品磁强计（VSM）研究了NaOH浓度对复合膜结构及性能的影响。结果表明：球形纳米Fe₃O₄能均匀分散并固定在纤维素膜基体上,且随NaOH浓度的增加,Fe₃O₄晶粒尺寸逐渐增大。复合薄膜红外谱图显示纳米Fe₃O₄与纤维膜之间形成较强的界面结合力。随NaOH浓度的从1.0 mol/L增加到3.0 mol/L,复合膜的热稳定性逐渐增强,其热失重残留量由19.3%提高到23.8%。VSM研究表明Fe₃O₄/纤维素复合膜具有良好的超顺磁性,NaOH浓度的增加能够提高复合膜的磁性能。     

Thermal properties and crystallinity of PCL/PBSA/cellulose nanocrystals grafted with PCL chains

Bionanocomposite films of poly(?‐caprolactone) (PCL) and poly(butilene succinate‐co ‐adipate) (PBSA) blends with cellulose nanocrystals (CNW) grafted with PCL chains (CNW‐g ‐PCL) were prepared by solution casting and their thermal properties and crystallinity were studied. The CNW surface was modified with PCL chains by grafting “from” approaches, in an effort to improve their compatibility with the polymer blends. The grafting efficiency was evidenced by FTIR and TGA analysis. The acicular morphology of CNW‐g ‐PCL was characterized by SEM. The TGA results showed an increase in the thermal stability of the CNW grafted with PCL chains. The PCL/PBSA blends showed higher thermal stability in comparison with the neat polymers and PCL/PBSA/CNW‐g ‐PCL bionanocomposites. DSC results showed the CNW‐g ‐PCL act as a nucleating agent in the bionanocomposites. Additionally, a better interaction of the CNW‐g ‐PCL in the blends of 30/70 composition in comparison with the blends of 50/50 composition was characterized. The results obtained for aforementioned films prepared by solution casting encourage the production of such bionanocomposites by melt compounding (extrusion), aiming the achievement of new bionanocomposites materials with improved thermal and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44493.     

Characterization of cellulose nanowhiskers extracted from alfa fiber and the effect of their dispersion methods on nanocomposite properties

In this study, cellulose nanowhiskers (CNW) were prepared from alfa fiber (Stipa tenacissima) by an alkali treatment at room temperature in association with a bleaching treatment followed by a sulfuric acid hydrolysis. Fourier Transform Infrared (FT-IR) spectroscopy was used to highlight the evolution of chemical composition. Atomic Force Microscopy and Zeta-sizer indicated that the transverse size of the particles varied between 30 nm and 170 nm. Thermal stability was higher for CNW as compared to alfa fiber. FT-IR, X-ray diffraction, and Thermogravimetric analysis studies confirmed the removal of hemicelluloses and lignin during the chemical treatment process. The swelling of CNW in water with Cloisite 30B (CNW/C30B) or with the Polyethylene glycol (CNW/PEG) was carried out. The properties of Polyvinyl Chloride (PVC) nanocomposites reinforced with CNW which was dispersed with two different methods were also compared. The results showed that the morphology of both samples have drastic differences which may explain the fact that the storage modulus prepared with CNW/C30B was higher than those prepared with CNW/PEG. However, PVC/CNW/PEG nanocomposites exhibited more thermal stability. In the end, the obtained CNW may have potential applications in alternative power sources as a reinforcement phase.     

Thermal and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites

Bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was reinforced with cellulose nanowhiskers (CNW) in 1-5 wt.% concentrations using a solvent casting method. The CNW was prepared from microcrystalline cellulose (MCC) using sulfuric acid hydrolysis. The influence of CNW on the PHBV crystallization, thermal, dynamic mechanical and mechanical properties were evaluated using polarized optical microscope (POM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), tensile and bulge tests, respectively. POM test results demonstrated that CNW was an effective PHBV nucleation agent. Tensile strength, Young’s modulus and toughness of PHBV increased with the increasing concentration of CNW. DMA results showed an increased tan δ peak temperature and broadened transition peak, indicating restrained PHBV molecular mobility in the vicinity of the CNW surface. Storage modulus of the PHBV also increased with the addition of CNW, especially at the temperatures higher than the PHBV glass transition temperature. These results indicated that the CNW could substantially increase the mechanical properties of PHBV and this increase could be attributed to the strong interactions between these two phases.     

竹材剩余物纳米纤维素晶体的制备及性能表征

以竹材加工剩余物为原材料,通过硫酸酸解法成功制备了竹纳米纤维素晶体（竹CNC）,考察酸解时间对竹CNC产率、形态及稳定性的影响。透射电镜（TEM）观察表明,竹CNC为刚性棒状结构,长度为160nm左右,直径为5-15nm;Zeta电位测试结果表明,竹CNC悬浮液具有较好的储存稳定性。随着酸解时间的延长,竹CNC产率出现先上升后下降的变化,酸解时间为60min时竹CNC产率最大,为34．4％。采用Simha理论,采用乌氏黏度计测定竹CNC悬浮液的特性黏数,估算了竹CNC的长径比为20左右,所得结果与TEM观察结果基本一致。     

纤维素-聚乳酸共混改性膜材料的制备及其性能的研究

将微晶纤维素溶于离子液体中,加入不同质量的聚乳酸,配制成共混溶液并成膜。通过红外光谱对其结构进行测定,证明共混物制备成功。X-衍射、SEM及DSC测试结果表明,共混物之间具有较好的相容性,当微晶纤维素与聚乳酸的质量比为60:40时共混效果较好,较易成膜,且二者的结晶过程得到互相促进,结晶完美度及晶体尺寸提高。同时,DSC测试结果表明,不同质量比的纤维素-聚乳酸共混物具有不同的结晶度,且纤维素与聚乳酸的质量比为60:40时亦具有较好的化学及生物降解性。     

玉米秸秆衍生碳基固体酸的制备及其催化纤维素水解糖化

以玉米秸秆为原料,通过碳化-磺化法制备了碳基固体酸（CSA）,采用XRD、FTIR、XPS、SEM、阳离子交换与返滴定法等手段对其结构形貌进行表征,并考察了制备条件对固体酸表面活性基团含量与催化活性的影响。以NaOH/尿素冻融预处理后的纤维素为底物,研究了CSA催化纤维素水解糖化的效果与条件。结果表明：NaOH/尿素冻融预处理能够有效辅助固体酸催化纤维素水解,在350℃碳化2h、100℃磺化5h条件下制备的CSA催化性能最好,其酸量达3.94mmol/g,其中磺酸基、羧基、酚羟基含量分别为1.09mmol/g、1.36mmol/g、1.49mmol/g。在m(CSA)∶m(纤维素)=3∶1、水解温度200℃、水解时间为0.5h的条件下,纤维素水解还原糖得率与转化率分别为47.1%和63%。CSA循环利用3次催化活性下降不大。本研究可为废弃生物质原料制备的固体酸催化纤维素水解转化利用提供科学参考。     

Improvement of filtration performance of polyvinyl chloride/cellulose acetate blend membrane via acid hydrolysis

Based on the hydrophilicity and biodegradability of cellulose acetate (CA), polyvinyl chloride (PVC)/CA blend membrane was prepared by solution comixing and phase transformation method. Then the CA in the blend membrane was partially hydrolyzed under acidic conditions to improve the hydrophilicity of the blend membrane, so as to improve the filtration performance of the PVC/CA blend membrane. The properties of the membranes were systematically characterized by Fourier transform infrared spectroscopy, differential scanning calorimeter, and scanning electron microscopy (SEM). The porosity, water contact angle, pure water flux (PWF), protein retention rate, and mechanical properties of the membrane were measured, and the effect of hydrolysis on the filtration performance of the blend membrane was analyzed. The results showed that the hydrophilicity and porosity of the blend membrane increased, the PWF and protein rejection rate enhanced after acid catalyzed hydrolysis, while the mechanical properties of PVC membrane were maintained. This simple preparation method endows PVC/CA blend membrane with desirable filtration performance, and also helps to overcome the disadvantages of poor hydrophilicity and easy pollution of pure PVC membrane.     

The effect of acid content on the poly(furfuryl) alcohol/cellulose composites

Cellulose/poly(furfuryl alcohol) (PFA) composites were prepared via in situ polymerization process using p‐toulene sulfonic acid as a catalyst. Cellulose was extracted from cotton fibers using chemical treatments with basic media of NaOH, NaClO₂ and KOH. Acid hydrolysis at different concentrations (30, 40 and 50%) of sulphuric acid was used and the final suspended cellulose was incorporated in PFA. The treatments of the cotton fibers ensued to higher crystalline cellulose which was proportional to sulphuric acid contents. Scanning electron microscopy studies (SEM) results showed a poor interfacial interaction when 50% acid content was used for hydrolyses. The effect of fiber reinforcement on thermal and dynamic mechanical properties of the composites was investigated using thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMTA). The TGA results showed higher thermal stability of cellulose/PFA composites as compared to the neat PFA. The DMA results showed that the incorporation of the cellulose fibers imparts significant enhancement in the storage modulus of the PFA matrix. There was also the clear decrease in intensity of the tan peak of the composites compared to the neat PFA. POLYM. COMPOS., 37:2434–2441, 2016. © 2015 Society of Plastics Engineers     

Permeation behaviour in cellulose triacetate dense membrane during pervaporation separation of methanol/methyl tert-butyl ether mixture

The pervaporation separation of methanol/methyl tert-butyl ether through cellulose triacetate dense membranes has been carried out under different feed compositions, permeation temperatures and temperature cycles to investigate the permeation behaviour of the membrane during pervaporation process. The experimental data indicate that the plasticization effect has a decisive influence on pervaporation flux, permselectivity and permeation activation energy. The results show that the penetrants of different feeds are transported through the membrane by different pathways with the influence of plasticization effect at different temperatures. It has also been observed that plasticization had great effect on the membrane swelling and sorption selectivity. Furthermore, DSC results show that the membranes retain the influence of the plasticization effect after pervaporation separations are tested. © 2000 Society of Chemical Industry     

Cellulose acetate–silica fume membrane: characterization and application for separation of starch and maltose

Maltose is one of the starch derivatives. Maltose can be produced by starch hydrolysis using any kind of hydrolytic process. One of the methods to separate a mixture of both compounds is using porous membrane. In this research, a novel type of hybrid membrane was prepared from a mixture of cellulose acetate and silica fume. Silica fume is widely used in the domain of construction as cement material, whereas in this research silica fume was successfully used as membrane material. Various compositions of membrane dope solutions were prepared for obtaining the membranes used for separation of starch and maltose. Such synthesized membranes demonstrate a good performance in separation processes. The best performance is achieved when the composition of cellulose acetate in membrane dope solution is 15 % (w/w) in N,N-dimethylacetamide solvent and the mass ratio between cellulose acetate and silica fume is 4:1. For this composition, the rejection of membranes towards starch and maltose is 87 and 2 %, respectively, at working pressure of 3 bar and compaction time of 2 h. Infrared spectrum indicates no new peaks are found compared to raw materials’ spectral peaks. Thus, it can be concluded that the interaction between the cellulose acetate and silica fume is merely a physical type. From the observation of cross-sectional SEM images, we can remark that the morphology of such a membrane is porous. X-ray diffractogram indicates that the synthesized membranes are amorphous.     

磁性碳基固体磺酸催化剂的制备及其催化性能研究

以自制纳米四氧化三铁、葡萄糖、发烟硫酸为原料,采用水热合成法制得了具有磁性的碳基固体磺酸催化剂.利用SEM、FTIR、VSM和TG等手段对催化剂进行了表征,评价了催化剂用于纤维素水解的催化活性.结果表明：在最佳炭化温度160℃、最佳磺化温度70℃下制备的催化剂的表面酸量达1.43 mmol·g-1,纤维素水解中的总还原糖（TRS）产率和葡萄糖产率分别达到48.2％和27.6％;且催化剂具有强磁性,可实现与产物的快速分离.     

Feasibility of recycled newspaper as cellulose source for regenerated cellulose membrane fabrication

An environmental friendly regenerated cellulose membrane (RCM) was successfully prepared via NaOH/urea aqueous solution system by utilizing recycled newspaper (RNP) as the cellulose source. The morphological and chemical structure of resulting membrane were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) spectroscopy, and thermogravimetric analysis (TGA). Results from FTIR and XRD verified that the transparent RCM possesses cellulose II structure. SEM observation revealed that the transparent RCM consist of homogeneous dense symmetric membrane structure and composed of a skin layer with mean roughness parameter R_a, obtained from AFM analysis of 29.53 nm. Pure water flux, water content, water contact angle, porosity, and pore size of the resulting membrane were also measured. This study promotes the potential of the cellulose‐based membrane obtained from low cost cellulose source for application in filtration and separation system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42684.     

皇竹草稀硫酸预处理研究

研究了中低温稀酸预处理对皇竹草化学组成变化、纤维素酶水解得率与总糖得率的影响,并采用扫描电镜(SEM)对皇竹草纤维结构变化进行了分析.结果表明,随着硫酸浓度的增大、温度的升高和时间的延长,半纤维素含量大幅度降低,且预处理后纤维素酶水解得率也逐渐增大.较好的预处理条件为100 g皇竹草原料,在固液比1:5(g:mL)条件下,用质量分数4.0%硫酸在温度110 ℃下,经过8 h预处理后,纤维素保留率为87.48%,半纤维素水解率为93.68%,所得固体渣经纤维素酶水解72 h后得率为86.3%(纤维素酶用量40 FPIU/g,以纤维素质量计),100 g原料可得到总糖量为54.53 g.预处理后皇竹草纤维表面和细胞壁受到破坏,表面积增大,有利于纤维素酶水解作用的进行.     

Effect of additives on the properties and performance of cellulose acetate derivative membranes in the separation of isopropanol/water mixtures

In this work, various cellulose acetate (CA) membranes for pervaporation were prepared by the incorporation of different additives, i.e. polyethylene glycol-600 (PEG-600), propylene glycol (PG), and ethylene glycol (EG) to enhance the separation of isopropanol (IPA)/water mixtures. These membranes were characterized by FTIR, DSC, TGA, SEM and UTM. Each additive was responsible for its characteristic effect on the membrane morphology, mechanical strength, permeation flux and separation factor. The SEM micrograph showed that the additives were evenly dispersed in the membrane matrix with the formation of dense membranes. The UTM tests for the membrane reveled that both the Young's Modulus and tensile strength increased with the increase in additive contents. TGA studies for the CA/PEG blend membrane exhibited the highest thermal stability as compared to the CA/PG and CA/EG blends. For each of these synthesized membranes, the separation factor decreased while the permeation flux increased with the increase in additive contents, while the CA/PG membrane with 20 wt.% additive content showed highest permeation flux of 452.27 g/m²h.     

Thin-film nanofibrous composite membranes containing cellulose or chitin barrier layers fabricated by ionic liquids

The barrier layer of high-flux ultrafiltration (UF) thin-film nanofibrous composite (TFNC) membranes for purification of wastewater (e.g., bilge water) have been prepared by using cellulose, chitin, and a cellulose-chitin blend, regenerated from an ionic liquid. The structures and properties of regenerated cellulose, chitin, and a cellulose-chitin blend were analyzed with thermogravimetric analysis (TGA) and wide-angle X-ray diffraction (WAXD). The surface morphology, pore size and pore size distribution of TFNC membranes were determined by SEM images and molecular weight cut-off (MWCO) methods. An oil/water emulsion, a model of bilge water, was used as the feed solution, and the permeation flux and rejection ratio of the membranes were investigated. TFNC membranes based on the cellulose-chitin blend exhibited 10 times higher permeation flux when compared with a commercial UF membrane (PAN10, Sepro) with a similar rejection ratio after filtration over a time period of up to 100 h, implying the practical feasibility of such membranes for UF applications.     

Fabrication of regenerated cellulose nanoparticles/waterborne polyurethane nanocomposites

Regenerated cellulose nanoparticles (RCNs) are ideal materials for new biomass polymer composites industries. RCNs and composites of RCNs and water‐borne polyurethane (RCN/WPU) were prepared using a facile and environmentally friendly approach without the use of any harmful chemicals. The morphological, thermal, and mechanical properties of the RCN/WPU nanocomposite were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), rheometer, wide‐angle X‐ray diffraction, and enzymatic hydrolysis. RCNs exhibited low crystallinity upon regeneration with an NaOH‐based aqueous solution, and were identified by SEM and TEM to consist of the more thermodynamically stable cellulose form. TGA showed that the thermal stability of RCN/WPU nanocomposites was increased by the addition of RCNs. Finally, enzymatic hydrolysis using cellulase indicated that the biodegradability of RCN/WPU nanocomposites was also improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46633.     

纳米微晶纤维素增强羟丙基纤维素复合膜的力学性能和透光度的研究

采用酸碱处理竹原纤维并辅以超声分散制备纳米微晶纤维素（NCC）,采用溶液浇铸/水分挥发的成型方法制备了纳米微晶纤维素增强羟丙基纤维素（HPC）全纤维素纳米复合膜.研究了NCC/HPC复合膜的力学性能、透光度以及热稳定性.随着纳米微晶纤维素含量的增加,复合膜的拉伸强度、拉伸模量、储能模量和热稳定性逐渐增大,与纯羟丙基纤维素膜相比,当纳米微晶纤维素质量分数为60％时,纳米复合膜的拉伸强度提高了8.5倍,拉伸模量提高了3.9倍,储能模量提高了3.7倍,而NCC/HPC复合膜的透光度没有出现明显的下降.     

超声波辅助纤维素酶水解制备纳米纤维素

以人纤浆为原料,利用超声波辅助纤维素酶水解制备纳米纤维素（NCC）,在单因素试验基础上,采用正交试验优化NCC的制备条件,并通过透射电镜（TEM）、X射线衍射（XRD）、红外光谱（FT-IR）、热重（TG）和Zeta电位测定对NCC的结构和性能进行了分析与表征。研究结果表明：NCC的最佳制备条件为酶用量为人纤浆质量的7%、50℃条件下酶解反应10 h,此时纳米纤维素的得率可达62.3%。TEM表征显示制备的纳米纤维素呈短棒状,纳米纤维素之间相互交织形成网络结构;XRD分析表明纳米纤维素的晶体结构并未发生改变,仍为纤维素Ⅰ型,结晶度由人纤浆的54.2%增大到73%;FT-IR分析显示纳米纤维素仍保持天然纤维素的化学结构;热重分析表明纳米纤维素的热稳定性较纤维素原料显著提高;Zeta电位测试结果表明纳米纤维素在水介质中具有良好的分散稳定性。