Functional cellulose fibers via polycarboxylic acid/carbon nanotube composite coating

In this study, carbon nanotubes (CNTs) were stabilized on a cotton surface using 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent and sodium hypophosphite as a catalyst. The influence of CNTs on the performance of the cellulose fiber was investigated using a Raman spectrophotometer, thermogravimetric analyzer, a scanning electron microscope, electrical contacting equipment, and an electromagnetic field detector. The possible interactions between CNTs, a crosslinking agent, and cellulose functional groups at the surface were elucidated by Raman spectroscopy. The results indicate that the stabilized CNTs modify the surface of the fibers and increase the functionality and thermal stability of the substrate. SEM showed a uniform coating of CNTs on the fiber surface.     

Physical and chemical properties of polypyrrole–carbon fiber interphases formed by aqueous electrosynthesis

The properties of carbon fibers modified by aqueous electrochemical synthesis of pyrrole has been determined by using the dynamic contact angle analyzer (DCA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Electrochemical process parameters such as the initial pyrrole concentration, electrolyte concentration, applied voltage, electrolyte type, and reaction time were systematically varied, and their impact on the polypyrrole–carbon fiber interphases surface free energy and morphology was ascertained. The surface free energies of the polypyrrole–carbon fiber interphases were obtained by using single fiber filaments. SEM analysis of the interphases revealed several distinct surface structures, including smooth, porous, granular, microspheroidal, and leafoidal morphologies. The noncoated but commercially surface oxidized carbon fibers have smooth surface morphology with occasional longitudinal striations. FTIR analysis of the polypyrrole interphases confirmed that the counterions derived from the electrolytes were incorporated into the film. The surface free energies of the electrochemically formed polypyrrole–carbon fiber interphases equivalent to 60–75 dynes/cm, was determined to be up to 40% higher than that for the surface oxidized but unsized carbon fibers equivalent to 50 dynes/cm. This improvement in the surface free energies of the polypyrrole–carbon fiber interphases suggests easy wettability by polymer matrices such as epoxy resin, γ ˜ 47 dynes/cm and, polyimide matrix, γ ˜ 45 dynes/cm. © 1996 John Wiley & Sons, Inc.     

纳米结晶纤维素表面修饰聚酰亚胺纤维及其润湿功能性

聚酰亚胺纤维在应用方面存在许多潜在问题,例如聚酰亚胺纤维的低表面活性,使得其界面的润湿性能差,且在水相中易团聚,分散性较差。为此,本文提出在复合路易斯酸及交联剂共同催化作用下,使纳米结晶纤维素（CNC）修饰碱处理后的聚酰亚胺（PI）短切纤维表面,测定了CNC修饰前后PI纤维在水溶液中的分散度及PI纤维成纸的接触角,结果表明PI纤维的浸润功能性得到提高。采用扫描电子显微镜（SEM）观察了纤维的微观形貌,利用傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）表征了纤维表面结构的变化,最后通过多孔材料孔径分析仪测定了纤维成纸的孔径分布变化。结果表明：经CNC处理后的纤维表面发生了酯化反应且存在交联现象,纤维表面氧元素物质分数增加,含氧极性基团和表面粗糙度的增加有助于改善润湿性能,与PI纤维原纸相比,经CNC表面修饰后的纤维所成的纸页与去离子水的接触角降低了14.9°,与乙醇的接触角降低了4.8°,纤维分散度增加了45％,纤维亲水性显著提高,经过表面处理后的纤维在水相体系中的分散性能得到改善。因此,本法可以作为制备高性能纤维和相应复合材料的有效方法。     

细菌纤维素/热塑性聚氨酯复合气凝胶纤维制备及性能

使用绿色有机材料细菌纤维素(BC),并掺杂增强材料热塑性聚氨酯弹性体(TPU)经过湿法纺丝制备复合气凝胶纤维,通过傅里叶变换红外光谱(FTIR)、X射线衍射光谱(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、全自动比表面孔隙度分析仪和单丝强力仪对制备的气凝胶纤维进行结构分析和性能表征,结果表明复合气凝胶纤维具有多孔结构,良好的力学性能和隔热性能,断裂强度达到24.69Mpa,断裂伸长为38.54%。     

羟丙基纤维素/明胶复合膜的制备及性能表征

以环氧氯丙烷(ECH)作为羟丙基纤维素(HPC)和明胶(GEL)的交联剂,通过均相混合、交联、溶液浇铸、蒸发等工艺制备了一系列ECH交联的HPC/GEL复合膜(EHGF)。利用傅里叶红外光谱(FTIR)、X射线衍射仪(XRD)、紫外-可见分光光度计(UV-Vis)、扫描电子显微镜(SEM)、热重分析仪(TG)、接触角、力学性能等测试手段对EHGF复合膜的结构、微观形貌、热稳定性、耐水性及拉伸断裂强度进行表征和分析。结果表明:交联作用存在于HPC和GEL组分之间,各组分间具有好的相容性;与HPC/GEL共混膜相比,EHGF复合膜显示了更均匀致密的断面形貌和更高的热稳定性,且ECH的交联作用显著提高了HPC/GEL复合膜的水接触角和断裂强度。     

醋酸纤维素的制备及其可纺性研究

以实验室自制的三醋酸纤维素(CTA)为原料,研究其最佳水解条件及水解产物二醋酸纤维素(CDA)的可纺性能。结果表明:60℃下水解时间为4 h,H_2O与CTA的质量比为5∶1,催化剂H_2SO_4的质量分数为CTA的12%,可得到取代度为2.60的CDA。水解产物CDA经湿法纺丝后得到的纤维的干态断裂强度为1.45 c N/dtex,优于目前国内市售的CDA纤维。用FTIR、XRD、TG、SEM对CDA及其纤维进行分析表征,结果显示:CDA经水解和纺丝后结晶度会下降,CDA热分解温度低于CTA和纤维素;SEM照片显示CDA纤维表面有少许沟槽,断面呈圆形结构。     

Chemical modification of hemp,sisal, jute,and kapok fibers by alkalization

Plant fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of surface impurities and the large amount of hydroxyl groups make plant fibers less attractive for reinforcement of polymeric materials. Hemp, sisal, jute, and kapok fibers were subjected to alkalization by using sodium hydroxide. The thermal characteristics, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X‐ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Following alkalization the DSC showed a rapid degradation of the cellulose between 0.8 and 8% NaOH, beyond which degradation was found to be marginal. There was a marginal drop in the crystallinity index of hemp fiber while sisal, jute, and kapok fibers showed a slight increase in crystallinity at caustic soda concentration of 0.8–30%. FTIR showed that kapok fiber was found to be the most reactive followed by jute, sisal, and then hemp fiber. SEM showed a relatively smooth surface for all the untreated fibers; however, after alkalization, all the fibers showed uneven surfaces. These results show that alkalization modifies plant fibers promoting the development of fiber–resin adhesion, which then will result in increased interfacial energy and, hence, improvement in the mechanical and thermal stability of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2222–2234, 2002     

离子液体法制备再生细菌纤维素纤维

以离子液体(氯化1-甲基-3-正丁基咪唑)溶解高聚合度细菌纤维素(BC),采用湿法纺丝制备再生细菌纤维素(RBC)初生纤维;通过红外光谱分析(FTIR)、广角X射线衍射(WAXD)分析、热失重(TG)分析、扫描电镜( SEM)、单丝强度拉伸等表征了RBC初生纤维的结构和性能.结果表明:该溶剂体系通过10 h的快速搅拌溶...     

Highly conductive polymer composites based on controlled agglomeration of carbon nanotubes

This paper reports an innovative approach to enhance electrical conductivity of fiber composites based on non-conductive fiber and polymer matrix. The dispersion of carbon nanotubes (CNTs) is carried out using a fiber sizing agent which contains uniformly distributed CNTs. The infusion of the sizing agent into the fiber preform prior to resin infusion gives rise to high agglomeration of CNTs on the fiber surface and results in electrical conductivities of 2-3 orders of magnitude higher than those of specimens prepared by a calendering approach.     

超高相对分子质量聚乙烯/碳纳米管复合纤维的制备

利用冻胶纺丝的方法制备了超高相对分子质量聚乙烯／碳纳米管(UHMWPE／CNTs)复合纤维,以高锰酸钾和硫酸为氧化剂对CNTs进行纯化处理,用DNZ-201钛酸酯对纯化处理后的CNTs进行功能化处理。采用TEM、SEM和FTIR对CNTs的形态、基团变化和CNTs在UHMWPE中的分散情况进行测试。结果表明,该氧化剂对CNTs的纯化有良好的效果,可以除去大部分附在CNTs上的杂质,产生了有利于功能化的有机基团;SEM和TEM测试结果表明,功能化处理后CNTs可以较为均匀地分散在UHMWPE基体中,没有出现明显的CNTs的团聚现象,而且使UHMWPE大分子排列趋于规整。     

Synthesis and processing of PMMA carbon nanotube nanocomposite foams

Poly(methyl methacrylate) (PMMA) multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by several methods using both pristine and surface functionalized carbon nanotubes (CNTs). Fourier transform infrared (FTIR) spectroscopy was used to characterize the presence and types of functional groups in functionalized MWCNTs, while the dispersion of MWCNTs in PMMA was characterized using scanning electron microscopy (SEM). The prepared nanocomposites were foamed using carbon dioxide (CO₂) as the foaming agent. The cell morphology was observed by SEM, and the cell size and cell density were calculated via image analysis. It was found that both the synthesis methods and CNTs surface functionalization affect the MWCNTs dispersion in the polymer matrix, which in turn profoundly influences the cell nucleation mechanism and cell morphology. The MWCNTs are efficient heterogeneous nucleation agents leading to increased cell density at low particle concentrations. A mixed mode of nucleation mechanism was observed in nanocomposite foams in which polymer rich and particle rich region co-exist due to insufficient particle dispersion. This leads to a bimodal cell size distribution. Uniform dispersion of MWCNTs can be achieved via synergistic combination of improving synthesis methodology and CNTs surface functionalization. Foams from these nanocomposites exhibit single modal cell size distribution and remarkably increased cell density and reduced cell size. An increase in cell density of ∼70 times and reduction of cell size of ∼80% was observed in nanocomposite foam with 1% MWCNTs.     

聚丙烯腈/醋酸纤维素共混纤维亲水性研究

将丙烯腈/醋酸乙烯酯/潜交联剂三元共聚物与醋酸纤维素共混纺丝,经交联水解处理后得到含交联结构的亲水性聚丙烯腈/醋酸纤维素共混纤维。分析了纤维的吸水性能,并利用傅里叶红外光谱仪、扫描电镜、单纤强力仪等测试仪器测试了其它性能。     

聚乳酸/酯化纤维素复合材料的制备与表征

通过气固反应利用马来酸酐（MA）对纤维素进行酯化改性,采用熔融共混工艺制备了聚乳酸（PLA）/酯化纤维素复合材料。红外分析表明纤维素与MA发生了酯化反应。力学性能测试、热重分析、差示扫描量热仪（DSC）、扫描电镜（SEM）等分析表明,PLA/酯化纤维素复合材料的拉伸模量和弯曲模量随酯化纤维素含量的增加而升高,拉伸强度、弯曲强度和热稳定性随酯化纤维素含量的增加而降低;复合材料的Tc相对纯PLA较高,说明酯化纤维素的加入起到了异相成核作用,使结晶速率提高。酯化纤维素在复合材料中分散充分,但两者的界面黏结力较弱。     

The nature of adhesion in composites of modified cellulose fibers and polypropylene

Cellulose fibers were surface modified with polypropylene–maleic anhydride copolymer. The physical properties of such fibers were characterized by contact angle measurements, and the chemical structure was identified with ESCA and FTIR. ESCA showed that the modifying agent was localized at the surface of the fibers. The modified fibers were compounded with polypropylene, and composites with various amount of fibers were manufactured by injection molding. All mechanical properties were improved when treated fibers were used. SEM showed improved dispersion, wetting of fibers, and adhesion. The nature of adhesion was studied using FTIR. It was found that the surface modifying agent is covalently bonded to the fibers through esterification. The degree of esterification is enhanced by activating the modifying agent before fiber treatment. This study has shown the effects of treatment conditions on activation of reactive species and chemical reaction between fiber and modifying agent. Moreover, a better understanding has been achieved of the nature of adhesion for the system.     

改性竹纤维增强聚丙烯复合材料的性能研究

以聚丙烯为基体材料,不同处理工艺改性的竹纤维为增强材料,采用密炼-注塑工艺制备聚丙烯/竹纤维复合材料。通过红外光谱仪(FTIR)、扫描电子显微镜(SEM)、热重分析仪(TGA)、万能试验机等对复合材料的化学结构、表面形态、热性能、力学性能等进行表征和测试。结果表明:偶联剂与碱处理均可改变竹纤维的表面特性,改善复合材料的界面相容性,其力学性能、热性能均随处理工艺有所改善。当偶联剂KH-550含量为2%时,复合材料有较好的力学性能,其断裂伸长率为14.5%,拉伸强度为30.48 MPa,冲击强度为22.4 kJ/m2。     

玻璃纤维表面的聚甲基丙烯酸甲酯接枝

本文用臭氧对表面涂有ＭＡＣ试剂的玻璃纤维进行了处理，使玻纤表面产生活性中心，引发甲基丙烯酸甲酯在玻璃纤维表面上接枝聚合，接枝纤维的密度减小，对水的浸润性下降，红外光谱及扫描电镜观察证明玻璃纤维表面上有聚甲基丙烯酸存在。     

Conversion of plastic/cellulose waste into composites. I. Model of the interphase

This article proposes a mechanism for a significant improvement in the mechanical performance of a simulated waste fraction, composed of an immiscible low-density polyethylene (LDPE) and high-impact polystyrene (HIPS) blend (70:30 proportion), when chemithermomechanical pulp (CTMP) fibers and maleic acid anhydride grafted styrene–ethylene/butylene–styrene block copolymer (MAH-SEBS) were added. SEM micrographs of composites showed an increased contact between the continuous LDPE phase and CTMP fibers when the functionalized compatibilizer (MAH-SEBS) was used. By employing a model study using LDPE and regenerated cellulose, we investigated the interphase properties between the plastic phase and the cellulosic component. The model study utilized ESCA, FTIR, and contact angle analysis to follow the reaction between the cellulose surface and the functionalized compatibilizer. All three methods showed that MAH-SEBS was bonded to the surface of the cellulose. The single-fiber fragmentation test showed that the adhesion between cellulose fibers and the plastic matrix was significantly improved for MAH-SEBS–modified samples. The effect of enhanced adhesion on increased mechanical properties of cellulose composites is also discussed, and a prediction of composite strength given, based on interfacial adhesion promotion and fiber properties. © 1995 John Wiley & Sons, Inc.     

Electrophoretic deposition of hydroxyapatite-chitosan-CNTs nanocomposite coatings

Three component suspensions of hydroxyapatite (HA), chitosan and CNTs were prepared in ethanol base solution (15 vol% water and 0.05 vol% acetic acid). The adsorption of HA nanoparticles on CNTs was investigated by FTIR and SEM analysis. It was found that HA nanoparticles are adsorbed on CNTs via chemical bonding between -NH₂ groups of chitosan (adsorbed on their surface) and -COOH groups of CNTs. Current density as well as kinetics of EPD was studied at 60 V. It was found that current density increases or remains nearly constant during EPD due to the rise in water electrolysis as deposit grows on the substrate. Deposition weight against EPD time showed a linear trend due to the absence of any voltage drop over the deposit during EPD. The incorporation of chitosan and CNTs in the microstructure of coatings was confirmed by TG/DTA and SEM analysis. CNTs exhibited high efficiency in reinforcing the microstructure of coatings and preventing from their cracking. CNTs incorporation in the coatings improved their mechanical properties (adhesion strength, hardness and elastic modulus) and corrosion resistance.     

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.     

Growth of carbon nanotubes on carbon fibers using the combustion flame oxy-acetylene method

Multi-walled carbon nanotubes (MWCNTs) were directly grown on carbon fibers (CFs) using the combustion flame oxy-acetylene method. Ferrocene deposited on the fiber surface acts as a catalyst for carbon nanotubes (CNTs) growth. The effects of ferrocene concentration on the morphology of the CNTs coating were investigated. Growth temperature ranges from 500 to 650 °C at atmospheric pressure, while growth surface is a continuous 10 × 1000 mm² tape. CNTs are produced with a dense entanglement, covering the CFs uniformly. Tube outer diameters are in the range of 20–40 nm. Tube length is quite long (about 4–5 μm) and uniform. Particularly, growth times are very short: about 0.3–0.6 s. Growth morphology and other characteristics of the as-grown tubes were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy dispersive X-ray (EDX) and by Raman spectroscopy.