纳米炭黑填充Lyocell基碳纤维的结构与性能

采用纳米炭黑填充Lyocell纤维制备碳纤维,并对纤维的结构与性能进行了分析。结果表明:经过不同温度预氧化处理后和最终得到的碳纤维的X射线衍射图谱中都保留着纳米炭黑的特征衍射峰;填充纳米炭黑的Lyocell基碳纤维的力学性能显著提高,填充质量分数10%纳米炭黑的Lyocell基碳纤维强度和模量分别比未填充的提高45%和56%;纳米炭黑填充的Lyocell基碳纤维结构致密、表面光洁,没有明显的裂纹和缺陷。     

纳米炭黑填充的Lyocell纤维的结构与性能

研究了纳米炭黑在Lyocell纺丝溶液中的分散性,制备不同含量纳米炭黑填充的Lyocell纤维,分析了纤维的结构与性能。结果表明:纳米炭黑在Lyocell纺丝溶液中具有良好的分散性;所得的纤维仍然具有纤维素Ⅱ晶型的结构,同时还保留了纳米炭黑的特征衍射峰;填充了纳米炭黑的纤维力学性能略有降低,但热稳定性不变;SEM结果表明纳米炭黑填充的Lyocell纤维表面光滑且截面为圆形,结构更加致密。     

Lyocell fibers as the precursor of carbon fibers

In this work, Lyocell fibers, used as carbon fiber precursors, were investigated. Lyocell fibers used for the carbon precursors and the carbon fibers themselves were produced in our laboratory. The mechanical properties morphology and structure of the precursors and the obtained carbon fibers were studied and compared to those of rayon. The results show that Lyocell fibers have higher tenacity and modulus, and better thermal stability than rayon fibers. Scanning electron microscopy (SEM) experiments show that Lyocell precursors have round cross‐sections and fewer defects in the fibers, while rayon fiber has an oval cross‐section and many defects. Wide angle X‐ray diffraction (WAXD) results for the Lyocell precursors indicate that the degree of crystallinity of the Lyocell precursor is higher than that of a rayon precursor. They also show that Lyocell based carbon fibers have better mechanical properties than those that are rayon‐based. WAXD data of the obtained carbon fibers show that the crystallinity of Lyocell‐based carbon fiber is higher than that of rayon‐based carbon fiber. It is concluded that the Lyocell fibers are better precursors for carbon fibers than rayon. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1941–1947, 2003     

纳米炭黑添加剂对纤维素/NMMO纺丝原液流变行为及其纤维结构性能的影响

研究了纳米炭黑添加剂对纤维素/NMMO·H2O溶液流变行为及Lyocell纤维结构与性能的影响。研究结果表明:添加了纳米炭黑的纤维素/NMMO·H2O溶液属典型的切力变稀型流体。纳米炭黑的加入使溶液的流动活化能有所增大,并且少量纳米炭黑的加入使体系的黏度有明显的降低,但随着炭黑含量的进一步增加,溶液黏度又逐渐增大。添加了适量纳米炭黑的Lyocell纤维的结构致密,其强度和模量虽略有降低,但结晶结构和热稳定性不变,由此制得的碳纤维不仅得率可有效提高,且强度和模量大大改善。     

Properties and structure of MWNTs/cellulose composite fibers prepared by Lyocell process

Lyocell fiber is a new kind of regenerated cellulose fiber and expected to replace the Rayon fiber to be not only used in the textile field but also used in the fields of industry and aerospace after being modified. In this work, the multi‐walled carbon nanotubes (MWNTs)/Lyocell composite fibers were prepared under different draw ratios by dry‐wet spinning and their electrical properties, mechanical properties, and structure were investigated. It was found that an appropriate amount of MWNTs could be dispersed homogeneously in the Lyocell matrix and could improve the mechanical and thermal properties of composite fiber. The results of wide angle X‐ray diffraction (WAXD) showed that the MWNTs in the composite fiber almost aligned along the axis of the fibers and the orientation of MWNTs increased with the increasing draw ratio. Furthermore, it was found that more MWNTs content and lower draw ratio could improve the electrical conductance of the composite fiber. The composite fiber containing 5 wt % MWNTs has a volume conductivity of 8.8 × 10^?4 S/cm, which is five orders higher than that of pure Lyocell fiber. These results indicate that the MWNTs/Lyocell composite fiber has potential applications in the areas of precursor of carbon fiber and conductive fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

新型碳纤维用原丝——高强高模Lyocell纤维纺丝工艺研究

采用天然高相对分子质量纤维素脱脂棉为原料 ,制备了高强高模纤维素纤维 ( L yocell纤维 ) ,并用此作为碳纤维原丝 ,成功制得了强度优于粘胶基碳纤维的 L yocell基碳纤维。考察了高相对分子质量纤维素的溶解特点 ,纺丝工艺对 L yocell纤维聚集态及性能的影响 ,比较了 L yocell纤维和粘胶原丝的表面及截面形态。实验表明 :高相对分子质量纤维素溶解的静溶胀时间和温度对其溶解有明显的影响 ;纺丝过程中 ,大的气隙长度对提高纤维的性能有利 ;随着凝固浴中 N -甲基吗啉 N -氧化物( NMMO )的浓度增加 ,纤维的强度和模量增加 ,当其在凝固浴中的质量分数达到 10 %时 ,强度模量最大 ,浓度继续增加 ,纤维的力学性能开始下降 ;拉伸比增加 ,L yocell纤维的强度模量增加 ,当拉伸比大于 3.0时 ,纤维的性能略有下降     

Lyocell-炭黑复合纤维的结构与性能

将纳米炭黑、N-甲基吗啉-N-氧化物(NMMO)溶液及纤维素共混得到纺丝液,通过干湿法制备了Lyocell-炭黑复合纤维。采用X射线衍射仪、扫描电镜、强度仪等分析了所得纤维的结构和性能。X射线衍射图谱显示复合纤维仍然具有纤维素II晶型的结构,同时还保留了炭黑的特征衍射峰。扫描电镜结果显示复合纤维中炭黑在纤维素基体中有一些团聚。对纤维的力学性能及电导率分析进一步表明:添加炭黑使得复合纤维的初始模量和断裂强度下降,但是可以在一定程度上提高复合纤维的电导率。     

Mechanical and viscoelastic properties of soybean oil thermoset reinforced with jute fabrics and carded lyocell fiber

Composites and hybrid composites were manufactured from renewable materials based on jute fibers, regenerated cellulose fibers (Lyocell), and thermosetting polymer from soybean oil. Three different types of jute fabrics with biaxial weave architecture but different surface weights, and carded Lyocell fiber were used as reinforcements. Hybrid composites were also manufactured by combining the jute reinforcements with the Lyocell. The Lyocell composite was found to have better mechanical properties than other composites. It has tensile strength and modulus of about 144 MPa and 18 GPa, respectively. The jute composites also have relatively good mechanical properties, as their tensile strengths and moduli were found to be between 65 and 84 MPa, and between 14 and 19 GPa, respectively. The Lyocell‐reinforced composite showed the highest flexural strength and modulus, of about 217 MPa and 13 GPa, respectively. In all cases, the hybrid composites in this study showed improved mechanical properties but lower storage modulus. The Lyocell fiber gave the highest impact strength of about 35 kJ/m², which could be a result of its morphology. Dynamic mechanical analysis showed that the Lyocell reinforced composite has the best viscoelastic properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comparison of the structures and properties of Lyocell fibers from high hemicellulose pulp and high α‐cellulose pulp

Lyocell fibers were produced from a cheap pulp with a high hemicellulose content and from a conventional pulp with a high α‐cellulose content. The mechanical properties, supermolecular structure, fibrillation resistance, and dyeing properties as well as the fibril aggregation size of the high hemicellulose Lyocell fiber and high α‐cellulose Lyocell fiber were compared. The results showed that the high hemicellulose spinning solution could be processed at a higher concentration, which improved the mechanical properties and the efficiency of the fiber process. Compared with the high α‐cellulose Lyocell fiber, the high hemicellulose Lyocell fiber had better fibrillation resistance and dyeing properties. Therefore, it is feasible that this cheap pulp with a high hemicellulose content can be used as a raw material for producing Lyocell fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure and properties of partially cyclized polyacrylonitrile‐based carbon fiber—precursor fiber prepared by melt‐spun with ionic liquid as the medium of processing

Carbon fiber has many excellent properties. Currently, the precursor fiber of polyacrylonitrile (PAN)‐based carbon fiber is made from solution by wet or dry spinning process that requires expensive solvents and costly solvent recovery. To solve this problem, we developed a melt‐spun process with ionic liquid as the medium of processing. The melt‐spun precursor fiber exhibited partially cyclized structure. The structure and properties of the melt‐spun PAN precursor fiber were analyzed by combination of scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, X‐ray diffraction, thermogravimetry, ultraviolet spectroscopy, flotation technique, sound velocity orientation test, linear density, and tensile strength tests. The results showed that the tensile strength of melt‐spun PAN precursor fiber was fairly high reached up to 7.0 cN/dtex. The reason was the low imperfect morphology and a cyclized structure formed by in situ chemical reaction during melt‐spun process. Due to the existence of partially cyclized structure in the melt‐spun PAN precursor fiber, exothermic process was mitigated and the heat evolved decreased during thermal stabilization stage in comparison with commercial precursor fibers produced by solution‐spun, which could shorten the residence time of thermal stabilization and reduce the cost of final carbon fiber. POLYM. ENG. SCI., 55:2722–2728, 2015. © 2015 Society of Plastics Engineers     

Effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites

A study was carried out to investigate the effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites. The influence of oxygen plasma treatment on the surface properties of carbon fibers was investigated by X‐ray photoelectron spectroscopy and atomic force microscopy. The results indicated that oxygen plasma treatment was capable of increasing the concentrations of the oxygen‐containing groups of the carbon fiber surface as well as enhancing surface roughness. Both the chemical bonding and mechanical interlocking gave rise to an increase of the interlaminar shear strength of composite. Scanning electron microscope photographs showed that the destruction mode of composites was changed after the carbon fibers were treated by oxygen plasma. The results also indicated that the flexural properties of plasma‐treated carbon fiber composites were improved. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Hybrid particulate and fibrous injection molded composites: Carbon black/carbon fiber/polypropylene systems

The electrical properties of injection molded composite systems based on a polypropylene matrix and two types of carbonaceous fillers—carbon black (CB) and carbon fibers (CF)—were investigated. In addition to conductivity as a function of system compositions, conductivity profiles were studied. Inhomogeneous spatial distribution of CB particles in moldings containing either CB as a single filler or in combination with CF was found. Furthermore, unexpected fiber orientation transverse to the melt flow direction and disappearance of skin‐core orientation pattern, typical for injection molded fiber filled composites, were observed in the two filler samples. An amplification of the shear‐thinning behavior, characteristic for the polypropylene (PP) matrix, imposed by the inhomogeneity of the CB distribution resulting in flattening of the advancing melt front and velocity profile is suggested as underlying the observed phenomena. POLYM. COMPOS., 26:454–464, 2005. © 2005 Society of Plastics Engineers     

Lyocell纤维原丝的性能对碳纤维强度的关联分析

运用灰色系统方法对新型纤维素原丝Lyocell纤维的性能与碳纤维强度之间的关系进行了关联分析，结果表明：Lyocell纤维的强度、纤度和断裂强力对碳纤维的强度有很大的影响，而对伸长和模量的影响较小。     

Processing,structure, and properties of gel spun PAN and PAN/CNT fibers and gel spun PAN based carbon fibers

Polyacrylonitrile (PAN) and PAN/carbon nanotube (PAN/CNT) fibers were manufactured through dry‐jet wet spinning and gel spinning. Fiber coagulation occurred in a solvent‐free or solvent/nonsolvent coagulation bath mixture with temperatures ranging from ?50 to 25°C. The effect of fiber processing conditions was studied to understand their effect on the as‐spun fiber cross‐sectional shape, as well as the as‐spun fiber morphology. Increased coagulation bath temperature and a higher concentration of solvent in the coagulation bath medium resulted in more circular fibers and smoother fiber surface. as‐spun fibers were then drawn to investigate the relationship between as‐spun fiber processing conditions and the drawn precursor fiber structure and mechanical properties. PAN precursor fiber tows were then stabilized and carbonized in a continuous process for the manufacture of PAN based carbon fibers. Carbon fibers with tensile strengths as high as 5.8 GPa and tensile modulus as high as 375 GPa were produced. The highest strength PAN based carbon fibers were manufactured from as‐spun fibers with an irregular cross‐sectional shape produced using a ?50°C methanol coagulation bath, and exhibited a 61% increase in carbon fiber tensile strength as compared to the carbon fibers manufactured with a circular cross‐section. POLYM. ENG. SCI., 55:2603–2614, 2015. © 2015 Society of Plastics Engineers     

Influence of hemicelluloses on the structure and properties of Lyocell fibers

In the present paper the difference in the structure and properties of Lyocell fibers with different hemicelluloses content was investigated. The supermolecular structure and the morphological characterization were compared. The fibril aggregation size was estimated by the cross‐polarization magic‐angle spinning carbon‐13 nuclear magnetic resonance (CP/MAS¹³C‐NMR) spectroscopy. Meanwhile, the difference in the mechanical, the fibrillation resistance and the dyeing properties of Lyocell fiber with different hemicelluloses content was also analyzed. POLYM. ENG. SCI., 47:702–706, 2007. © 2007 Society of Plastics Engineers.     

Effect of annealing on the structure and properties of polyvinylidene fluoride hollow fiber by melt‐spinning

Polyvinylidene fluoride hollow fibers were prepared by melt‐spinning technique under three spinning temperatures. The effects of annealing treatment on the structure and properties of hollow fiber were studied by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), tensile test, and scanning electron microscopy (SEM) measurements. DSC and WAXD results indicated that the annealing not only produced secondary crystallization but also perfected primary crystallization, and spinning and annealing temperature influenced the crystallinity of hollow fiber: the crystallinity decreased with the increase of spinning temperature; 140°C annealing increased the crystallinity, and hardly influenced the orientation of hollow fiber; above 150°C annealing increased the crystallinity as well, and furthermore had a comparative effect on the orientation. The tensile tests showed that the annealed samples, which did not present the obvious yield point, exhibited characteristics of hard elasticity, and all the hollow fiber had no neck phenomenon. Compared with the annealed sample, the precursor presented a clear yield point. In addition, the annealed samples had a higher break strength and initial modulus by contrast with the precursor, and the 140°C annealed sample showed the smallest break elongation. SEM demonstrated the micro‐fiber structure appeared in surface of drawn sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 935–941, 2007     

Microwave pre‐oxidation for polyacrylonitrile precursor coated with nano‐carbon black

A surface coating was successfully applied through dipping the polyacrylonitrile (PAN) precursor fibers in a carbon black (CB) bath containing a hydrolyzed binder. The coated fibers were pre‐oxidized over the microwave furnace at temperatures ranging from 100°C to 170°C for different heating times. The changes in chemical structure were studied by Fourier transfer infrared spectroscopy combined with elemental analyzer. X‐ray diffraction was employed to study the crystalline structure and its related parameters. Differential scanning calorimeter and thermogravimetry were used for thermal analysis. In addition, the fiber morphology and the mechanical properties were also evaluated. Scanning electron microscopy results confirmed the presence of CB on the surface of PAN precursor. The analysis in the chemical structure showed an apparent response of coated PAN fibers to the microwave heating, since the microwave field induced the cyclization and crosslinking reactions. The crystallinity and the crystallite height decreased. Furthermore, the tensile strength and elongation of pre‐oxidized fibers decreased with the increase of heating time. The measured oxygen content revealed that the pre‐oxidized fibers can withstand the high temperatures on the following stage (carbonization). POLYM. ENG. SCI., 59:457–464, 2019. © 2018 Society of Plastics Engineers     

Rare earth compounds modified carbon black filled powdered natural rubber: Preparation,morphology and properties

Ten types of rare earth (RE) compounds modified carbon black (HAF‐RE) were prepared using chemical‐deposit method, then HAF‐RE were mixed with natural rubber latex to prepare HAF‐RE filled powdered natural rubber [P(NR/HAF‐RE)] by a carbon black/rubber latex coagulation method. It is found that most of the P(NR/HAF‐RE) vulcanizates showed better mechanical properties, especially higher tensile modulus, and tensile strength, compared with none‐rare earth modified carbon black filled powdered natural rubber [P(NR/HAF)]. Dysprosium (Dy) modified carbon black (HAF‐Dy) filled powdered natural rubber [P(NR/HAF‐Dy)] was chosen for intensive investigation because of its better comprehensive mechanical properties. It is found that the adding of Dy compounds could help to get smaller particles with narrower particle size distribution, and results from the SEM analysis show that carbon black has been dispersed in rubber matrix uniformly with diameter of 50–150 nm. The TEM analysis showed that Dy compounds could obviously reduce the aggregation of primary particles of carbon black, and promote the dispersion of carbon black in P(NR/HAF‐Dy) particles. © 2008 Wiley Periodicals, Inc. JAppl Polym Sci 2008     

超拉伸过程中UHMWPE纤维结构与性能的研究

利用密度梯度仪、声速取向仪、Instron材料强力仪、WAXD、DSC等手段 ,对超高相对分子质量聚乙烯 (UHMWPE)纤维在超拉伸过程中的结构和性能进行了测试研究。结果表明 ,不同拉伸倍数的UHMWPE纤维的结晶度、取向度、力学性能和熔融温度随着拉伸倍数的增大而增加 ;DSC图谱上的 Tm4 峰和WAXD分析证实了在超拉伸过程中UHMWPE纤维发生了正交晶相向六方晶相的转变 ,超拉伸后期结晶结构的变化对纤维的力学性能影响很大。     

Effect of carbon nanotubes growth topology on the mechanical behavior of hybrid carbon nanotube/carbon fiber polymer composites

In this study, carbon nanotubes (CNTs) were incorporated into carbon fiber‐reinforced polymer composites (CFRPs) by growing them on the surface of PAN‐based carbon fibers utilizing a relatively low temperature technique. The effect of various surface treatments of the carbon fibers on the in‐plane and out‐of‐plane mechanical performance of the hybrid CFRPs (e.g., exposure to or shielding against elevated temperatures, patterned vs. unpatterned growth of the CNTs over the carbon fibers) were investigated. The in‐plane quasi‐static mechanical properties and out‐of‐plane dynamic properties of the hybrid CFRPs were examined utilizing tension and dynamic impact tests, respectively. To study the progressive damage mechanism of the hybrid CFRPs, spherical punch tests as well as X‐ray radiography of the impact damaged hybrid CFRPs were carried out. The results revealed that the strength and impact energy dissipation of the CFRPs improved by 11% and 127%, respectively, utilizing patterned growth of CNTs on the surface of the carbon fibers. POLYM. COMPOS., 37:2639–2648, 2016. © 2015 Society of Plastics Engineers