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     

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     

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     

Etherification of hemicelluloses from sugarcane bagasse

Conditions for the preparation of etherified hemicelluloses from sugarcane bagasse with 2, 3‐epoxypropyltrimethylammonium chloride (ETA) using sodium hydroxide as a catalyst in aqueous solution were studied comparatively. The extent of the etherification was measured by yield percentage and degree of substitution. The effects of reaction time of 3–7 h, reaction temperature of 50–80°C, temperature of alkaline activation of 30–60°C, and time of alkaline activation of 0–60 min on the reaction yield and degree of substitution were investigated in detail. The overall yield and degree of substitution were varied from 35.2 to 41.9% and from 0.14 to 0.33, respectively, by changing the reaction temperature and duration as well as time and temperature of alkaline activation. The new materials were characterized by FT‐IR and 13C NMR spectroscopy, thermal analysis as well as GPC. It was found that the thermal stability of the hemicellulosic ethers decreased after chemical modification, and the molecular weights of the etherified hemicelluloses were lower than those of the native hemicelluloses. ¹³C NMR spectra gave the evidence for etherification reaction and the quaternization of hemicelluloses occurred mainly at C‐3 position. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

A new method to visualize and characterize the pore structure of TENCEL® (Lyocell) and other man‐made cellulosic fibres using a fluorescent dye molecular probe

The internal porous structures of the man‐made cellulosic fibers Lyocell (TENCEL®), Modal, and Viscose fibers were visualized by applying fluorescence microscopy on fiber cross sections. The fiber pore structure was probed by the optical brightener Uvitex BHT, and the dye penetration depth was measured. The main differences in the pore structures of these three fiber types could be visualized. Only TENCEL shows a significant difference between dried and never‐dried fibers. A fiber structure model of TENCEL was obtained, which discriminates three different porous zones with respect to dye diffusion kinetics. The results are discussed in relationship with the fiber physical and chemical properties. The dye penetration depth and kinetics in TENCEL fibers was found to be sensitive to the production and treatment conditions, in particular to changes in the pore system by drying, and following alkali swelling processes. The performance of surface‐specific enzymatic peeling could also be observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of cationic hemicellulosic derivatives with a low degree of substitution in dimethyl sulfoxide media

A series of water‐soluble cationic 2‐hydroxylpropyltrimethylammonium hemicellulosic derivatives with low average degrees of substitution (DS's) were prepared by the incorporation of the cationic moiety 2,3‐epoxypropyltrimethylammonium chloride (ETA) onto the backbone of hemicelluloses in the presence of NaOH as a nucleophilic catalyst in homogeneous dimethyl sulfoxide (DMSO) media. The dependence of the homogeneous reaction on the different affecting factors was investigated. The average DS was calculated from the N/C ratio in the products and from the weight gain. The degree of substitution determined by the nitrogen content (DS_N) values up to 0.25 in a one‐step synthesis of the etherified hemicelluloses could be controlled by the adjustment of the amount of solvent used and the molar ratio of NaOH or ETA to the anhydromonomer units in the hemicelluloses. The structure of the cationic hemicellulosic derivatives formed was determined by Fourier transform infrared spectroscopy and further confirmed with solution‐state ¹³C‐NMR spectroscopy. In comparison, no significant degradation of the hemicellulosic derivatives occurred during the etherification of the polymers in the homogeneous DMSO system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nano‐carbon black filled Lyocell fiber as a precursor for carbon fiber

In this work, Lyocell fibers filled with various amounts of carbon black were prepared. Wide angle X‐ray diffraction (WAXD) results showed that carbon black filled Lyocell fibers still had a cellulose II crystal structure and kept the characteristic peak of carbon black at the same time. The results of mechanical properties showed a slight reduction in the carbon black filled Lyocell fiber. Moreover, the heat stabilities of the carbon black filled Lyocell fibers showed no obvious change. The residue of carbon black filled Lyocell fiber at 1000°C was higher than that of Lyocell fiber, implying higher carbon yield could be obtained for the carbon black filled Lyocell precursor. Scanning electron microscopy (SEM) experiments showed that the surface and the cross section of carbon black filled Lyocell fiber were smooth and round, which are consistent with the carbon fiber precursor. The WAXD pattern of carbon black filled Lyocell‐based carbon fiber was different from that of Lyocell‐based carbon fiber. The addition of carbon black transfers the diffraction peak of carbon fiber while keeping the characteristic structure of carbon black. The results of mechanical properties of carbon fibers show that, if an appropriate amount of carbon black was chosen, carbon fiber with better properties than Lyocell‐based carbon fiber could be obtained by using the carbon black filled Lyocell fibers as the precursor. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 65–74, 2006     

Effect of heat treatment on the structure and properties of Lyocell fibers

Lyocell fibers were heat‐treated under different conditions. The tensile strength and initial modulus of the heat‐treated Lyocell fibers increased sharply, whereas the elongation at break decreased. Moreover, applying tension to the fibers during the heat treatment further improved the tensile strength and initial modulus. In addition, the crystallinity of the heat‐treated fibers increased slightly, and there was no obvious change with an increase in the tension; the general orientation of the heat‐treated fibers increased, the crystalline orientation little changed, and the amorphous orientation improved. Also, the improved mechanical properties of the Lyocell fibers via the heat treatment could not be preserved for long. The reason may be that the crystalline structure of the Lyocell fibers was not destroyed and no new crystallites were formed during the heat‐treatment process. Therefore, the heat‐treated Lyocell fibers reverted to their original state with time because there was no crosslinking point to fix the orientation, although the cellulose molecules of the amorphous region of the Lyocell fibers were more oriented by the heat treatment with tension. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1738–1743, 2006     

Chemical and structural characterization of alkaline‐extractable hemicelluloses from various eucalyptus species

Eucalyptus species are currently one of the main feedstock for pulping and papermaking industry in China. In the present study, alkali‐extractable hemicelluloses were isolated from different eucalyptus species (Eucalyptus camaldulensis, E. urophylla × grandis, and E. urophylla × E. tereticornis) at mild conditions prior to pulping. Structural characterization of these hemicellulosic polymers based on monosaccharide, molecular weight, Fourier transform infrared, ¹H, ¹³C, and two‐dimensional heteronuclear single quantum coherence nuclear magnetic resonance analysis revealed that these alkali‐extractable polysaccharides shared the common structure composed of the (1→4)‐linked‐β‐D‐xylopyranosyl backbone with 4‐O‐methyl‐α‐D‐glucuronic acid attached to O‐2 of the xylose residues. The potential structures of the alkali‐extractable hemicelluloses were proposed based on the comprehensive analysis. The well‐characterized structures of these hemicelluloses could enlarge the industrial application of these hemicelluloses from the Eucalyptus species in a biorefinery process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2390–2398, 2013     

Mechanical and morphological properties of lyocell blends: Comparison with lyocell nanocomposites (I)

The mechanical properties and morphologies of polyblends of lyocell with three different fillers are compared. Poly(vinyl alcohol) (PVA), poly(vinyl alcohol‐co‐ethylene) (EVOH), and poly(acrylic acid‐co‐maleic acid) (PAM) were used as fillers in blends with lyocell produced through solution blending. The variations of their properties with polymer matrix filler content are discussed. The ultimate tensile strength of the PVA/lyocell blend is highest for a blend lyocell content of 30 wt %, and decreases as the lyocell content is increased up to 40 wt %. The ultimate tensile strengths of the EVOH/lyocell and PAM/lyocell blends are highest for a lyocell loading of 20 wt %, and decrease with the increasing filler content. The variations in the initial moduli of the blends with filler content are similar. Of the three blend systems, the blends with PVA exhibit the best tensile properties. Lyocell/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium–Mica (C₁₂PPh‐ Mica) as the organoclay. The variation of the mechanical tensile properties of the hybrids with the matrix polymer organoclay content was examined. These properties were found to be optimal for an organoclay content of up to 5 wt %. Even polymers with low organoclay contents exhibited better mechanical properties than pure lyocell. The addition of organoclay to lyocell to produce nanocomposite films was found to be less effective in improving its ultimate tensile strength than blending lyocell with the polymers. However, the initial moduli of the nanocomposites were found to be higher than those of the polyblend films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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。     

Succinoylation of wheat straw hemicelluloses with a low degree of substitution in aqueous systems

The reaction of wheat straw hemicelluloses with succinic anhydride in aqueous alkaline systems was studied. The products showed a rather low degree of substitution, ranging from 0.017 to 0.21. The effects of reaction times of 0.5–16 h, temperatures of 25–45°C, and molar ratios of succinic anhydride to anhydroxylose units in hemicelluloses of 1:5–1:1 on the succinoylation yield and degree of substitution were examined. With the reaction kept within a pH range of 8.5–9.0, a temperature range of 25–28°C, a reaction duration of 1–2 h, and a 1:1 molar ratio of succinic anhydride to hemicelluloses were preferred. The structure of the resulting polymers was determined with Fourier transform infrared and ¹H‐ and ¹³C‐NMR spectroscopy, which indicated monoester substitution. The thermal stability of the esterified polymer increased with chemical modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 757–766, 2002     

Synthesis,characteristic, and properties of waterborne polyurethane based on natural rubber

A series of new waterborne polyurethanes (WPUs) was successfully prepared by prepolymer process from renewable source, hydroxytelechelic natural rubber (HTNR), with different amounts of DMPA (1.6–8.4 wt %), different molecular weights (1000–4000 g mol^?1), and different levels of epoxide (0%–20%) of HTNR. It was found that the urethane conversions of prepolymer were over 80% as calculated by FTIR technique. The resulting HTNR2000‐based WPUs exhibit a uniform particle size, which decreases from 420‐ to 83‐nm diameters with an increase in the amount of DMPA from 2.9 to 6.6 wt %. The particle size also decreases with an increase of soft segment or with an increase of epoxide content. They are well stable more over 6 months and without a significant difference in particle size compared with starting of them. Chemical structure of WPU films was confirmed by FTIR, ¹H‐NMR, and ¹³C‐NMR. Molecular weight and polydispersity were determined by SEC. In addition, thermal and water uptake properties were investigated. The experimental results reveal that the DMPA content, molecular weight of HTNR, and epoxide content play an important key role in water uptake and thermal properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fractional Separation of Hemicelluloses and Lignin in High Yield and Purity from Mild Ball-Milled Periploca sepium

Abstract

A novel three-step procedure for separation of hemicelluloses and lignin with high yield and purity was proposed in this study, where wood is mildly milled and successively extracted to produce three hemicellulosic and lignin fractions representing the total hemicelluloses and lignin in wood. The sequential treatments of the mild ball-milled Periploca sepium with 80% aqueous dioxane containing 0.05 M HCl at 85°C for 4 h, DMSO at 85°C for 4 h, and 8% NaOH at 50°C for 3 h resulted in a total release of over 85% of the original hemicelluloses and 86% of the original lignin. In particular, approximately 36% of the original hemicelluloses and 50% of the original lignin were separated during the first mild acidolytic hydrolysis process after low intensity milling. The structure of the acidic dioxane-, DMSO-, and alkali-soluble hemicellulosic and lignin fractions were elucidated using wet chemical analysis, FT-IR, and solution-state ¹H, ¹³C, and ³¹P NMR techniques. Results showed that both the mild ball milling and the mild acidolysis under the conditions given did not affect the separated lignin macromolecular structure. On the other hand, the mild acidolytic hydrolysis condition did cause substantial hemicellulosic depolymerization exception for a significant cleavage the ether linkages between lignin and hemicelluloses. The acidic dioxane-soluble lignin fraction was structurally different from the DMSO- and alkali-soluble lignin preparations and may originate mainly from the primary wall, while the alkali-soluble lignin preparation was mainly released from the secondary wall of Periploca sepium. Furthermore, it was found that the acidic dioxane-soluble hemicelluloses mainly contained more branched and less acidic arabinoxylans, and the 8% NaOH-soluble hemicellulosic fraction H₃ was both less branched and less acidic in structure, whereas the DMSO-soluble hemicelluloses were more acidic but less branched and consisted mainly of 4-O-methylglucuronoarabinoxylan.     

氯化铵改性Lyocell纤维的制备及其热处理

研究了不同NH4Cl含量的纤维素／NMMO·H2O溶液的流变性能,在此基础上制备了NH4Cl改性Lyocell初生纤维,并探讨了NH4Cl添加量及后续热处理对纤维结构与性能的影响。结果发现：随着NH4Cl添加量的增加,纤维素溶液体系的表观黏度、结构化程度、表观相对分子质量增加而表观相对分子质量分布变窄。结合广角X-射线衍射和双折射分析结果还发现：对Lyocell纤维采用NH4Cl改性或进一步结合热处理,都可以有效提高纤维的结晶度和取向度,完善最终纤维的聚集态结构。对纤维的性能分析结果表明：在本研究条件下,当NH4Cl添加量为5％时,经适当条件热处理后,最终得到Lyocell纤维断裂强度7．21cN／dtex、初始模量92．6cN／dtex、干热收缩率小于0．8％,并且蠕变率也有一定的下降．     

Development of linseed oil based polyesteramide without organic solvent at lower temperature

Linseed oil based polyesteramide was synthesized at lower temperature in the absence of organic solvent through condensation polymerization reaction [Sf‐LPEA]. In this reaction N,N‐bis(2‐hydroxyethyl) linseed oil fatty amide and phthalic anhydride were heated at temperature lower than their onset of melting points and the by‐product, such as water was removed by application of vacuum technique. This approach was employed to overcome the use of volatile organic solvents used during processing and application of resin, which are ecologically harmful. The solubility of Sf‐LPEA was checked in different polar and nonpolar solvents. The FTIR, ¹H NMR, and ¹³C NMR spectral techniques were used to confirm the structure of Sf‐LPEA. The physicochemical, physicomechanical, and chemical resistance properties of the resin were investigated by standard methods. DSC and TGA were used to determine, respectively, the curing behavior and thermal stability of the resin. The comparative study of these properties of Sf‐LPEA with reported polyesteramide [LPEA], which are normally synthesized at higher temperature in organic solvent, was done. It was found that Sf‐LPEA exhibited improved physicomechanical, chemical resistance properties, and higher thermal stability compared with LPEA, and hence can find application as corrosion protective coating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1143–1148, 2007     

Characteristics of hemicelluloses obtained from sweet sorghum based on successive extractions

Hemicelluloses were successively extracted from sweet sorghum by hot water, dioxane, DMSO, and different concentrations of NaOH between 0.5% and 6.0%. The yields of the seven fractions together accounted for 88.6% of the original hemicelluloses. The obtained hemicellulosic subfractions were comprehensively investigated by both destructive methods such as alkaline nitrobenzene oxidation and acid hydrolysis and nondestructive techniques such as gel permeation chromatography, Fourier‐transform infrared, ¹³C‐nuclear magnetic resonance, and 2D‐heteronuclear singular quantum correlation. Sugar composition studies showed that the water‐soluble polysaccharides consisted mainly of glucose, while xylose, arabinose, and glucuronic acid were the major sugars in other hemicellulosic fractions. It was found that the hemicelluloses from sweet sorghum were l‐ arabino‐(4‐O‐methyl‐d‐ glucurono)‐xylans. Comparison with the hemicellulosic fractions dissolved by the alkali treatment, the hemicellulosic fraction extracted by DMSO had lower molecular weight. In addition, it was also found that the hemicelluloses prepared by dioxane and DMSO were more branched since that they had higher nonxylose/xylose ratios than those extracted by the alkali treatment, which were more linear and contained higher amounts xylose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42790.     

Synthesis of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine and its application as latent curing agents

A kind of new compound of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was successfully synthesized by addition–condensation reaction of phenyl aldehyde and β‐hydroxylethanolamine and purified by vacuum distillation. Its purity was examined by gas chromatographic analysis. Its structure was confirmed by ¹³C NMR and FTIR. When this compound was added as a latent curing agent in single‐component moisture‐curable polyurethane system (SPU), bubbles of SPU formed during curing was obviously restrained, and the elongation at break of the cured SPU contained a certain content of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was increased to 16 times when compared with that uncontained this oxazolidine derivative. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mathematical Model for Predicting the Dissolution Behaviors of Hemicelluloses During Cold Caustic Extraction Process

Cold caustic extraction (i.e., CCE) is widely used in mill practice for hemicelluloses removal, and the parameters of which can significantly affect the hemicelluloses dissolution. Therefore, the dissolution behaviors of hemicelluloses under different CCE process parameters have been investigated. The results showed that with the temperature increases, the dissolution of hemicelluloses also increases. However, the effect of alkali content showed complicated, since lower content (<9.0 wt %) was good for the swelling of fibers (i.e., good for hemicelluloses dissolution), but higher content (>9.0 wt %) would accelerate the competing hydration of sodium ions with water and thus limited the dissolution of hemicelluloses. Besides, a mathematical model has been also developed for predicting the hemicelluloses dissolution during CCE process, which can provide a good guidance for enhancing the purification efficiency in the CCE process operation. © 2018 American Institute of Chemical Engineers AIChE J, 65: 13–17, 2019