高半纤维素浆粕纺制Lyocell纤维的结构与性能

采用成本低、半纤维素含量高的浆粕纺制Lyocell纤维,重点对制得的高半纤维素Lyocell纤维的结晶、取向、力学性能、原纤化和染色性等进行了研究。研究表明:这种用高半纤维素浆粕纺制的Lyocell纤维与用高α-纤维素浆粕纺制的Lyocell纤维相比,它的模量、结晶度、取向度、抗原纤化能力和染色性等都好于后者。     

高半纤维素浆粕制备Lyocell纤维的研究

采用半纤维素质量分数21%的高半纤维素浆粕在N-甲基吗琳-N-氧化物(NMMO)水溶液中制备Lyocell纤维,并与半纤维素质量分数为10%的高α-纤维素浆粕的可纺性进行了对比。结果表明:高半纤维素浆粕在溶剂NMMO·H_2O中更易溶解,其过滤性能和可纺性能好,可在较高浆粕浓度下纺丝,制备成Lyo- cell纤维的产率高,且能提高Lyocell纤维的力学性能。高半纤维素浆液的稳定性能略低,在溶剂回收中需要消耗较多的双氧水进行氧化回收溶剂NMMO。     

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     

Investigation of eco-friendly chemical treatments of apple pomace for producing high quality molded pulp biocomposite

Eco-friendly chemical treatments using citric acid (CA) and sodium bicarbonate were employed to remove pectin, hemicellulose, and extractives from apple pomace (AP) for improving AP fiber quality and maximizing its utilization in producing biocomposite boards with newspaper (NP) fibers (AP:NP ratio of 2:1) using molded pulp technique. CA treatment was further optimized at different pH and temperature and cellulose nanofiber (CNF, 0.15, 0.3% w/w pulp solids) was used as reinforcement agent to enhance mechanical property and water resistance of biocomposite boards. CA treatment improved AP fiber strength and cellulose content. AP treated by CA at pH 2.5 and 75°C with 0.15% CNF reinforcement produced AP/NP biocomposite board with high flexural strength, and dimension stability, and low density. Thermal analysis verified increased cellulose content, crystallinity, and thermal stability of CA treated AP fibers. This study provided new insight to improve fiber functionality and utilize AP for developing sustainable packaging.     

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.     

用于制备高强Lyocell纤维的纤维素混合浆粕的研究

研究了在高聚合度的纤维素浆粕中添加少量的中等聚合度浆粕,所形成的混合浆粕的纺丝情况及得到的Lyocell纤维的性能。在此基础上,利用凝胶渗透色谱法(GPC)测定了混合浆粕的相对分子质量及其分布,分析了混合浆粕的相对分子质量及其分布对可纺性及纤维性能的影响。结果表明:这种混合浆粕的相对分子质量分布明显变宽,其中高相对分子质量的峰几乎没有变化,但中低相对分子质量部分含量增多,出现了较小的中低相对分子质量峰。这些中低相对分子质量部分的纤维素起了增塑作用,使加工更容易,而高相对分子质量部分则赋予纤维良好的力学性能。     

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     

浆粕性质对纤维素/[Bmim]Cl纺丝原液性能的影响

选用棉浆和木浆3种纤维素浆粕为原料,以离子液体1-丁基-3-甲基咪唑氯盐([Bmim] Cl)为溶剂,探讨了浆粕的聚合度(DP)和α-纤维素含量对其在[Bmim] Cl中的溶解情况、纺丝液的流变行为及其纤维性能的影响.结果表明:浆粕的DP和α-纤维素含量越高,其在[Bmim] Cl中完全溶解所需时间就越长;相对于α-纤...     

改性剂PVA对Lyocen纤维结构和性能的影响

将聚乙烯醇（PVA）加入到纤维素／NMMO-H20溶液中进行纺丝,制备了不同PVA含量的Lyocell纤维,并对纤维的结构和性能进行了表征。结果表明,添加适量的PVA可以降低纺丝原液的黏度,提高纺丝液的可纺性,明显提高Lyocell纤维的强度和模量;通过x射线衍射测试,发现添加PVA之后Lyocell纤维仍然具有纤维素II晶型的结构;此外,PVA的加入还可以改善Lyocell纤维的抗原纤化性能,提高Lyocell纤维的热稳定性。     

以离子液体为溶剂的纤维素纤维的结构与性能

以离子液体氯化1-丁基-3-甲基咪唑([BMIM]Cl)为溶剂,制备了纤维素/[BMIM]Cl溶液,探讨了该体系的流变性能,并对所纺得的纤维素纤维的结构与性能进行了分析。结果表明:纤维素/[BMIM]Cl溶液为切力变稀流体,当剪切速率较大时,温度对体系黏度几乎没有影响,因此可以在较高剪切速率下降低纺丝温度;由该体系纺制的纤维具有纤维素II晶型的结构;随着拉伸比的提高,纤维的取向程度及结晶度增大,从而使纤维力学性能提高,所得纤维的表面光滑、结构致密,其染色性能及抗原纤化性能与Lyocell纤维基本相近。从而证明了用离子液体[BMIM]Cl所纺制的纤维素纤维性能良好,可望成为继Lyocell纤维之后的又一新型绿色纤维素纤维。     

纤维素浆粕和Lyocell纤维在LiCl/DMAc中溶解差异的研究

为了研究Lyocell工艺中纤维素相对分子质量分布的变化,分析了纤维素浆粕和相应的由浆粕生产出的Lyocell纤维在LiCl/DMAc中的溶解情况,发现两者存在很大差异,分别从纤维素的晶型、取向和形态结构等方面分析原因。结果表明:由于Lyocell纤维(纤维素II)比纤维素浆粕(纤维素I)在热力学上更稳定,分子间的氢键更多,且Lyocell纤维的取向较纤维素浆粕高,纤维结构较致密,使得溶剂的渗透和氢键的破坏更加困难,因此Lyocell纤维在LiCl/DMAc中的溶解比纤维素浆粕差。     

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。     

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。     

以高半纤维素浆粕为原料的Lyocell产品得率及可纺性

测定高半纤维素和高α-纤维素含量的两种浆粕在粘胶生产工艺和Lyocell生产工艺中纤维的得率,及两种浆粕的动态流动性能。结果表明:浆粕中α-纤维素含量在粘胶生产工艺中,决定着最终纤维素产品的得率;但在Lyocell生产工艺中,却无必然联系,所以高半纤维素含量的浆粕可适合于Lyocell工艺,且浆粕中的高半纤维素更有益于纺丝加工。     

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     

Bleached extruder chemi‐mechanical pulp fiber‐PLA composites: Comparison of mechanical,thermal, and rheological properties with those of wood flour‐PLA bio‐composites

An environmentally friendly bleached extruder chemi‐mechanical pulp fiber or wood flour was melt compounded with poly(lactic acid) (PLA) into a biocomposite and hot compression molded. The mechanical, thermal, and rheological properties were determined. The chemical composition, scanning electron microscopy, and Fourier transform infrared spectroscopy results showed that the hemicellulose in the pulp fiber raw material was almost completely removed after the pulp treatment. The mechanical tests indicated that the pulp fiber increased the tensile and flexural moduli and decreased the tensile, flexural, and impact strengths of the biocomposites. However, pulp fiber strongly reinforced the PLA matrix because the mechanical properties of pulp fiber‐PLA composites (especially the tensile and flexural strengths) were better than those of wood flour‐PLA composites. Differential scanning calorimetry analysis confirmed that both pulp fiber and wood flour accelerated the cold crystallization rate and increased the degree of crystallinity of PLA, and that this effect was greater with 40% pulp fiber. The addition of pulp fiber and wood flour modified the rheological behavior because the composite viscosity increased in the presence of fibers and decreased as the test frequency increased. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44241.     

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     

Synthesis and characterization of polypropylene reinforced with cellulose I and II fibers

Recently, cellulose fiber–thermoplastic composites have played an important role in some applications. Plastics reinforced with cellulose and natural fibers have been widely studied. However, composites with regenerated cellulose have rarely been investigated. In this study, the lyocell fiber of Lenzing AG (cellulose II) and its raw material a bleached hardwood pulp (cellulose I) were used as reinforcement materials. The mechanical and thermal properties of polypropylene (PP) reinforced with pulp and lyocell fibers were characterized and compared with regard to the content of the fiber and the addition of maleated polypropylene (MAPP). PPs with cellulose I or II as a reinforcement material had similar mechanical properties. However, when MAPP was used as coupling agent, the mechanical properties of the composites were different. The crystallinity of the composites were determined by differential scanning calorimetry. Cellulose I (pulp) promoted the crystallization of PP, whereas cellulose II did not. MAPP reduced this effect in cellulose I fibers, but it induced crystallization when cellulose II (lyocell) was used as a reinforcement material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 364–369, 2006     

Thermal behavior of vinyl ester resin matrix composites reinforced with alkali‐treated jute fibers

The thermal behavior of vinyl ester resin matrix composites reinforced with jute fibers treated for 2, 4, 6, and 8 h with 5% NaOH was studied with Thermo‐gravimetric analysis and differential scanning calorimetry. The moisture desorption peak shifted to a higher temperature, from 37 to 58.3°C, for all the treated‐fiber composites because of improved wetting of the fibers by the resin and stronger bonding at the interface. The degradation temperature of the vinyl ester resin in the composites was lowered to 410.3°C from that of the neat resin, 418.8°C. The X‐ray diffraction studies showed increased crystallinity of the treated fibers, which affected the enthalpy of the α‐cellulose and hemicellulose degradation. The hemicellulose degradation temperature remained the same (299.7°C) in all the treated‐fiber composites, but the enthalpy associated with the hemicellulose degradation showed an increasing trend in the treated composites with a small increase in the weight loss. This could be attributed to the increased hydrogen bonding between the more accessible ? OH groups of the hemicellulose in the noncrystalline region of the jute fiber and the resin. The degradation temperature of α‐cellulose was lowered from 364.2 to 356.8°C in the treated composites. The enthalpy of α‐cellulose degradation showed a decreasing trend with a lowering of the weight loss. The crystalline regions of the fiber, consisting of closely packed α‐cellulose chains, were bonded with the resin mainly on the surface through hydrogen bonds and became more resistant to thermal degradation; this reduced the weight loss. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 123–129, 2004     

A new approach for the production of cellulose acetate: Acetylation of mechanical pulp with subsequent isolation of cellulose acetate by differential solubility

A heretofore uninvestigated approach to the production of cellulose acetate, the acetylation of whole wood pulp with subsequent isolation of the cellulose derivative by differential solubility, is described. The mechanical pulp used was produced by refining aspen wood chips with a disc refiner. Two conventional acetylation techniques, the fibrous and solution process, were employed to acetylato all components of the pulp. The cellulose acetate was isolated from the acetylated lignin and hemicellulose by dissolving in dichloromethane/methanol (9:1, v/v). The advantage of this new approach is that the high cost involved in using an extensively purified dissolving pulp are avoided. Both acetylation techniques yielded a product that was about 84% cellulose acetate. The remaining acetylated components were lignin and hemicellulose. The yield of cellulose acetate, based on the cellulose content of the original pulp and the product, was 75–80%.