纤维素/NMMO/水溶液流变性能的研究

研究了不同聚合度的纤维素/NMMO/水溶液以及在添加剂NH_4Cl存在下的溶液的流变性能,并将流变性能与纺丝性能进行对照分析,此外,还通过动态流变实验的分析比较了不同纤维素浆粕的相对分子质量及其分布。     

纤维素浆粕性质对其在NMMO溶液中的溶胀性能的影响

将4种聚合度及α-纤维素含量不同的纤维素浆粕在85℃下分别溶解于质量分数为74%,78%,80%的N-甲基吗啉-N-氧化物(NMMO)溶液中,研究了纤维素浆粕性质对其在NMMO溶液中的溶胀性能的影响。结果表明:纤维素浆粕的结晶度越高、聚合度越大、α-纤维素含量越高,溶胀效果越差;在相同实验条件下,浆粕的疏松性对其溶胀效果影响很大,浆粕越疏松,其溶胀效果越好;溶胀过程不会改变纤维素的晶型,但会使纤维素结晶度有所下降;聚合度适中、结晶度较低,疏松的纤维素浆粕适宜作为Lyocell纤维的原料。     

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。     

落叶松和毛白杨制备纳米结晶纤维素的性能对比

本研究以落叶松和毛白杨浆粕为原料,用酸水解法、超声处理分别制备纳米结晶纤维素,并研究原料的α-纤维素含量和聚合度等性质对制备所得纳米结晶纤维素得率、结构、结晶度和热稳定性的影响。实验所选用落叶松浆粕的α-纤维素质量分数为 88.93 %,平均聚合度达到1048.11,而毛白杨浆粕的α-纤维素质量分数为 85.90 %,平均聚合度为976.07。结果表明:酸水解处理对浆粕纤维中排列致密的结晶区影响不明显,但是会破坏非结晶区造成结晶度提高,而超声处理会使结晶度下降;由落叶松浆粕制备所得纳米结晶纤维素的得率高、晶面特征吸收峰显著,且热稳定性较好(热降解温度为 295.2 ℃),而由毛白杨浆粕制备所得的纳米结晶纤维素的热降解温度为 283.1 ℃。     

甘蔗渣制人纤浆粕蒸煮和漂白试验研究

采用甘蔗渣制备人纤浆粕,在预水解前提下使用较强的蒸煮条件,并加蒸煮助剂以加速木素的脱除,且使高聚合度部分的纤维素适当降聚;漂白阶段中,在常规CEH三段漂白的基础上增加二氧化氯漂白段,形成CEHD四段漂白,并进行酸处理,可提高聚合度分布均一性。从而改善甘蔗渣浆粕反应性能。     

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...     

GPC测定纤维素聚合度分布

一、前言 国外曾用GPC法研究了纤维素及其衍生物的聚合度及其分布,并应用于浆粕制造和粘胶纤维生产工业中。 为提高粘胶纤维的质量,研究纤维素聚合度分布对粘胶纤维质量的影响,从1975年我们     

纤维素性质对纤维素溶液可纺性以及纤维性能的影响?

采用热台偏光显微镜跟踪观察了不同纤维素浆粕在N-甲基吗啉-N-氧化物一水合物(NMMO·H_2O)中的溶解过程,并利用哈克旋转流变仪分析了其溶液的流变性能。研究结果发现:纤维素的聚合度越高,温度对纤维素的溶解过程影响越大;相同纤维素浓度下,随着纤维素的聚合度的增加,溶液的结构粘度指数(△_η)、粘流活化能(E_η)以及弹性增大,即溶液可纺性下降,粘度对温度更加敏感。在此基础上,进一步探讨了纤维素性质对纤维性能的影响,结果表明Lyocell纤维的力学性能随纤维素聚合度以及纺丝液浓度的提高而提高,可纺浓度随聚合度的提高而下降。     

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。     

用自制GPC仪测定纤维素聚合度分布

在完成简易凝胶渗透色谱法(GPC)测定纤维素聚合度分布的基础上,又研制成自动凝胶渗透色谱仪,并用此仪器测定了浆粕、碱纤维素等粘纤半成品的聚合度分布,结合生产的工艺条件,作了一些探讨。     

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     

Molecular weight distribution of cellulose as its tricarbanilate by high performance size exclusion chromatography

Cellulose tricarbanilates (CTCs) were prepared from a range of cellulose samples (cotton linters, wood pulps, Avicel, amorphous cellulose, and cellulose II) for molecular weight distribution (MWD) studies by high performance size exclusion chromatography (HPSEC). The HPSEC columns were calibrated using CTC standards with the aid of a microcomputer. CTCs were prepared by reaction of cellulose samples with phenylisocyanate in pyridine at 80°C. For some samples, e.g., cellulose II, activation with liquid ammonia and pyridine was necessary prior to reaction in pyridine. All samples tested were also derivatised in dimethylsulfoxide at 70°C, although for high molecular weight (MW) cellulose samples some MW reduction occurred in this solvent. Conditions were determined for optimum precipitation of CTCs in aqueous methanol without coprecipitation of low MW impurities.     

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     

浆粕性质对离子液体法再生竹浆纤维性能的影响

以6种不同性质的竹浆粕为原料,选用1-乙基-3-甲基咪唑醋酸盐{[EMIM] Ac]为溶剂,采用干喷湿纺的方式制备了再生竹浆纤维,探讨了竹浆粕性质对再生竹浆纤维制备过程中溶解、流变行为以及纤维性能的影响.结果表明:离子液体对竹浆粕具有非常强的溶解能力;6种竹浆粕/[EMIM] Ac纺丝液都属于切力变稀流体;高聚合度和高α纤维素的竹浆粕制备的纤维的断裂强度和模量较高,但是纺丝过程不连续,发生断头较多.     

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。     

Effect of cellulose concentration in NMMO·H2O solution on prediction of MW and MWD of cellulose using a rheology‐based method

Prediction of molecular weight (MW) and molecular weight distribution (MWD) of cellulose by means of a rheology‐based method is developed. In this method, the effect of cellulose concentration in N‐methlymorpholine‐N‐oxide monohydrate (NMMO·H₂O) solution on predicting results is discussed. It is shown that there is no significant effect of cellulose concentration on predicting results when the cellulose concentration in NMMO·H₂O solution is high enough. Meanwhile, the obtained results are compared with those of gel permeation chromatograghy (GPC) method. The comparison shows that the calculated peak MW, polydispersity index (PDI) and MWD curves have the same trends. Consequently, it may be feasible to compare the MW and MWD of cellulose by using the rheology‐based method. In addition, the rheology‐based method is simple and fast. Therefore it is a useful and easy way to analyze the MW and MWD of cellulose in the fiber industry. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

High-temperature SEC coupled with MALLS detector for evaluating the end-use performance of LDPE

Low-density polyethylene (LDPE) is the most widely used plastic material in the film-packaging industry. To improve its tensile strength and elongation, it is blended with linear LDPE. Three commercial samples of LDPE, which were found to give different performances in the sealing strength of films prepared from their blends, have been evaluated for their molecular weight (MW), molecular weight distribution (MWD), and long-chain branching by high-temperature size exclusion chromatography (SEC) and SEC coupled with a multiangle laser light-scattering (MALLS) detector. It has been shown that the differences in MW and MWD that remain unnoticed by conventional SEC are detected by SEC/MALLS. Wide MWD and a low weight-average MW of the resin has been found to favor film-sealing strength. © 1994 John Wiley & Sons, Inc.