Analysis of sliver thickness variation from process perturbations in roller drafting

In processing fiber bundles in staple yarn manufacturing, the bundles are doubled and attenuated to an appropriate thickness via drafting. The process conditions are optimized with respect to the fiber and bundle properties. Otherwise, the output fiber bundle becomes non-uniform in its linear density. This research deals with finding the changes in linear density of the output bundle when perturbations are applied to the drafting conditions. Perturbations with specific autocorrelation functions were generated by the random phase spectral method. Along with the stochastically generated test signals, the transient linear density profiles of the fiber bundle in the drafting zone were simulated by using a mathematical model describing the dynamics of the roller drafting, and thus, the linear density of the output bundle could be predicted. Our results showed that the disturbances in input linear density affected the transient profiles of the linear density of the fiber bundle inside the draft zone. It was also shown that the output irregularities were strongly influenced by the perturbation in the input bundle thickness. During drafting, the perturbations in the draft ratio perturbations were not shown to have influenced the transient profiles of the bundle linear density inside the draft zone. However, the variation in the linear density appeared again in the output bundle following exactly the changes in the daft ratio. Disturbances in the process speed, however, were not shown to have influenced the output variation.     

Fibre breakage during drafting on ring frame

Fibres are subjected to forces while undergoing drafting in any drafting zone. Various factors, such as fibre bulk, roller setting, roller pressure, draft, fibre length, fineness and friction between fibres, affect the magnitude of this force. It is usually considered that the drafting force in the ring frame is too low to have any consequence as far as fibre breakage is concerned. The present investigation, however, shows a substantial increase in short fibre percentage and reduction in upper quartile length, giving a clear evidence of fibre breakage during drafting process.     

聚丙烯腈纳米纤维束的预氧化过程

为给高性能碳纳米纤维的预氧化制备过程提供数据参考,通过多针静电纺的方法制备具有高取向的聚丙烯腈（PAN）纳米纤维束。通过研究纳米纤维结构,探讨了预氧化温度及时间对纳米纤维的结构和性能的影响。结果表明：整个纺丝过程可以持续5h以上,纳米纤维的直径在218nm左右,同时其沿纤维束轴向的取向度达到76.52%。纳米纤维的横截面成典型的外层致密内层松软的皮芯结构。随预氧化温度或者时间的增加,脱氢、环化以及氧化反应程度提高;随温度的提高,纳米纤维的结晶度先增加后减小,其最大结晶度达到54.57%。红外光谱、X射线衍射曲线以及芳构化指数表明：预氧化温度在260℃到280℃、时间1~2h之间较为合适。     

Weathering,fibre strength and colour properties of processed white cashmere

Weathering refers to the degradation of wool fibres that occur during growth from exposure of the fleece to sunlight, water and air. Weathering damage to Merino wool reduces quantities of fibre that are harvested, reduces length in both raw and processed wools, reduces spinning performance and dyeing outcomes. This work aimed to aimed to quantify if and to what extent weathering occurred in 38 lots of commercial dehaired white cashmere and cashmere top sourced from traditional and new origins of production and the extent of any association between weathering and tensile strength properties of the dehaired cashmere and cashmere top. The cashmere was tested for physical properties, bundle tenacity and extension, tristimulus values brightness (Y) and yellowness (Y-Z) and reflectance. Dye uptake was used as an index of weathering. Linear models, relating to weathering, bundle tenacity and Y-Z were fitted to origin and other objective measurements. Mean attributes (range) were: mean fibre diameter, 17.0 μm (13.5–21.3?μm); bundle tenacity of tops, 10.3 cN/tex (8.3–12.9?cN/tex), for dehaired fibre, 10.1 cN/tex (9.1–11.4 cN/tex). Stain uptake varied from 0.92 to 6.34 mg/g fibre indicating a six-fold variation in the extent of weathering. Both the extent of weathering and the bundle tenacity of commercial lots of cashmere were affected by the origin of the cashmere. Increased weathering reduced bundle tenacity, bundle extension, increased the yellowness and reduced reflectance of white cashmere. Bundle tenacity of cashmere declined as fibre diameter variability increased from 20 to 22.5%. For the samples tested, the cashmere from China, Mongolia, Afghanistan and Iran showed more weathering than cashmere from Australia, New Zealand and the USA. The differences in the extent of weathering and of bundle tenacity between cashmere from different origins were of commercial significance.     

Research on fiber distribution in front draft zone of super high draft ring spinning based on cut-middles method

A super draft ring spinning machine was designed to spin high-count cotton yarns. It was equipped with four-line draft system (FLDS) and four aprons. For yarns spun on FLDS, it often occurs that yarn unevenness increased compared with three-line draft system (TLDS). In the paper, by cut-middles method, the fiber distribution in front draft zone of FLDS draft system was studied, and corresponding yarn qualities were analyzed. First, comparison analysis of yarn quality between FLDS and TLDS was presented. Cotton yarns of 9.7 and 7.3 tex were spun by TLDS and FLDS ring spinning machine, respectively. The results shows that for 9.7 tex cotton yarn, slower fibers in yarns spun on FLDS are more than that in yarns spun on TLDS. For FLDS, the friction field at the back of front draft zone is stronger, which improves yarn evenness. However, for 7.3 tex cotton yarn, accelerated point of fibers on FLDS is nearer to nipper bite of front roller than that on TLDS. Thus, evenness of yarns spun on FLDS is better. Then, 4.9 tex cotton yarn was taken as an example, and they were spun by four kinds of draft distributions on FLDS. The results indicate that for 4.9 tex cotton yarns spun by 64.1 × 1.60 × 1.15, slower fibers at the back of front draft zone are mostly found. And accelerated point of fibers is nearest to nipper bite of front roller. Therefore, 4.9 tex cotton yarns spun by 64.1 × 1.60 × 1.15 have best yarn evenness.     

Effect of bipolar configuration on morphology of electrospun webs

The diameter of the nanofiber and area of deposition are the two most important properties that define the morphology of nanofiber webs. This study aims at exploring the effect of electrospinning parameters on the area of deposition of nanofibers. The area of deposition of the nanofiber web was found to be dependent on the process parameters such as needle to collector distance, collector voltage, and flow rate as well. Based on the observations, a simple model has been proposed to explain the behavior of electrospinning in a bipolar configuration.     

棉纺牵伸系统的技术进步(下)

阐述了环锭棉纺牵伸系统的牵伸形式、加压机构、牵伸元件及牵伸传动的技术发展状况.牵伸形式以有效控制纤维、减少浮游区长度、稳定牵伸为目的,并条由简单直线牵伸发展到附加压力棒曲线牵伸,粗纱由曲线牵伸、三罗拉双短胶圈牵伸发展到四罗拉双短胶圈牵伸,细纱现采用三罗拉长短胶圈牵伸、三罗拉双短胶圈牵伸及V形牵伸.牵伸加压机构由摇架加压向气动加压发展.罗拉、胶辊、胶圈等牵伸元件的纺纱性能也得到改善,适应新型牵伸形式和工艺的要求.牵伸传动向着传动合理、平稳、轻快及维护方便发展,出现电子牵伸系统.     

棉纺牵伸系统的技术进步(上)

阐述了环锭棉纺牵伸系统的牵伸形式、加压机构、牵伸元件及牵伸传动的发展状况.牵伸形式以有效控制纤维、减少浮游区长度、稳定牵伸为目的,并条由简单直线牵伸发展到附加压力棒曲线牵伸,粗纱由曲线牵伸、三罗拉双短胶圈牵伸发展到四罗拉双短胶圈牵伸,细纱采用三罗拉长短胶圈牵伸、三罗拉双短胶圈牵伸及V形牵伸.牵伸加压机构由摇架加压向气动加压发展.罗拉、胶辊、胶圈等牵伸元件的纺纱性能也得到改善,适应新型牵伸形式和工艺的要求.牵伸传动向着传动合理、平稳、轻快及维护方便发展,出现电子牵伸系统.     

炭化温度对静电纺碳纳米纤维结构及导电性能的影响

用静电纺的方法制得聚丙烯腈（PAN）纳米纤维,在250℃对PAN纳米纤维毡进行预氧化,然后在不同温度下进行炭化得到碳纳米纤维。利用X光衍射和拉曼光谱分析碳纳米纤维的内部结构,用四探针法测碳纳米纤维毡的导电率。研究表明：随着炭化温度的提高,微晶尺寸（Lc）和石墨摩尔分数（La）逐渐增大,碳纳米纤维毡的导电性也逐渐增大。石墨摩尔分数（La）与电导率呈很好的线性关系。     

细纱气动V形牵伸纺制CJ 3.6 tex纱的工艺配置

为了在气动V形牵伸细纱机上顺利生产CJ 3.6 tex纱,保证成纱质量,对粗纱定量、后区牵伸倍数、罗拉隔距、胶辊加压及前胶辊前冲量等工艺参数进行了优化试验.结果表明,采用较大的粗纱定量,通过合理配置细纱牵伸工艺,采用紧隔距、适当加压、增大前胶辊前冲量及配用软弹胶辊,可使CJ 3.6 tex纱条干CV控制在18.2%以下.     

Fabrication of poly(vinylidenefluoride‐co‐hexafluoropropylene) nanofiber yarns by conjugate electrospinning

Conventional electrospinning is an efficient method to fabricate polymer nanofibers which are usually collected as non‐woven mats. Recently, in order to fabricate a nanofiber yarn, conjugate electrospinning has been developed using coupled spinnerets applied with two high electrical voltages of opposite polarities In this paper, poly(vinylidenefluoride‐co‐hexafluoropropylene) (PVDF‐HFP) nanofiber yarns are prepared by conjugate electrospinning. The effects of the concentration and delivery rate of polymer solution and the distance between coupled spinnerets on the structure of PVDF‐HFP nanofiber yarns are investigated. The structure of the nanofiber yarns is observed by scanning electron microscopy (SEM). The mechanical properties of the nanofiber yarns are measured by electronic fiber strength tester. The results show that the PVDF‐HFP nanofiber yarn consists of a large number of nanofibers aligned well along the longitudinal axis of the yarn, and the nanofibers have diameters ranging from several hundred nanometers to a few microns. The diameter of nanofibers in yarns increases with the increase in the polymer concentration, which significantly affects the structure of nanofiber yarns. The PVDF‐HFP nanofiber yarn electrospun from the polymer solution with a concentration of 45% has the highest tensile strength of 0.25 cN/dtex and an elongation of 180.13%.     

并条机后区牵伸倍数的模拟设计

为快速确定不同条子并条工艺的后区牵伸倍数,采用拉伸的方法模拟并条机后牵伸区的牵伸,进行后区牵伸倍数的设计,并以棉、涤纶和粘胶为原料进行实验。结果表明,拉伸曲线和牵伸力牵伸倍数曲线有很大的相似性。由拉伸曲线中最大拉伸力所对应的伸长转化而来的牵伸倍数和并条牵伸力测试的实验数据拟合的三次方程得出的最大牵伸力所对应的牵伸倍数非常接近,此牵伸倍数下牵伸力不匀和并条牵伸后输出须条的条干不匀都小,故根据拉伸曲线的结果来设计并条机的后区牵伸倍数是可行的,为并条机后区牵伸倍数的快速离线设计提供了参考。     

不同引纱方法对云纹纱成纱外观及质量的影响

为改善云纹纱外观及提高其成纱质量,探究了3种不同引纱方法对云纹纱成纱外观及质量的影响。在牵伸细纱机上分别纺制29.2、14.6、9.7、7.3 和5.8 tex的云纹纱,对每种线密度的云纹纱,保证其他工艺参数一致,通过改变饰纱的喂入方式纺制而得,即饰纱分别从细纱机后罗拉、中后罗拉、中前罗拉喂入。通过观察成纱外观,并对其强伸性能、条干、毛羽指标进行测试和对比分析。结果表明：不同的引纱方法会产生不同的成纱外观,较其他2种方式,饰纱从中后罗拉喂入时,所纺成的云纹纱成纱3 mm内有益毛羽较多,3 mm以上有害毛羽较少,强力及成纱品质指数均高于其他2 种方式,成纱质量较优,且成纱包缠结构较为紧密,立体感更强。     

基于切断称重法的细纱机牵伸区内纤维变速点分布研究

为探究细纱机牵伸区内纤维的变速点分布,以纺制29.2、22.4、18.2 tex棉纱为例,采用CCZ-X三罗拉双区牵伸细纱机进行纺纱实验,采用等长切断称重法对牵伸区内须条的质量分布进行测试,以其质量变化分布表征变速点分布,得到质量变化折线图,对比分析纤维在牵伸区内变速集中的位置,从而探究牵伸区内纤维变速规律。结果表明:等长切断称重法可得到牵伸区内纤维变速点分布的位置;在此次牵伸区内纤维变速点分布实验中,须条中的纤维在距前罗拉钳口线20 mm处变速相对集中,且在一定范围内随着前区牵伸倍数的增大,纤维变速点的位置变得不稳定、分散,且远离前罗拉前钳口。     

Study on drafting force and sliver irregularity on drawing frame

A new device was designed and constructed on drafting frame to measure the dynamic force during roller drafting. The effects of draft ratio, number of input slivers, and roller velocity on drafting force, coefficient of variation (CV) of drafting force, and the irregularity of output slivers were all analyzed. Rayon and cotton slivers were used in the experiments, respectively, the results showed that the number of input slivers had a significant linear relation with the mean drafting force; the draft ratio had an obvious effect on mean drafting force and CV of drafting force; the lower CV of drafting force promised better output sliver evenness.     

立达环锭纺纱系统的应用实践

探讨立达环锭纺纱系统的应用技术。针对立达环锭纺纱系统设备的性能特点,开清棉工序优选各部隔距及速度,降低了筵棉棉结的增长率及短绒;梳棉工序采取优化各部隔距、适当降低刺辊速度、增大锡林刺辊的线速比等措施,加快纤维转移,减少纤维损伤;并条工艺配置中重点提高纤维的伸直度,合理设计牵伸分配和罗拉隔距;粗纱工序重点掌握好纺纱张力,合理配置工艺参数,改善粗纱内在质量;细纱采用"两大两小"针织纱工艺,并对前胶辊与中铁辊的中心距进行了优化,最终使所生产的C 14.6 tex纱的主要质量指标达到了Uster 2007公报5%水平。     

Evaluation and Impact Factors of the Mechanical Properties of Phloem Bundle Fibers Obtained from Kenaf Germplasm

The mechanical properties of kenaf phloem bundle fibers are valuable for reinforced composites or boards, more so than similar materials also used in textile or papermaking applications. 55 kenaf germplasm studied here showed an average phloem bundle fiber tensile strength of 643.6 MPa and an average elastic modulus of 23.3 GPa after chemical retting treatment. 19 of these kenaf germplasm had fiber tensile strengths >700 MPa, which can be attributed to intensive breeding programs. The fiber tensile strength and elastic modulus of kenaf germplasm had a significant positive correlation, but there was no such correlation between a fiber’s mechanical properties and its diameter or agronomic characteristics. Among 56 hybridized combination F₁ generations, the highest tensile strength was 928.3 MPa from a combination of No.30 of Xinan Wuchi × Guatemala 4. Therefore, breeding and screening are both useful for improving the mechanical properties of kenaf phloem bundle fibers. However, the effects of the used bundle fiber preparation method or cultivation year on the fiber’s mechanical properties were more pronounced than those of the type of kenaf germplasm or breeding operation used. The mechanical properties of kenaf phloem bundle fibers treated by chemical retting were superior to those treated using natural retting.     

提高CJ11.7tex纱条干均匀度的工艺配置

在生产CJ11.7tex纱的基础上分析了纱线条干均匀度的影响因素。为了提高细纱条干均匀度,对影响成纱条干均匀度的前区工艺参数、后区牵伸工艺进行了工艺配置。实验结果证明,采用较小的粗纱定量、细纱捻系数、前中罗拉隔距、较小的钳口隔距、较小的后区牵伸倍数,以及较大的前胶辊压力,采用较大前胶辊直径,适当增加粗纱捻系数等措施,可以提高成纱条干CV值。     

细纱机前后压力棒对涤棉混纺纱线条干均匀度的影响

细纱条干不匀主要来自细纱牵伸区,在细纱牵伸区施加压力棒与否的条件下,通过变化隔距块、后牵伸倍数、后区罗拉中心距等进行纺纱试验对比;分析了压力棒对纱线条干均匀度的影响,得到了较理想的工艺配置。     

细纱牵伸器材及工艺配置对成纱细节的影响

简要分析了成纱细节产生的原因,就细纱上销、胶圈、胶辊与集合器等关键牵伸器材以及加压牵伸形式、粗纱捻系数与细纱后区牵伸倍数等工艺配置对成纱细节的影响进行了试验分析.结果表明,将宽面钳口尼龙上销与新型下销进行配置、采用适当的胶圈张力、较小的钳口隔距、使用集合器、加大粗纱捻系数、减小细纱后区牵伸倍数并采用适宜的胶辊表面粗糙度,对控制成纱细节有利.