A note on permeability simulation of multifilament woven fabrics

A conventional approach for modeling permeability of multifilament fabrics is to consider their warps and wefts to be individual thick filament made of homogeneous porous media and solve the flow equations for such monofilament fabrics. In this work, for the first time, the full 3-D geometry of an idealized multifilament woven fabric, wherein the filaments are packed in hexagonal arrangement, is generated to compute its permeability and compare with the homogeneous anisotropic lumped model of Gebart (1992. Permeability of unidirectional reinforcements for RTM. Journal of Composite Materials 26(8), 1100-1133). While a relatively good agreement is obtained, our results indicate that Gebart's model slightly underestimate the permeability of multifilament fabrics even at high yarn's solid volume fractions.     

高速纺丝拉伸一步法(FDY法)生产细旦异形涤纶长丝的工艺技术及其仿真丝效果

本文论述了采用高速纺丝拉伸一步法(FDY法)生产细旦异形涤纶长丝的工艺特点和关键技术,并对其织物的光泽度以及弯曲、压缩,摩擦和抗起球起毛等性能进行分析评价。结果表明,细旦异形涤纶FDY织物能满足仿真风格的要求,具有良好的仿真丝效果和宽广的发展前景。     

New method of determining contact angle between monofilament and liquid

This paper describes a method to obtain contact angle by observing the shape of a liquid drop attached to a monofilament. The relations between contact angle and the dimensions of drops are theoretically obtained. Thus, it is possible to calculate the contact angle if drop shape is measured. Through use of this method, the contact angles of epoxy resin on various kinds of monofilaments were measured. It was found that this method has practical utility for measurement of the contact angle between liquid and monofilament.     

Novel Process for the Preparation of Fiber-Reinforced Ceramic-Matrix Composites

A procedure for the reproducible production of monofilament/powder composites has been developed. The process consists of making a slurry of the powder in a solventless ultraviolet-curing resin, and coating the fiber with this slurry in a continuous process whereby the coating solidifies immediately after leaving the coater. The fast curing prevents the breakup of coating into globules, which usually occurs with monofilaments. This technique can be applied to any composite using continuous filaments and matrices available in the form of particulate precursors. The application of the technique for preparing a silicon carbide monofilament/glass composite is demonstrated.     

How is it possible to produce highly oriented yarns of electrospun fibers?

Electrospinning of polymeric nanofibers onto a stationary grounded target produces a nonwoven mat-like material. Using a rapidly rotating grounded target in the form of a wheel or belt, it is possible to produce significant lengths of highly oriented yarns of electrospun filaments. This observation is difficult to explain when one compares the calculated velocity of an electrospun monofilament with the surface velocity of the grounded target. This study was undertaken to attempt to answer this question. Are the calculated fiber velocities correct? Is the collected electrospun filament really a monofilament? Does the electrospun filament split into multiple filaments or do fibers loop in an oriented manner on the collection wheel? POLYM. ENG. SCI., 47:1530–1535, 2007. © 2007 Society of Plastics Engineers     

PTT抗折皱织物的开发及服用性能测试

将聚对苯二甲酸丙二酯(PTT)长丝分别与PTT长丝、聚酯(PET)长丝、棉纱以交织的方法开发了PTT抗折皱平纹织物,对产品的服用舒适性、织物风格、抗折皱效果进行了测试、分析与评价。测试结果表明:PTT抗折皱织物具有较好的弹性,在拉伸变形时的回复能力较好,同时在弯曲和剪切变形时也具有相当高的回复能力,即织物拥有较好的抗折皱功能,其各项服用性能也符合开发PTT抗折皱机织类产品的标准。     

Effect of dryer fabric structure on the performance of contact paper drying

Existing measurement techniques have prevented extensive investigations of the effect of dryer fabric structure on contact drying of paper. Using a novel optical measurement method, the moisture content (MC) of paper can be accurately quantified at high spatial and temporal resolution while it is sandwiched between the heater surface and the dryer fabric. To study the paper drying process, an experimental setup is designed to simulate realistic conditions of a typical paper dryer while providing optical access for the measurement system. Ten commercially available fabrics manufactured by weaving synthetic filaments are used in the investigations. The 3D structure of the fabrics is characterized using optical coherence tomography (OCT). The fabrics are used in the experiments to investigate the effects of the filament structure and paper/fabric contact on the drying process. It is shown the fabric structure affects the drying rate and the drying time. Fabrics that have a relatively large drying rate at high paper MC may have a relatively small drying rate at low levels of MC. The contact area and 3D arrangement of the filaments have the greatest impact on the drying process. Adjacent filaments result in larger blocked regions of the paper surface, which reduces the drying rate. The spatial distribution of moisture as a function of time reveals that frequent rewetted spots appear during the drying. These rewetting spots are caused by reabsorption of water condensed on the fabric filaments.     

涤纶细旦变形仿真丝加工技术

本文对仿真丝织物用的涤纶细旦变形丝的POY和DTY加工技术进行了探讨。通过理论分析和实验证明,加工最终总纤度55dtex以下,单丝纤度1.11～1.65dteX的DTY,采用现有设备和适当选择工艺条件是可行的。     

细旦丙纶长丝针织服用产品的开发研究

研究了用国产ＰＰ原料制得的细旦丙纶针织物的开发应用，并对各类针织物的服用舒适性进行了评价。研究表明，棉盖丙双层和多层织物的服用舒适性优于涤盖棉织物和纯棉织物；细巨丙纶变形丝与棉交织成单层或多层针织物是ＰＰ纤维服用的主要开发方向。     

异形截面聚酯纤维显深色效果试验及其评价

主要研究了异形截面聚酯纤维织物的显深色性以及异形度对显深黑色性的影响。采用K/S值、L*值和Integ值3个指标表征织物的显深黑色效果,结果表明:异形截面聚酯纤维织物具有较好的显深黑色效果;同时,聚酯纤维截面异形度对纤维织物的显深色效果影响颇大,高截面异形度可以提高织物的显深黑色效果。定性分析了所设计的异形截面纤维的反光特性,解释了其显深色性的原因,对设计纤维的色光特性有参考价值。     

Comparative Analysis of Methods of Measuring Fibre and Filament Diameters

A comparative analysis of methods of determination of polycaproamide, poly(ethylene terephthalate), and polypropylene fibre and (filament) and monofilament diameters is reported. The following methods are examined: calculation with the linear density and density of the fibre; microscopic; shadow and projection on a screen; diffraction; micrometric; close winding of monofilaments and measurement of the length of the wound section with calculation of the number of filaments. Each method of measuring the fibre (filament) and monofilament diameters applies to a certain fibre size and has its own limitations; the use of methods outside of the established applicability limits will produce significant systematic errors. The values of the errors in measuring the fibre diameter by the different methods are estimated.     

聚乙烯瞬时释压纺丝法无纺布制备及其性能研究

以不同熔体流动速率的高密度聚乙烯为原料,二氟一氯甲烷和四氟二氯乙烷混合物为溶剂,通过瞬时释压纺丝法制备加工成无纺布,制备得到聚乙烯无纺布材料.通过扫描电子显微镜、动态接触角测量仪、自动比表面积和孔径分析测试仪、差示扫描量热仪、热失重分析仪、电子强度仪和数字透气度仪对所制备的无纺布的形貌、接触角、比表面积、断裂强度和断裂...     

Tensile and elastic behavior of tencel continuous filaments

Tencel is a regenerated cellulose fiber produced using an environmentally‐responsible dry‐jet wet‐spinning process, which contributes to its excellent mechanical properties. In this study, the tensile properties of Tencel continuous filaments are characterized and the effect of twist on mechanical properties, including breaking load and extension, are considered. Peak strength was obtained in Tencel filaments of 140 t m^?1. The elastic behavior of Tencel monofilament was observed by assessing the recovery from strain‐induced energy and the elastic recovery was found to be low. Along with time dependency, Tencel has the ability to stabilize its deformed state by forming new crosslinks, and this influences the elastic behavior. In simple extension cycles, the same low elasticity was observed. Cumulative extension cycles were also performed to characterize the behavior of filaments subjected to repeated strain and to determine the resultant hysteresis effects. Permanent elongation was observed at 2% imposed strain, which suggests that the filament has low extensibility. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1496–1503, 2006     

Development of Structure and Properties during Spunbonding of Metallocene Catalyzed Polypropylene

Spunbonding is one of the most widely used processing techniques to convert polymers into nonwoven fabrics. metallocene-catalyzed polypropylene is becoming more and more important. A study was carried out to understand the development of structure and properties of a metallocene-catalyzed isotactic polypropylene during spunbonding. This research was conducted using the Reicofil spunbond line at the University of Tennessee, Knoxville. The filaments at three different throughput rates were studied for tensile properties and for structural features by birefringence, X-ray diffraction, and thermal measurements. The fabrics produced at different process conditions were tested for various mechanical properties. The failure mechanism of the fabrics at different bonding temperatures was studied using the scanning electron microscope. The results are compared with a conventional polypropylene processed under similar conditions. The results showed that the mPP produced fabrics with better strength and elongation at comparable processing conditions. Also, failure mechanisms were found to be different for the fabrics produced from the two polymers, which are due to differences in the produced structures.     

Effect of linear density of elementary viscose filaments on the properties of complex yarns and fabrics made from them

Conclusions A decrease in the linear density of the elementary filaments essentially does not affect the physicomechanical properties of complex viscose yarns. However, with decrease in the linear density of the elementary filaments, important changes are observed in properties which determine their wear resistance; durability against repeated double bends is increased, but the resistance to abrasion is reduced.The use of complex viscose yarns having a reduced elementary filament linear density aids in the preparation of fabrics with greater covering power, which creates conditions for reducing the volume of material.Translated from Khimicheskie Volokna, No. 5, pp. 32–34, September–October, 1984     

Acoustic emission in investigation of the characteristics of fracture of complex viscose fibres and textile materials based on them

Acoustic emission methods were used to study deformation and fracture of viscose fibres, fabrics, and tricots. The effect of twisting and the frictional effect of the filaments in the complex fibre on the character of their fracture and acoustic spectrogram was demonstrated. The study of fracture of fabrics (in stretching and tearing) and tricots based on the character of the acoustic spectrograms revealed a significant difference in them determined by the characteristics of stretching and failure of individual fibres. The method of recording acoustic emission signals in deformation and failure of fibres, fabrics, and tricots combined with the strain diagram before break provides new information on the process of their fracture and the existence of defective structural elements — correspondingly filaments in the complex fibre or complex fibres in textile materials. Translated from Khimicheskie Volokna, No. 6, pp. 43–46, November–December, 1997     

A new mthod for determining oven aging stability of polypropylene monofilament

A precise method of oven-aging polypropylene monofilament has been developed employing a tubular oven in which temperature and air velocity within each tube are accurately controlled. The monofilaments are suspended within each tube by means of specially construced heat stabilized polypropylene holders (no metal contact), which facilitate handling and record keeping. Each filament is held in an attitude perpendicular to the air flow. Failures almost invariably occur in the middle of each filament. Oxidative stabilities of filaments aged in the tubular oven at a constant temperature and air flow were found to be dependent upon (a) distance of the filaments from the incoming air side and (b) whether the exposure was continuous or intermittent. If these parameters are kept constant, relatively good precision can be obtained. The 95% confidence level for a single observed value was found to be on the order of ±10% of the average oven stability within the whole oven and ±7% within a single tube. Precisions of about ±2.5% can be obtained by employing averages of 10 replicates exposed on the same specimen holder.     

Correlation Between Wettability and Cleanability of Polyester Fabrics Modified by a Soil Release Polymer and Their Topographic Structure

In this study, it was found that images scanned by a non-contact optical instrument for topographic characterisation based on the principle of chromatic aberration give sufficient information to know the exact location of soil release polymer (SRP) deposition over fabrics. Through the comparison of reflected luminous intensity histograms, it is possible to determine mathematically the zones of fabric on which the SRP molecules settle. For this study, two plain weave fabrics were manufactured in a needle band weave machine from polyethylene terephthalate (PET) filament yarns made from two different cross-sectional shaped filaments, circular and cruciform. Both the fabrics were desized and heat-set. Topographic characteristics of polyester fabrics were determined by the optical instrument before and after their impregnation with a SRP. Differences between soiling behaviour, cleanability and wettability of the fabrics before and after impregnation were revealed and discussed. It was verified that micro-topography of textiles determines the amount of SRP and its location. The results obtained correlate well with the wetting behaviour and cleanability of the fabrics studied.     

Structure and property characterization of spunbonded filaments and webs using thermal analysis

The thermal history and inherent properties of the filaments are of utmost importance in spunbonded webs. A good understanding of the structure and properties development of individual filaments is helpful in comprehending the whole process better. Polypropylene homopolymer and a copolymer were processed using the Reicofi® spunbonding line at the Textiles and Nonwovens Development Center of the University of Tennessee, Knoxville. The properties of the filament samples taken before thermal bonding were determined through a variety of thermal analyses, such as differential scanning calorimetry, thermomechanical analysis, thermal deformation analysis, and dynamic thermal analysis, as well as mechanical properties. The performance properties of the bonded nonwoven fabrics from these filaments were evaluated, and the structure and properties of the fibers were compared with those of the bonded fabrics. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 421–434, 1998     

二醋酯长丝及其变形丝和织物的性能特点

在烟用二醋酸纤维丝束小试设备上,采用不同纺丝工艺参数,纺制了5个二醋酯长丝样品,对二醋酯长丝及其空气变形丝和织物的性能进行测试分析。发现:二醋酯长丝强度偏低,变形、织造等后加工技术要求较高;二醋酯长丝空变纱在小负荷下的卷曲稳定性较好,而在重负荷下的丝圈稳定性不理想;二醋酯长丝织物的拉伸强力和撕裂强力均较低,耐磨性能较差,但色牢度远远优于粘胶长丝织物。