Anisotropy in wrinkle properties of woven fabric

In this paper, the wrinkle resistance of plain fabrics woven with weft yarn in S‐ and Z‐twist directions and at various twist levels in different test directions has been measured and then analysed. Results show that the wrinkle resistance increases as the weft yarn twist increases. The wrinkle properties of the fabric show that the direction of test has an obvious effect on the results and the wrinkle resistance depends on the method of folding such as face‐to‐face and back‐to‐back methods. The experimental results showed that there is anisotropy in wrinkle properties of the fabric made of yarns with different twist directions. When the fabric is folded face‐to‐face and the weft twist direction is S, the wrinkle resistance of fabric in various test directions shows a convex curvature, whereas when the same fabric is folded in a back‐to‐back manner then results show a linear curvature. This means that the wrinkle resistance of a fabric differs in various directions and in the method of folding (back‐to‐back or face‐to‐face) and shows an anisotropic wrinkle resistance nature.     

亚麻纱线前处理工艺探讨

研究了亚麻酶精练和碱氧一浴前处理工艺因素对前处理效果的影响.用单因素试验优化各工艺条件,测试各工艺的整理效果.结果表明,酶精练优化工艺条件为:亚麻脱胶酶Superzyme B-YM 3 g/L,渗透剂JFC 2 g/L,pH=7,浴比1∶20,温度65℃,时间40min;碱氧一浴法前处理优化工艺条件为:30%双氧水12 g/L,烧碱10 g/L,精练剂2 g/L,尿素3 g/L,浴比1∶20,温度100℃,时间60 min.酶精练法特点:工艺流程短、反应条件温和、污染小以及节约能源.碱氧一浴法特点:前处理流程短,省时节能;强碱作用下纤维的损伤大,试验设备要求较高.2种工艺相比,酶精练处理的产品木质素降低量大于果胶质降低量,且在失重率、毛效、纤维强力、白度上均优于碱氧一浴法优化工艺.酶精练处理后,亚麻纱线白度为73.8,毛效为12.5 cm/30 min,单纤维强力为23.69 cN/tex,纱线中果胶质含量为1.85%,木质素含量为1.22%.     

Study of yarn twist angle using numerical simulation

The twist angle is an important parameter of the yarn which determines the degree and shape of the filament’s deformation produced along their length. So, in this paper, a 3D numerical modelling of filaments assemblies has been developed. The twist behaviour of the multifilament was simulated using ABAQUS finite element package by modelling the yarns as 3D continuum elements. The distribution of filament helix angle according to the radial position of the yarn is evaluated. Results show that the helix angle draws near zero in the yarn axis but does not fall to zero in presence of migration, and becomes bigger as the filaments are positioned on the surface. Moreover, the twist angle is calculated for different twist level which proves that twist angle is highly affected by torsion level. The target of the research was to establish a relationship between twist angle, twist value and yarn linear density for a series of models varying in the filament radius, twist value and filament number.     

Effect of elastane linear density and draft ratio on the physical and mechanical properties of core-spun cotton yarns

The aim of this study was to investigate the effect of elastane linear density and draft ratio on the physical and mechanical properties of core-spun yarns. Twenty yarn samples were prepared on industrial scale in a spinning mill with two different yarn linear densities, each with different two elastane deniers and five draft ratios. It was found that core-spun yarn’s tenacity, elongation and hairiness are affected not only by the overall yarn linear density but also by the elastane linear density and the draft ratio. However, the effect of elastane linear density and draft ratio was not found to be statistically significant on the yarn mass variations and total imperfections, which are only affected by the overall yarn liner density. A statistically significant interaction for yarn elongation at break was found between the yarn liner density and the elastane linear density concluding that elastane linear density used in the core must be compatible with the overall yarn liner density for attaining the best yarn elongation.     

Entropy and bulk of yarns

As a function of state, the entropy of yarns characterizes the possible manners in which fiber or filament structure change in different directions. It affects every parameter of the structure and properties of yarns. Defined as the ratio of the volume of inner space to the whole body, the bulk of yarns could be calculated when the factors, such as linear density and diameter of yarns, were measured. Theoretical derivations showed that an exponential relationship exists between entropy and bulk of yarns. Further experiments proved that compared with classical yarns, textured yarns possessed higher bulk and entropy. In case of bundle filaments, the bulk and relative entropy were far lower than that of other linear fiber assemblies, approximately within a narrow scope of around 24% of bulk and 0.27 of relative entropy.     

The effect of air-jet nozzle structural parameters on new cotton rotor-jet spun yarn properties

In this paper, a hybrid spinning system the so-called “rotor-jet spinning method” which utilizes the air-jet nozzle in rotor spinning process is presented. Thus, air-jet nozzles with different structures of 90S, 90Z, 60Z, and 30Z (the values of 90, 60, and 30 are orifice angles and S and Z are air rotational directions) were designed and constructed and then mounted between the take-up nozzle position and doffing tube in a rotor spinning machine. The air-jet pressure was changed at 0.2, 0.5, 0.8, 1, 1.2 and 1.5 bar values. The physical properties of cotton rotor-jet spun yarns with yarn count 20 Tex and nominal yarn twist of 938 TPM were investigated and compared with that of normal rotor-spun yarn. The experimental results indicated that by utilizing a 90Z air-jet nozzle at 1 bar air pressure, the highest yarn tensile strength, abrasion resistance, and twist, and lowest elongation are obtained compared with those of normal rotor as well as rotor-jet spun yarns with 30Z, 60Z, and 90S air-jet nozzle types. However, the rotor-jet spun yarn irregularity produced with 90Z air-jet nozzle is almost identical to normal rotor-spun yarn. It is also shown that the rotor-jet spun yarn hairiness properties which were produced with a 90Z air-jet nozzle at air pressure values of 0.2, 0.5 and 1 bar is almost similar to normal rotor-spun yarn while the lowest yarn hairiness is achieved at air pressure value of 0.8 bar. The experimental results of this paper suggest that the newly developed rotor-jet spun yarn is superior to normal rotor-spun yarn from the point of view of yarn tensile, abrasion resistance, twist, and partially hairiness properties.

     

Spinning preparation parameters selection for rotor spun knitted fabric using VIKOR method of multicriteria decision-making

Selection of spinning preparation parameters which affects properties of the final yarn and subsequent process is a multicriteria decision-making problem. Different statistical methods and multicriteria approaches have been used to solve such kind of problems. This paper presents a new multicriteria decision-making technique to select the suitable drawing frame parameters for 30Ne rotor spun yarn intended to be used for weft knitting process. Three important variables in drawing frame including distance between back and middle rolls, delivery speed, and break draft were considered. Their performances were evaluated on the basis of seven quality parameters of the 48 rotor spun yarns using VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method. The final ranking of the parameters was elicited in accordance with this procedure. Consequently, the stability of the proposed final ranking was verified after sensitivity analysis.     

The effect of blend ratios of unrelaxed and relaxed acrylic fibres on physical properties of high-bulk worsted yarns

Abstract

High-bulk acrylic yarns which contract and increase in bulk during the heat relaxation process are produced by blending two types of fibres with different shrinking power in the spinning process. In this paper, high-bulk acrylic yarns (steamed and dyed) with different shrinkable fibre blending ratios were produced. Experimental results show that by increasing the shrinkable fibre blending ratio up to 40%, the specific volume and shrinkage of both dyed and high-bulk acrylic yarns are steadily increased while their tensile strengths are decreased. Further increasing the shrinkable fibre blending ratio causes the specific volume and tensile strength properties to decreased and increased respectively. However, the yarn shrinkage does not change significantly. It is also found that both dyed and high-bulk acrylic yarns have the highest elongation at 20% shrinkable fibre blending ratio. In general, the specific volume and tensile strength of high-bulk acrylic yarns are more than those of dyed acrylic yarns but their shrinkage and elongation values are similar.     

A study of the drafting force in roller drafting and its influence on sliver irregularity

Drafting force is the direct and intuitive factor resulting in fiber motion in a drafting zone. Utilizing data collected from an ITT Draftometer, this paper discusses the effect of draft ratio and ratch in both the break and the main draft zones on drafting force and the coefficient of variation (CV) of drafting force, and how these in turn affect sliver and yarn irregularity. It is shown that: the draft settings in the break draft zone have a significant effect on the drafting force; the break draft ratio shows distinct relationship with sliver irregularity; the ratch in the main drafting zone has considerable influence on drafting force; and in the experiments reported the drafting force does not directly relate to final yarn irregularity.     

Objective yarn bulk measurement through image analysis

A novel objective yarn bulk measurement method has been developed through image analysis technique. Two orthogonal images are taken from the same part of a yarn and then transformed into gray scale. Each gray scale image is further processed separately by extracting the yarn image from background with the help of intensity histogram using adaptive threshold. This gives rise to a binary image which is used as input for the second part of the algorithm measuring yarn volume. The processing on the input image starts with omitting the long rare loops, considered as noise, by morphological operations. This is followed by measuring the width of the two orthogonal images pixel by pixel along the yarn. Finally, the total volume of the yarn is ascertained by integrating the volume of all the individual imaginary ovals with their two diameters replaced by the two widths of orthogonal images at the corresponding pixel.