Auxetic Yarn: Fundamentals, Influencing Parameters, Application Areas and Challenges

The mechanical behaviour of auxetic materials and structures is the most distinctive characteristic, which differs from that of conventional engineering materials due to the negative Poisson’s ratio. Auxetic materials have the fascinating feature of widening when stretched and contracting when compressed. In recent times, the research of auxetic materials based on textile structures has received a lot of interest. Auxetic effect development at the yarn phase is a new and exciting field of study. Many researchers already developed different types of auxetic yarns, such as the helical auxetic yarn, the plied auxetic yarn, the semi-auxetic yarn etc. The helical auxetic yarn (HAY) is the most commonly mentioned auxetic yarn. It is made up of a rigid wrap and an elastic core yarn. However, it is interesting that auxetic yarns can be produced from conventional non-auxetic fibres through the conventional spinning system as well. The helical auxetic yarn is a new type of yarn with a wide variety of possible applications. Moreover, pore-opening characteristics of auxetic yarns make it a potential candidate in the fields of technical textiles, such as medical textiles, filter application, protective textiles etc. Fabrication of auxetic textiles by utilizing auxetic yarns through simple weaving and knitting technology opens the door to new applications. The aim of this paper is to address the fundamentals of auxetic yarns, such as structure, shortcomings, production techniques, as well as the influencing process parameters. From various research works, it is evident that the wrap helical angle, the core/wrap diameter ratio, and the initial moduli of wrap component are the most vital processing parameters during the production of auxetic yarns. Finally, some potential application areas and challenges of auxetic yarns are also addressed briefly in this paper.

Impact of Weft Yarn Density and Core-yarn Fibre Composition on Tensile Properties, Abrasion Resistance and Air Permeability of Denim Fabrics

Characteristics and serviceability of denim fabrics have undergone major changes. Nowadays denim is commonly used for casual wear. Durability and comfort are important parameters for consumers when choosing a denim garment. Therefore, in this study, abrasion resistance, tear and tensile properties of core–spun yarns and air permeability of denim fabrics with different weft yarns per centimetre and fibre content were analysed. The test results showed that weft yarns per centimetre influences fabric air permeability negatively but abrasion resistance increases. Higher weft yarns per centimetre influences fabric air permeability negatively but abrasion resistance increases. Polyester, elastane, modal, viscose and Lycra T400 were used in the core of weft yarn to analyse the impact of those fibres on the durability and comfort properties. Elastane is used to add stretchability to the fabric, which provides comfort to the wearer. The higher the elastomeric fibre content in the fabric, the greater is its elasticity; however, the tensile properties of the woven fabric decrease. The tear strength of the fabric was increased by the presence of the polyester fibre in the core.

The prediction of quality characteristics of cotton/elastane core yarn using artificial neural networks and support vector machines

Core yarn is a type of yarn that has a filament fiber in the center with a different fiber wrapped around it. This type of yarn is of growing importance in the textile industry. It is important to predict the quality characteristics of a core yarn before production to prevent the faulty production of fabrics. Therefore, the development of predictive models is a necessity in the textile industry. In this study, artificial neural network (ANN) and support vector machine (SVM) models are proposed to predict the quality characteristics of cotton/elastane core yarn, using fiber quality and spinning parameters. Principal component analysis and analysis of variance techniques are also used to reduce input dimensions, since high dimensional data may reduce a model’s potential for success in prediction. The prediction models are trained and tested using the data obtained from a textile production plant. The results of all the models are compared with each other on test data. Mean absolute percentage error (MAPE), mean absolute error (MAE) and correlation coefficient (R) are used to assess the prediction power of the models. Although on most of the tests SVM models fared slightly better than ANN models, both models provide accurate predictions for most of the yarn quality characteristics. The results show that the best models have over 90% success rate in MAPE and R. In particular, the Coefficient of Variance of mass (CVm) along the yarn, hairiness and Reisskilometer quality characteristics of the cotton/elastane core yarn are predicted with 91%, 93% and 95% accuracy, respectively.

Effects of spinning process and core yarn contents on yarn shape retention

Purpose In order to develop high shape retention yarn and investigate the effects of spinning process and core yarn contents on the shape retention of yarn, in this paper, three kinds of yarns, JC/T400 18.5tex (55.6dtex) core-spun yarn, JC/T400 18.5tex (44.4dtex) core-spun yarn and JC18.5tex pure cotton yarn were spun by using the complete condensing Siro-spinning technology. The paper aims to discuss these issues. Design/methodology/approach In this paper, the core-spun yarns were spun by using the complete condensing spinning and Siro-spinning technology. Two key spinning processes, yarn twist factor and core yarn pre-draft ratio, were optimized by using the orthogonal test method first. Then, via the variable control method, the position of the core yarn, the position of the bell mouth and the center distance between two bell mouths were optimized, respectively, and corresponding optimal spinning process of the three yarns was determined. Finally, the yarns were spun under the optimal process, and the performance of the spun yarns was tested and compared. Findings Results show that the yarn twist factor affects yarn strength and hairiness, the position of bell mouth affects the evenness and hairiness of the yarn mainly, and the position of the core yarn affects the coverage and hairiness of the yarn. For the Z-twist spinning, the core yarn enters the front roller from the left side of two strands center, which is beneficial to improve the covering effect of core yarn, and reduce the pilling phenomenon of the yarn. The contents of core yarn affect indicators of the yarn shape retention, such as yarn strength, elastic recovery and abrasion resistance. Originality/value The shape retention of yarns affects the shape retention of fabrics, and the production of yarn with high shape retention is a key step in achieving shape retention of fabrics. At present, there are little studies on the shape retention of yarns, most researchers shave focused on shape retention of fabrics. Using the complete condensing Siro-spinning method to spin the core-spun yarn can improve the quality of the yarn. Compared with traditional ring-spinning yarns, the addition of the core yarn can improve the shape retention of the yarn.

Preparation and fuzzy evaluation of wool hollow yarn

Wool hollow yarn not only has the characteristics of being skin-friendly and warm, it also has good air and moisture permeability; thus, it has great development potential. Here, we first show that the water-soluble (polyvinyl alcohol (PVA)) fiber ratio in core-spun yarn should not exceed 30%; to ensure smooth spinning, a core yarn linear density of 3.4–5.6 tex was selected by theoretical analysis. Second, using rabbit hair fiber with tencel fiber, which has high tenacity, as an environmentally friendly blended outsourcing fiber, and water-soluble (PVA) fiber for the core yarn, we prepared five types of core-spun yarns. Water-soluble (PVA) fiber was removed in 20 min to prepare wool hollow yarn using room temperature water. Finally, properties of the wool hollow yarn produced, such as breaking strength, breaking elongation, evenness of CV (coefficient of variation) value, >3 mm hairiness index, and deviation from linear density after removing PVA, were tested and analyzed, and evaluated comprehensively by means of fuzzy mathematics. The results showed that the hairiness of wool hollow yarn was improved, the mechanical properties and evenness of sliver and hairiness were decreased, and the overall properties of hollow yarns with a core yarn content of 25% were the best.

Structural design and performance characterization of stable helical auxetic yarns based on the hollow-spindle covering system

Helical auxetic yarns (HAYs) spun by ring spinning have a large residual torque, which restricts their application. To address this problem, the hollow-spindle covering system was adopted to prepare structurally stable HAYs consisting of the core yarn and the wrap yarn. Four types of HAYs were manufactured, and a self-designed automatic stretching device was prepared for recording the alteration of yarn diameter. These as-fabricated yarns were measured and characterized in terms of their deformation behavior and auxetic performance. The strain–stress curves of these HAYs have two peaks corresponding to their respective two component yarns during stretch until completely failure, and also it was found that the wrap component is always broken before the core yarn. By comparison, the maximum negative Poisson's ratio (NPR) of −2.55 was achieved with as-prepared HAYs composed of spandex and stainless steel monofilaments. Meanwhile, the structural stability of these yarns was discussed with respect to the residual torque, and the experimental results indicate that the residual torque of these HAYs is obviously smaller than that of conventional ring-spun yarns. These confirm the superiority of our proposed hollow-spindle method. Furthermore, the effects of the diameter of the core yarn and tensile modulus of the wrap yarn on the auxetic behavior were systematically investigated. It is found that a larger NPR can be obtained with a thicker diameter of core yarn and a higher tensile modulus of wrap yarn. It is also demonstrated that an appropriate combination of the component modulus and geometric parameters is essential to fabricate HAY with an obvious auxetic behavior.

Characterization of flame-retardant performance of polyester/flame-retardant viscose blended yarn

In this paper, a flame-retardant blend yarn was designed with flame-retardant viscose fiber and polyester. Flame-retardant viscose fiber was blended with polyester by core-spun method. Polyester was set as a core and the flame-retardant viscose fiber was set as a sheath to change the flame retardancy and disadvantage of moisture permeability. After the flame-retardant viscose fiber was spun into roving, polyester was added in spun yarn. The core yarn samples with different ratios were prepared by adjusting the amount of flame-retardant viscose fiber. The flame retardancy of core-spun yarn was evaluated by limiting oxygen index, scanning electron microscope, thermogravimetric analysis, and thermogravimetric/Fourier transform infrared techniques. Limiting oxygen index of the yarn with 50% flame-retardant viscose fiber and 50% polyester was 27.6% and just decreased slightly to 27.1% after 30 washing cycles. Polyester begins to melt from inside core-spun yarn after heating and the molten polyester flows to outer layer of yarns by the diversion effect of higher temperature. Then it was carbonized by the polymetaphosphate which was generated by the flame-retardant viscose fiber. In thermal processes, the major product of thermal decomposition was CO2.

Effect of process variables on the properties of dual-core yarns containing wool/elastane

The denim, having a large customer base irrelevant of age, gender and social status limitation, has been one of the most important products for thegarment sector. Denim fabric demand has diversified with the changing consumer’s sense of life day by day. The denim manufacturers develop alternative production techniques and materials by turning towards new researches in order to adapt to consumer demands. One of the alternative materials, which are used in denim fabric structure, is the dual-core yarns. The dual-core yarn is manufactured through the modified ring-spinning machine in order to benefit at the same time from the properties of two core components. In this study the influence of some production parameters such as twist level, wool draft and elastane draft on the properties of dual-core yarns containing wool/elastane is investigated.The results indicated that the twist level is significantly effective parameter for the unevenness, hairiness, tenacity and elongation values of dual-core yarns. In addition, wool draft is significantly effective parameter for hairiness and breaking elongation values. It was also observed that variation of elastane draft level affects tenacity and elongation values of dual-core yarns.