R. S. Rengasamy

Airflow simulation in nozzle for hairiness reduction of ring spun yarns. Part I: influence of airflow direction, nozzle distance, and air pressure

Abstract An air nozzle having a axial angle of 50° and inner diameter of 2.2 mm was placed below the front roller nip in a ring frame, at various distances. Simulation of the airflow pattern inside the nozzle provides some useful insight into the actual mechanism of hairiness reduction. A CFD (computational fluid dynamics) model has been developed to simulate the airflow pattern inside the nozzle using Fluent 6.1 software, to solve the three-dimensional flow field. To create a swirling effect, four air holes of 0.4 mm diameter are made tangential to the inner walls of the nozzle. Airflow directions viz., against and along the direction of yarn movement are studied by changing the nozzle position, and the best results are obtained for the former case. Thirty tex Z-twisted ring spun yarns were produced with and without nozzle and tested for hairiness, tensile, and evenness properties. The total number of hairs equal to or exceeding 3 mm (i.e., the S3 values) for yarn spun with nozzle (NozzleRing yarn) is nearly 36–58% less than that of ring spun yarns (without placing nozzle), while both the yarn types show little difference in evenness and tensile properties. Hairs are wrapped along the direction of twist in the NozzleRing yarns. It is observed that air pressure, distance of the nozzle from the nip of the front roller, and direction of airflow affects the hairiness. An air pressure of 0.5 kgf/cm2 (gauge) is found sufficient to reduce S3 values. Finally, based on the airflow simulation inside the nozzle, a mechanism of hairiness reduction has been proposed.

Stress–strain characteristics of different spun yarns as a function of strain rate and gauge length

Abstract The influence of strain rates and gauge lengths on the characteristics of the stress–strain curves of ring, rotor, air-jet, and open-end friction spun yarns is investigated. A modified form of Vangheluwes model is used in describing the stress–strain characteristics of spun yarns. The proposed model can fairly well replicate these characteristics.

Some studies on hairiness reduction of polyester ring spun yarns by using air-nozzles during winding

Abstract This paper reports on the hairiness reduction of polyester yarns at winding using air-nozzles. Three yarns of the same count were spun each from fibres of 1.0, 1.2 and 1.4 deniers respectively. Using a CFD (computational fluid dynamics) model, airflow inside the nozzles is simulated to explain the role of nozzle parameters viz., axial angle of air inlets and yarn channel diameter on yarn hairiness reduction during winding. Air drag forces acting on hairs are calculated. Transverse drag forces acting on hairs play a major role in bending the hairs. Vortex nature of air and air velocity profile inside the nozzle are the important phenomena in reducing yarn hairiness. Box and Behnken factorial design of experiments is used to optimize nozzles parameters, fibre denier, and air pressure to maximize the hairiness reduction. Axial angle of 45° for air inlets, 2.2 mm yarn channel diameter, 1.4 denier fibre, and 0.9 bar (gauge) air pressure are the combinations to get maximum reduction in S3 hairiness values of nozzle wound yarns. Fibre denier is a major influencing factor in reducing yarn hairiness.

Thermo-physiological comfort characteristics of polyester air-jet-textured and cotton-yarn fabrics

Air-jet-textured polyester yarns were produced using two feed yarns differing in filament fineness and number of filaments. By varying the overfed rates of feed yarns and changing their positions in core and effect, five textured yarns were produced. Woven fabrics were prepared using these textured yarns as weft and cotton yarns in warp. To study the effect of air-jet-texturing parameters on the thermo-physiological comfort characteristics of fabric, the woven fabrics were tested for thickness, thermal properties, transverse wicking and air permeability. It is observed that thermal conductivity and resistance of fabrics are not influenced by the texturing parameters/textured yarn structure. These properties are mainly dependent on the entrapped air present in fabrics. Thermal absorptivity is a transient phenomenon of heat flow reflecting that the ‘warm-cool feeling’ effect of fabrics depends on smoothness/roughness of fabric surface. Fabrics with smooth surfaces have higher thermal absorptivity values as they provide a large area of contact with human skin. The roughness of fabrics depends on the number of surface loops and filament fineness. Transverse wicking of fabrics depends on the size, continuity and alignment of the capillaries present in the core of textured yarns.

Airflow simulation in nozzle for hairiness reduction of ring spun yarns. Part II: Influence of nozzle parameters

Abstract In this present work we report the influence of nozzle parameters viz., axial angle and diameter of the nozzle in reducing yarn hairiness during NozzleRing spinning. Three nozzles having varying nozzle axial angles of 40°, 45°, and 50° and a constant nozzle diameter of 2.2 mm, and another nozzle having axial angle of 40° with a nozzle diameter of 2.6 mm were placed at a fixed distance of 10 cm below the front roller nip at ring frame for reducing yarn hairiness. Thirty tex carded cotton yarns were produced with and without nozzles. A CFD (computational fluid dynamics) modeling of airflow inside the nozzle indicates that a nozzle axial angle of 45° and 2.2 mm diameter gives best results in terms of reduction of S3 values. Swirling intensity plays a major role in reduction of yarn hairiness. The change of nozzle diameter plays a lesser role in reducing the S3 values. The difference in yarn diameter and bending rigidity values of NozzleRing yarns and ring yarns spun without nozzle are not statistically significant. Fabrics made from NozzleRing yarns show lesser pilling tendency as compared to those produced from yarns spun without nozzles.

Analysis of Spun Yarn Failure. Part II: The Translation of Strength from Fiber Bundle to Different Spun Yarns

A generalized mathematical model has been developed for predicting the strength of spun yarns produced by ring, rotor, air-jet and open-end friction spinning systems. The model is based on the translation of fiber bundle tenacity into the yarn tenacity and it is applicable to all spun yarns. The model describes the failure behavior of spun yarns. Experimental strength results are compared with the predicted ones on the basis of theory, and a satisfactory agreement is reached. The limitations of the model are also analyzed.

Ultraviolet Absorbers for Textiles

The incidences of skin cancer have been rising worldwide due to excessive exposure to sunlight. Increase in exposure to ultraviolet (UV) radiation from sunlight results in skin damage such as sunburn, premature skin ageing, allergies and skin cancer. Medical experts suggest several means of protection against ultraviolet radiation, including use of sunscreens, avoidance of the sun at its highest intensities, and wearing clothing that covers as much of the skin surface as possible. This paper provides insight on how UV absorbers can be efficiently used with textile material to protect human skin from harmful UV radiation. The manufacturers of various UV absorbers and their commercial products are reviewed and discussed. The interacting mechanism of UV absorbers with textile clothing for providing UV protection and an evaluation of the performance of UV absorbers are summarized.

Study on the static and dynamic strengths and weavability of spun yarns

This study reports on the analysis of tenacity and breaking elongation of ring-, rotor- and air-jet-polyester/viscose spun yarns measured using static- and dynamic tensile testers. The weavability, a measure of performance of these yarns in post spinning operations is quantified. The yarn diameters and helix angles of fibres in these yarns are measured in order to analyze the effect of types of spun yarn and blend proportion on yarn elongations. The dynamic tenacity is highly correlated with the weavability than the average static tenacity measured at 500 mm gauge length. The minimum static tenacity obtained from 100 tests has high correlation with the dynamic tenacity. The present study indicates that it is appropriate to evaluate the performance of spun yarns in winding, warping and weaving based on the dynamic yarn tenacity measured while running a 200 m length of yarn in a constant tension transport tester or the minimum static yarn tenacity obtained using any conventional constant rate extension (CRE) tensile testers corresponding to a total test length of 50 m.

Hairiness of spun yarns and their reduction using air-nozzle in winding

Abstract Using ring, rotor, air-jet, and open-end friction spinning, viscose yarns of same count were spun and compared for hairiness in terms of types of hair and hair-length distributions. Hair-length distributions present on as-spun yarns, regular wound yarns, and yarns wound passing them through an air-vortex nozzle were obtained using microscope and instrument. Hairiness of Dref-II yarn is the maximum followed by ring, air-jet, and rotor yarns. Rotor and Dref yarns have higher proportion of looped hairs followed by air-jet and ring yarns. Contribution of looped hair to hairiness is predominant followed by leading or trailing hair. Smaller hair (class interval of 0–1 and 1–2 mm) are major contributors to the total number of hairs on all the yarns. Hairiness of all these yarns increases by winding without the nozzle and hairiness decreases by winding with nozzle and this is found for all types of hairs. The total number of hairs ≥ 3 mm (i.e. S3 values) for nozzle-wound yarns is about 16–30% less than that observed for the corresponding spun yarns. When many hairs are present on the yarns before feeding into the nozzle, a higher percentage reduction in hairiness is achieved by nozzle-winding. An empirical equation has been proposed based on exponential distribution to characterize the hair-length distribution present on various yarns. The number of longer hairs counted by the instrument is higher compared to that estimated by the equation and opposite is the case for the shorter hairs.

Study on dynamic needle thread tensions in a single needle lock stitch (SNLS) sewing machine. II. Effect of sewing speed, thickness of fabric plies, thread linear density and pre-tensions of threads

This paper reports on the effect of pre-tensions on needle and bobbin threads, sewing speed, thickness of fabric plies and the linear density of the threads on the tension peaks occurring on needle thread during sewing on a single needle lock stitch machine. The needle thread tensions are measured at two locations: above the needle bar (bottom segment) and above the needle thread tensioner (top segment). A factorial design approach is used to study the four parameters. The role of bobbin tension is studied in a separate experiment, while keeping the pre-tension on the needle thread constant. The highest tension observed on the needle thread is the stitch tightening tension which is directly affected by the pre-tension set on the needle thread disc tensioner. Heavier threads develop lower tightening tension which may affect the seam balance. The thickness of fabric plies does not affect the needle thread tension. Sewing speed has marginal influence on the stitch tightening tension near the needle thread tensioner. The pre-tension on the bobbin thread affects only the needle thread tension when the take up lever pulls up the needle thread loop to release it from the rotary shuttle hook gib.