V. K. Kothari

A Neural Network System for Prediction of Thermal Resistance of Textile Fabrics

The objective of this paper is to report a study on the predictability of the steady-state and transient thermal properties of fabrics using a feed-forward, back-propagation artificial neural network system. A comparison was made with two different network architectures, one with two sequential networks working in tandem fed with a common input and another with a single network that gave two outputs. A three-layered network was used in both the cases. The networks were then subjected to a set of untrained inputs and the output thermal properties, namely thermal resistance and Qmax, were compared with the values obtained experimentally. The architecture with two networks working in tandem with a common set of inputs gave better results than the architecture with one set of inputs used to give two outputs.

Tensile stress-strain and recovery behavior of Indian silk fibers and their structural dependence

The tensile stress–strain and recovery behavior of all the four commercial varieties of Indian silk fibers, namely Mulberry, Tasar, Eri, and Muga, have been studied along with their structures. Compared to the non-Mulberry silk fibers, Mulberry silk fiber is much finer and has crystallites of smaller size, higher molecular orientation, and a more compact overall packing of molecules. These structural differences have been shown to result in (1) the presence of a distinct yield and a yield plateau in non-Mulberry silk and their absence in Mulberry silk, and (2) relatively higher initial modulus and tenacity along with lower elongation-to-break and toughness and superior elstic recovery behavior of mulberry silk compared to non-Mulberry silk. It is also observed that fine silk fibers have a relatively more ordered and compact structure with higher orientation compared to their coarse counterparts, and this gives rise to higher initial modulus and higher strength in the finer fibers.

Studies on cotton–acrylic bulked yarns and fabrics. Part II: Fabric characteristics

Abstract The present work is concerned with the study of the characteristics of plain-woven fabric produced with cotton–acrylic high-bulk yarns. Cotton–acrylic blended bulked yarns of various yarn counts, proportion of shrinkable acrylic fibre and twist levels have been prepared by relaxing shrinkable component of the yarns using boiling water treatment. A three-variable factorial design technique proposed by Box and Behnken has been used to study the interaction effects of the variables on the characteristics of fabrics. The influence of these three variables on the physical, handle and comfort properties of fabrics is studied, the response surface equations for all the properties have been derived and the design variables are optimized for various fabric properties. These fabrics have improved thermal resistance, air permeability and moisture vapour transmission as compared to that of 100% cotton fabric. The reduction in initial modulus and bending rigidity is also observed.

A study on thermophysiological comfort properties of fabrics in relation to constituent fibre fineness and cross-sectional shapes

The present study reports the effect of linear densities and profiles of polyester fibres on the physiological properties of their fabrics. Four different polyester fibre finenesses along with microdenier and four cross-sectional shapes (circular, scalloped oval, tetrakelion and trilobal) were selected to produce two sets of 2/1 twill fabrics; one composed of 100% polyester and the other 67:33 P/V blends. In studying the thermophysiological component of the clothing comfort, heat, air and moisture transmission characteristics of the fabrics were assessed. The principal thermal properties, such as thermal absorptivity, thermal resistance and thermal conductivity, were experimentally evaluated, using the Alambeta instrument. The study of the obtained results established the fabrics of non-circular cross-sections as against circular ones, and increase in the linear density results in higher thermal resistance, lower thermal conductivity and lower thermal absorptivity. Wicking behaviour of fabrics was studied under two conditions–wicking from an infinite liquid reservoir (transverse wicking) and wicking from a finite liquid reservoir (single drop wicking into the fabrics). Increase in fibre linear density enhances transplaner wicking but slows down the spreading speed of water drops. Air permeability and moisture vapour permeability are found to be positively correlated with fibre decitex. The role of fibre cross-sectional shapes in influencing mass-flow characteristics is quite considerable. Use of non-circular polyester in place of a circular one augments the wickability of liquid water along with the permeability of air and moisture vapour through the fabrics, revealing their high porosity, which assists air and moisture to propagate. Mixing viscose into polyester brings down the air permeability and moisture vapour transmission rate (MVTR) of fabrics. Results show that moisture absorption of viscose is an important factor in influencing the moisture transport characteristics including both wickability and MVTR of 100% viscose and P/V-blended fabrics.

Effect of comonomer on structure and properties of textured cationic dyeable polyester

Cationic dyeable polyester (CDPET) yarns were produced through melt blending of cationic dyeable chips having 2 mol % of sodium salt of dimethyl ester of 5-sulfoisophthalic acid (DMS salt) and normal polyester chips in different proportions to obtain yarns having varying amount of comonomer in the fiber. These different partially oriented CDPET yarns were texturized under identical conditions on a draw-texturing machine. It has been observed that with increase in the amount of salt content in the CDPET, the dye uptake increases, but the tensile and crimp properties are adversely affected. The crystalline content, crystal size, overall orientation, and heat of fusion decrease with increase in salt content in CDPET yarns. The dyeability of CDPET yarns with both disperse dyes and cationic dyes improves with increase in DMS salt content. The changes in the mechanical and dyeing properties of textured CDPET have been explained on the basis of structural studies.

Compressional behaviour of nonwoven geotextiles

Abstract The compressional behaviour of a nonwoven geotextile is an important mechanical property, affecting the tensile and hydraulic properties and it is necessary to characterize the compressional and recovery behaviour of these fabrics when predicting their behaviour in use. Two parameters, α and β, describing the compressional and recovery behaviour of different types of nonwoven geotextiles have been evaluated, and the effects of some processing parameters on the compressional and recovery properties of needle-punched fabrics have been studied. The effect of cyclic loading and ultimate compressional pressure has also been reported. It has been shown that compressibility and percentage energy loss are dependent on the porosity of the fabric, mode of bonding and the characteristics of constituent fibres. Staple needle-punched nonwoven fabrics show a higher percentage of energy loss than continuous-filament fabrics, and needle-punched fabrics are more compressible than thermobonded fabrics. The adhesive-bonded fabrics show higher compressibility.

Effect of process variables and feeder yarn properties on the properties of core-and-effect and normal air-jet textured yarns

Tensile and dimensional properties of air-jet textured yarns are affected by air pressure, overfeed, and different overfeed levels of the core and effect components. There is considerable deterioration in the tenacity and modulus of yarns after texturing. Yarn breaking extension mostly decreases after texturing. Yarns textured at higher air pressures have poor strength and low instability. Yarns textured at higher overfeeds have poor strength and higher extension, instability, and shrinkage. Normal (parallel-feed) textured yarns are stronger and less stable with lower shrinkage values. When the difference is greater between the overfeed amounts of the core and effect components, the tensile properties deteriorate and the stability of the textured yarns improves. The stability of yarns textured with the core end wetted is better than with the effect end wetted.

Studies on moisture transmission properties of PV-blended fabrics

Moisture transmission properties are most important for fabric comfort. We have studied the moisture transmission properties of the plain-woven fabric produced with polyester–viscose-(PV) blended yarns. PV-blended yarns of varying blend proportion, yarn count and twist levels have been used for fabric manufacture. A three-variable Box and Behnken factorial design technique has been used to study the interaction effects of the above variables on the aforesaid characteristics of fabrics. The interactive effect of these three variables on the air permeability, water vapour permeability, in-plane wicking and vertical wicking of PV-blended fabrics has been studied and the response surface equations for all the properties have been derived; also, the design variables have been optimized for all the moisture transmission-related properties. Most of the moisture transmission characteristics were found to be affected significantly by blend proportion, count and twist levels at 95% level of significance with the present variables.

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.

Comfort characteristics of fabrics made of compact yarns

Comfort is one of the most important aspects of clothing. Thermal comfort is related to fabric’s ability to maintain skin temperature and allow transfer of perspiration produced from the body. Properties like thermal resistance, air permeability, water vapor permeability, and liquid water permeability are suggested as critical for thermal comfort of clothed body. In this study the fabrics developed from the EliTe compact yarns are compared with the fabrics made from normal yarns. The thickness of the fabrics made from EliTe® compact yarns is also slightly less than the fabrics made from normal yarns. Fabrics made from EliTe® compact yarns have shown greater air permeability as compared to the fabrics made from normal yarns. It is observed that, thermal resistivity values of the fabrics developed from EliTe® compact yarns are lower than the fabrics made from normal yarns indicating they are cooler fabrics compared to normal fabrics. Fabrics developed from the EliTe® compact yarns have shown slightly higher values of MVTR (moisture vapor transmission rate) as compared to the fabrics made from the normal yarns. The wicking characteristic of fabrics developed from EliTe® compact yarns was slightly higher than the fabrics developed from normal yarns.