G. Ramakrishnan

Comparison of different methods to measure the transverse wicking behaviour of fabrics

In this article, three test methods are described to measure the water spreading behaviour of textiles such as rate of absorbency and total absorbent capacity. The methods described are manual method, commercial image analysis method using Photoshop and embedded image analysis method using digital signal processor through MATLAB software (EIAS). With these methods the rate of absorbency and total water absorbent capacity were analysed in 12 different knitted/woven fabrics. In order to compare the three test methods, the correlation among the methods were analysed. A very good correlation (more than 0.9) was found between the manual water spreading tests and commercial image analysis method using Photoshop when compared to manual versus EIAS method. Also Photoshop versus EIAS method correlation was found better than manual versus EIAS method.

A study of the thermal properties of single jersey fabrics of cotton, bamboo and cotton/bamboo blended-yarn vis-a-vis bamboo fibre presence and yarn count

In this study, the thermal properties of 100% cotton, 50/50 cotton/bamboo and 100% bamboo single jersey fabrics with differing yarn linear density are evaluated and analysed. The linear densities of the yarns composing the fabrics are 20s, 25s, 30s Nec and the twist level in the yarns is kept the same. An increasing the presence of bamboo fibre in the fabric causes a reduction in fabric thickness and GSM for all linear densities of yarn. Air permeability and water-vapour permeability also increase with increase in bamboo fibre content while both thermal conductivity and thermal resistance show a decreasing trend. As the constituent yarn gets finer, fabric air and water-vapour permeability both increase in value while the thermal conductivity falls.

Effect of blend proportion on thermal behaviour of bamboo knitted fabrics

This study presents the thermal comfort properties of single jersey knitted fabric structures made from cotton, regenerated bamboo and cotton–bamboo blended yarns. Cotton, bamboo fibre and blends of the two fibres (100% cotton, 100% bamboo, 50:50 cotton:bamboo, 67:33 cotton:bamboo, 33:67 cotton:bamboo) were spun into yarns of identical linear density (20 tex). Each of the yarns so produced was converted to single jersey knitted fabrics with loose, medium and tight structures. The thermal conductivity of the fabrics was generally found to decrease with increase in the proportion of bamboo fibre. The relative water vapour permeability and air permeability of the fabrics were observed to increase with increase in bamboo fibre content. Statistical analysis also indicates that the results are significant for air permeability, thermal resistance, thermal conductivity and relative water vapour permeability of the fabrics.

Effect of blend proportion on moisture management characteristics of bamboo/cotton knitted fabrics

This study reports an investigation of the effect of the blend-ratio of bamboo and cotton fibres on the moisture management properties of single jersey knitted fabrics composed of them. The moisture management properties of the fabrics were measured in SDL-ATLAS moisture management tester. The liquid transport properties of textiles, such as wetting time, maximum moisture absorption rate, maximum wetted radii, spreading speeds, cumulative one-way transport capacity and overall moisture management capacity (OMMC), have been considered and correlated to the blend ratio of bamboo/cotton yarn single jersey knitted fabrics. It was observed that as the bamboo content increased, the wetting time decreased, maximum wetted radius decreased, rate of absorption increased, spreading speed decreased and OMMC decreased.

Comfort properties of functional warp-knitted polyester spacer fabrics for shoe insole applications

The use of cushioned insoles has been recommended as a method to reduce the impact forces on feet associated with running. This study is used to determine the influence of insole structure and thickness on the permeability and conductivity properties of air and temperature. The insoles are constructed with warp-knitted polyester spacer fabrics with 3D construction and have good cushioning, permeability, and conductivity properties. The middle layer is made up of polyester monofilament yarn which decides the thickness of fabric, and the two outer surfaces of the fabric were made from polyester multifilament yarns which is a closed and open structure. The comfort properties of spacer fabric have been studied by measuring air permeability, water vapor permeability, and thermal properties with respect to fabric porosity. One-way analysis of variance is used to analyze the significant of fabric thickness and surface structures. The experimental result shows that the vertical gap of the two outer surface layers and the horizontal pore size of the face surface decide the permeability and conductivity properties of spacer fabrics. The fabric with higher porosity show high permeability of air and water vapor. Depending on the fabric thickness and structure, the 4-mm thickness of spacer fabric with locknit structure resulted in low air and water vapor permeability. It is found that the 3.1-mm thickness spacer fabric with hexagonal net structure proves to have good air and water vapor permeability and comparatively lower thermal conductivity.

A dynamic sweat transfer tester for analyzing transverse sweat transfer properties of multi-weave structure fabrics

The dynamic sweat transfer tester for analyzing the sweat transfer behavior of multi-weave structure fabrics (single fabric contains different weave structures) has been designed and developed. This instrument has been developed to evaluate the sweat transfer rate in 16 different directions and 48 different regions for a test specimen of 7 cm diameter. The concept of the sweat measurement is to measure the sweat transport time required to reach the unit area of the fabric. The instrument works under the principle of electrical conductivity, that is, wetted cotton fabric acts as an electrical conductor between the power connected (5 V) copper pins and ground connected copper pins. The unique feature of this instrument is that the sweat transfer rate can be measured in fabrics which have irregular spreading behavior (single fabric that has different weave structures) at one step. Twelve different woven fabrics have been analyzed for the sweat transfer behavior using the instrument, and the results were well correlated (R2 = 0.925) with manual test method.

Effect of cyclic stress on the transverse wicking behaviour of cotton/lycra knitted fabrics

It is extremely important to evaluate transverse wicking behaviour of elastic knitted fabric while the fabric simulated in different body motions. In this paper, the effects of short interval dynamic extension and recovery on fabric transverse wicking behaviour were evaluated as the samples were subjected to different rate of extension (speed), different percentage of cyclic extension and different liquid flow rate. For this application, a new cyclic stress instrument was designed and developed to apply repeated dynamic extension and recovery on the fabric. The developed instrument is operated through embedded micro controller programme. The effect of speed, percentage of cyclic extension and flow rate with respect to the dynamic transverse wicking behaviour of elastic knitted fabric has been studied using Box–Behnken experiment model. The experiment model identifies the principal experimental variables such as flow rate, percentage of cyclic extension which has the greatest effect on the transverse wicking behaviour of elastic knitted fabric.

Study of thermal properties of jute and hollow conjugated polyester fibre reinforced non-woven composite

Sandwich structure of non-woven composite is produced by using a compressive hot pressing method. It is ranging from 2500 grams per square meter (gsm) to 3500 gsm. Composite sample is designed using Box and Behnken model. Considering 50–70% weight of jute fibre content with 30–50% weight of hollow conjugated polyester fibre, ideal thickness of the composites is maintained in the range from 4 to 5 mm. Thermal properties such as thermal conductivity, thermal resistance, thermal transmittance and thermal diffusivity were evaluated by considering three factors: weight of jute (A), weight of hollow conjugated polyester (B) and thickness of the composite (C). The thermal conductivity of the composite material is determined by heat flow meter method ASTM C518. Experiment result will help to make a suitable standardized panel composite for thermal insulation. It requires 3600 gsm 51/49 parts of contribution of jute/hollow conjugated polyester fibre with 5.0 mm thickness and 3200 gsm 76.5/23.5 parts of contribution of jute/hollow conjugated polyester fibre with 4.5 mm thickness of the composites. The composite weight of 3280 gsm shown optimized thermal responses, it was predicted from response surface method graph. Contribution of jute/hollow conjugated polyester fibre of 54/46 parts with 5.0 mm thickness would be considered to make standardized composite panel. Mostly air conditioning process reduces the energy cost spent for the thermal stability in indoor climate of dwellings.

Permeability and impact properties of warp-knitted spacer fabrics for protective application

An experimental investigation was carried out to study the effect of interlining material on the comfort and dynamic deformation characteristics of body armour. Suitable plies of interlining materials were selected based on the fabric comfort properties and the impact resistance specified for ballistic application. Kevlar woven fabric was used to block the projectile, and the spacer fabric was used as an interlining material to ensure wearing comfort and for imparting impact resistance. The yarn denier of the middle and bottom layers of the spacer fabrics was maintained constant, and three different deniers were used for the face layer. Three different plies of spacer fabrics were analysed by means of thermophysiological comfort properties to select the suitable interlining material for body armour. The experimental results confirm that the number of plies of spacer fabrics has significant influence on the ballistic armour characteristics than the face layer denier as proved by two-way ANOVA. The substantiated spacer fabric was used as an interlining material, and the depth and area of deformation were analysed. The research findings demonstrated that the three-plied warp-knitted polyester spacer fabric produced better results than single- and five-plied spacer fabrics. One-way ANOVA and Turkey’s HSD also confirmed the influence and interaction of different plies of spacer fabrics.

Influence of porosity on water vapor permeability behavior of warp knitted polyester spacer fabrics

Linear density of filament, fabric structure, and number of loops per unit area are the major factors which influence the porosity of warp knitted spacer fabrics. The characteristics of air and water permeability of textile fabrics are chiefly influenced by the porosity of the fabric. An attempt has been made to analyze the water vapor permeability of warp knitted polyester spacer fabric. Spacer fabric face and back surface layers are constructed by polyester multifilament and the middle layer is connected to the two surface layers by polyester monofilament. The behavior of porosity and water vapor permeability were analyzed with respect to the linear density of polyester. The experimental result indicates that the water vapor permeability is highly influenced by porosity of a fabric. The statistical analysis proves the degree of correlation between polyester linear density of spacer fabric layers and their responses. The face and middle layers of fabric are highly significant with the porosity and water vapor permeability. Box–Behnken model was adopted for optimization and a better R2 value of 96.5% is achieved in porosity and the water vapor permeability is 92%.