Zenun Skenderi

Impact of raw material, yarn and fabric parameters, and finishing on water vapor resistance

The objective of this study was to explore a number of technical–technological parameters affecting the water vapor resistance of knitted fabric and clothing, as well as to develop a predictive model that describes the prominent affecting parameters. Thirty-four knitted fabrics were carefully produced and measured on a sweating guarded hotplate and thermal manikin. The study focused on the influence of the following parameters on the transfer of water vapor: type of textile fibers, yarn and knitted fabric parameters, finishing of fabrics (recipes include bleaching, dyeing, and softening), and body activity. The statistical analysis, performed to examine the relationship between observed parameters, indicated medium correlation between water vapor resistance and moisture regain (R = 0.7). Furthermore, the relationship between water vapor resistance and the following knitted fabric parameters is especially prominent: mass per unit area, knitted fabric thickness, and tightness factor (R = 0.9). When the fabrics are made into ensembles, however, effects of material differences become small and the differences between garments more difficult to discriminate; even more so when movement is present.

Determining Yarn Tension in Ring Spinning

A procedure is established to determine yarn tension for various regions of a yarn path by measuring two yarn force components at the yarn guide as well as by using well known theoretical and empirical equations. Two components of ring rail acceleration are measured in the direction of the measured force to eliminate the influence of various disturbances on the measurement of force at the yarn guide. Yarn tension is analyzed without the influence of air drag force or gravitational and Coriolis acceleration. To track the influence of spinning position, winding diameter, feeding yarn angle, and balloon angle at the yarn guide on yarn tension, a slowly variable force component is analyzed. The slowly varying component of the measured force is determined by numerical filtering with a computer. The angle of the yarn balloon at the yarn guide is determined by recording the balloon with an SVHS camera, whereas the feeding yarn angle at the yarn guide is determined mathematically from the kinematics of ring rail and yarn guide movement.

Impact of calendering process on nonwoven geotextiles hydraulic properties

The influence of the calendaring process of nonwoven geotextiles on the water permeability normal to their planes, including influence of different loads, as well as pore characteristics investigated by two different methods has been studied. Methods of pore characteristics differ in obtaining different pore parameters. Two groups of samples were produced whereas first group is bonded by needle punching, while second group is needle punched samples taken from first group and additionally bonded by calendaring. Mass per unit area for both groups is in range of 150 to 500 g/m2, with increasing by 50 g/m2 for the next sample within groups. Calendaring process decrease water permeability of geotextile, but also decreases interval of geotextile water permeability change due to the applied pressure. Calendared geotextiles have controlled and predictable compressibility, respectively structure which will not significantly change in the practical application.

Thermal resistance of polyurethane-coated knitted fabrics before and after weathering

Polyurethane-coated knitted fabrics are of interest because they exhibit several positive properties, they are more stretchable, elastic and comfortable than coated woven fabrics and yet they are little studied. Information of weather durability, as well as thermal properties, is essential to ensure thermal protection for textile materials intended for outdoor use. In the presented research, a series of coated knitted fabrics for protective clothing were developed and exposed to weathering in summer and winter seasons. After three months of outdoor exposure, thermal resistance of all the tested materials decreased by 13% after the summer season and 25% after the winter season. A very good correlation of knitted fabric mass per unit area and thermal resistance of knitted fabric, coated fabric and aged coated fabric occurred. The studied materials experienced a partial degradation of the polyurethane layer, which is not related to the deterioration of the knitted substrate. The presented investigation of thermal resistance of coated fabrics and their dependence on the knitted substrate, as well as the influence of environmental conditions, allows the improvement of coated fabrics with the aim of better thermal protection.

The Simulation of Heat and Vapour Transfer Trough Fibrous Materials

The heat and water vapour transmitting properties of fibrous materials are important factors that affect the clothings comfort as well as the quality of special functional clothing that is worn in extreme environmental conditions. The paper introduces advanced system for the simulation of physiological processes that appear next to the human skin. Its use enables the measurement of heat and vapour transfer trough fibrous structures, as well as determination of vapour permeability and permeability index. The experiments reported here refer to the measurement of a number of fibrous materials used for the next-to-skin wear. For the measurement have been produced materials that differ either in their structure or raw material in order to observe the influences of different parameters to the transfer properties. The transfer trough fibrous materials is mainly affected by its structure that comprises of a repeat units with cellular geometry containing air pores, yarns that form basic structure and intersection points of two or more yarns. Therefore, the structure of materials is also investigated and described by means of fabric moduli. Dynamics of heat and vapour transfer is observed through the experimentally obtained data and the influence of a number of structural parameters is discussed. The statistical methods are used to qualify the effects of investigated variables on the heat and vapour resistance.

Impact of substrate on water vapor resistance of naturally weathered coated fabrics

The aim of the study was to investigate changes of water vapor resistance of coated fabrics with different knitted substrates. For the study different knitted structures were designed and produced, while the conditions for the coating process were kept constant. All structures were exposed to natural weathering in the summer and winter seasons. Thus, the experimental setup enabled the comparison of changes in water vapor resistance of various structures as a result of aging, as well as giving an insight into the differences in resistance after aging in different seasons. After exposure, changes in fabric mass per unit area, thickness and water vapor resistance were observed. The outcomes of the study gave a good insight into the behavior of coated fabrics and may be used when protecting coated materials in order to improve their performance.

Influence of nonwoven fabric pore sizes on water vapor resistance

The influence of nonwoven fabric pores using the Brunauer–Emmet–Teller method, dry sieving and capillary flow porometry on water vapor resistance were investigated. For a better understanding of the nonwoven thickness impact on pores and water vapor resistance (and therefore the influence on comfort), two types of samples were investigated: nonwoven fabric bonded with the needling and nonwoven fabric additionally bonded with the calendering process. Water vapor resistance increased with increasing nonwoven fabric thickness, whereby it ranged from 11.33 to 15.62 m2 Pa W−1 for the non-calendered samples and it ranged from 5.19 to 9.85 m2 Pa W−1 for the calendered ones. Water vapor resistance showed a good linear correlation with the specific surface area, pore volume, apparent opening size and mean flow pore diameter.

Analysis of Anisotropic Behaviour of Polyurethane Coated Knitted Fabric

Anisotropic behaviour of polyurethane coated knitted fabrics in elongation to break is described. Although previous studies suggest that coating generally reduces the anisotropy of textile materials, this study shows that polyurethane coating typically increases the anisotropic behaviour of knitted fabrics. Research explains the effect the coating has on knitted fabric. The aim of this study is to analyze anisotropic properties of polyurethane coated knitted fabrics in order to predict their behavior, and get the desired properties of the textile composite.

Comfort and microbial barrier properties of garments worn next to the skin

Compared with viscose fibre, modal fibre is characterized by some advantageous properties such as higher dry and wet tenacities, higher wet modulus, lower water retention capacity and lower level of swelling. Impact of different knitted fabric structure made of cotton and 97 % CMD/3 % EL fibres on thermo-physiological comfort and microbial barrier properties were investigated. All knitted fabrics have very good physiological properties. The microbial barrier permeability of knitted fabric after extreme contamination with bacterial spores in dry state showed that double jersey offered more effective microbial barrier than the single jersey knitted fabrics respectively the greater thickness of double jersey knitted fabric provide more difficult barrier to bacterial spores to pass. In wet state all knitted fabrics have more effective microbial barrier which could be explained by cellulose fibres swelling. In wet state 97 % CMD/3 % EL single jersey knitted fabric have more effective microbial barrier then cotton double and single jersey knitted fabrics.

Effect of finishing treatments on heat resistance of one- and two-layered fabrics

A series of cotton knitted fabrics was produced and finished according to three different recipes in order to compare the changes of their heat resistances. The heat resistance was measured using the sweating guarded hotplate. Measurements were carried out on one layer of produced knitted fabrics, as well as on two layers of fabrics. The results indicated significant influence of all carried finishing treatments to the decrease of heat resistance of knitted fabrics. It was shown that the high influence of finishing treatment to the total heat transfer trough fabric remains if the fabric is worn with additional knitted fabric layer. The presented results and performed statistical analysis indicated significant effect of finishing treatments to the changes of fabric parameters and furthermore to the changes of heat resistance what directly affects the total thermophysiological comfort of knitwear.