Fabric Porosity Research Articles

Study on effect of blend ratio on thermal comfort properties of cotton/nylon-blended fabrics with high-performance Kermel fibre

This study presents the thermal comfort properties of woven fabrics made of Kermel, cotton/nylon and cotton/nylon /Kermel-blended yarns. Our aim in this study is to combine the high comfort properties of cotton/nylon fibres with high thermal protective properties of Kermel fibre in different woven fabrics. Thus, Kermel (100%), cotton/nylon (50:50) and four blends of the 50% cotton fibres with nylon and Kermel (40:10, 30:20, 20:30 and 10:40) were spun on a ring-spinning frame and twisted into two-folded yarns with the same yarn count of 30/2(Ne) and twist level of 560 TPM. Using the produced yarns, woven fabrics with identical characteristic and structure were also produced. Then, the thermal comfort and physical properties of fabrics were studied in terms of fabric porosity, thermal resistance, thermal conductivity, water vapour resistance and air permeability. The results show that the porosity, air permeability and thermal resistance increase with Kermel fibre blend ratio. Conversely, the water vapour resistance decreases with increase of Kermel fibre blend ratio up to 40%, while 100% Kermel-woven fabric exhibits a higher water vapour resistance value. Nevertheless, the thermal conductivity of cotton/nylon-blended Kermel woven fabric is unchanged with increase of Kermel fibre blend ratio up to 40%, whereas at 100% Kermel fibre blend ratio, the lowest thermal conductivity is obtained. The obtained results implied that woven fabric produced from cotton/nylon (50/10) blended with 40% Kermel fibre resulted in proper thermal comfort properties.

Relating thin film composite membrane performance to support membrane morphology fabricated using lignin additive

In this study, three nonwoven fabrics were used as supports to form thin film composite membranes for forward osmosis (FO) applications. Lignin additive was added to the polysulfone layer in two different concentrations to increase the porosity of the substructure. The fabrics were characterized in terms of their Frazier permeability, tortuosity, porosity, thickness, structural parameter and capillary pressure. It was found that the fabric tortuosity and thickness had strong negative correlations with FO water flux, while fabric porosity had a strong positive correlation. The fabric capillary pressure was found to be indicative of how well the polysulfone layer adhered to the fabric layer. The membrane structural parameter of the fabric, unsupported and supported polysulfone layers were measured and compared using a “resistance-in-series” model. Although seepage of the casting solution into the fabric layer was physically observed, the addition of the individual structural parameters of the layers offered a good approximation of the composite membrane structural parameter. Membrane structural parameters calculated for fabric supported composite membranes using reverse osmosis (RO) permeability parameters and FO/RO established transport equations were much larger than structural parameters obtained from physical measurements. The difference may be due to compaction of composite membranes in reverse osmosis experiments, casting solution seepage partially plugging the upper layers of the support fabric and other non-idealities not captured in the established FO/RO transport equations.

Endoleak therapy (Zertifzierung: Modul A Spezialkurs)

Endoleaks (ELs) are common (10 – 50%) after Endovascular Aortic Aneurysm Repair (EVAR). Type I ELs are caused by failure of sealing at the attachment sites of the endograft, either proximally (EL Ia), or distally (EL Ib). Type II ELs are caused by retrograde flow into the aneurysm sac from aortic or iliac branches. ELs type II occur in 20 – 30% of EVAR cases at 30 days. Mostly they disappear spontaneously. Type III ELs are caused by modular disconnection or fabric disruption. Type IV ELs are attributed to the porosity of the endograft fabric, and they resolve spontaneously. Type V ELs (endotension) are defined as sac enxpansion without evident EL.

Study on thermal and evaporative resistances of multilayered fabric ensembles

The present work deals with the study on thermal and evaporative resistance of multilayered fabric ensembles meant for cold weather applications. Three-layered structure is used to study the thermal comfort properties. Knitted fabric and polytetrafluoroethylene coated fabrics were used in inner and outer layer, respectively. Needle punched fabrics produced from polyester fibre were used in middle layer. Fifteen different non-woven fabrics were produced according to Box and Behnken experimental design for three variables and three levels by varying mass per unit area, punch density and depth of needle penetration. The produced fabrics were evaluated for thermal and evaporative resistances with and without inner and outer layer fabrics. Thickness, air permeability, bulk density and porosity of the needle punched fabrics were studied. The properties of the fabrics were analyzed for statistical significance by using ‘Design-Expert’ statistical software. Artificial neural network model was developed to predict the properties of fabrics and validation of model was done with the testing data-set. The performance of prediction was evaluated by mean square error, mean absolute error percentage and correlation coefficient. It was concluded that the predicted properties of fabric correlated well with the experimental results.

Regional Variations in Urban Fragmentation Among U.S. Metropolitan and Megapolitan Areas

In this paper we investigate the regional variations in the fragmentation of urban landcover among 86 metropolitan areas and 19 megapolitan areas in the United States. Urban fragmentation was evaluated using nine spatial metrics that collectively quantified the continuity and shape complexity of urban landcover. Spatial metrics were calculated for each metropolitan and megapolitan area using a high urban threshold containing the urban core and surrounding suburbs, and a low urban threshold that further encompassed the outer exurban fringe. A principal component analysis was used to collapse the nine spatial metrics into two components of urban form: “shape complexity”, which describes the porosity of the urban fabric, and urban “continuity”, which represents the aggregation of urban patches or pixels. Urban “continuity”, and seven of nine spatial metrics, varied significantly by U.S. census region. A hot-spot analysis further revealed a high degree of spatial autocorrelation, with metropolitan areas in the Northeast and South regions generally exhibiting a more fragmented urban landscape than those in the Midwest or West regions. Relative to metropolitan areas, megapolitan areas exhibited more complex and fragmented patterns of urban landcover, presumably due to the high level of inter- and intra-urban polycentricism at this broader scale.

Influence of Laundering on the Quality of Sewn Cotton and Bamboo Woven Fabrics

In the presented study the effect of laundering on the quality of sewn cotton and bamboo plain woven fabrics was investigated considering both the textile parameters and the type of chemical treatment. Quality parameters of sewn cotton and bamboo woven fabrics such as: fabric strength, seam strength and seam slippage at the moment of 4 mm seam opening were evaluated before and after washing with “Tide” washing powder without softeners or with softeners: “Surcare” and “Pflege Weicspuler”. There was also determined surface density, warp and weft densities as well as thicknesses under the pressures 0.625 kPa and 3.125 kPa, and calculated the comparative thickness that was considered as softness or porosity of fabrics. Notwithstanding that both the investigated fabrics were cellulosic their behavior after laundering was different. Under the tested conditions, unwashed and laundered with or without chemical softeners cotton fabric didn’t demonstrate seam slippage. The seam slippage resistance of laundered without or with softener specimens of bamboo fabric was increased in respect to control fabric. The larger changes in seam efficiency and seam strength because of laundering were determined for bamboo woven fabric then for cotton fabric. They could be influenced by the higher changes in bamboo fabric’s structure. The highest difference between the structure parameters of both fabrics was determined for comparative thickness. It was significantly increased for cotton fabric and decreased for bamboo fabric after chemical softening comparing to untreated fabrics.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3831

Surface roughness and wettability of wool fabrics loaded with silver nanoparticles: Influence of synthesis and application methods

Hydrophilization of wool fabrics was performed by silver nanoparticles with different surface charge using three different methods: exhausting, pad–dry–cure and in situ synthesis. Dynamic wetting measurements and surface topography analysis were used to evaluate surface changes on wool fabrics. The wool samples in situ loaded revealed the highest fabric roughness and porosity, while the use of the pad–dry–cure method leads to the lowest fabric porosity, and its roughness values approximately were the same as those for samples loaded with the exhaustion method. The results revealed that loading silver nanoparticles with high surface charges onto wool fabrics via the exhaustion method can significantly improve the hydrophilicity of wool fibre surface. The possible reasons for this improvement are discussed.

Effect of Selected Fabric Construction Elements on Wicking Rates of PET Fabrics

Apparel has an important role in keeping the body comfortable by maintaining the needed equilibrium state between the human body and the environment by getting rid of sweat which is exerted due to the physical activity. This happens through a multitude of mechanisms, one being the capillary action which is also known as wicking. Wicking is defined as “A spontaneous transport of liquid driven into a porous system by capillary forces”. This paper is concerned by studying effect of basic fabric weaves and weft densities of synthetic fabrics (PET) on vertical and horizontal wicking rates and their relation to fabric packing factor. For this aim, 9 samples 100% PET woven samples varying in weave type (plain 1/1-basket 2/2-twill 1/3) and three pick densities were produced, taking into account that the other production parameters were constant. The experiment showed that wicking rate was influenced by fabric porosity. Vertical wicking rate increases with the increase of the porosity, while horizontal wicking rate decreases with the increase of porosity.

Research on the Porosity and Pore Size of Spun-Bonded Fabrics Based on Matlab7.0 Image Processing Technology

The image with high resolution was obtained through scanning the spun-bonded fabric, and processed with the help of Matlab7.0 software to calculate the pore structure of the spun-bonded fabric. On the basis of the relationship between number of pixels and area, the porosity and average pore size of spun-bonded fabric were analyzed; pore size and porosity were calculated by using the equation method and the air bubble test method as well. By comparing the data of the two methods, the correlation between them was gotten. Finally, it was shown that using the image processing technology to research the pore structure of spun-bonded fabric was a feasible way. There are various factors affecting the performance of textile filtering materials, and the porosity and pore size of the fabrics play an important role in filtration. As is known to all, fabric porosity and pore size are indicators to measure the size of fabric pore volume, one is the ratio of pore volume with the total fabric volume, and the other one refers to the average diameter of the holes in the textile filter material. They directly affect the permeability, the hydraulic conductivity of the fabric and the ability to prevent the particles getting through. Generally speaking, the bigger the porosity and pore size, the greater the permeability coefficient and the better the permeability of the filter material. Porosity and pore size directly affect the product's function and application. Therefore, the pore structure has a great impact on textile filter performance [1]. Nowadays, the formula method was generally used to calculate the porosity, and the bubble method was always used in testing pore size.

Influence of knitted fabric construction on the ultraviolet protection factor of greige and bleached cotton fabrics

The alarming increase of incidence of skin cancer has hastened development of ultraviolet (UV) protective clothing and research on UV protection of apparel. Although various fabric parameters that affect ultraviolet radiation (UVR) transmission were studied by researches, most of them focused on woven fabrics and chemical approach in enhancing UV protection. There were few studies concerning knitted fabrics, in particular the influence of fabric constructions on ultraviolet protection factor (UPF) and structural properties. The magnitude of transmission and scattering of UVR through a fabric is decided by fabric construction or knit structure, which is classified by geometrical arrangement of yarns and fibers of the fabric. This paper aimed at studying the influence of different knit structures upon the UPF with the three main knit stitches incorporated in the knitted fabric constructions, namely the knit, tuck and miss stitches. The UPF and structural characteristics, including thickness, weight, stitch density and porosity of greige and bleached knitted fabrics with different knit structures, are compared by adopting factorial analysis of variance. The results show that fabrics with miss stitches possess a higher UPF than fabrics with tuck stitches. The double-knitted fabrics have better UV protection than the single-knitted fabrics overall, but bleaching has different impacts on the UPF of single- and double-knitted fabrics. The study reveals that fabric thickness or weight cannot be used solely in explaining the UV protective performance of knitted fabrics. However, fabric porosity can be a good indicator for UV protection when comparing fabrics with similar fabric weight and thickness but different structures or fiber contents.

Investigation of pore parameters of woven fabrics by theoretical and image analysis methods

Fluid permeability property is an important performance feature of fabrics and must be considered during the designing processes of products. Since the rate of fluid flow through a textile is a function of viscosity, density, pressure gradient of fluid, and the pore properties of fabric, it is necessary to define pore properties by controlling the structural parameters of fabric for a certain area of use. Due to the complexity of fabric structure, modeling of pore structure and predicting the pore parameters are difficult. In this study, the interyarn porosity, pore size, and pore-size distribution of cotton woven fabrics were calculated by using two-dimensional (2D) and three-dimensional (3D) geometrical pore models and image analysis method. The effect of weave types and weft settings on the pore parameters and air permeability of fabrics were investigated, and the advantages of 2D, 3D geometrical pore models and image analysis method were compared.

Dynamic Permeability of Porous Elastic Fabrics

This paper describes permeability measurements for porous fabrics as influenced by strain, humidity, air flow rate, and fabric elasticity. The focus is on standard parachute fabrics, where the fabric's porosity and air permeability influence the rate of steady-state descent, and also affect the complicated fluid-structure interactions taking place during parachute opening and deployment. High strength nylon parachute fabrics showed relatively small permeability changes due to strain, humidity, and flow rate. Comparative measurements on elastomeric fabrics showed much larger changes in air flow due to fabric dimensional changes at high pressures and flow rates. Elastomeric fabrics that stretch and change permeability in response to higher pressures and flow rates may be able to reduce the “opening shock” during the parachute deployment phase.

The analysis of acoustical characteristics and sound absorption coefficient of woven fabrics

The amount of research conducted on sound absorption properties of woven fabrics in comparison to nonwoven and spacer textile fabrics is very limited. The main aim of this research is to study acoustical and sound absorption properties of woven fabrics. Normal incident sound absorption coefficient was determined via the impedance tube method. To achieve the objective of the research, general acoustical properties of textiles together with existing standards were thoroughly studied. Samples of woven fabrics having varying structural elements, such as weave type, weft yarn linear density, thickness created by layering of test fabrics, yarn spinning system and depth of air space at the back of samples were tested. Results showed that, for most samples while the maximum value of the sound absorption coefficient occurred at a frequency of 1000 Hz, the minimum value was observed at frequencies of 250 and 2000 Hz. Results showed that, the sound absorption coefficient of woven fabrics is influenced by both density and porosity of fabrics. It was found that, plain fabric absorbed sound wave more than the other weave types. Results also indicated that, for a given weft density, fabrics produced with weft yarn linear density of 24.5 tex has a higher absorption than fabrics woven with weft yarns of other counts. It was found that, finer weft yarn and higher thickness of fabric causes the noise reduction coefficient or NRC of the fabric to be increased. It was established that, fabrics woven using rotor-spun yarns exhibited the highest absorption in comparison to samples woven using ring-spun or compact yarns.

The impacts of thermal treatments on the physical properties of textile vascular prostheses

For nearly half a century textile prostheses have been intensively used in vascular surgery. They have saved millions of human lives, but they are not yet perfect. Graft failures have been, in part, attributed to the prostheses finishing processes, generally based on thermal treatments. These treatments permit to reduce fabric porosity and fix the wavy form of prosthetic tube walls involved by crimping process. Four tubular fabrics have been woven with different polyethylene terephthalate (PET) yarns spun under different industrial processes: Setila, Dacron, Diolen and Viscosuisse. Three heat setting techniques were investigated for prostheses crimping: dry heat, vapor heat and autoclaving. Crystallinity index and crystal growth in the equatorial directions have been calculated from Wide Angle X-ray Scattering scans. The aim was to analyze physical structural changes of PET fibers after thermal finishing processes applied to textile vascular prostheses and highlight fiber morphological evolutions related to these treatments. Viscosuisse yarns held the largest crystalline domains built up of numerous crystals but smaller than Dacron ones. However, the best crystalline configurations for the overall yarns were generally obtained for dry heat processes. Compromise regions of treatment conditions for prosthetic Dacron tubes were also obtained to optimize crystal development for the different crimping processes.

Influence of chitosan and porosity on heat and mass transfer in chitosan-treated porous fibrous material

This paper focuses on a theoretical investigation of the coupling mechanism of heat transfer and liquid moisture diffusion in chitosan-treated porous fibrous material. The porous fibrous materials made of cotton with different porosities are modified by chitosan solution with different concentrations. The moisture regain of the chitosan-treated porous fibrous material increases and the contact angle of the chitosan-treated fiber decreases significantly after modification. For comparison, the simultaneous heat and liquid moisture transfer in porous fibrous materials with different porosities modified by chitosan solution with different concentration are discussed. With specification of initial and boundary conditions, the distributions of the water vapor concentration in the void spaces, the volume fraction of the liquid water in the void spaces, the distribution of the water content in fibers and the temperature changes in chitosan-treated porous fibrous material are obtained numerically. The comparison with the experimental measurements shows the superiority of the numerical model in resolving the coupled heat and mass transfer in chitosan-treated porous fibrous material. Analysis of the computational and experimental results illustrates that the heat and mass transfer in chitosan-treated porous fibrous material is influenced by chitosan concentration and fabric porosity significantly.

Prediction of one-layer woven fabrics air permeability using porosity parameters

Air permeability is one of the fundamental textile properties influencing the design of comfortable clothes. In particular, it is very important in the field of technical textiles. Air permeability depends mainly on the fabric structure, which can be described by yarn linear density, type of yarn, warp/weft density and weave. The purpose of our study was to identify a small number of parameters that have the strongest influence on air permeability of cotton fabrics and enable its good prediction. Rather than focusing on the constructional parameters, we decided to include a composite parameter known from the theory of fluids, hydraulic diameter of pores, which treats rectangular-shaped pores as circular ones. In addition to the hydraulic diameter of pores, two other parameters were used for the prediction of air permeability: the number of macro pores and the total porosity of woven fabrics. 36 woven fabric samples were produced using nine frequently implemented weave types together with two warp densities (29.3 and 22 ends/cm) and two weft densities (15 and 20 picks/cm), resulting in four different densities of woven fabrics. The yarns had the same linear density and material in warp and weft directions. Air permeability measurements were performed with the Air Permeability tester FX 3300 Labotester III (Textest Instruments) according to the ISO 9237:1995 (E) standard. Principal components analysis revealed that the four investigated plain weave specimens behave differently than the other samples, which might be explained by weave structure. This multivariate statistical method also confirmed the appropriateness of the three selected parameters for air permeability prediction which was done using multiple linear regression. The high adjusted coefficient of determination (R2) value of 0.94 indicates that the model explains variability in the air permeability to a large extent.

Structure and Tensile Properties of Nano-Filament Knitted Fabrics by Alkali Treatment

Knitted fabrics have been widely used in different fields due to their high strength and elastic properties. However, these can only be used in limited applications due to poor liquid absorption owing to the large pore size of knitted fabrics. This study is focused on the structural characteristics of micro- and nano-filament warp as well as weft knitted fabrics. Nano-filament fabrics are manufactured by means of alkali treatment. Filament diameters are significantly reduced according to SEM micrographs. The decreased porosity of nano-filament fabrics indicates that nano-filament knitted fabrics possess excellent water absorptive capacity due to capillary action in the fabrics. Tensile behaviors of knitted fabrics in the wale and course directions are investigated as well.

Space–time finite element computation of complex fluid–structure interactions

AbstractNew special fluid–structure interaction (FSI) techniques, supplementing the ones developed earlier, are employed with the Stabilized Space–Time FSI (SSTFSI) technique. The new special techniques include improved ways of calculating the equivalent fabric porosity in Homogenized Modeling of Geometric Porosity (HMGP), improved ways of building a starting point in FSI computations, ways of accounting for fluid forces acting on structural components that are not expected to influence the flow, adaptive HMGP, and multiscale sequentially coupled FSI techniques. While FSI modeling of complex parachutes was the motivation behind developing some of these techniques, they are also applicable to other classes of complex FSI problems. We also present new ideas to increase the scope of our FSI and CFD techniques. Copyright © 2009 John Wiley & Sons, Ltd.

Computational and Experimental Investigation of Moisture Transport of Spacer Fabrics

This paper investigates the moisture transfer behavior of spacer fabrics. Spacer structures are knitted fabric constructions comprising two separate fabrics which are joined together by spacer threads. In order to investigate the dynamic moisture transfer of spacer fabrics, an experimental apparatus was developed which made the simulation of human body sweating possible. In the experimental section, the influence of some parameters such as the kind of spacer threads and also heat setting under drawing on moisture transport properties is investigated. Heat setting under drawing affects air permeability, thickness and porosity of spacer fabrics. The Results showed that water vapor produced by sweating can be easily and quickly transferred from the skin to the outer surface to keep the skin dry. In the computational section, a mathematical model was developed to describe moisture transport behavior of spacer fabric. The model was in high good agreement with the observations in the experiments.

Permeability in Engineered Non-woven Fabrics Having Patterned Structure

The patterned non-woven fabric structure is a typical non-homogeneous non-woven fabric and is frequently used as a hygienic medical absorbent material to control fluid transport for directional delivery. In this paper, the characteristics of the structural variation in both strip and point patterned non-woven fabrics are examined, and the relationship between the global permeabilities in both the transverse and in-plane directions in the patterned non-woven fabrics and the local fabric structural parameters (e.g. fiber diameter, fiber orientation distribution, fabric porosity, and local pattern dimensions) is established.