Relative Air Permeability Research Articles

Linear regression analysis of properties related to moisture management using cotton–polyester knitted fabrics

The complex evaluation of thermo-physiological comfort for a particular garment is still challenging, as it depends on the different structural parameters and individual properties of textiles. Measurement of relevant fabric characteristics requires very specific laboratory equipment, such as an M 290 moisture management tester (SDL ATLAS) or similar. For this reason, it is obvious that there is a great demand to predict the overall moisture management capability ( OMMC) based on the individual properties that are responsible for clothing comfort and testing according to different standards rather than OMMC-specific calculation using the M 290 tester. Therefore, in this research, linear regression analysis was performed using MATLAB software to predict the OMMC for cotton–polyester fabrics knitted in two patterns, namely 1 × 1 rib and half-Milano rib, using four percentages of fibers. Water vapor permeability, water vapor resistance, water absorption capacity, water absorption time, and air permeability were used as input variables for linear regression analysis to predict the OMMC of fabrics. The performed analysis has shown that the OMMC is directly dependent on the relative water vapor permeability and air permeability, and the linear regression equation suggested in this research can predict the suitability of a textile for a particular garment concerning its moisture management behavior.

Thermal Comfort Properties of 100% Cashmere Knitted Fabrics

The purpose of this research is to investigate the effects of knitting type (plain, rib, purl), knitting tightness (three different loop lengths), and plied-yarn (single-ply, two-ply and three-ply) on the thermal comfort properties of cashmere knitted fabrics. Thermal comfort properties of the sample fabrics were measured using Alambeta, Permetest, Textest 3300. Subsequently, the results were statistically evaluated with SPSS program. The findings of this research revealed that the knitting type, knitting tightness and plied-yarn usage significantly affect certain thermal comfort properties of cashmere knitted fabrics. Specifically, the plain knitted fabric exhibits the lowest thermal resistance value and the highest relative water vapor permeability value. The loose knitted fabric demonstrates the highest air permeability, while the fabric knitted with single-ply yarn has the lowest thermal conductivity and thermal resistance values, as well as the highest relative water vapor permeability and air permeability values.

Evaluation of the moisture management and air permeability of cotton/antistatic polyester knitted fabrics

This research fills in the missing knowledge on the moisture management and air permeability of knitted fabrics developed using mixed cotton/antistatic polyester yarns with both antibacterial and antistatic behavior to enhance their functionality. The effect of the knit pattern, technical side, percentage of fiber mixture and treatment on water absorption capacity and time, relative water vapor permeability and resistance, and air permeability of developed fabrics was investigated. The 1x1 rib knit and half-Milano rib knit patterns were applied in each 4 percentages of cotton and antistatic polyester and 3 types of finishing to prepare 24 fabrics. The water absorption capacity for 1x1 rib knit fabrics was in the range of 182–231% and 162–237% for the half-Milano knitted fabric with the ∼20% increase when increasing the percentage of antistatic polyester or applying the treatment. The water absorption time depended on the pattern, the fabric treatment, and the percentage of the fiber mixture. The applied antibacterial treatment significantly prolonged the water absorption time of most of the dyed and softened samples. The 1x1 rib knitted fabrics showed significantly higher water vapor and air permeability than the half-Milano rib knitted fabrics. The relative water vapor and air permeability of the treated samples increased significantly with an increasing percentage of polyester. Research results are of great practical value when designing new textiles and simulating mathematically their comfort behavior when choosing them for a particular garment.

Towards the effects of moss-dominated biocrusts on surface soil aeration in drylands: Air permeability analysis and modeling

Soil aeration is an important factor influencing soil biological and biochemical processes because it directly affects soil microbial activity and respiration. As an important living skin of the soil, biocrusts strongly impact various soil properties and play a vital role in maintaining surface soil structure and multifunctionality. Although there are several studies concerning the effects of biocrusts on soil respiration processes, it is still not well understood how biocrusts affect air permeability (Ka) and soil aeration in drylands. In a semiarid climate region of the northern Chinese Loess Plateau, the Ka and air-filled porosity (εa) of moss-dominated biocrusts established on aeolian sand and loess soil were measured as a function of soil water content under laboratory and in situ conditions and compared to measurements of bare soils. The relative air permeability (Kra) of biocrusts and bare soils was further analyzed and estimated with commonly applied Kra models that are based on the soil water retention curve (SWRC), and the performance of these models was specifically assessed for biocrusts. The in situ measurements yielded a 51.8% and 76.7% higher Ka for the biocrust-colonized aeolian sand and loess soil, respectively, when compared to the bare soils. Correspondingly, in comparison to the bare soils, the εa of the biocrusts also increased by 38.0% for the aeolian sand and by 52.4% for the loess soil. The laboratory measurements showed an 8.5%–9.3% increase of Ka for the biocrust-colonized soils from wet to dry conditions when compared to their bare counterparts, which was mainly attributed to their higher fine particle and organic matter contents as well as to the moss rhizoids. Moreover, a positive linear relationship (R2 > 0.43) was found between the log Ka and log εa for both biocrusts and bare soils. Additionally, the biocrusts exhibited higher water content at almost all matric potentials in comparison to the bare soils. The Kra of biocrusts was 22.0% higher for aeolian sand and 42.1% higher for loess soil when compared to the bare soils. The van Genuchten-Burdine and Brooks and Corey-Burdine models performed best with regard to the estimation of Kra (RMSE ≤ 0.100, bias ≤ 0.018). In general, biocrusts may greatly increase surface soil aeration due to their higher Ka and εa, and the soil aeration status of biocrusts can be indirectly assessed through their effective degree of soil water saturation. Our findings suggest that biocrusts should be carefully considered in further studies of soil aeration related to biological processes and gas and vapor transport in dryland ecosystems.

Generalized hydraulic constitutive model of unsaturated flow in heterogeneous soils

This study develops a generalized constitutive model to describe hydraulic properties of soils that consider the soil heterogeneity and water distribution. In this model, pore size distribution in a cross-section of representative element volume is assumed as a fractal characteristic. The heterogeneity of soils is described by two heterogeneous factors that calibrate the difference between local and bulk properties (i.e., porosity and water distribution). Based on the capillarity, adsorptive mechanism, and laminar flow assumption, we derive a physics-based hydraulic model containing the water retention curve (WRC), relative water permeability (RWP) curve and relative air permeability (RAP) curve. Various data sets are employed to validate the proposed model and the results show that the RWP and RAP of unsaturated soils can be well predicted by parameters obtained from WRC data sets. Besides, in comparison with other models, the proposed model has a much better performance for most data sets. Finally, the influence of the dual-porosity characteristic of structured soils on hydraulic properties is also addressed.

Relationships among water and gas transport properties in soils from natural and induced clay gradients

AbstractClay content in soil potentially has strong influence on soil structure and thereby controls soil physical, hydraulic, and gas transport properties. Only few studies have investigated the effect of clay content on saturated hydraulic conductivity (Ks) and gas transport parameters such relative gas diffusivity (Dp/D0) and air permeability (Ka) under varying conditions of clay contents. In this study, two clay gradients were investigated: a natural clay gradient and an induced (clay mineral attapulgite‐controlled) clay gradient. We determined the effect of the two clay gradients on soil air and water parameters and identified the potential relationships between these parameters and other physical properties. The results indicated that all Dp/D0, Ka, and Ks decreased with increasing clay content. The differences among the various treatments were dependent on the soil pore characteristics (air‐filled porosity, ε; pore continuity, POA; pore tortuosity, τ; and pore size distribution). Under the natural clay gradient, the increased clay content resulted in 52.8% more micropores and 35.2% fewer macropores. The slope of τ vs. clay content under the induced clay gradient was found to be higher than that under the natural gradient. Statistically meaningful correlations could be found between Ks and Ka (|r| = .904) and also between Ks and Dp/D0 (|r| = .810), whereas Dp/D0 was evidenced to be better correlated with Ks regardless of the type of clay gradient (P < .01). The results thus provide a valuable experimental and numerical insight to develop useful correlations among Ks, Ka, and Dp/D0 under differing clay gradients.

Research on preparation and characterization of Ti-Ti5Si3 gradient composite porous material via in-situ reactive process

Gradient composite porous material can reach a high filtering accuracy with larger filtration flux, and the filter elements applied in separation equipment can enhance the filtration efficiency and reduce the energy consumption. Ti-Ti5Si3 gradient composite porous material was successfully prepared by in-situ reaction process with the raw materials of Ti powder and high purity quartz tablets. Microstructures and filtration properties prepared under different synthesized conditions have been studied, including the parameters of pressure sintering (additional loads and temperatures) and powder particle sizes. The synthesized granules on the membrane are well distributed with the size of ∼1.0 µm, and the thickness of the membrane is 3.0∼6.3 µm. The relative air permeability coefficient of porous membrane reduces raptly compared to the sample matrix due to the decrease of pore size. The all synthesized membranes show the presence of Ti and Ti5Si3 phases. There are two distinct layers observed in the membrane layers prepared by fine powder due to in-situ over-reaction.

Effects of Water Retention Curves and Permeability Equations on the Prediction of Relative Air Permeability

AbstractAppropriate simulation of air flow in porous media needs an accurate estimate of relative air permeability (RAP). Combining 2 traditional and 2 fractal water retention curves (WRCs) respectively with 6 permeability equations, we obtained 12 statistical and 12 fractal RAP models. All these models were subsequently tested with 31 experimental datasets of disturbed soils to examine their predictive ability for RAP. Results showed that irrespective of using traditional or fractal WRCs, the six permeability equations exhibit consistent performances for RAP prediction. The modified Burdine (Yang & Mohanty, 2015, https://doi.org/10.1002/2014wr016190) permeability equation best fits the published soil data. In addition, the selection of a proper permeability equation is critical for accurately predicting the RAP, whereas the choice of WRCs has little effect on RAP prediction. This finding suggests that for disturbed soils, air permeability is primarily dictated by the pore tortuosity‐connectivity but not the pore size distribution inferred from the WRCs.

Evaluation of the Moisture and Thermal Characteristics of Knitted Sport Wear Fabrics (Dept.T)

The main aim of this work was study the effect of fiber composition on the moisture and thermal properties for sport wear knitted fabrics. We also studied the effect of using single and double layer fabric on the moisture and thermal properties of these fabrics. To know how heat and water are transported through each fabric, measurements of their physical properties (thermal resistance, thermal conductivity, thermal absorptivity, heat flow, relative water vapor permeability and air permeability) were made in laboratories. The effects of fiber composition and the clothing assembly (one or two layers) have a highly significant effect on both moisture and thermal properties of sport wear knitted fabrics and also there were a high correlation between fabric thickness, fabric porosity, fabric air permeability, the relative water vapor permeability and fabric thermal properties

A fractal capillary model for multiphase flow in porous media with hysteresis effect

Multiphase flow in unsaturated porous media exhibiting hysteretic phenomenon is of great significance to oil and gas recovery, agriculture, and hydrology etc. Water retention curve (WRC) and relative hydraulic conductivity function (RHC) as well as relative air permeability function (RAP) are usually employed to characterize the transport properties of porous media. A new fractal capillary model accounting for the hysteresis effect is developed in this paper for the multiphase flow in unsaturated porous media. The analytical expressions for WRC, RHC and RAP under drying and wetting paths are derived accordingly. The proposed fractal capillary model shows good consistent with available experimental results. It has been found that the pore-throat structure in the proposed fractal capillary model takes an important influence on the hysteresis effect and fluid flow, especially for the non-wetting phase. The present work may be helpful for understanding the complex mechanisms of hysteresis effect and transport processes in unsaturated porous media.

Measurement of the relative air permeability of compacted earth in the hygroscopic regime of saturation

The hygroscopic behavior of earthen materials has been extensively studied in the past decades. However, while the air flow within their porous network may significantly affect the kinetics of vapor transfer and thus their hygroscopic performances, few studies have focused on its assessment. For that purpose, a key parameter would be the gas permeability of the material, and its evolution with the relative humidity of the air. Indeed, due to the sorption properties of earthen material, an evolution of the water content, and thus of relative permeability, are foreseeable if the humidity of in-pore air changes. To fill this gap, this paper presents the measurement of relative permeabilities of a compacted earth sample with a new experimental set-up. The air flow through the sample is induced with an air generator at controlled flow rate, temperature, and humidity. The sample geometry was chosen in order to reduce, as much as possible, its heterogeneity in water content, and the tests were realized for several flow rates. The results, which show the evolution of gas permeability with the relative humidity of the injected air and with the water content of the material, either in adsorption or in desorption, were eventually successfully compared to predictions of the well-known Corey's law.

Prediction of Relative Air Permeability of Porous Media With Weibull Pore Size Distribution

AbstractModeling convective air movement in unsaturated porous media requires appropriate characterization of the relative air permeability (RAP). Adopting Assouline et al. (1998, https://doi.org/10.1029/97WR03039) water retention function that is based on the Weibull pore size distribution, this study was conducted to derive seven new predictive RAP models. These 7 new models, together with another 3 models developed by Assouline et al. (2016, https://doi.org/10.1002/2015WR018286), were then compared with data from 30 disturbed soil samples to investigate their predictive RAP performances. The model and data comparison results showed that the modified Burdine, modified Mualem, and modified Alexander and Skaggs relative permeability models proposed by Yang and Mohanty (2015, https://doi.org/10.1002/2014WR016190) had the highest accuracy for the RAP prediction among the 10 investigated models, which indicated that the tortuosity and connectivity exponent of water phase should be smaller than that of air phase for the disturbed soil samples. The modified Burdine, modified Mualem, and modified Alexander and Skaggs models were then the suggested RAP parameterizations for the subsurface multiphase flow numerical simulation.

Actual and Relative Soil Air Permeability as Soil Physical Quality Index

Developing indices to evaluate soil physical quality can facilitate diagnosis and decision-making. In this context, intrinsic soil air permeability (Kair) is a physical parameter very sensitive to structural changes due to soil management. However, it is important to establish a standard Kair, considering a reference soil physical state. Thus, the present study proposes to create an index called relative soil air permeability (Kairr), taking as reference the physical state of maximum bulk density, obtained by normal Proctor test. Kairr is the ratio between compacted soil air permeability (Kairc) and actual soil air permeability (Kair). Kairr was evaluated using disturbed and undisturbed samples of a Latossolo and a Planossolo. The experimental design was completely randomized, with four treatments (T1-Latossolo 0-0.1 m; T2-Latossolo 0.1-0.2 m; T3-Planossolo 0-0.1 m and T4-Planossolo 0.1-0.2 m) and eight replicates. Kairr was equal to 0.1032 and 0.3547 in the Latossolo and to 0.4115 and 0.1923 in the Planossolo, in the 0-0.1 and 0.1-0.2 m layers, respectively. These characteristic values observed in both soils and layers are due to the management adopted in the area. In Latossolo, the use of medium harrow has made the 0.1-0.2 m layer more restrictive to air movement, whereas the Planossolo showed lower values of relative soil air permeability in the 0-0.1 m layer due to animal grazing, which has greater impact on the superficial portion of the soil.

MODIFIED POLYSACCHARIDES APPLICATION FOR ANTISEPTIC LEATHER PROCESSING

Urgency of the research. The leather is very sensitive to microbial degradation during processing, storage, transportation and use. Therefore, it is important to search for preparations and methods of leather treatment, providing specific fungicidal properties, depending on the purpose. Target setting. To establish the possibility of using a composition based on modified polysaccharides with the addition of PVA and Quaternary ammonium salts for leather treatment to give fungicidal properties. Actual scientific researches and issues analysis. Recent open access publications have been reviewed regarding polymeric materials, antiseptic and fungicidal preparations used to obtain of insole leather with special properties. Uninvestigated parts of general matters defining. The principle of action of many fungicidal or bactericidal products when used together has not been established. In particular, in the case of the simultaneous use of modified polysaccharides and quaternary ammonium salts for antiseptic treatment of the leather. The research objective. The purpose of the work is to research antiseptic properties of the coating based on modified polysaccharides with the addition of quaternary ammonium salts (QASc) for insole leather. The statement of basic materials. It is established that the polymer composition based on modified starch and polyvinyl alcohol with the addition of a quarter of ammonium salts gives the leather antiseptic properties, this is proved by the delay of growth of microorganisms by 3-4 mm from the edge of the sample. The relative air permeability of the leather is reduced by almost half (from 1.18 · 103 to 0.54 · 103 cm3 / cm2 • h), the leather porosity is also reduced by 5-10 % and the stiffness is increased by 40 %. Conclusions. As a result of the conducted researches it is established that although treatment of leather surface by a solution CMS: PVA and QASс reduction of the tensile strength of leather but in its physical and mechanical properties the treated leather meets the requirements for the lining, has antiseptic properties and can be used for the manufacture of insoles.

Development of biobased socks from sustainable polymer and statistical modeling of their thermo-physiological properties

Abstract Polylactic acid (PLA) is a biodegradable and compostable polymer obtained from annually renewable resources and is acknowledged to be sustainable and eco-friendly polymer with substantial commercial prospective as a textile fiber however, this polymer has not been investigated much in apparel applications. Therefore in this study it was aimed to develop biobased compostable socks from PLA draw textured melt spun yarns and to examine the effect of yarn linear density, fabric structure and stitch density on thermo-physiological characteristics of PLA based socks. 100% PLA based multifilament yarns of two different linear densities were melt spun and later draw textured on false twist texturing machine to be used for socks knitting. Single jersey and rib structures were produced with two different stitch densities to investigate their effect on thermal resistance, relative water vapour permeability, thermal conductivity, vertical wicking and air permeability of the socks. Minitab statistical software was employed to analyze the results of test samples. The coefficients of determinations (R2 values) presented good estimation capability of the established regression models. The outcomes of this research may be useful in determining suitable manufacturing requirements of PLA based socks to accomplish precise thermo-physiological properties.

Statistical Modeling of Thermal Properties of Biobased Compostable Gloves Developed from Sustainable Polymer

Polylactic acid (PLA) is a biodegradable and compostable polymer obtained from annually renewable resources and is acknowledged to be sustainable and non-polluting polymer with substantial commercial prospective as a textile fiber however, there is lack of literature on apparel applications of this polymer. Therefore in this study it was aimed to develop biobased compostable gloves from PLA draw textured melt spun yarns and to examine the effect of yarn linear density, fabric structure and stitch density on thermo-physiological comfort and moisture management properties of PLA based gloves. 100 % PLA based multifilament yarns of two different linear densities were melt spun and later draw textured on false twist texturing machine to be used for gloves knitting. Single jersey and rib structures were produced with two different stitch densities to investigate their effect on thermal conductivity, thermal resistance, relative water vapour permeability, air permeability and moisture management properties of the gloves. Minitab statistical software was employed to analyze the results of test samples. The coefficients of determinations (R2 values) presented good estimation capability of the established regression models. The outcomes of this research may be useful in determining suitable manufacturing requirements of PLA based gloves to accomplish precise thermo-physiological and moisture management properties.

Influence of stress and water content on air permeability of intact loess

Air permeability is one of the key parameters in performing consolidation analysis of unsaturated soil. Few data are available regarding the air permeability for intact loess under different applied stresses. The work reported in this paper evaluated the air permeability at isotropic stress using data obtained from laboratory investigations for intact loess. Air permeability tests were performed on specimens of intact loess at various water contents and isotropic stresses. Stress remarkably affected air permeability as a function of both liquid saturation and volumetric air content. There were all unique relationships not only between relative air permeability and liquid saturation as well as relative volumetric air content, but also between air permeability and modified air saturation for different stresses. The relative air permeability against liquid saturation could be well described by the Parker–van Genuchten–Mulaem (P-vG-M) model in terms of total liquid saturation. The relationship between relative air permeability and relative volumetric air content could be more conveniently expressed by the reference point power law (RPL) model, using the reference point values at natural water content rather than that at air-dried water content. Compared with the other two models, the proposed modified air saturation power law (MAPL) model was more appropriate to predict the air permeability.

Evaluating the relative air permeability of porous media from their water retention curves

AbstractAccurate modeling of water and air flow in porous media requires the definition of the relevant hydraulic properties, namely, the water retention curve (WRC) and the relative hydraulic conductivity function (RHC), as well as the definition of the relative air permeability function (RAP). Capitalizing on the approach developed previously to represent the RHC, a new model allowing the prediction of RAP based on information resulting from the WRC is proposed. The power value ηa in the model is a decreasing exponential function of the coefficient of variation, ɛ, characterizing the pore size distribution of the porous medium, and derived from its WRC. The model was calibrated using data from 22 disturbed and undisturbed soil samples and was validated using data from eight soil types ranging from quartz sand to silty clay loam. The proposed model provided accurate prediction of the soil RAP and performed in some cases (sandy loam and silty clay loam soils) better than available alternative models.

Intrinsic and relative permeabilities of shredded municipal solid wastes from the Qizishan landfill, China

Testing specimens for laboratory analysis were created from borehole samples of municipal solid waste (MSW) drilled from different depths at the Qizishan landfill, China. Laboratory water retention curve (WRC), water permeability, and air permeability tests were carried out to study the effects of compression and biodegradation on intrinsic permeability and the effect of water content on the relative permeability of the borehole specimens. The value of intrinsic permeability coefficient, k0, in the Kozeny–Carman model was found to be influenced by both the compression and biodegradation processes. Furthermore, the intrinsic permeability, ki, measured by air was found to be about one order of magnitude larger than that measured by water. Based on the regression results of WRC, relative water and air permeabilities were analyzed through the van Genuchten–Mualem (vG–M) model. The measured relative air permeability could be well fitted by the vG-M model. The value of parameter γv was found to be critical for a good prediction of relative water and air permeabilities using the vG-M model.

Role of filament cross-section in properties of PET multifilament yarn and fabric. Part I: Effect of fibre cross-sectional shape on transmission behaviour of fabrics

The transmission property of a fabric is a key factor that affects clothing’s comfort and decides the functional potential of clothing. The dependence of filament cross-section with varying shape factor (SF) on air, moisture and thermal transmission behaviour of fabric is determined in case of polyester multifilament woven fabrics. The linear density of each filament is kept identical for all 12 cross-section shape filaments. The SF of filament cross-section is an important factor which remained the prime factor to influence the transmission behaviour of fabric samples directly in many cases. Other indirect factors that influence the transmission behaviour of fabrics when the SF is identical are yarn structure, inter-fibre and inter-yarn space. Twelve different novel cross-sectional shapes are considered to make the multifilament woven polyester fabrics. The fabrics made from multifilament yarns having different SFs show that relative moisture vapour permeability and air permeability decrease with the rise in SF. Wickability increases with the rise in the SF of a filament cross-section. Multilobal, hexalobal and plus shapes were made a part of novel cross-sectional shapes in order to develop fabrics of higher comfort index.