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Unsaturated fluid flow in thin porous media depends on hydraulic properties, such as the capillary pressure, P c , as a function of saturation, S. We measured this relationship for two different types of compressible thin hydrophilic fibrous layers under varying conditions. Among other factors, we changed the number of layers and the overburden pressure (i.e. the confined solid pressure applied on top of the sample) imposed on one layer or a stack of layers. Applying an overburden pressure drastically affected the P c (S) curves. However, increasing the number of fibrous layers had little impact on the capillary pressure–saturation curves. We also investigated the effect of multiple imbibition–drainage cycles on the P c (S) data. Measured data points were used to find general expressions for the P c (S) relationships of compressible thin porous media. Existing quasi-empirical correlations used in vadose zone hydrology, notably expressions by van Genuchten (Van Genuchten MTh. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 1980; 44: 892-898) and Durner (Durner W. Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resour Res 1994; 32: 211–223) for single- and dual-porosity media, respectively, were employed to fit the measured data points. [ABSTRACT FROM AUTHOR]

The current study fabricated nylon/high-resilience bonding polyester (HRPET) nonwoven fabric with various needlepunching parameters and investigated the effect of these variations on the response of high-density flexible foam under static loading and low-velocity impact. The needle-punching depth and frequency are selected as variations. The HRPET fiber generates bonding-points when being thermally treated, which provides resilience properties on the sandwich flexible composites. The results find a substantial relationship between the temperature of thermal treatment and the absorption of low-velocity impact energy which is mainly because of the increase of fiber connection force. The impact force is eliminated by 8255 N at most. Needle-punching depth contributes to resistance to static loading and the highest resistance was 2043 N. [ABSTRACT FROM AUTHOR]

A three-part practical study was conducted on a commercial-grade hydroentanglement system to determine the progressive and cumulative fabric effects of multiple hydroentangling impacts at three different high (hydroentangling) water pressures (HWPs) on classical properties of the resulting nonwoven fabrics made with a substrate of commercially cleaned greige cotton lint. In the first part of the study, the progressive and cumulative effects of a series of four hydroentangling passes (equal to eight hydroentangling exposures or impacts) were studied at a relatively low HWP of 65 bars. In the second and third parts, the progressive and cumulative effects of multiple hydroentanglements at relatively higher HWP(s) of 90 bars and 130 bars were studied. The hydroentangling energy required for the various fabrics (made with the different HWPs and number of hydroentangling passes or impacts) was calculated to assess the overall impact of the energy on the fabric properties. The study has shown that each successive hydroentangling pass and each elevated HWP generally resulted in decreased fabric weight, thickness and air permeability and increased fabric whiteness and water absorbency. The tensile properties of the fabrics, in both the machine direction (MD) and the cross direction (CD), generally increased progressively with each successive hydroentangling pass at the low HWP of 65 bars, but this trend, especially in the CD, was not pronounced at the HWPs of 90 bars and 130 bars, perhaps indicating the attainment of optimum hydroentanglements and hence of tensile properties in the first pass alone at the higher HWPs. The hydro energy imparted to formation of the various fabrics made with the above stated process parameters of interest have shown that the two or four passes of the substrate at the low 65-bar HWP required less energy and yielded greater fabric absorbency compared to the one or two passes of the substrate at (twice) the HWP of 130 bars. On the other hand, only one pass of the substrate at 90 bars and 130 bars yielded greater tensile strength with reduced energy requirement, compared to the four passes at 65 bars. These results show that, depending on the required or preferred fabric properties, the stated hydroentangling process parameters can be considerably manipulated to achieve efficient hydroentanglement and improved energy efficiency. [ABSTRACT FROM AUTHOR]

A sound absorption model of kapok-based fiber nonwoven fabrics, based on the Biot–Allard model, has been developed by considering the heat conduction performance of the materials and the limpness of the fiber frame. Comparisons of sound absorption coefficients and specific surface impedance calculated by the Biot–Allard model and the new model with the measured values for four different kinds of kapok-based fiber nonwoven fabrics have been made. It is shown that the new model provides better predictions than the Biot–Allard model. The new model may be the theoretical foundation for the design of industrial products for kapok materials. [ABSTRACT FROM PUBLISHER]

Previous research had shown that processing greige cotton on a commercial-grade hydroentanglement (HE) system at a water pressure greater than 120 bar resulted in a low-weight hydrophilic nonwoven fabric. With that ability to make hydrophobic greige cotton easily wettable and hence absorbent without the conventional scouring phase, an investigation was conducted to determine whether a fabric made by hydroentangling greige cotton fibers at a high water pressure could be successfully bleached without the traditional scouring. The investigation involved production of greige cotton nonwoven fabrics at a low hydroentangling water pressure of 60 bar and at a high hydroentangling water pressure of 135 bar and their subsequent evaluations before and after scour only, one-stage bleach only, and two-stage scour and bleach. In the results, both the 60 bar and 135 bar fabrics bleached successfully in the two-stage bleaching process and yielded acceptable absorbency and whiteness values. However, when bleached in the single-stage bleaching process with no separate scour, the 135 bar fabric still produced the whiteness index almost equal to that obtained in the two-stage bleaching process and even equal to that of a fabric made with commercially scoured and bleached cotton fibers, but the 60 bar fabric yielded about 15% lower whiteness index value while its wettability-induced improved water absorbency still was comparable to that obtained via the two-stage bleaching. This shows that a hydroentangled greige cotton fabric produced at a high enough water pressure (hydro energy) could be bleached satisfactorily without the traditional scouring chemicals and that a fabric produced even at a lower water pressure and bleached without scouring could still be satisfactory for subsequent aqueous treatments for certain end-use applications where the whiteness may not be as critical as the absorbency. [ABSTRACT FROM PUBLISHER]

Through nonwoven hydroentanglement of greige cotton blends with polyester and nylon, varying degrees of fiber surface polarity, swelling, and absorbance can be achieved. Electrokinetic properties of nonwoven blends made with Ultra Clean™ cotton (100% greige or virgin cotton) and polyester or nylon in 40:60 and 60:40 ratios demonstrated distinct differences in charge, swell, and per-cent moisture uptake capability. An electrochemical double layer analysis of charge based on a pH titration (pH 1.5–11 in 1 mM KCl) was employed to measure the relative fiber and fabric surface polarity (ζplateau), which ranged from −60 to −26 millivolts. A linear relationship of fiber swelling (Δζ) and per cent moisture content is apparent when greige cotton and synthetic fibers are blended. Water contact angles revealed that the cotton/synthetic fiber blends were hydrophobic (contact angle >80°) while retaining significant absorbency. The greige cotton/synthetic nonwoven materials, however, possess absorbent properties characterized by varying degrees of moisture uptake, fiber polarity, and swelling attributes similar to absorbent fluid transport materials present in the layers of incontinence products. Electrokinetic properties of the blended greige cotton/synthetic nonwovens are correlated to absorbent incontinence materials. [ABSTRACT FROM AUTHOR]

Two sets of nonwoven fabrics of nominal density, 80 g/m2, have been produced on the pilot plant equipment comparable to that used in commercial production, using two different forms of greige (non-bleached) cotton lint. One was regular cotton taken from a randomly picked classical bale and the other was mechanically pre-cleaned cotton produced by a well known US cotton producer and ginner. The fabrics were produced by using a pre-needling, needlepunch system and a hydroentanglement system. Some of the fabric in each set was scoured only and some was both scoured and bleached. All the fabrics were tested for a comparison of their typical physical and mechanical properties, which, along with the fiber and fabric processing metrics, are discussed in this article. The information obtained from this comparative study has shown that although both the regular and the pre-cleaned greige cottons can be satisfactorily processed on the conventional cotton opening, cleaning and carding equipment to ultimately produce acceptable nonwoven fabrics, the pre-cleaned cotton may be processed without the traditional cotton cleaning/carding equipment that is not available at almost all nonwovens manufacturing entities today. A ‘nonwovens card’ (i.e., without the revolving flats) should be adequate to efficiently card the pre-cleaned greige cotton, since the latter is indeed very clean to start with. [ABSTRACT FROM PUBLISHER]

In this paper we report on the water permeability behavior of nonwoven fabrics produced from flax fibers. Three different types of needle punched nonwoven fabrics are produced by varying the depths of needle penetration during the needle punching process. The pore size and its distribution in the nonwoven fabrics are measured by liquid extrusion porometry. Water permeability is measured by the water permeability testing instrument working on the principle of falling hydraulic head method. A finite element analysis is employed to predict the flow velocity through the nonwoven fabrics. A good correlation is achieved between the average velocity data obtained from water permeability test and theoretical prediction based on finite element analysis. The pore size and its distribution play an important role in water permeability characteristics. [ABSTRACT FROM AUTHOR]

The nature of bonds in staple nonwovens bonded with thermoplastic fibers is examined with optical and scanning elec tron microscopes. The adhesive joints in rayon-vinyon and polyester-polyester systems are of the improper type, i.e., failure occurs at the bond interface.A quantitative method of characterizing the level of bonding in lightly bonded nonwovens is presented, based on dis tributions of effective fiber length and orientation. The first two moments of the effective length distribution are linearly related to binder concentration and bonding temperature in lightly bonded webs. An empirical relationship between breaking strength and bonding variables is also presented. [ABSTRACT FROM PUBLISHER]

The performance characteristics of nonwoven fabrics have been studied as a function of fiber properties, binder properties, and web construction. The particular type of nonwoven selected for study was a web of random-laid base fibers in which randomly placed thermoplastic fibers provide the bonds. The responses studied were those related to rupture, elastic, and handle (aesthetic) properties. Fourteen variables were investigated: Base fiber linear density, base fiber staple length, amount of crimp in base fiber, post-yield extension of base fiber, type of binder, linear density of binder, staple length of binder, binder concentration, mass per unit area of nonwoven, amount of needle looming, number of laminations per web weight, pressure of bonding, temperature of bonding, and time of bonding. The performance characteristics measured as a function of these variables were maximum tenacity at dry and wet conditions, elongation at dry and wet conditions, tear strength, abrasion resistance, elastic modulus at dry and wet conditions, proportional limit at dry and wet conditions, crease recovery, bending length, flexural rigidity, bending modulus, bulk density, and air permeability. Crimp, linear density, and staple length of the base fiber influence rupture, elastic, and handle prop erties, as expected. Binderproperties, other than type, have no effect due to the destruction of the fiber in the bonding process. Bonding conditions, particularly pressure and temperature, are extremely influential in all types of properties. These variables govern the effectiveness of the bonds. Concentration of binder is extremely important to all types of responses since it governs the number and distribution of bonds. Needle looming affects only rupture properties. [ABSTRACT FROM PUBLISHER]