Behnam Pourdeyhimi | North Carolina State University (original) (raw)

Papers by Behnam Pourdeyhimi

Journal of Membrane Science, 2013

Meltblowing is a unique one-step process for producing self-bonded fibrous nonwoven membranes dir... more Meltblowing is a unique one-step process for producing self-bonded fibrous nonwoven membranes directly from polymer resins, with average fiber diameter ranging between 1 and 2 mm. Determining routes for making nano-or submicron-fibers using this process are desirable since there are many manufacturing assets that are already in place. It is envisaged that these nonwoven membranes will find applications in critical areas such as medical, hygiene, filtration, bioseparation, and others. In this study, we investigate the influence of different die configurations and operating conditions on fiber and web characteristics. We also report on strategies for reducing the fiber size below one micron to achieve higher filtration quality at lower basis weight relative to the conventional meltblown webs. Their performance is compared to a control meltblown sample produced by using a typical die design. We find that production of nano-meltblown membranes with an average fiber size in the range of 300-500 nm using this new die design is possible and report on process operating conditions that result in such structures. These samples achieve equal filtration efficiencies to that of our control sample at 88% reduced basis weight but at a lower polymer throughput. The lower basis weight also resulted in a lower pressure drop and overall, the new samples exhibited a higher quality factor, twice that of the control. These results show significant promise for the use of nano-meltblown fibers in filtration applications.

Polymer, 2016

In this work the three-dimensional architecture and properties of solution-blown laydown formed o... more In this work the three-dimensional architecture and properties of solution-blown laydown formed on a rotating drum are studied using the system of quasi-one-dimensional equations of the dynamics of free liquid polymer viscoelastic jets moving, evaporating and solidifying, while being driven by a surrounding high-speed air jet. Solution blowing of multiple polymer jets simultaneously issued from a nosepiece and collected on a rotating drum is modelled numerically. The numerical results on the volumetric porosity of nonwoven laydown are compared with the experimental data of the present work. The numerical predictions are in good agreement with the experimental data and elucidate the effect of the angular drum velocity on the 2 mass and angular fiber distribution, as well as the volumetric porosity and permeability of the solution-blown nonwovens. It was found that instead of doing any upstream modification of the solution blowing process, the easiest way to control the laydown structure (the mass and angular fiber distribution, as well as the volumetric porosity and permeability) is to vary the angular velocity of the collecting drum.

Journal of Applied Physics, Feb 15, 2012

Soy protein=nylon 6 monolithic and core-shell nanofibers were solution-blown and collected on a r... more Soy protein=nylon 6 monolithic and core-shell nanofibers were solution-blown and collected on a rotating drum as fiber mats. Tensile tests of rectangular strips of these mats revealed their stress-strain dependences. These dependences were linear at low strains which correspond to their elastic behavior. Then, a plastic-like nonlinearity sets in, which is followed by catastrophic rupture. Parameters such as Young's modulus, yield stress, and specific strain energy were measured. The results were rationalized in the framework of the phenomenological elastic-plastic model, as well as a novel micromechanical model (the latter attributes plasticity to bond rapture between the individual overstressed fibers in the mat). Besides, the effects of stretching history, rate of stretching, and winding velocity of the collector drum on the strength-related parameters are studied. The results for soy protein=nylon 6 nanofiber mats are also compared to those for solution blown pure nylon 6 mats, which were produced and tested in the same way. V

Annals of Biomedical Engineering, May 1, 1986

A study of the fracture behaviour of Kevlar 29 reinforced dental cement is undertaken using both ... more A study of the fracture behaviour of Kevlar 29 reinforced dental cement is undertaken using both linear elastic and nonlinear elastic fracture mechanics techniques. Results from both approaches-of which the nonlinear elastic is believed to be more appropriate-indicate that a reinforcing effect is obtained for the fracture toughness even at very low fibre content. The flexural strength and modulus are apparently not improved, however, by the incorporation of Kevlar 29 fibres in the PMMA cement, probably because of the presence of voids, the poor fibre/matrix interfacial bonding and unsatisfying cement mixing practice. When compared to other PMMA composite cements, the present system appears to be probably more effective than carbon/PMMA, for example, in terms of fracture toughness. More experimental and analytical work is needed so as to optimize the mechanical properties with respect to structural parameters and cement preparation technique.

Journal of Engineered Fibers and Fabrics, Jun 1, 2006

In this work we report on our algorithm for generating 3-D virtual structures resembling un-bonde... more In this work we report on our algorithm for generating 3-D virtual structures resembling un-bonded fibrous webs. The paper discusses short and infinitely long fibers, each emulating a category of nonwoven fibrous medium. The structure Solid Volume Fraction (SVF), being the most important characteristic of a fibrous porous medium, is calculated for different fiberwebs and discussed in details. It is shown that the SVF of the fibrous structures generated by our algorithm is independent of the basis weight. In other words, the porosity of the medium is only a function of the fiber properties-this is as expected. It is also demonstrated that by decreasing the fiber diameter while keeping other properties of the virtual fiberweb constant causes the SVF to decrease almost linearly. The same is not observed for the fiber rigidity. The capability of our algorithm for generating fibrous webs made up of layers of different fibers is demonstrated and their properties are discussed. The application of such virtual fibrous structures in modeling transport phenomena in nonwoven materials and their potential applications in loaddeformation studies are discussed.

International nonwovens journal, Jun 1, 2001

The mechanical properties, namely, tensile modulus, maximum stress in tension and elongation at m... more The mechanical properties, namely, tensile modulus, maximum stress in tension and elongation at maximum stress of thermally point-bonded nonwoven fabrics with different bonding temperature have been evaluated. Image acquisition and analysis techniques have been used to quantify structural parameters such as fiber orientation distribution function, bond-region strain, and unit cell strain during controlleddeformation experiments and to identify failure mechanisms. We have shown that an in situ experimental visualization and measurement of the structural changes occurring during controlled-deformation experiments can help establish links between mechanical properties and the structure properties of nonwoven fabrics. Load Cell

Journal of Applied Polymer Science, Sep 20, 2022

Journal of Engineered Fibers and Fabrics, 2019

Carding is a common web-forming process used for staple fibers in the nonwovens industry. Carded ... more Carding is a common web-forming process used for staple fibers in the nonwovens industry. Carded webs can be produced with bicomponent staple fibers designed to split into fine fibers. Splittable bicomponent fibers offer benefits such as increased surface area, improved hand, decreased pore size, improved cover, and enhanced strength. Splittable bicomponent fibers within carded webs can be split and bonded utilizing high-pressure water jets during the hydroentangling process. Staple fibers may be produced in many different lengths. However, the effect of staple fiber length on the nonwoven carding process and structure-property relationships of carded, hydroentangled nonwoven fabrics composed of splittable bicomponent fibers is not well understood. During this research, polyester/polyethylene 16-segmented pie, bicomponent fibers with lengths ranging from 2.54 to 15.24 cm were produced, carded and bonded by hydroentangling. All fiber lengths used during this research were successfully carded, and no significant challenges were observed during carding. Fabric performance was evaluated with air permeability and burst strength testing. Data sets were statistically evaluated with one-way and two-way analysis of variance to determine whether fiber length significantly affected fabric structure and properties. In general, the solid volume fraction and air permeability of the samples were affected by fiber length. However, fiber length did not strongly affect the burst strength of hydroentangled fabrics.

Journal of Composite Materials, Dec 6, 2020

Calendered nonwovens, formed by polymeric fibres, are three-phase heterogeneous materials, compri... more Calendered nonwovens, formed by polymeric fibres, are three-phase heterogeneous materials, comprising a fibrous matrix, bond-areas and interface regions. As a result, two main factors of anisotropy can be identified. The first one is ascribable to a random fibrous microstructure, with the second one related to orientation of a bond pattern. This paper focuses on the first type of anisotropy in thin and thick nonwovens under uniaxial tensile loading. Individual and combined effects of anisotropy and strain rate were studied by conducting uniaxial tensile tests in various loading directions (0 , 30 , 45 , 60 and 90 with regard to the main fabric's direction) and strain rate (0.01, 0.1 and 0.5 s À1). Fabrics exhibited an initial linear elastic response, followed by nonlinear strain hardening up to necking and final softening. The studied allowed assessment of the extent the effects of loading direction (anisotropy), planar density and strain rate on the mechanical response of the calendered fabrics. The evidence supported the conclusion that anisotropy is the most crucial factor, also delineating the balance between the fabric's load-bearing capacity and extension level along various directions. The strain rate produced a marked effect on the fibre's response, with increased stress at higher strain rate while this effect in the fabric was small. The results demonstrated the differences of the mechanical behaviour of fabrics from that of their constituent fibres.

Journal of The Textile Institute, Oct 3, 2008

Hydroentangling is a process that uses waterjet curtains issued from a series of parallel jethead... more Hydroentangling is a process that uses waterjet curtains issued from a series of parallel jetheads (manifolds) for entangling and interloping fibres in a loose fibre web carried on a belt or perforated surface. The efficient removal of the stagnant water remaining from each waterjet curtain is crucial for the success of fibre entanglement when the web reaches the next jet-head. In this article, we discuss different methodologies that can be used to calculate the minimum vacuum pressure required for extracting the hydroentangling water from non-woven fabrics. A distinction has been made between hydroentangling on tightly and openly woven screens and different modelling strategies are recommended for each. In particular, it is demonstrated that a one-dimensional flow pattern coupled with available analytical permeability expressions can be used to predict the required vacuum pressure in the case of tightly woven screens. In the case of open woven screens where the flow pattern becomes three-dimensional, numerical simulation is needed for calculating the vacuum pressure required for complete removal of hydroentangling water. We also demonstrated that the vacuum pressure increases by decreasing the fibre diameter or increasing the fabrics' solid volume fractions.

Science and engineering of composite materials, Mar 1, 1992

Industrial & Engineering Chemistry Research, Feb 28, 2020

Textile Research Journal, Jul 1, 2005

Hydroentanglement is the fastest growing bonding method in the nonwoven arena. Its strengths are ... more Hydroentanglement is the fastest growing bonding method in the nonwoven arena. Its strengths are good fabric aesthetics, and the lack of any complex binder chemistry with its inherent environmental concerns. Hydroentanglement is used for mechanically bonding both staple and filament nonwovens as well as being used for post-treatment of fabrics. As hydroentangling uses fine, closely spaced, high-speed waterjets, they create ridges or streaks that are quite visible to the naked eye. This may be undesirable if it interferes with other textures on the surface or if a smooth flat surface is desired. This study reports on methodology used for the analysis of jet streaks using texture-based methods.

Journal of Applied Polymer Science, Feb 27, 2008

Modifications of polypropylene (PP) are often carried out to either functionalize them or meet sp... more Modifications of polypropylene (PP) are often carried out to either functionalize them or meet specific property demands. This study considered the process of PP grafting with glycidyl methacrylate (GMA) as an intermediate step to achieve improvements in surface properties of this polymer. Abundant literature is available on this grafting process but little is known about the surface properties of the grafted PP. Present work considered both experimental and computational approaches to attain this goal. Experimentally, it was established that the melting temperature of modified PP changed with the addition of GMA, and at higher concentrations of GMA in the PP matrix, heterogeneous nucleation took place. Experimental results revealed a decrease in the surface energy (SE) as well. To discern the underlying reasons behind these changes, molecular dynamics simulations were undertaken. The computational results revealed that the changes in SE could be associated with the location of the functional group.

Textile Research Journal, Nov 1, 2004

Photoluminescent fibers with a sheath-core morphology are produced to impart good mechanical prop... more Photoluminescent fibers with a sheath-core morphology are produced to impart good mechanical properties. Both photoluminescent and mechanical properties are examined for these fibers with respect to photoluminescent pigment concentrations in the core, draw ratios, and polymer types. The photoluminescent pigment concentration in the core of the fibers directly influences their luminance intensity and afterglow properties as well as their mechanical properties.

Textile Research Journal, Nov 1, 1990

Our research emphasis has been on identifying several key features of carpet quality combining bo... more Our research emphasis has been on identifying several key features of carpet quality combining both objective (instrumental) and subjective (human perception, HPA) approaches. Previously, HPA was used to determine a set of user terms and descriptions for assessing carpet quality features such as tuft geometry, luster, soiling, and overall appearance. The work reported here expands on the development of objective or instrumental methods for quantifying user perception of carpet appearance. A cus tomized, personal computer-based image analysis system, using an AT&T image cap ture board, has been developed. This new endeavor permits moderate resolution video capture of color images, with digital storage, retrieval, measurement, analysis, and enhancement. Special programming and illumination specifically designed for carpet surface analyses as well as carpet fiber-yarn properties are underway. The work reported here includes measurement of yam bundle or tuft size distribution through a regime of image enhancement, binary conversion, edge detection, and area measurement. Data are presented on various worn and unworn polyester Saxony tufted carpets using these techniques. Major new findings demonstrate the importance of color (RGB) imaging or colorimetric image analysis, in addition to gray level image processing, for determining appearance changes in carpet.

Experiments in Fluids, Jun 13, 2006

We study the possibility of obtaining an intense fluctuating force during the steady-state operat... more We study the possibility of obtaining an intense fluctuating force during the steady-state operation of a waterjet. In this paper, characteristics of waterjets in the so-called first wind-induced breakup regime are briefly explained and the impaction between such waterjets and a smooth flat plate is discussed. We consider these waterjets to consist of three different regions: (1) a continuous portion, (2) a discrete portion (a stream of drops) and (3) a spray region. Using fluid dynamics simulation we obtain an impulsive impact force for the discrete portion of these waterjets. The peak of this impulsive impact force is found to be 3.5-4 times greater than that of the continuous portion. We validate our simulations by conducting an experiment for a stream of large low-speed drops. The impact force of these drops is in good agreement with that of simulation.

Textile Research Journal, Sep 1, 1993

Changes in the appearance of carpet pile due to mechanical wear may be evaluated with respect to ... more Changes in the appearance of carpet pile due to mechanical wear may be evaluated with respect to changes in global image properties, i.e., those based on one-dimensional characterizations of the intensity surface. This paper describes the application of gray scale image analysis to the measurement of microtexture variation and roughness or relief. We attempt to characterize microtexture with intensity mean, variance, skewness, and spatial co-occurrence. Surface relief is quantified as normalized intensity area and fractal dimension. Our samples show that simple mechanical wear generally entails a loss of relief and variation, but carpet construction has an important effect on the observed trends. Intensity mean and fractal dimension are promising candidates for automated evaluation of carpet appearance.

Biomacromolecules, May 16, 2011

Solution blowing of soy protein (sp)/polymer blends was used to form monolithic nanofibers. The m... more Solution blowing of soy protein (sp)/polymer blends was used to form monolithic nanofibers. The monolithic fibers were blown from blends of soy protein and nylon-6 in formic acid. The sp/nylon-6 ratio achieved in dry monolithic nanofibers formed using solution blowing of the blend was equal to 40/60. In addition, solution blowing of core-shell nanofibers was realized with soy protein being in the core and the supporting polymer in the shell. The shells were formed from nylon-6. The sp/nylon-6 ratio achieved in dry core-shell fibers was 32/68. The nanofibers developed in the present work contain significant amounts of soy protein and hold great potential in various applications of nonwovens.