Browsing by Author "Pourdeyhimi, Behnam"
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Item Acoustical absorptive properties of spunbonded nonwovens made from islands-in-the-sea bicomponent filaments(Taylor & Francis, 2013-04) Maze, Benoit; Pourdeyhimi, Behnam; Suvari, Fatih; Ulcay, Yusuf; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 0000-0001-5708-7993; N-1770-2019; 55512827100; 6601918936In this paper, we report on the acoustical absorptive behavior of spunbonded nonwovens that contain bicomponent islands-in-the-sea filaments. Nylon 6 (PA6) and polyethylene were used as the islands and the sea polymers, respectively. Spunbonded webs made with islands-in-the-sea bicomponent filaments with island counts of 1, 7, 19, 37, and 108 were produced at the Nonwovens Institute's pilot facilities at NC State University. The filaments were fibrillated by hydroentangling, where high-speed water jets were used to fibrillate the fiber and free' the islands. The influence of the number of islands on acoustical absorptive behavior of the spunbonded nonwovens was investigated. A comparison of acoustical absorptive properties of multi-layer islands-in-the-sea nonwoven and high loft nonwoven was also performed to evaluate the potential use of spunbonded nonwovens made from islands-in-the-sea bicomponent filaments in place of bulky fibrous sound absorbers. Results have shown that multi-layer 108 nonwoven islands were better acoustic absorbers at nearly half of the frequency range. Spunbonded nonwovens made from islands-in-the-sea bicomponent filaments can be a good alternative in applications where there is desire to replace bulky fibrous sound absorbers.Item Catalytic graphitization and formation of macroporous-activated carbon nanofibers from salt-induced and H2S-treated polyacrylonitrile(Springer, 2013-05-23) Pourdeyhimi, Behnam; Khan, Saad A.; Aykut, Yakup; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 55320835000We present here a facile method to produce macroporous-activated carbon nanofibers (AMP-CNFs) by post-treating electrospun cobalt(II) chloride (CoCl2) containing polyacrylonitrile (PAN/CoCl2) nanofibers with hydrogen sulfide (H2S) followed by carbonization. A range of techniques including scanning and transmission electron microscopy, FTIR and Raman spectroscopy is used to examine and characterize the process. Because of the phase behavior between carbon and cobalt, cobalt particles are formed in the nanofibers, some of which leave the fibers during the heat treatment process leading to macroporous fibrous structures. The number of the macroporous increase significantly with increasing CoCl2 concentration in the precursor H2S-treated PAN/CoCl2 nanofibers. The cobalt phase in the fibers also leads to catalytic graphitization of the carbon nanofibers. The produced AMP-CNFs may be a promising candidates in many applications including anode layer in lithium ion batteries, air and liquid purifiers in filters, as well as in biomedical applications.Item Effect of dilation on the mechanical characterization of vascular prostheses(Korean Fiber Society, 2005-03) Pourdeyhimi, Behnam; Ulcay, Yusuf; Uludağ Üniversitesi/Mühendislik Mimarlık Fakültesi/Tekstil Mühendisliği Bölümü.; 6601918936The purpose of this study has been to investigate the effect of dilation on the some mechanical properties of several types of warp-knitted vascular grafts. The structures of warp knit vascular grafts used in the experiments were reverse locknit, locknit, and Tricot. Various mechanical properties of these grafts were determined using devices developed for the purpose. Clinical data obtained were compared with experimental results of warp knit vascular grafts. The most important mechanical properties are found to be creep extension, bursting strengths, and compliance. Preliminary results indicate that vascular grafts are non-compliant and exhibit creep which is predictive of the long term dilation that has been noted in the clinical results. It is found that there is a positive correlation between experimental data and clinical results for at least the grafts tested.Item Effect of sea component dissolution on fibrous structure of islands-in-the-sea spunbond nonwovens(IOP Publishing, 2017) Pourdeyhimi, Behnam; Suvari, Fatih; Ulcay, Yusuf; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 0000-0001-5708-7993; N-1770-2019; 55512827100; 6601918936This work presents the preliminary results of our efforts that focused on the development of lightweight and more fibrous nonwoven. For this objective, nonwoven webs that contain bicomponent filaments with island-in-the-sea cross section was produced by spunbonding, which involves extruding of sea and island polymer melts through dies, cooling, and attenuating the bicomponent filaments by high velocity air streams. Nylon-6 and Polyethylene were chosen as the island and sea polymers, respectively. Bonding process was applied to web first to keep structural integrity after removing the sea polymer. The web was hydroentangled with high speed water jets prior to the dissolving process to obtain fiber entanglement. Xylene, which is one of the few chemical that can dissolve Polyethylene, was used for the dissolution of the sea component from the fibrous structure of the spunbond nonwoven. Removal of the sea polymer from spunbond nonwovens that contain bicomponent filaments with islands-in-the-sea cross section was achieved by the developed dissolution process. Weight, thickness, and area of the nonwoven samples changed after the dissolution. After removing the sea polymer, spunbond nonwoven contains only thin island fibers and also gets lighter. Lightweight and more fibrous nonwovens can be obtained with the method given in this study.Item Effects of surfactants on the microstructures of electrospun polyacrylonitrile nanofibers and their carbonized analogs(Wiley, 2013-12-05) Pourdeyhimi, Behnam; Khan, Saad A.; Aykut, Yakup; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 55320835000In this study, the influence of surfactants on the processability of electrospun polyacrylonitrile (PAN) nanofibers and their carbonized analogs was investigated. The surfactants employed in this effort are Triton X-100 (nonionic surfactant, SF-N), sodium dodecyl sulfate (SDS) (anionic surfactant, SF-A), and hexadecyltrimethylammonium bromide (HDTMAB) (cationic surfactant, SF-C). Interactions between electrospun PAN and the surfactants, reflected in effects on as-spun and carbonized nanofiber morphologies and microstructures, were explored. The results show that uniform nanofibers are obtained when cationic and anionic surfactants (surfactant free and nonionic surfactants) are utilized in the preparation of electrospun PAN. In contrast, a bead-on-a-string morphology results when the aniconic and cationic surfactants are present, and defect structure is enhanced with cationic surfactant addition. Moreover, fiber breakage is observed when the nonionic surfactant Triton X-100 is employed for electrospinning. After carbonizaition, the PAN polymers were observed to have less ordered structures with addition of any type of surfactant used for electrospinning and the disorder becomes more pronounced when the anionic surfactant is utilized. Owing to the fact that microstructure defects create midband gap states that enable more electrons to be emitted from the fiber, an enhancement of electron emission is observed for PAN electrospun in the presence of the anionic surfactant.Item Influence of sea polymer removal on sound absorption behavior of islands-in-the-sea spunbonded nonwovens(Sage Publications Ltd, 2019-06) Pourdeyhimi, Behnam; Suvari, Fatih; Ulcay, Yusuf; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; N-1770-2019; 55512827100; 6601918936This work presents the results of efforts focused on the development of relatively lightweight and fibrous acoustic webs. For this objective, nonwoven webs that contain bicomponent filaments with islands-in-the-sea cross sections were produced by spunbonding, which involves the extrusion of sea and island polymer melts through dies, cooling and attenuating the bicomponent filaments by high-velocity air streams. Nylon 6 and polyethylene were used as the island and sea polymers, respectively. Webs were hydroentangled with high-pressure water jets prior to the dissolving process to obtain fiber entanglement. Sea polymer was removed from the spunbonded nonwovens by using a reflux dissolution setup. Weight, thickness, air permeability, pore size and sound absorption coefficients of the nonwoven samples were measured before and after the sea polymer removal. Results demonstrated that sea polymer removal led to further bicomponent filament fibrillation, which affected sound absorption positively. The structure with the higher number of island fibers had better acoustical properties. Lightweight and fibrous acoustic nonwovens can be obtained with the method given in this study.Item Sound absorption analysis of thermally bonded high-loft nonwovens(Sage Publications, 2016-05) Pourdeyhimi, Behnam; Süvari, Fatih; Ulcay, Yusuf; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 0000-0001-5708-7993; N-1770-2019; 55512827100; 6601918936Sound absorption characteristics of specially designed high-loft nonwovens with minimum thickness were reported in this study. Three different polypropylene and polyester fiber-based high-loft, air-laid, and thermally bonded nonwovens varying in basis weight were produced. Heavier high-loft nonwoven samples at various thicknesses were formed using a specially designed mold. The sound absorption coefficients of samples with mass per unit areas ranging from 350 to 1575 g/m(2) and with thicknesses ranging from 5 to 45 mm were measured. Acoustical absorptive behavior of the high-loft nonwovens was explained by analyzing the displacements of small air control volumes in a high-loft nonwoven and the air velocities in the impedance tube. Results indicate that the velocity and the total displacement of the small air volumes inside the fiber network have a major effect on sound absorption. High-loft nonwovens can be much more effective in terms of sound absorption if they are produced at the thickness at which average maximum velocity of the air is calculated highest. If there is a desire to absorb more acoustic energy, heavier nonwovens can be produced. It is suggested that relatively heavy nonwovens (from 700 to 1575g/m(2)) can be produced thinner (5-10 mm) than the calculated thickness value based on the average maximum air velocity to get maximum sound absorption at lower thickness.Item Synthesis and characterization of silver/lithium cobalt oxide (Ag/LiCoO2) nanofibers via sol-gel electrospinning(Elsevier, 2013-05-21) Pourdeyhimi, Behnam; Khan, Saad A.; Aykut, Yakup; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 55320835000We report on the preparation and characterization of Ag/LiCoO2 nanofibers (NFs) via the sol-gel electrospinning (ES) technique. Ag nanoparticles (NPs) were produced in an aqueous polyvinyl pyrrolidone (PVP) solution by using AgNO3 precursor. A viscous lithium acetate/cobalt acetate/polyvinylalcohol/water (LiAc/(CoAc)(2)/PVA/water) solution was prepared separately. A Ag NPs/PVP/water solution was prepared and added to this viscous solution and magnetically stirred to obtain the final homogeneous electrospinning solution. After establishing the proper electrospinning conditions, as-spun precursor Ag/LiAc/Co(Ac)(2)/PVA/PVP NFs were formed and calcined in air at a temperature of 600 degrees C for 3 h to form well-crystallized porous Ag/LiCoO2 NFs. Various analytical characterization techniques such as UV-vis, SEM, TEM, TGA, XRD, and XPS were performed to analyze Ag NPs, as-spun and calcined NFs. It was established that Ag NPs in the precursor Ag/LiAc/Co(Ac)(2)/PVA/PVP NFs are highly self-aligned as a result of the behavior of Ag in the electric field of the electrospinning setup and the interaction of Ag ions with Li and Co ions in the NE Ag/LiCoO2 NFs exhibit a nanoporous structure compared with undoped LiCoO2 NFs because the atomic radius of Ag is larger than the radius of Co and Li ion; thus, no substitution between Ag and Li or Ag and Co atoms occurs, and Ag NPs are located at the interlayer of LiCoO2 while some are left in the fiber.Item Two-stage desorption-controlled release of fluorescent dye and vitamin from solution-blown and electrospun nanofiber mats containing porogens(American Chemical Society, 2013-12) Khansari, S.; Ray, Suman Sinha; Yarin, Alexander L.; Pourdeyhimi, Behnam; Düzyer, Şebnem; Hockenberger, Aslı Şengönül; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; 0000-0003-3737-5896; 36815823800; 6507435813In the present work, a systematic study of the release kinetics of two embedded model drugs (one completely water soluble and one partially water soluble) from hydrophilic and hydrophobic nanofiber mats was conducted. Fluorescent dye Rhodamine B was used as a model hydrophilic drug in controlled release experiments after it was encapsulated in solution-blown soy-protein-containing hydrophilic nanofibers as well as in At electrospun hydrophobic poly(ethylene terephthalate) (PET)-containing nanofibers. Vitamin B-2 (riboflavin), a partially water-soluble model drug, was also encapsulated in hydrophobic PET-containing nanofiber mats, and its release kinetics was studied. The nanofiber mats were submerged in water, and the amount of drug released was tracked by fluorescence intensity. It was found that the release process saturates well below 100% release of the embedded compound. This is attributed to the fact that desorption is the limiting process in the release from biopolymer-containing nanofibers similar to the previously reported release from petroleum-derived polymer nanofibers. Release from monolithic as well as core-shell nanofibers was studied in the present work. Moreover, to facilitate the release and ultimately to approach 100% release, we also incorporated porogens, for example, poly(ethylene glycol), PEG. It was also found that the release rate can be controlled by the porogen choice in nanofibers. The effect of nanocracks created by leaching porogens on drug release was studied experimentally and evaluated theoretically, and the physical parameters characterizing the release process were established. The objective of the present work is a detailed experimental and theoretical investigation of controlled drug release from nanofibers facilitated by the presence of porogens. The novelty of this work is in forming nanofibers containing biodegradable and biocompatible soy proteins to facilitate controlled drug release as well as in measuring detailed quantitative characteristics of the desorption processes responsible for release of the model substance (fluorescent dye) and the vitamin (riboflavin) in the presence of porogens.