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    Aerosol filtration performance of nanofibrous mats produced via electrically assisted industrial-scale solution blowing
    (Wiley, 2021) Gungor, Melike; Toptas, Ali; Calisir, Mehmet Durmus; Kilic, Ali
    Highly efficient polyamide 6 (PA6)-based nanofibrous air filter media was developed for particulate matter (PM) removal in the ambient atmosphere. The PA6 nanofibrous mats exhibited 85% PM0.3 capture performance at a cost of 164 Pa pressure drop when the multiple-nozzle solution blowing system was set to 8 m/h fabric winding speed. However, an increase in the winding speed at a constant feeding rate lowered the filtration efficiency to 62% due to the less amount of nanofibrous mats collected on the substrate. The application of electrical field at the same parameters allowed us to produce a filter media having FFP3-level filtration performance, which means 99% PM0.3 capture performance. This was attributed to a fine fiber diameter (116 nm), higher solidity value (0.149), and lower average pore size (2.28 mu m). These results show that the electrically assisted solution blowing provides a feasible route for the production of high-quality nanofibrous filter media.
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    Aerosol Filtration Performance of Solution Blown PA6 Webs with Bimodal Fiber Distribution
    (Amer Chemical Soc, 2022) Gungor, Melike; Selcuk, Sule; Toptas, Ali; Kilic, Ali
    A bimodal web, where both nanofibers and microfibers are present and distributed randomly across the same web, can deliver high filter efficiency and low pressure drop at the same time since in such a web, filter efficiency is high thanks to small pores created by the presence of nanofibers and the interfiber space created by the presence of microfibers, which is large enough for air to flow through with little resistance. In this work, a bimodal polyamide 6 (PA6) filter web was fabricated via a modified solution blowing (m-SB) technique that produced nanofibers and microfibers simultaneously. Scanning electron microscope (SEM) images of the webs were used to analyze the fiber morphology. Additionally, air permeability, solidity, porosity, filtration performance, and tensile strength of the samples were measured. The bimodal filter web consisted of nanofibers and microfibers with average diameters of 81.5 +/- 127 nm and 1.6 +/- 0.458 mu m, respectively. Its filter efficiency, pressure drop at 95 L min-1, and tensile strength were 98.891%, 168 Pa, and 0.1 MPa, respectively. Its quality factor (QF) and tensile strength were 0.0268 Pa-1 and 0.1 MPa, respectively. When compared with commercially available filters, the bimodal web produced had superior filter performance, constituting a suitable alternative for air filter applications.
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    Clogging performance of micro/nanofibrous laminated composite air filter media
    (Sage Publications Inc, 2022) Calisir, Mehmet D.; Gungor, Melike; Toptas, Ali; Donmez, Utkay; Kilic, Ali; Karabuga, Semistan
    The performance of fibrous filter media relies on factors such as particle capture efficiency, pressure drop and clogging time. Fiber diameter, porosity and packing density are important web-based factors to improve final filtration performance. In this study, composite nonwoven webs were produced using spunbonded, meltblown and electroblown mats to obtain filter media with different fiber diameter, porosity and packing density. Such a layered composite approach caused huge differences in porosity and packing density, which resulted with improved clogging performance. The average fiber diameter was found to be 65 +/- 19.4 nm for electroblown layer (N), while that was 1.17 +/- 0.38 mu m for meltblown (M) and 17.64 +/- 2.65 mu m for spunbond (S) layers. NM (nanofiber+meltblown) configuration provided 12-13% lower mean flow pore size, which resulted in faster clogging compared to NS (nanofiber + spunbond) mats. The thicker nanofibrous layer resulted in lower pore size and quality factor. Additionally, the composite samples showed a faster-rising pressure drop than the thick microfibrous mats due to smaller pores that clogged quickly. It was also shown that nanofiber coating causes a linear increase in pressure drop with dust loading, while microfibrous samples exhibited smooth plateau and linear increase after clogging point. Nanofiber layer facilitates cake formation which causes more difficult airflow, and lower dust holding capacity. Among the layered composite mats, the NM configurations were found to be more advantageous due to higher initial filtration efficiency and almost similar dust loading performance.
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    Electrically assisted solution blow spinning of PVDF/TPU nanofibrous mats for air filtration applications
    (Tubitak Scientific & Technological Research Council Turkey, 2023) Eticha, Andinet Kumella; Toptas, Ali; Akgul, Yasin; Kilic, Ali
    In this study, pure polyvinylidene fluoride (PVDF), pure thermoplastic polyurethane (TPU), and PVDF/TPU blend nanofibers (1:3, 2:2, 3:1 ratios) were produced via electrically assisted solution blow spinning for air filtration applications. Scanning electron microscopy (SEM) analysis was conducted to investigate the diameters and morphology of nanofibers. The filtration performance of nanofibrous mats was examined by air filtration test with challenging with 0.26 +/- 0.07 mu m salt particles. Moreover, the flexibility and strength of the samples were determined via tensile tests. Results showed that pure TPU nanofibers had better mechanical properties, while pure PVDF nanofibers showed better filtration performance. However, 3PVDF/1TPU nanofibrous sample had high filtration efficiency (98.86%) close to pure PVDF (99.85%) and better flexibility (32.80% elongation) compared to pure PVDF (11.64% elongation).
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    Enhancing filtration performance of submicron particle filter media through bimodal structural design
    (Wiley, 2024) Toptas, Ali; Calisir, Mehmet D.; Gungor, Melike; Kilic, Ali
    Depth filtration is a widely utilized mechanism for submicron aerosol filtration using disposable filter cartridges and facemasks. The filter media should be carefully engineered to reach high filtration efficiency and dust-loading capacity at the expense of a low-pressure drop (Delta P). Filter media with bimodal fiber diameter distribution enhance particle capture by creating small pores with tiny fibers, while microfibers improve airflow, reduce Delta P, and increase the effective filter area for particle retention. In this study, bimodal filters were achieved through the homogeneous distribution or layered use of nanofibers and microfibers. The impact of the bimodal design was explored using fibrous mats produced through melt-blowing, solution-blowing, and electroblowing methods. Keeping the basis weight of filter samples at 30 gsm, using four-layered filters (4L) improved air permeability compared to single-layer samples. The 4L sample exhibited the highest performance, achieving 99.52% efficiency at 148 Pa. Moreover, replacing the melt-blown layer with bimodal mats in the 4L design increased the filtration efficiency to 99.61% keeping Delta P nearly the same. The corona discharge treatment yielded the highest efficiency (99.99%) in the 4BML sample, even after 1 month the efficiency was maintained at 99.90%, highlighting the advantage of bimodal fiber distribution in electret filters.HighlightsFour-layered filter (4L) structures resulted in improved air permeability.Bimodal layer (BL) achieved by adding SB nanofibers into the melt blowing.BL in 4L structure increased the efficiency from 99.52% to 99.61%.Modified BL sample (4BML) provides the highest QF (0.044 Pa-1) after 1 month. Production of the layered bimodal mats in different structural designs and their filtration performance.image
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    Production of Ultrafine PVDF Nanofiber-/Nanonet-Based Air Filters via the Electroblowing Technique by Employing PEG as a Pore-Forming Agent
    (Amer Chemical Soc, 2023) Toptas, Ali; Calisir, Mehmet Durmus; Kilic, Ali
    Particles with diameters smaller than 2.5 mu m (PM2.5) can penetrate the respiratory system and have negative impacts on human health. Filter media with a porous surface and nanofiber/nanonet structure demonstrate superior filtration performance compared to traditional nano- and microfiber-based filters. In this study, nanostructured filters were produced using the electroblowing method from solutions containing different ratios of poly(vinylidene fluoride) (PVDF) and polyethylene glycol (PEG) polymers for the first time. By increasing the water-soluble PEG ratio in PVDF/PEG blend nanofibers and employing a water bath treatment to the produced mat afterward, a more porous fibrous structure was obtained with a lower average fiber diameter. Notably, the removal of PEG from the PVDF/PEG (3-7) sample, which had the highest PEG content, exhibited clustered nanofiber-/nanonet-like structures with average diameters of 170 and 50 nm at the points where the fibers intersect. Although this process resulted in a slight decrease in the filtration efficiency (-1.3%), the significant reduction observed in pressure drop led to a 3.2% increase in the quality factor (QF). Additionally, by exploiting the polarizability of PVDF under an electric field, the filtration efficiency of the nanostructured PVDF filters enhanced with a ratio of 3.6% after corona discharge treatment leading to a 60% improvement in the QF. As a result, the PVDF/PEG (3-7) sample presented an impressive filtration efficiency of 99.57%, a pressure drop (Delta P) of 158 Pa, and a QF of 0.0345 Pa-1.