Polimer Malzeme Mühendisliği Bölümü Yayın Koleksiyonu

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https://hdl.handle.net/20.500.12885/1688

Listeleniyor 1 - 20 / 93

Nanomaterials with potential EMI shielding properties
(2019) Altın, Yasin; Bedeloğlu, Ayşe
Nanomaterials exhibit unexpected superior properties such as electrical, magnetic, optical, etc., compared with bulk materials. In this chapter, electromagnetic interference (EMI) shielding properties of different nanomaterials based on metal, metal oxide, ceramic, conductive polymer-modified, and their hybrids are reviewed. The effects of size, shape, structure, and morphology of nanomaterials on EMI shielding properties were also discussed. EMI shielding is mainly realized by three mechanisms, which are absorption, reflection, and multiple reflections. In recent years, academic studies have mostly focused on hybrid nanostructures, which often combine absorption and reflection properties. Meanwhile, an evaluation covering most of the important advancements related to nanomaterials with potential EMI shielding properties is also provided.
A review of critical residential buildings parameters and activities when investigating indoor air quality and pollutants
(Wiley, 2022) Teresa Baeza-Romero, Maria; Dudzinska, Marzenna R.; Torkmahalleh, Mehdi Amouei; Barros, Nelson; Gazioğlu Rüzgar, Duygu
Indoor air in residential dwellings can contain a variety of chemicals, sometimes present at concentrations or in combinations which can have a negative impact on human health. Indoor Air Quality (IAQ) surveys are often required to characterize human exposure or to investigate IAQ concerns and complaints. Such surveys should include sufficient contextual information to elucidate sources, pathways, and the magnitude of exposures. The aim of this review was to investigate and describe the parameters that affect IAQ in residential dwellings: building location, layout, and ventilation, finishing materials, occupant activities, and occupant demography. About 180 peer-reviewed articles, published from 01/2013 to 09/2021 (plus some important earlier publications), were reviewed. The importance of the building parameters largely depends on the study objectives and whether the focus is on a specific pollutant or to assess health risk. When considering classical pollutants such as particulate matter (PM) or volatile organic compounds (VOCs), the building parameters can have a significant impact on IAQ, and detailed information of these parameters needs to be reported in each study. Research gaps and suggestions for the future studies together with recommendation of where measurements should be done are also provided.
Co-loading of Temozolomide with Oleuropein or rutin into polylactic acid core-shell nanofiber webs inhibit glioblastoma cell by controlled release.
(Elsevier B.V., 2023) Ercelik, Melis; Tekin, Cagla; Parın, Fatma Nur; Mutlu, Büşra; Doğan, Hazal Yılmaz; Tezcan, Gulcin; Aksoy, Secil Ak; Gurbuz, Melisa; Yıldırım, Kenan; Bekar, Ahmet; Kocaeli, Hasan; Taskapilioglu, Mevlut Ozgur; Eser, Pinar; Tunca, Berrin
Glioblastoma (GB) has susceptibility to post-surgical recurrence. Therefore, local treatment methods are required against recurrent GB cells in the post-surgical area. In this study, we developed a nanofiber-based local therapy against GB cells using Oleuropein (OL), and rutin and their combinations with Temozolomide (TMZ). The polylactic acid (PLA) core-shell nanofiber webs were encapsulated with OL (PLA), rutin (PLA), and TMZ (PLA) by an electrospinning process. A SEM visualized the morphology and the total immersion method determined the release characteristics of PLA webs. Real-time cell tracking analysis for cell growth, dual Acridine Orange/Propidium Iodide staining for cell viability, a scratch wound healing assay for migration capacity, and a sphere formation assay for tumor spheroid aggressiveness were used. All polymeric nanofiber webs had core-shell structures with an average diameter between 133 ± 30.7-139 ± 20.5 nm. All PLA webs promoted apoptotic cell death, suppressed cell migration, and spheres growth (p < 0.0001). PLA and PLA suppressed GB cell viability with a controlled release that increased over 120 h, while PLA caused rapid cell inhibition (p < 0.0001). Collectively, our findings suggest that core-shell nano-webs could be a novel and effective therapeutic tool for the controlled release of OL and TMZ against recurrent GB cells.
Effect of Microcrystalline Cellulose Filler on Mechanical and Water Absorption Properties of Ramie/Glass/Carbon Hybrid Laminated Composite
(American Institute of Physics Inc., 2023-12-28) Yudhanto, Ferriawan; Jamasri, Jamasri; Ilyas, Rushdan A.; Terzioğlu, Pınar
Hybrid composites laminated (HLC) combined with various types of fibers have less poor interfacial bonding. It is due to the different physical and chemical properties of various fibers used. HLC consists of six layers with a stacking sequence arranged are ramie (R), glass (G), and carbon (C) fiber manufactured by the vacuum infusion process. Adding the microcrystalline cellulose (MCC) 0.5 wt.% into the unsaturated polyester resin (UPE) at 350 RPM for 5 minutes. It increases the tensile strength and elasticity modulus on the HLC with the stacking sequence of CRGGRC by 15% and 34%. The significant effect on flexural strength and elasticity modulus by 47% and 16%. Adding MCC filler inhibits propagation crack in the interlaminar interface of HLC. The addition of MCC filler has a slight impact on water absorption behavior. The water absorption increases by 0.9% on HLC with MCC caused it has hydrophilicity properties.
Fabrication of nano composite membrane filter from graphene oxide(GO) and banana rachis cellulose nano crystal(CNC) for industrial effluent treatment
(Korean Society of Industrial Engineering Chemistry, 2023-12-25) Shamim Sheikh, Md.; Mahmudur Rahman, Md.; Safiur Rahman, Md.; Yıldırım, Kenan
Agricultural bio-waste based cellulosic materials are highly biodegradable and naturally occurring with high adsorption and capable of outstanding physico-chemical properties. This study elicits neoteric upliftment and impending significance of graphene oxide(GO) – cellulose nanocrystal(CNC) nano-filter composite membrane (NFCM) for high removal of Cr3+, Co2+, Ni2+, Pb2+, Cd2+ and Methylene blue molecules from industrial wastewater. We tried to direct comparison between conventional filter and NFCM composites filter and their physical and chemical properties, production costs, use and disposal in order to show the potential of Nano structural cellulose materials as a sustainable replacement for NFCM filter for removal of heavy metals and dyes from industrial wastewater treatment technologies. The prepared GO, CNC, and NFCM were characterized by using X-ray Diffraction(XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscopy(FESEM), Thermogravimetric Analysis(TGA) etc. The efficiency of wastewater purification of fabricated NFCM were determined by Ultra Violet(UV)-vis spectrophotometer and Inductively Couple Plasma Optical Emission Spectroscopy(ICP-OES). Whereas the fabricated NFCM were highly crystalline, thermally stable, have good surface activity, exhibit remarkable removal efficiency against the toxic heavy metals and soluble dye. The maximum R% was found for Cd2+ and Pb2+, around 99%. Beside this all dye molecules were removed from the wastewater simultaneously and successfully. © 2023 The Korean Society of Industrial and Engineering Chemistry
The Mechanical Properties of 3D-Printed Polylactic Acid/Polyethylene Terephthalate Glycol Multi-Material Structures Manufactured by Material Extrusion
(MARY ANN LIEBERT, 2022) Demir, Emre; Duygu, İnal Kaan; Bedeloğlu, Ayşe
The mechanical properties of polylactic acid (PLA), polyethylene terephthalate glycol (PETG), and PLA/PETG structures manufactured using the multi-material additive manufacturing (MMAM) method were studied in this work. Material extrusion additive manufacturing was used to print PLA/PETG samples with various PLA and PETG layer numbers. By varying the top and bottom layer numbers of two thermoplastics, the effect of layer number on the mechanical properties of 3D-printed structures was investigated. The chemical and thermal characteristics of PLA and PETG were investigated using Fourier transform infrared spectroscopy and differential scanning calorimetry. Tensile and flexural strength of 3D-printed PLA, PETG, and PLA/PETG samples were determined using tensile and three-point bending tests. The fracture surfaces of the samples were evaluated using optical microscopy. The results indicated that multi-material part containing 13 layers of PLA and 3 layers of PETG exhibited the highest ultimate tensile strength (65.4 MPa) and a good flexural strength (91.4 MPa). MMAM was discovered to be a viable way for producing PLA/PETG materials with great mechanical performance.
Investigation of mechanical properties of hybrid stainless steel/acrylic and carbon fiber reinforced epoxy composite
(SAGE PUBLICATIONS LTD, 2022) Yılmaz, Ayten Nur Yüksel; Yunus, Doruk Erdem; Bedeloğlu, Ayşe
Hybrid composite specimens were produced with stainless steel-acrylic (SSA) and carbon fiber reinforcement in order to achieve ductile behavior compared to CF reinforced epoxy composites. Laminated composites containing CF and SSA fabrics in with different ply configurations were manufactured using vacuum infusion method. In addition, CF fabric was used in two different ply orientations (0-45 degrees). In both the flexural and tensile test results, composites having CF oriented at 0 degrees showed higher strength and modulus but lower strain than composites having CF oriented at 45 degrees. When the number of carbon fiber layers increased, the composites showed high strength and modulus, but low strain. Increasing the number of SSA significantly increased the flexural and tensile strains of laminated composites. After the mechanical tests, the fracture surfaces of the specimens were examined with an optical microscope and matrix cracks, fiber breakage, fiber pull-out and delamination failures were observed.
Immobilization of propolis extract on PET fabric for biomedical applications
(GAZI UNIV, 2022) Gümüş, Ömer Yunus; İsmahane, Yssaad
Propolis has biological activity due to its wide variety of phenolic compound content. Propolis usage in many areas such as cosmetics, food, medicine, and biomedicals is becoming widespread day by day due to its antibacterial, antifungal, antiviral properties. In this study, phenolics extracted from propolis were covalently bonded and immobilized on the surface of polyethylene terephthalate (PET) fabric with the aim of developing a technical textile for biomedical applications. To do so, PET fabric was aminated, and then the phenolics were immobilized using polyethylene glycol diglycidyl ether (PEGDGE) as the crosslinking agent. Formation of amine groups in PET structure and immobilization of the phenolics were proved by ATR-FTIR spectrums. Water contact angle of PET being 121 degrees decreased to 110 degrees and 97 degrees after the amination and the immobilization, respectively. Optical microscope images were taken to monitor morphological changes after the processes. DSC results revealed a new endothermic peak at around 40 degrees C for modified PET. Tensile tests showed that tensile strength of the fabric weakens upon modification, while a healing effect occurs during immobilization. Antibacterial tests revealed that propolis extract immobilized fabric has an antibacterial activity against gram negative (E. coli) bacteria.
Fabrication and properties of graphene oxide and reduced graphene oxide reinforced Poly(Vinyl alcohol) nanocomposite films for packaging applications
(SAGE Publications Ltd, 2022) Doğan Yılmaz, Hazal; Altın, Yasin; Bedeloğlu, Ayşe
Petroleum-based polymers have a wide range of uses in the packaging industry, including films, food packaging, rigid containers, foamed containers, medical products, etc. This study focuses on improving the properties of polyvinyl alcohol (PVA) based material systems, one of the most popular water-soluble biopolymers, to reduce the waste of petroleum-based plastics, which are widely used. Polyvinyl alcohol (PVA) nanocomposite films containing low concentrations (0.05-1%) of graphene oxide (GO) and reduced graphene oxide (rGO) were produced via the solution casting method. When electrical properties of nanocomposite films were evaluated, the addition of 1 wt% GO and rGO resulted in a 36% and 45% decrease in the volumetric resistance of the films as well as a decrease in surface resistance of 24.5% and 34.9%, respectively. The maximum tensile strength of 1% GO and rGO-reinforced PVA nanocomposites was found to be similar to 59 MPa and similar to 68 MPa with an increase of 20% and 38% compared to neat PVA films, respectively. The average Young's modulus of 1% GO and rGO-reinforced PVA nanocomposites also increased from 2561 MPa to 3515 MPa and 4219 MPa with an increase of 37% and 65%, respectively. As a result, the electrical conductivity, Young's modulus, maximum tensile strength, thermal properties, and optical absorption of nanocomposite films increased by adding GO and rGO to PVA. The results show that the produced nanocomposite film may be a promising material for packaging applications.
Development of thermo-regulating fabrics with enhanced heat dissipation via graphene-modified n-octadecane microcapsules
(Wiley, 2021) Hiçyılmaz, Ayşe Sezer; Teke, Sengul; Islek Cin, Zeynep; Bedeloğlu, Ayşe
Phase change materials (PCMs) are of great importance in thermal regulation applications, but low thermal conductivity is the most critical disadvantage of these materials. Especially in the textile field, while there are many studies on the production of PCM-coated fabrics, studies on improving heat dissipation are quite limited. Therefore, in this study, first, n-octadecane was encapsulated with melamine formaldehyde shell modified with graphene as a thermal conductivity enhancer, and then, synthesized PCM microcapsules were coated on polyester fabrics. Chemical, morphological, thermal properties, as well as phase change behavior of microcapsules and coated fabrics were analyzed. The thermal conductivity of the PCM microcapsule-coated PET fabrics was increased by 31% with the addition of very low amount of graphene (0.1%).
Spinnability and characterization of poly(D-lactic acid)-blended poly(L-lactic acid) filament yarns
(Wiley, 2021) Çelen, Onur; Koçer, Hasan Basri
Conventional textiles are produced mainly by petroleum-based polymeric materials, which are not biodegradable, cause serious pollution, and waste problems. Especially, poly(ethylene terephthalate) is the most used thermoplastic polyester in various textile applications. At this point, poly(lactic acid) (PLA), a biodegradable polyester, stands out forward with its unique properties. PLA is derived from renewable sources such as corn, sugar cane, and so on. In this study, poly(D-lactic acid) (PDLA) was blended to poly(L-lactic acid) (PLLA) to reduce its highly crystalline morphology and rigidity. Introduction of PDLA would be expected to speed up its degradation by decreasing the amount of crystalline regions. PDLA was compounded into PLLA in amounts of 3, 6, and 9 wt%. First, PDLA-blended PLLA compounds were produced, and then successfully spun/drawn into filament yarns by using a pilot-scale melt spinning equipment. The compounds and the filament yarns were characterized by SEM, DSC, viscosity, carboxyl number, tenacity, elongation at break, unevenness, and shrinkage. Results showed that the amount of crystalline regions was decreased with increasing PDLA amount in both compounds and filament yarns. On the other hand, PDLA blending enhanced the rigidity of filament yarns by increasing their elongation at break.
Investigation of Properties Graphene Reinforced Epoxy Nanocomposites
(Gazi Universitesi, 2021) Doğan Yılmaz, Hazal; Altın, Yasin; Bedeloğlu, Ayşe
In recent years, graphene has attracted the attention of scientists and industry due to its superior electronic, thermal and mechanical properties and has been used in different fields and advanced applications. Graphene and its derivatives have also attracted great interest in the field of polymer composites, since the use of graphene as a small amount of additive brings about advanced properties to the polymers. Therefore, in this study, graphene was added to the epoxy at certain rates (0.05%, 0.1%, 0.25%, 0.5% and 1%) to obtain nanocomposites with improved electrical conductivity and mechanical properties. The properties of obtained nanocomposite films were examined by fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), mechanical test, scanning electron microscope (SEM), UV-Vis-NIR spectrophotometer and electrical conductivity measurements. 1% graphene additive caused a 28.2% decrease in the volumetric resistance and 9.7% in the surface resistance of the nanocomposite films. The maximum tensile value of graphene/epoxy nanocomposites was obtained as similar to 20 MPa by increasing 33.84% in 1% graphene additive compared to neat epoxy-based nanocomposites. As a result, it has been observed that as the amount of graphene added to the epoxy increases, the electrical conductivity, tensile values and light absorption of nanocomposite films increase. The nanocomposite films obtained can be used in industrial applications thanks to the improved electrical conductivity and mechanical properties.
POSS-based hybrid nanocomposites
(Elsevier, 2021) Bekin Acar, Seda; Özdoğan, Reyhan; Tasdelen, Mehmet Atilla
Hybrid nanocomposites have attracted considerable attention since they could combine superior advantages of two or more nano-fillers. Owing to the multifunctional properties of nano-fillers, they have emerged as a promising new class of materials for high-tech applications. Various nano-fillers including clay, carbon nanotubes, graphene, metal oxides, and polyoctahedral oligomeric silsesquioxane (POSS) have been extensively used for the preparation of hybrid nanocomposites. Among them, POSS derivatives have received significant attention due to their precisely defined hybrid structures with a variety of functional groups helping to chemically or physically combine with other nano-fillers to enhance stiffness performance and reduce the electrical conductivity of the material. In this chapter, hybrid nanocomposites prepared by POSS with other one-dimensional nano-clays, two-dimensional graphene and graphene oxides, carbon nanotubes and boron nitrides, and three-dimensional fullerenes, gold, silver, and iron nanoparticles, and titanium and silicon dioxides are explored in detail.
Production and characterization of n-halamine based polyvinyl chloride (pvc) nanowebs
(Ege Universitesi, 2021) Çobanoğlu, Batuhan; Parın, Fatma Nur; Yıldırım, Kenan
Antibacterial agent N-halamine, 7,7,9,9-tetramethyl-1,3,8-triazaspiro [4.5]-decane-2,4-dione (TTDD), was synthesized, and it was added into the polyvinyl chloride (PVC) nanoweb. A versatile, and relatively simple method, electrospinning, was used to fabricate continuous and uniform nanowebs. 7,7,9,9-tetramethyl-1,3,8-triazaspiro [4.5]-decane-2,4-dione (TTDD) is a cyclic N-halamine that can be chlorinated easily due to three functional groups (imide, amide, and amine). Therefore, TTDD was preferred for PVC regarding having high stability, non-toxic, non-irritant for skin, and renewable. The rechargeable chlorination process was applied to webs using dilute hypochlorite solution. The antibacterial activity of the webs were evaluated using the ASTM 2149 procedure. FTIR, TGA, and SEM were used to investigate the morphology, thermal characteristics, and chemical structures of PVC webs. Scanning electron microscopy (SEM) displayed that the average diameter of the fibers increased with TTDD concentration. The thermal properties of the PVC webs did not changed significantly. All chlorinated webs indicated highly effective antibacterial activities against both Staphylococcus aureus and Escherichia coli with increased inactivation. Furthermore, the antibacterial efficacy of nanowebs is reformed again by the rechargeable process. The rechargeable chlorination capacity of obtained PVC non-wovens is over >60% (within 6 hours, in pH 5), for four rechargeable chlorine cycles. The new antibacterial PVC nanowebs have the potential for especially useful in medical applications.
Polyacrylonitrile/polyvinyl alcohol-based porous carbon nanofiber electrodes for supercapacitor applications
(John Wiley and Sons Ltd, 2021) Altın, Yasin; Bedeloğlu, Ayşe
Porous carbon nanofibers (PCNFs) were produced from polyacrylonitrile (PAN)/polyvinyl alcohol (PVA) hybrid nanofibers with different mixing ratios and used as the free-standing, flexible, high performance electrodes for the supercapacitors. The effect of PAN/PVA ratio, PVA removing and stabilization/carbonization process on the chemical structure, and the morphology of PAN/PVA hybrid nanofibers and PCNF were investigated by Fourier transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analyzer (TGA). It was proved by FT-IR and FE-SEM analyses that PAN/PVA hybrid nanofibers are successfully produced and carbonized. In addition, the electrochemical performance of PCNF electrodes was analyzed by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) methods. Results showed that PCNFs exhibit higher specific capacitance and better electrochemical performance than neat carbon nanofibers (N-CNF). The specific capacitance of the EK5 PCNF (67/33 PAN/PVA wt ratio) was 157 F/g at 5 mV/s scan rate in 1 M H2SO4, while the specific capacitance of N-CNF was 96 F/g at the same conditions. Moreover, the PCNF showed excellent cyclic stability without losing performance through 2500 charge/discharge cycles at a current density of 2 A/g. As a result, free-standing, flexible, and high-performance PCNFs are excellent candidates as supercapacitor electrodes for flexible energy-storage devices.
Fabrication and characterization of electrospun folic acid/hybrid fibers: In vitro controlled release study and cytocompatibility assays
(MDPI, 2021) Parın, Fatma Nur; Ullah S.; Yıldırım, Kenan; Hashmi M.; Kim I.-S.
The fabrication of skin-care products with therapeutic properties has been significant for human health trends. In this study, we developed efficient hydrophilic composite nanofibers (NFs) loaded with the folic acid (FA) by electrospinning and electrospraying processes for tissue engineering or wound healing cosmetic applications. The morphological, chemical and thermal characteristics, in vitro release properties, and cytocompatibility of the resulting composite fibers with the same amount of folic acid were analyzed. The SEM micrographs indicate that the obtained nanofibers were in the nanometer range, with an average fiber diameter of 75–270 nm and a good porosity ratio (34–55%). The TGA curves show that FA inhibits the degradation of the polymer and acts as an antioxidant at high temperatures. More physical interaction between FA and matrices has been shown to occur in the electrospray process than in the electrospinning process. A UV-Vis in vitro study of FA-loaded electrospun fibers for 8 h in artificial acidic (pH 5.44) and alkaline (pH 8.04) sweat solutions exhibited a rapid release of FA-loaded electrospun fibers, showing the effect of polymer matrix–FA interactions and fabrication processes on their release from the nanofibers. PVA-CHi/FA webs have the highest release value, with 95.2% in alkaline media. In acidic media, the highest release (92%) occurred on the PVA-Gel–CHi/sFA sample, and this followed first-order and Korsmeyer–Peppas kinetic models. Further, the L929 cytocompatibility assay results pointed out that all NFs (with/without FA) generated had no cell toxicity; on the contrary, the FA in the fibers facilitates cell growth. Therefore, the nanofibers are a potential candidate material in skin-care and tissue engineering applications.
Fabrication and characterization of polyaniline functionalized graphene nanosheets (GNSs)/polydimethylsiloxane (PDMS) nanocomposite films
(SAGE Publications Ltd, 2021) Altın, Yasin; Ünsal, Ömer Faruk; Bedeloğlu, Ayşe
In this study, graphene nanosheets (GNSs)/poly(dimethylsiloxane) (PDMS) nanocomposites and the novel polyaniline (PANI)-functionalized graphene nanosheets (GNSs)/poly(dimethylsiloxane) (PDMS) nanocomposites were fabricated successfully. GNSs and PANI-functionalized GNSs were dispersed in PDMS matrix at different nanofiller concentration and nanocomposites were prepared via solution casting method. PANI functionalization were performed by in-situ polymerization of aniline in the presence of GNSs and was used in order to be dispersed homogenously and efficiently in the PDMS matrix. Besides graphene layers were also isolated to hinder aggregation in the polymeric matrix. The effect of PANI functionalization of GNSs and filler concentration on dielectric, electrical and mechanical properties of nanocomposite films were investigated. According to dielectric measurements, the dielectric constant of polymer nanocomposites highly dependant on frequency, so dielectric constant was characterized in a wide frequency range (1 Hz–10 MHz) at room temperature, in this study. The dielectric constant of PDMS nanocomposites containing 1.50% GNSs and 1.50% PANI-GNSs increased by 111 times and 24 times, at 1 Hz, compared to pure PDMS, respectively. Besides, electrical conductivity increased 6868 and 1474 times with the addition of GNSs and PANI-GNSs, respectively. Optimized GNSs/PDMS and PANI-functionalized GNSs/PDMS nanocomposites can be candidate for soft actuators to be used in artificial muscle applications, in the future.
Synergistic effect of talc/calcined kaolin binary fillers on rigid PVC: Improved properties of PVC composites
(John Wiley and Sons Ltd, 2021) Mallem O.K.; Zouai F.; Gümüş, Ömer Yunus; Benabid F.Z.; Bedeloğlu, Ayşe; Benachour D.
This study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance–Fourier-transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea-treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.
Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate-coated carbon nanofiber electrodes via dip-coating method for supercapacitor applications
(Springer, 2021) Altın, Yasin; Bedeloğlu, Ayşe
The conducting polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is used to modify carbon nanofibers via the dip-coating method. The modification process is carried out by immersing the carbon nanofibers 3, 6, and 9 times in PEDOT:PSS solution. As a result, the production of flexible, homogeneous, self-standing, bead-free carbon nanofibers has been accomplished. The PEDOT:PSS coating process is carried out without negatively affecting the porosity between the nanofibers and the average diameter of the nanofibers increases linearly with the dipping number. Initially, the specific capacitance of the neat carbon nanofiber is 199 F/g in the voltage range of − 0.5 to + 0.5 V at a scan rate of 10 mV/s, while specific capacitance was measured as 278, 311, 350 F/g after the 3, 6, and 9 times PEDOT:PSS coating process, respectively. Additionally, the 9P-CNF sample shows a very high capacitance value, such as 1321 F/g, at a scanning speed of 1 mV/s in 1 M H2SO4 electrolyte. On the other hand, it has been observed that the performance of the hybrid electrode retains approximately 80% of its performance after 2500 CV cycles. The performance of the carbon nanofiber electrode is enhanced by dip-coating with PEDOT:PSS, which is simple, fast, and suitable for large-scale production. The resulting hybrid electrode is suitable for a variety of energy storage applications, most notably supercapacitors.
Cam Elyaf Takviyeli Polyester (CTP) Kompozit Malzemelerde Kullanılan Doğal Elyaflar ve Dolgu Maddeleri
(2019) İlhan, Recep; Feyzullahoğlu, Erol
Teknolojinin gelişmesiyle birlikte saf haldeki malzemelerin yetersiz kalmasından dolayı kompozit malzemeler geliştirilmiş ve zamanla kullanım alanları çoğalmıştır. Cam elyaf takviyeli polyester (CTP) kompozit malzemeler, iyi mekanik dayanım, elastiklik, yüksek korozyon dayanımı ve ekonomiklik gibi özelliklere sahip olmalarından dolayı dünyada yaygın kullanıma sahiptirler. Bu nedenle günümüzde CTP kompozitlere farklı takviye ve dolgu malzemeleri eklenilerek malzeme özelliklerinin geliştirilmesi amaçlanmaktadır. Bu çalışma sisal, jüt, kenaf vb. farklı doğal elyaf takviyesi ve cam kürecik, grafit, alümina vb. farklı dolgu maddesi kullanımının CTP kompozit malzemelerin özelliklerine etkisinin incelendiği çalışmaları ele almaktır. Çalışmanın ilk bölümünde genel olarak doğal ve cam elyaf takviyeli polimer kompozitler hakkında bilgi verilmiştir. Çalışmanın ikinci ve üçüncü bölümünde ise CTP kompozit malzemelerde kullanılan doğal elyaf takviyesinin ve dolgu maddelerinin malzeme özelliklerine etkisinin incelendiği çalışmalar sunulmuştur. Yapılan çalışmalarda doğal elyafların ve dolgu maddelerinin farklı üretim yöntemleriyle CTP kompozit malzemelere başarıyla dahil edilebildikleri, malzeme özelliklerini iyileştirici etki yapabildikleri ve maliyeti düşürebildikleri görülmektedir.

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