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  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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%).
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    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.
  • Öğe
    Grafen ve Grafen Üretim Yöntemleri
    (2016) Bedeloğlu, Ayşe; Taş, Mahmut
    2010 yılı nobel fizik ödülünün grafen hakkındaki ''Çığır açan deneyleri'' dolayısıyla Hollandalı Andre Geim ve Rus kökenli İngiliz vatandaşı Konstantin Novoselov'a verilmesi dikkatleri ''mucize materyal'' olarak da bilinen bu malzeme üzerine çekmiştir. Grafen tek atom inceliğinde olduğundan dolayı iki boyutlu kabul edilen, kovalent bağ ile bağlı karbon atomlarının altılı balpeteği örgüsünde kusursuzca dizilmesiyle oluşturduğu üstün özelliklere sahip bir nanomateryal olarak tanınmaktadır. Grafen yapısında karbon-karbon arası bağ uzunluğu 0,142 nm'dir. Grafen içindeki elektronlar oda sıcaklığında kütlesiz rölativistik parçaçıklar gibi davranır, bu sayede grafen kuantum boşluğu etkisi gibi kendine has özellikler sergiler. Grafenin temel üstün özellikleri geniş yüzey alanı (2630 m 2 g - 1) yüksek elektron mobilitesi (200000 cm2/(V s) yüksek ısıl iletkenliği (5000 Wm-1K-1) ve yüksek young modülü (~1100 Gpa) olarak sıralanabilir. Bu malzeme sahip olduğu üstün özellikler nedeniyle bir çok uygulama alanı bulmaktadır bunların başlıcaları transparan elektrotlar, alan etkili transistörler, sensörler, temiz enerji cihazları, nanokompozitler ve organik fotovoltaik cihazlar olarak sayılabilir. Bu çalışmada üstün özellikleri ile ön plana çıkan grafen nanomateryalinin üretim yöntemleri ele alınacaktır.
  • Öğe
    Twist setting temperature and time effects on morphology of polyethylene terephthalate yarn
    (2014) Yıldırım, Kenan; Köstem, A. Melek; Aydın, Nurcan; Tuna, Hüseyin; Cenan, Ayhan
    İpliğe verilen bükümün sabitlenmesi için ısıl işlem gereklidir. Bu işlem polietilen teraftalat (PET) ipliğin hem morfolojisinin hem de mekaniksel özelliklerini değiştirmektedir. İplik özellikleri ısıl işlem faktörlerinden ısıl işlem metodu, sıcaklık ve süreden büyük ölçüde etkilenmektedir. Bu çalışmada ısıl işlem sıcaklık ve süre parametrelerinin iplik özellikleri üzerine etkisi incelenmiştir. İplik özelliklerinin değişimi çekme testi, diferansiyel taramalı kalorimetre (DSC), kaynama çekmesi, bobin sertliği ve büküm miktarı testleri ile belirlenmiştir. Isıl işlem süresindeki değişimin özellikle kaynama çekmesi ve çekme özellikleri olmak üzere iplik özellikleri üzerine büyük oranda etkisinin olmamasına karşın, sıcaklığın etkisinin yüksek olduğu görülmüştür. Isıl işlem sıcaklığının düşmesiyle kopma uzama oranı ve bobin sertliğinin arttığı, kaynama çekmesinin azaldığı görülmüştür. Bu sonuç ısıl işlem sıcaklığının ipliğe verilen bükümden dolayı oluşan iç gerilimlerin giderilmesi, iç yapıdaki molekülerin yeniden yerleşimi ve amorf bölgedeki moleküler oryantasyon ile yakından ilgili olduğunu göstermiştir.
  • Öğe
    Biochar Reinforced Polyvinyl Alcohol /Corn Starch Biocomposites
    (2020) Terzioğlu, Pınar; Parın, Fatma Nur
    The utilization of biochar in polymer composites can be considered as a sustainable approach that provide valorization of a waste to a value-added material and at the same time diminish biowaste in a smart way.This study is focused on the evaluation of biochar as a filler in polyvinyl alcohol /corn starch composites. The composites were prepared via solution mixing and castingmethod using citric acid as a plasticizer and glutaraldehyde as a cross-linker. Distribution of biochar in the PVA/starch matrix was evaluated by optical microscopy. The structural features of composites were characterized using FTIR spectroscopy. Effectsof biochar loading ratio (0-12 wt%) on the thermal stability of the PVA/starch blends were determined bydifferentialscanning calorimetry andthermogravimetric analyses. The decomposition temperatures of the PVA/starch/biochar composites decreased in comparison to PVA/starch composites.
  • Öğe
    İletken Polimer Esaslı Nanojeneratörler
    (2018) Ünsal, Ömer Faruk; Bedeloğlu, Ayşe
    Gerek doğada, gerekse şehir hayatında mekanik enerjiye di ğer enerji türl eri ne kıya s l a da ha kol a y ul a şılabilmektedir. Suyun yüksek debi de a ktığı bi r a ka rs u ya ta ğı, rüzgâ rın s a l l a dığı a ğa ç da l l a rı, üzeri nden araçların geçtiği bir köprü, yürüyen bir i nsanın eklem hareketleri ve zemine p eriyodik olarak uygul adığı basınç aslında birer a tık mekanik enerji kaynağıdırlar. Rüzgar enerjis i , hi drol i k enerji gi bi büyük mi ktarlarda mekanik enerji sağlana bi l en mecra l a rda uzun yıl l a rdır enerji dönüşüm i şl emi endüstriyel olarak gerçekleştirilmektedir. Son yıllarda daha küçük miktarlarda atık enerjinin dönüşümü ve kul l a nıma s unul ma s ı i çi n na nojenera törl er üzeri ne a ra ştırma l a r yoğunl a şmıştır.
  • Öğe
    Effect of molar ratio of PVP/AgNO3 and molecular weight of PVP on the synthesis of silver nanowires
    (Old City Publishing, 2017) Sağlam, Gökçenur; Borazan, I.; Hoşgün, Halit Levent; Demir, A.; Bedeloğlu, Ayşe
    In this paper, the effect of different parameters including the molar ratio of PVP/AgNO3 and the molecular weight of PVP on the silver nanowires synthesized by polyol method was investigated. The polyol method was performed in the presence of glycerol to obtain silver nanowires with optimum shape and therefore, experiments were repeated using different molecular weights of PVP and aspect ratios of PVP/AgNO3. Optical, structural and morphological characterizations were carried out to understand the effect of parameters on formation of silver nanowires. The results indicated that both molar ratio and molecular weight have influence on silver nanowire synthesis reaction. Silver nanowires with desired shape and high aspect ratio were obtained when PVP with low molecular weight and low molar ratio of PVP/AgNO3 were used. ©2017 Old City Publishing, Inc.