Browsing by Author "Özmeral, Nimet"

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Citation - WoS: 1
Badem Kabuğu Atığı Dolgulu Epoksi Biyokompozit Özelliklerinin İncelenmesi
(Pamukkale Univ, 2023) Özmeral, Nimet; Kocaman, Süheyla; Soydal, Ülkü; Ahmetli, Gülnare
Bu çalışmada biyobazlı kompozit malzeme elde etmek için dolgu malzemesi olarak badem kabuğu atığı (BK), saf (ER) ve atık polistirenle modifiye bisfenol-A tipi epoksi reçine (ER-PS) kullanılmıştır. BK'nin modifikasyonu, NaOH ve linoleik asit (LnA) ile gerçekleştirilmiştir. BK'nin karakterizasyonunda Fourier dönüşümlü kızılötesi spektroskopisi (FT-IR), taramalı elektron mikroskopisi (SEM), termogravimetrik analiz (TGA) ve partikül boyut dağılım analizleri kullanılmıştır. Kompozitler, döküm tekniği kullanılarak kütlece %10-20-30-40-50 dolgu oranlarında hazırlanmıştır. Kompozitlerin morfolojisi SEM ile karakterize edilmiştir. Epoksi matris tipi ve BK dolgu oranının kompozitlerin mekanik, termal ve su sorpsiyonu özelliklerine etkileri araştırılmıştır. ER-PS/BK kompozitlerinin çekme mukavemeti ve elastise modül (e-modül) değerleri daha düşük, çekme uzama değerleri ise ER/BK kompozitlerine göre daha yüksek bulunmuştur. En yüksek çekme dayanımı değerleri (95-129 MPa) LnA ile modifiye BK kompozitleri için elde edilmiştir. Hazırlanan ER matrisli kompozitlerin dolgu tipine göre çekme mukavemetleri sırası ile: linoleik asit ile modifiye edilmiş BK (LnA-BK) > NaOH ile muamele edilmiş BK (NaOH- BK) > modifiye edilmemiş BK’dir. En uygun BK oranı kütlece %30 olarak belirlenmiştir. Tüm modifiye BK kompozitlerinin e-modül değerleri epoksi matristen daha yüksek bulunmuştur. Sertlik testi sonuçlarına göre kompozitler arasında önemli bir fark belirlenmemiştir. Kompozitlerin su sorpsiyonu BK oranına bağlı olarak artmış ve mekanik özellikleri zayıflatıcı yönde etki etmiştir.
Coating and Flammability Properties of Modified Epoxy-Based Hybrid Composites
(IKSAD Publications, 2022) Özmeral, Nimet; Kocaman, Süheyla; Soydal, Ülkü; Ahmetli, Gülnare
In this study, phenolic novolac-type epoxy resin (EPN) modified with 4 wt% polystyrene (PS) waste, was used as the polymer matrix (EPN-PS) for the first time. Hybrid composites were prepared using red mud waste (RMW) waste at 15-35 wt% and montmorillonite-type nanoclay (NC) at a 2 wt% constant ratio. RMW was a waste material produced during the production of bauxite alumina with the Bayer process. The modification of NC has been made with tetramethylammonium chloride (TMAC). The NC and RMW particle sizes were determined by Particle Size Distribution Analysis. The average sizes were determined as 1631 d.nm and 1064 d.nm, for NC and modified NC (MNC), respectively. Chemical structures of nanoclays were elucidated by FTIR. The effect of the type and ratio of fillers on the coating and flammability properties of the composites were examined. The corrosion protection properties of the composite coatings were determined by immersion test in 5 wt% NaOH, HCl, and NaCl solutions. Surface morphologies of hybrid composites were examined by scanning electron microscopy (SEM) before and after corrosion tests. In addition, the changes in composite coatings in corrosive environments were also examined with a microscope. The modification of NC and the application of hybrid reinforcement were more effective in corrosion resistance of composite coatings in basic and salty environments. The maximum enhancement of corrosion resistance was achieved at 2 wt% MNC-35 wt% RMW. Combustion of the EPN-PS matrix (115 sec) decreased with adding NC/MNC and RMW, and these composites were extinguished in 69 sec and 47 sec, respectively.
Citation - WoS: 8
Citation - Scopus: 9
Effect of Various Aging Conditions and Treatment Methods on Thermal Degradation of Coffee Waste/Epoxy Composites
(Elsevier, 2024) Işık, Murat; Özmeral, Nimet; Ahmetli, Gülnare; Kalem, Merve Soğancıoğlu
In composites containing lignocellulosic fillers, the chemical composition of the filler mostly determines the heat resistance. Based on the rules of green chemistry, new bio-based composites were developed from the waste of industrial crop product coffee (CW), and their thermal stability in different aging environments was examined by thermogravimetric analysis (TGA). Alkali (NaOH), microwave (MW), ultrasound (US), and alkali pretreatment followed by microwave (NaOH+MW) were applied to modify the CW. The effect of various applied treatment methods and environmental conditions such as UV radiation, water sorption, seawater, and hydrothermally agings on the thermal properties of the composites was investigated. Fourier-transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FE-SEM) were used in the characterization of composites. Among the environmental factors tested, seawater and hydrothermal aging affected the thermal resistance of the composites the most, while NaOH+MW affected it most among the processing methods. Although the thermal stability of unaged and UV-exposed MW-CW composites was found to be the highest, it was more affected by aging in seawater, pure water, and hydrothermal environments. As a result, MW was found to be more effective among the treatment methods in terms of thermal properties under UV conditions, confirming that the adoption of environmentally friendly methods and surface modification of the filler can provide superior composites.
Evaluation of Rubber Wastes in Composites
(2022) Özmeral, Nimet; Türkben, Merve; Kocaman, Süheyla; Soydal, Ülkü; Ahmetli, Gülnare
The composition of solid waste is divided into several types, including rubber waste. About 17,000,000 tons of scrap tires are generated in the world every year, and this amount is around 180,000-300,000 tons per year in Turkey. Most of the rubber waste produced comes from automobile, truck, and motorcycle tires. Only 40% of rubber waste is recyclable, excluding energy recovery and landfill applications. In 2018, the amount of rubber waste burned for energy recovery and disposed of in landfills was 7.2% and 3.4%, respectively. Reliable industrial technology and processes are needed to reuse and recycle these wastes. Processed waste can be transformed into cheaper and more sustainable materials. The cycle of producing new tires from used, worn rubber waste increases sustainability. The use of worn tires and scrap tire granules in new products is significantly. It helps reduce the carbon footprint by one-third compared to products made without recycled materials. Using waste tires as filler material to create new composites seems to be one of the most important methods of sustainable management. In this way, it can contribute to the reduction of the waste tire rubber amount after consumption. In this study, two-type of rubber wastes: ground tire rubber (GTR) and ethylene propylene-diene monomer rubber (EPDM) was used as reinforcement in an epoxy matrix. Bisphenol A-type epoxy resin and its blend with polyurethane-modified epoxy in a 1:1 ratio were used as matrices. The effect of rubber and epoxy matrix type on composites’ mechanical properties was investigated. Also, the effect of water sorption and low temperature on mechanical properties was studied.
Citation - WoS: 11
Citation - Scopus: 12
Lignocellulose Coffee Waste-Based Epoxy Composites: Effect of Various Treatment Methods on Composite Properties
(Springer, 2023) Özmeral, Nimet; Işık, Murat; Soğancıoglu Kalem, Merve; Ahmetli, Gülnare
Spent coffee waste (CW) was used as a reinforcement in the bisphenol A-type epoxy resin. Various methods such as alkali (NaOH), microwave (MW), ultrasound (US), and alkali pretreatment followed by microwave (NaOH-MW) treatments were applied for CW filler. For the characterization of CW, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) were used. The composites were characterized by SEM, mechanical, thermal, water sorption, and contact angle measurement analyses. The effects of treatment methods and filler ratios on the properties of epoxy composites were investigated. The highest tensile strength (81-106 MPa) for composites was found with NaOH-CW filler, while the highest decrease in thermal values was determined in the (NaOH + MW)-CW composites. Water sorption of composites which is affected by treatment methods of CW increased with filler loading in all composites. The best results were obtained for with MW-CW composites water absorption and wettability properties. [GRAPHICS]
New Approach Study for the Evaluation of Epdm Rubber Waste
(2022) Temiz, Melisa; Özmeral, Nimet; Kocaman, Süheyla; Cerit, Alaaddin; Ahmetli, Gülnare
Ethylene propylene diene monomer rubber (EPDM) finds applications in several industrial branches due to its properties. EPDM (ethylene propylene diene monomer) is an important synthetic rubber and is used in many different sectors. In parallel with the increase in the amount of use, EPDM waste occurs. EPDM wastes are not likely to be remelted and reprocessed due to their cross-linking and are a significant loss for the plastics industry and are often consumed as fuel. Another method of evaluating EPDM residues is to reduce them to small sizes and use them as fillers in different polymers. In this study, new epoxy composites were created using EPDM waste filler. EPDM waste was used in bisphenol-A type epoxy resin at a ratio of 5-10-15-20-30 wt%, either alone or as a hybrid filler with nano-carbon black (CB). The EPDM:CB ratio was selected as 1:1, 1:3, and 3:1 by weight. The composites were prepared according to ASTM D 638 standards using the casting technique. Composites’morphology was characterized by Scanning Electron Microscopy (SEM). Effect of EPDM:CB ratio, filler amount, water sorption, and low temperature on the mechanical properties of the composites were investigated. In order to determine the effect of water sorption and low temperature, the samples were tested for 3-21 days. A decrease was observed also in the mechanical properties (tensile strength, e-modulus, and hardness) of 30 wt% filler composites formed with both EPDM and hybrid filler, considering the effect of low temperature (freezing) and water sorption. Moreover, the mechanical properties of composites decreased as the test time increased.
Polistirenle Modifiye Epoksi Reçine Bazli Nanokompozit ve Hibrit Kompozitlerin Üretimi ve Karakterizasyonu
(Konya Teknik Üniversitesi, 2023) Özmeral, Nimet; Ahmetli, Gülnare
Bu çalışmada, matris belirlenmesinde ilk önce bisfenol-A tipi epoksi reçine ile epoksi fenolik novolak (EFN) reçinelerinin kürleşme dereceleri hesaplanmış ve çalışmaya EFN ile devam edilmesine karar verilmiştir. EFN reçinesi, kütlece %1-5 termoplastik polistiren (PS) atığı ile modifiye edilerek en uygun oran %4 PS seçilerek ilk kez polimer matris olarak kullanılmıştır. İki tip kompozit hazırlanmıştır: (i) kütlece %1-4 nanokil (NK) içeren nanokompozitler ve (ii) hibrit kompozitler. Saf (NK) ve tetrametilamonyum klorür (TMAC) ile modifiye edilmiş nanokil (MNK), kütlece %15-35 kırmızı çamur atığı (KÇ) içeren hibrit kompozitlerde en uygun kütlece %2 oranında kullanılmıştır. Nanokillerin kimyasal yapıları Fourier Dönüşümlü Kızılötesi Spektroskopisi (FTIR) ile aydınlatılmış, partikül boyutu analizi ile karakterize edilmiştir. Nano ve hibrit kompozitlerin yüzey morfolojisi, Taramalı elektron mikroskobu (SEM) ve X-ışını kırınımı (XRD) ile karakterize edilmiştir. PS, NK ve KÇ'nin kompozitlerin mekanik, dinamik-mekanik, termal ve yanıcılık özellikleri üzerindeki etkileri araştırılmıştır. EFN-PS matrisinin yanması, NK/MNK ve KÇ eklenmesiyle azalmıştır. Ayrıca, hibrit kompozit kaplamaların korozyona karşı koruma özellikleri, %5 NaOH, HCl ve NaCl çözeltilerine daldırma testi ile belirlenmiştir. Hibrit kompozitlerin su sorpsiyonu %1-3,6 ile %1-5,3 arasında değişirken EFN-PS/NK nanokompozitlerde %0,82-1,02 arasında değişmiştir. Hibrit kompozitlerin korozif ortamda baz ve tuz çözeltileri için kütle artış yüzde değerleri (sırasıyla %0,59-0,75 ve %0,46-0,59) su sorpsiyonuna göre çok daha düşük olarak belirlenmiştir. Hibrit kompozit kaplamaların morfolojileri, korozyon testlerinden önce ve sonra taramalı elektron mikroskobu (SEM) ile, yüzey özellikleri ise mikroskop ile incelenmiştir. %2 MNK-%30 KÇ hibrit kompozit, bazik ve tuzlu ortamlardaki yüksek korozyon direnci, depolama modülü, kayıp modülü ve camsı geçiş sıcaklığı (Tg) değerleri (90,6°C) nedeniyle %2 NK-%30 KÇ kompozitine göre daha uygun bulunmuştur.
Citation - WoS: 15
Citation - Scopus: 18
Polystyrene Waste-Modified Epoxy/Nanoclay and Hybrid Composite Coatings
(Wiley, 2023) Özmeral, Nimet; Kocaman, Süheyla; Soydal, Ülkü; Ahmetli, Gülnare
In this study, phenolic novolac-type epoxy (EPN) resin was modified with 4 wt% thermoplastic polystyrene (PS) waste and was used as the polymer matrix for the first time. Two types of composites were prepared: (i) nanocomposites with 1-3 wt% nanoclay (NC) and (ii) hybrid composites. Pristine (NC) and tetramethylammonium chloride modified nanoclays (MNC) were used at a 2 wt% ratio in hybrid composites with 25-35 wt% red mud waste (RMW). The corrosion protection properties of the coatings were determined by immersion test in 5 wt% NaOH, HCl, and NaCl solutions. The water sorption of hybrid composites varied between 1%-3.6% and 1%-5.3%, while it was between 0.82% and 1.02% in EPN-PS/NC nanocomposites. The weight gain percentage values of hybrid composites in corrosive media for the base and salt solutions were determined much lower (0.59%-0.75% and 0.46%-0.59%, respectively) than water sorption. Surface morphologies of hybrid composites were examined by scanning electron microscopy before and after corrosion tests. MNC-30 wt% RMW hybrid composite was found more suitable due to high corrosion resistance in basic and salty environments, storage modulus, loss modulus, and glass transition temperature (T-g) values (90.6 & DEG;C) as compared with NC-30 wt% RMW hybrid composite.
Citation - WoS: 13
Citation - Scopus: 14
Red Mud Waste/Nanoclay Epoxy Hybrid Composites: Mechanical, Thermal, and Flammability Properties
(Wiley, 2023) Özmeral, Nimet; Soydal, Ülkü; Kocaman, Süheyla; Ahmetli, Gülnare
In this study, bisphenol A-type epoxy (ER) and epoxy phenol novolac resins (EPN) with two amine-type curing agents (KH 816 and IPOX EH 2041) having different total amine values were selected. The mechanical properties and density of the EPN resin were found higher in the case of both curing agents. EPN was modified with polystyrene (EPN-PS) and used as a matrix using an IPOX hardener. Nano- and hybrid composites were prepared with pristine and modified with tetramethylammonium chloride nano montmorillonite (NC and MNC), and red mud waste (RMW). The chemical structure was elucidated by the Fourier transform infrared (FT-IR). The composites were characterized by scanning electron microscopy and x-ray diffraction. Appropriate PS and NC ratio was accepted as 4% and 2% by weight, respectively. Curing degrees calculated from the FT-IR spectra of ER, EPN, and EPN-PS were 99.3%, 99.9%, and 86.5%, respectively. A comparative study of the two binary systems; (i) 2 wt% NC-(15-35) wt% RMW; and (ii) 2 wt% of MNC-(15-35) wt% of RMW on the mechanical, thermal, and flammability properties of EPN-PS matrix was carried out. The appropriate RMW ratio was 30 wt%. Hybrid composites with 25-30 wt% RMW can be considered self-extinguishing materials.
Study on Thermal Properties of Coffee Waste-Based Composites
(2023) Özmeral, Nimet; Murat Işık; Kalem Soğancıoğlu, Merve; Ahmetli, Gülnare
Coffee is the most consumed daily beverage by millions of people worldwide and therefore its production is constantly growing. In 2021, coffee production reached 7.7 million tons, which is almost double what it was 30 years ago (Bijla et al., 2022:e14190). In coffee-producing countries, more than 50% of the fruit mass consists of residue from the coffee fruit, and used coffee powder is the waste residue obtained during the brewing process (Campos-Vega et al., 2015:24). Different ways of evaluating SCG are being explored. For example, it is popular to use SCGs as a soil fertilizer (mineral addition) to promote plant growth. Due to their high nutritional value, SCGs have also been additionally tested in animal feed, or, phenolic extracts isolated from SCGs can be used as antioxidants. Carbohydrates present in SCGs are valuable carbon sources for the biotechnological production of polyhydroxyalkanoates, carotenoids, and bioethanol (Kovalcik et al., 2018:104). Apart from these, coffee waste can also be used as a filler in polymer matrices. Many different parameters such as filler type and ratio, the chemical structure of the matrix, modification processes, water and humidity, and UV rays can affect the composite properties. It is known that natural fiber composites exposed to direct sunlight are exposed to radiation and thus the covalent bonds in the organic polymer are broken, causing changes such as discoloration, weight loss, surface roughness, deterioration of mechanical properties, and brittleness (Mahzan et al., 2017:e012021). In this study, biocomposite materials have been developed by using untreated and treated with various methods (alkali (NaOH), microwave (MW), ultrasound (US), and alkali followed by microwave (NaOH+MW)) coffee wastes (CW) in the epoxy matrix. The filling ratio in composites was selected as 10-30-50 wt%. Composites were exposed to UV rays for 360 h. The changes in the chemical structure due to the effect of UV light were illuminated by Fourier-transform infrared spectroscopy (FTIR). The effect of UV radiation on the thermal properties of composites has been investigated using thermogravimetric analysis (TGA). As a result, it was determined that the thermal properties slightly increased as a result of the formation of free radicals from the groups in the epoxy structure and increasing cross-link density under the influence of UV (Korkmaz and Gültekin, 2022:e110004).
Citation - Scopus: 23
Water Sorption, Thermal, and Fire Resistance Properties of Natural Shell-Based Epoxy Composites
(John Wiley and Sons Inc, 2022) Zamani, Kianoosh; Kocaman, Süheyla; Işık, Murat; Soydal, Ülkü; Özmeral, Nimet; Ahmetli, Gülnare
In this study, walnut shell (WSh), hazelnut shell (HSh), and mussel shell (MSh) waste as inexpensive reinforcements were recycled for the preparation of epoxy composite materials. Subsequent used inexpensive fillers are chars (WShC and HShC), which are the pyrolysis solid products of the natural WSh and HSh wastes. Three types of epoxy resins: bisphenol-A type (DGEBA), modified with polyurethane (MER with PU), and rubber modified (MER with rubber) epoxy resins were used as the matrix in MSh composites. Thermogravimetric analysis of the composites showed that the thermal strength of the epoxy matrix increased significantly with the MSh and chars. The best water sorption results were obtained with the MSh. The contact angle values of MSh composites prepared with DGEBA epoxy resin were quite high (111°–113.5°) and their water retention values ranged from 0.2% to 0.32%. The composites that were produced using 50 wt% chars and the same epoxy resin showed better flammability stability. The full extinction times were determined as 63 and 58 s for WShC and HShC composites, respectively. © 2022 Wiley Periodicals LLC.