Tirkeş, Seha
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Name Variants
Tirkes, Seha
S.,Tirkes
T., Seha
T.,Seha
Tirkeş, Seha
Tirkes,Seha
Seha Tirkeş
S., Tirkes
S.,Tirkeş
Seha, Tirkeş
Seha, Tirkes
Tirkes S.
Tirkeş,S.
Tirkes,S.
Tirkeş S.
S., Tirkeş
S.,Tirkes
T., Seha
T.,Seha
Tirkeş, Seha
Tirkes,Seha
Seha Tirkeş
S., Tirkes
S.,Tirkeş
Seha, Tirkeş
Seha, Tirkes
Tirkes S.
Tirkeş,S.
Tirkes,S.
Tirkeş S.
S., Tirkeş
Job Title
Profesör Doktor
Email Address
seha.tirkes@atilim.edu.tr
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Scholarly Output
36
Articles
23
Citation Count
350
Supervised Theses
12
36 results
Scholarly Output Search Results
Now showing 1 - 10 of 36
Article Citation Count: 26Mechanical, thermal, melt-flow and morphological characterizations of bentonite-filled ABS copolymer(Emerald Group Publishing Ltd, 2020) Tirkeş, Seha; Tirkes, Seha; Tayfun, Umit; Chemical EngineeringPurpose This study aims to investigate the mechanical, thermal, melt-flow and morphological behavior of acrylonitrile-butadiene-styrene (ABS)-based composites after bentonite inclusions. Melt mixing is the most preferred production method in industrial scale and basically it has very near processing parameters compared to 3D printing applications. Rheological parameters of ABS and its composites are important for 3D applications. Melt flow behavior of ABS effects the fabrication of 3D printed product at desired levels. Shear thinning and non-Newtonian viscosity characteristics of ABS make viscosity control easier and more flexible for several processing techniques including injection molding, compression molding and 3D printing. Design/methodology/approach ABS copolymer was reinforced with bentonite mineral (BNT) at four different loading ratios of 5%, 10%, 15% and 20%. ABS/BNT composites were fabricated by lab-scale micro-compounder followed by injection molding process. Mechanical, thermo-mechanical, thermal, melt-flow and morphological properties of composites were investigated by tensile, hardness and impact tests, dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA), melt flow index (MFI) test and scanning electron microscopy (SEM), respectively. Findings Mechanical tests revealed that tensile strength, elongation and hardness of ABS were enhanced as BNT content increased. Glass transition temperature and storage modulus of ABS exhibited increasing trend with the additions of BNT. However, impact strength values dropped down with BNT inclusion. According to MFI test measurements, BNT incorporation displayed no significant change for MFI value of ABS. Homogeneous dispersion of BNT particles into ABS phase was deduced from SEM micrographs of composites. Loading ratio of 15% BNT was remarked as the most suitable candidate among fabricated ABS-based composites according to findings. Research limitations/implications The advanced mechanical properties and easy processing characteristics are the reasons for usage of ABS as an engineering plastic. Owing to the increase in its usage for 3D printing technology, the ABS became popular in recent years. The utilization of ABS in this technology is in filament form with various colors and dimensions. This is because of its proper rheological features. Practical implications Melt-mixing technique was used as preparation of composites, as this processing method is widely applied in industry. This method is also providing similar processing methodology with 3D printing technology. Originality/value According to the literature survey, to the best of the authors' knowledge, this study is the first research work regarding the melt-flow performance of ABS-based composites to evaluate their 3D printing applications and processability. ABS and BNT containing composites were characterized by tensile, impact and shore hardness tests, DMA, TGA), MFI test and SEM techniques.Master Thesis Elyaf yüzeyine uygun işlemler uygulanarak poliüretan elastomer jut elyaf eko-kompozitlerinin mekanik ve fiziksel özelliklerinin geliştirilmesi(2017) Tirkeş, Seha; Tirkeş, Seha; Tayfun, Ümit; Chemical EngineeringBu çalışmada, kesik jut elyaf (JF) örneklerine, alkali (Na), silan(Si) ve eko-tip epoksi reçine(EP) ile yüzey işlemi uygulanmıştır. Jut elyafların yüzey özellikleri FTIR ve EDX analizleri ile incelenmiştir. JF katkılanmış polyiüretan elastomer (TPU) kompozitleri eriyik karıştırma ile hazırlanmıştır. JF yüzey işlemlerinin TPU bazlı eko-kompozitlerin mekanik, sönümleme, eriyik-akış ve morfolojik özellikleri sırasıyla, çekme ve Shore sertik testleri, dinamik mekanik analiz (DMA), erime akış indisi (MFI) testi ve taramalı elektron mikroskopisi (SEM) teknikleri uygulanarak ortaya çıkarılmıştır. Mekanik test sonuçları göstermiştir ki silan and epoksi uygulanmış JF, eklentisiz TPU'nun çekme dayanımı ve çekme modülünü arttırmıştır. TPU'nun kopmada uzaması, tüm çeşitteki JF eklenmeleri ile bariz şekilde düşmüştür. Bütün yüzey işlemleri TPU'nun sertlik değerinde artış ile sonuçlanmıştır. Mekanik test sonuçlarına benzer şekilde, Si-JF ve EP-JF içeren kompozitler depolama modülünde yükselme göstermişlerdir. TPU'nun camsı geçiş sıcaklığı (Tg), JF eklemeleri ile daha yüksek sıcaklıklara ulaşmıştır. JF eklemeleri, saf TPU'nun MFI değerinde artışa neden olmuştur. SEM mikrofotoğraflarına gore, silan ve epoksi uygulanmış JF, TPU içerisinde homojen dağılım göstermiş ve yüzeyleri polimer fazı ile kaplanmıştır.Article Citation Count: 11Hybrid nanocomposites of elastomeric polyurethane containing halloysite nanotubes and POSS nanoparticles: tensile, hardness, damping and abrasion performance(Cambridge Univ Press, 2020) Tirkeş, Seha; Tirkes, Seha; Akar, Alinda Oyku; Tayfun, Umit; Chemical EngineeringThermoplastic polyurethane (TPU) matrix was reinforced with polyhedral oligomeric silsesquioxane (POSS) and halloysite nanotubes (HNT), both separately and combined. Composite samples were fabricated using a melt-compounding method. Characterization of the composites obtained was performed via tensile and hardness tests, melt-flow index measurements (MFI), abrasion tests, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) to investigate the mechanical performance, flow behaviour, tribological characteristics, thermo-mechanical response and morphological properties. The greatest tensile strength value was obtained for the smallest HNT content. Further addition of HNT resulted in agglomerations for both POSS and HNT particles. The shore hardness of TPU was enhanced by filler inclusions. The TPU/POSS composites displayed significant improvement in terms of abrasion resistance compared to TPU at lower loading levels. The DMA study showed that composites containing 0.5% POSS and 1.0% HNT displayed the greatest storage modulus. The glass-transition temperature of TPU shifted to smaller values with the addition of both nanoparticles. The HNT inclusions increased the MFI value of TPU because of their large aspect ratio. Homogeneous mixing of nanoparticles in the TPU matrix was confirmed by a SEM study of the composites. Their dispersion decreased as the concentrations of POSS and HNT increased. An adjuvant effect of POSS with HNT was achieved in their hybrid composites.Article Citation Count: 18Design and synthesis of new 4,4′-difluoro-4-bora-3a,4a-diaza-s-indacene based electrochromic polymers(Pergamon-elsevier Science Ltd, 2013) Tirkeş, Seha; Ertan, Salih; Cihaner, Atilla; Ergun, Emine Gul Cansu; Cihaner, Atilla; Algi, Fatih; Chemical EngineeringDesign, synthesis, optical and electrochemical properties of two novel 4,4'-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) based donor-acceptor compounds, 1 and 2, are reported in order to elucidate the structure-property relationships in BODIPY based materials. Importantly, these compounds provide opportunity to be used as crosslinkers, since they have three electroactive donor sides. Furthermore, these compounds are polymerized successfully via electrochemical polymerization. The corresponding polymers (P1 and P2) are also characterized by using electrochemical and optical methods in monomer-free electrolyte solutions. It is found that both polymers P1 and P2 exhibit reversible oxidation peaks with half wave potentials of 0.70 V and 0.98 V vs. Ag/AgCl, respectively, and they have low optical band gaps (1.88 eV for P1 and 1.72 eV for P2). It is also noted that the polymers exhibit multielectrochromic properties upon doping: P1 can be switched from pink color in the neutral state to blue color in the oxidized state and P2 can be switched from transmissive pink color when neutralized to transmissive blue color when oxidized. (C) 2013 Elsevier Ltd. All rights reserved.Article Citation Count: 12Development of barite-filled acrylonitrile butadiene styrene composites: Mechanical, thermal, melt-flow and morphological characterizations(Elsevier, 2021) Tirkeş, Seha; Tirkes, Seha; Tayfun, Umit; Chemical EngineeringBarite mineral (BRT) was compounded with acrylonitrile butadiene styrene terpolymer (ABS) with four varied filling ratio of 5%, 10%, 15% and 20% by weight. ABS/BRT composites and unfilled ABS were fabricated by twin screw micro-extruder and test samples were shaped using injection molding process. Tensile tests, shore hardness measurements and impact tests, dynamic mechanical analysis (DMA), melt-flow index (MFI) study and scanning electron microscopy (SEM) characterization techniques were performed in order to investigate mechanical, thermo-mechanical, melt-flow and morphological performance of composites, respectively. Mechanical tests results showed that tensile strength and hardness of unfilled ABS were enhanced as BRT content increased. DMA study revealed that in addition to glass transition temperature, storage modulus of ABS raised by BRT inclusions. However, impact energy of ABS exhibited decreasing trend with the loading level of BRT. According to MFI measurements, BRT additions caused no significant change for MFI parameter of ABS regardless of concentration. It was confirmed by SEM microphotographs that the dispersion of BRT particles was found to be more homogeneous into ABS phase for their lower contents. The filling ratio of 10% BRT yield the highest performance among fabricated ABS based composites according to test results.Article Citation Count: 10Evaluation of flammability, thermal stability and mechanical behavior of expandable graphite-reinforced acrylonitrile-butadiene-styrene terpolymer(Springer, 2022) Tirkeş, Seha; Tirkes, Seha; Tayfun, Umit; Chemical EngineeringAcrylonitrile-butadiene-styrene (ABS) terpolymer was loaded with expandable graphite (EG) at four different concentrations of 5%, 10%, 15% and 20% using micro-compounder followed by injection molding process. Mechanical, thermomechanical, thermal, flame retardancy, melt flow and morphological characterizations of composites were done by tensile, hardness and impact tests, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), melt flow index (MFI) test and scanning electron microscopy (SEM), respectively. According to test results, tensile strength and storage modulus of ABS were improved with the increase in EG content. Storage modulus and glass transition temperature of ABS yielded enhancement with the inclusion of EG. However, percent elongation and impact strength values showed decreasing trend with EG additions. ABS/EG composites gave higher fire performance relative to ABS including enhancement in LOI and reduction in heat release rate. MFI test revealed that incorporation of EG with the lowest amount displayed no dramatic change for MFI value of neat ABS. EG flakes exhibited well-dispersion and exfoliated structure for all of the filling ratios as the SEM microimages of composites were examined. 15% and 20% EG containing ABS composites were remarked as the most suitable candidates among prepared composites. [GRAPHICS] .Article Citation Count: 11Atomistic Engineering of Chemiluminogens: Synthesis, Properties and Polymerization of 2,3-Dihydro-Pyrrolo[3,4-d]Pyridazine-1,4-Dione Scaffolds(Springer/plenum Publishers, 2017) Tirkeş, Seha; Cihaner, Atilla; Tirkes, Seha; Cihaner, Atilla; Algi, Fatih; Chemical EngineeringTwo chemiluminescent compounds containing 2,5-di(thien-2-yl)pyrrole and pyridazine units, namely 5,7-di(thiophen-2-yl)-2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione (5) and 6-phenyl-5,7-di(thiophen-2-yl)-2,3-dihydro-1H-pyrrolo[3,4-d]pyridazine-1,4(6H)-dione (6), were successfully synthesized and electrochemically polymerized. The compounds have chemiluminescent properties and glow in the presence of hydrogen peroxide in basic medium. The intensity of the glow can be increased dramatically by using Fe3+ ions, hemin (1.0 ppm) or blood samples (1.0 ppm) as catalyst. The compounds 5 and 6 have one well-defined irreversible oxidation peak at 1.08 V and 1.33 V vs Ag/AgCl, respectively. Electrochemical polymerization of both 5 and 6 were carried out successfully by repeating potential scanning in the presence of BF3. Et2O in an electrolyte solution of 0.1 M LiClO4 dissolved in acetonitrile. The electronic band gaps (E-g) of the polymers P5 and P6 were found to be 2.02 eV and 2.16 eV, respectively. On the other hand, the corresponding polymers are electroactive and exhibited electrochromic features.Master Thesis Bentonit ile katkılandırılmış akrilonitril-bütadien-stiren kompozitlerinin mekanik ve termal özellikleri(2017) Tirkeş, Seha; Tirkeş, Seha; Tayfun, Ümit; Chemical EngineeringAkrilonitril-bütadien-stiren polimerinin geniş uygulama alanlarından dolayı fiziksel, termal ve reolojik özellklerini geliştirmeye yönelik çalışmalar halen devam etmektedir. Bu çalışmada Akrilonitril-bütadien-stiren matrisine bentonite eklenerek kompozit hazırlanmıştır. Kompozitlerin hazırlanması işlemleri çift vidalı (aynı yönde dönen) mikro-karıştırıcı ile yapılmıştır. Testler için kullanılacak numunelerin hazırlanması da laboratuvar tipi enjeksiyon ile gerçekleştirilmiştir. Akrilonitril-bütadien-stiren polimerinin içerisine eklenen bentonit oranları %5, %10, %15 ve %20 olarak seçilmiştir. Elde edilen kompozitlerin karakterizasyonları çekme ve darbe testleri, dinamik mekanik analizleri, erime akış indisi ve taramalı elektron mikroskobu ile gerçekleştirilmiştir.Article Citation Count: 12Physical and mechanical performance of bentonite and barite loaded low density polyethylene composites: Influence of surface silanization of minerals(Sage Publications Ltd, 2020) Tirkeş, Seha; Tirkes, Seha; Hacioglu, Firat; Tayfun, Umit; Chemical EngineeringIn this study, two kinds of mineral fillers, bentonite (BNT) and barite (BRT), were incorporated into low density polyethylene (LDPE) by extrusion process. Silane treatment was applied to BRT and BNT surfaces in order to increase their compatibility with LDPE matrix. Surface characteristics of fillers were examined by Fourier transformed infrared spectroscopy (FTIR). LDPE-based composites were prepared at a constant concentration of 10%wt for each additives. Test samples were shaped by injection molding process. Mechanical, thermo-mechanical, water repellency, melt-flow and morphological characterizations of LDPE and its composites were performed by tensile and impact tests, dynamic mechanical analysis (DMA), water absorption test, melt flow index (MFI) measurements and scanning electron microscopy (SEM) technique, respectively. Test results showed that surface treatments led to increase for final properties of composites since they promoted to stronger adhesion between minerals and LDPE matrix compared to untreated ones. Tensile and impact strength values, storage modulus and glass transition temperature of LDPE were improved by inclusion of silane treated minerals. BRT and BNT additions caused no remarkable changes with regard to MFI of LDPE. Additionally, silane modified mineral filled composites exhibited remarkable water resistance behavior. According to SEM analysis of composites, silane treated BNT and BRT containing samples displayed homogeneous dispersions into LDPE phase whereas debondings were observed for untreated BNT and BRT filled composites due to their weak adhesion to polymer matrix.Master Thesis Keten elyaf ve bazalt elyaf içeren poli(laktik asit) hibrit eko kompozitlerin incelenmesi(2017) Tirkeş, Seha; Tirkeş, Seha; Tayfun, Ümit; Chemical EngineeringBu çalışmada, poly(laktik acid) (PLA) keten elyaf (FF) ve basalt elyaf (BF) ile tek başlarına ve birlikte hibrit formlarında eklenerek güçlendirilmiştir. BF ve FF içeren PLA eko-kompozitler, % 30 sabit karıştırma oranında çift vidalı mikro-karıştırıcı kullanılarak hazırlanmıştır. Test numuneleri, laboratuvar ölçekli enjeksiyon kalıplama ile şekillendirilmiştir. Kompozitlerin mekanik özellikleri, ısısal-mekanik karakteristikleri, akış davranışları ve morfolojik özellikleri sırasıyla çekme, Shore sertlik, darbe testleri, dinamik mekanik analiz (DMA), erime akış indisi (MFI) testi ve taramalı elektron mikroskopisi (SEM) tekniği ile incelenmiştir Mekanik test sonuçları, hibrit kompozitlerde BF miktarı arttıkça çekme dayanımı, yüzde uzama, elastik modül ve darbe dayanımı değerlerinin arttığını göstermektedir. Bunun aksine, FF eklenmesi ters etki sergilemektedir; bu değerler FF konsantrasyonu arttıkça gözle görülür şekilde düşmektedir. Diğer bir yandan, yüksek FF yüklemelerinde bir miktar fazla sertlik değerleri saptanmaktadır. DMA analizi göstermektedir ki, BF eklenmesi PLA'nın camsı geçiş sıcaklığını bir derece arttırırken hibrit ve FF içeren kompozitlerde bu sıcaklığı daha düşük değerlere kaydırmaktadır. Mekanik test sonuçlarına benzer şekilde kompozitlerin depolama modülleri BF konsantrasyonu ile artmakta, FF eklenmiş kompozitlerde belirgin düşüşler saptanmaktadır. MFI testi sonuçları, tek başlarına FF ve BF eklemeleri PLA'nın MFI değerinde sırasıyla dört ve iki kat artışa neden olduğunu göstermektedir. Hibrit kompozitler, PLA/FF ve PLA/BF kompozitlerinin MFI değerlerinin arasında ortalama değerler sergilemektedir. SEM analizine göre, basalt elyaflar PLA matrisi içinde keten elyaflara kıyasla daha homojen dağılım göstermektedir.
