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Öğe A comprehensive characterisation of wollastonite-filled low-density polyethylene composites(Springer, 2025) Tuna, Sibel; Sen, IbrahimIn this study, wollastonite (WOL)-filled low-density polyethylene (LDPE) composites were developed taking into account cost, environmental considerations and performance parameters that are essential for composite materials. For this purpose, LDPE composites containing 5, 10, 15 and 20 (wt%) WOL were produced by injection moulding process. When the results are examined, the effect of the addition of WOL can be seen in Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses. As a result of the microstructural analyses, it was observed that the WOL particles can be homogeneously distributed in the matrix, but there are interfacial voids. Accordingly, elongation at break (EB) and notched impact strength (NIS) values decreased, tensile strength (TS) values did not change significantly, while flexural strength (FS) and flexural modulus (FM) performance increased. The addition of WOL did not significantly change the melting and crystallisation temperatures (Tm and Tc) and the degree of crystallinity (Xc) of the composites, but had a positive effect on the temperatures at which the composites degraded by 5% (T5) and 50% (T50). When analysing the effect of WOL addition on the viscoelastic properties, an increase in storage modulus (SM) and loss modulus (LM) values was observed as the amount of WOL increased.Öğe An overview of polymer foam technologies with a focus on polylactic acid, polypropylene, and polyamide 6-based materials(Sage Publications Ltd, 2026) Tuna, Sibel; Akkoyun Kurtlu, MeralPolymer-based composite materials are widely used in a number of engineering applications owing to their light weight, mechanical strength, chemical resistance and versatility in design. Using these materials in foam form offers several additional advantages, including reduced density, improved heat and sound insulation, and increased impact resistance. In the contemporary era, intensive research is being conducted into the evaluation of petrochemical-based polymers, such as polypropylene (PP) and polyamide 6 (PA6), and biopolymers, particularly polylactic acid (PLA), in foamed composite structures. Furthermore, hybrid systems formed by the combination of these different polymer types offer great potential for balancing environmental sustainability and performance. This review discusses the general structure, foam formation mechanisms, production techniques and basic properties of polymer-based foam composite materials. Prominent polymer-based systems, such as PP, PA6 and PLA, were examined comparatively. Additionally, contemporary methodologies concerning hybrid foam systems formed by PLA with PP and PA6, as presented in the existing literature, were evaluated.Öğe Artemisinin Yield and Cyto/Genotoxic Properties of Naturally Grown Artemisia Annua L. In Uludag, Turkey(Bursa Teknik Üniversitesi, 2022) Yaşa, Belkıs; Angın, Naile; Ertaş, Murat; Tuna, Sibel; Çınar, AycanArtemisia annua L. known as sweet wormwood in ancient literature is an essential oil bearing and medicinal aromatic plant and belongs to Asteraceae family. It has been used for many years in traditional eastern medicine especially in the treatment of malaria and some parasitic diseases, and it gives successful results. Recently, it has been addressed with its potential effect against coronavirus. In this study, naturally growing Artemisia annua L. sample in Uludag, in Bursa province of Turkey, was used as raw drug. The aim of this study is to determine the yields of artemisinin in three different solvent phase extracts using High Performance Liquid Chromatography (HPLC) and examine cytotoxic/genotoxic effect of total ethanol extract on epithelial cells isolated from human bronchial epithelium. The highest amount of artemisinin was found as 0.19 mg/g in ethanol extract. As a result of cell toxicity assay, no cytotoxicity or genotoxicity effect was observed at doses less than 500 µg/mL.Öğe Biowaste orange peel incorporated chitosan/polyvinyl alcohol composite films for food packaging applications(Elsevier Ltd, 2021) Terzioğlu, Pınar; Güney, Fatma; Parın, Fatma Nur; Şen, İbrahim; Tuna, SibelEcofriendly chitosan/polyvinyl alcohol (PVA) composite films enriched with orange peel were developed by solvent casting technique. The effect of various orange peel contents (0.25–1.25 % w/w) on the barrier, bioactivity, color, microstructure, mechanical, optical, physical, structural, and wettability properties of the chitosan/PVA films were investigated. Fourier Transform Infrared spectroscopy results showed the interaction between the orange peel and the polymers. The addition of orange peel increased the thickness, flexibility, thermal stability and water vapor permeability of the chitosan/PVA films. Orange peel loading improved the ultraviolet–visible light barrier characteristic of neat films by lowering the transparency value. The presence of orange peel in the composite films resulted in decrease of hydrophobicity and oxygen transmission rate. Furthermore, orange peel notably improved the antioxidant activity of films. Consequently, chitosan/polyvinyl alcohol/orange peel composite films may be potential ecofriendly bioactive packaging candidates for food preservation.Öğe Characterization of Olive Seed Powder Incorporated Low Density Polyethylene Composites(Sakarya University, 2025) Tuna, Sibel; Şen, İbrahimGlobal warming, increasing production and consumption rates, environmental concerns have revealed the need for some innovative material studies, and studies on the use of polymeric composites prepared with natural based fillers have become widespread to increase environmental awareness and ensure sustainable production. Composite materials prepared by using easily accessible, affordable, lightweight, high-strength plant based fillers can be used in many areas. In this study, composites of low density polyethylene (LDPE), which is one of the most widely used thermoplastics, were prepared by injection moulding process using the waste seeds of olives (OS), which have an important place in Turkey's agriculture and economy, and the density, hardness (Shore D), spectroscopic (Fourier transform infrared (FTIR) spectroscopy), morphological (Scanning electron microscopy (SEM)), mechanical, thermal (Differential Scanning Calorimetry (DSC), Heat Deflection Temperature (HDT) and Vicat softening temperature) analyses of OS filled LDPE composites were performed. As a result of the study, an increase in hardness and elastic modulus values of OS filled LDPE composites was observed, while no noticeable decrease in thermal properties was seen. © 2025, Sakarya University. All rights reserved.Öğe Characterization of Olive Seed Powder Incorporated Low Density Polyethylene Composites(2025) Tuna, Sibel; Şen, İbrahimGlobal warming, increasing production and consumption rates, environmental concerns have revealed the need for some innovative material studies, and studies on the use of polymeric composites prepared with natural based fillers have become widespread in order to increase environmental awareness and ensure sustainable production. Composite materials prepared by using easily accessible, affordable, lightweight, high-strength plant based fillers can be used in many areas. In this study, composites of low density polyethylene (LDPE), which is one of the most widely used thermoplastics, were prepared by injection moulding process using the waste seeds of olives (OS), which have an important place in Turkey's agriculture and economy, and the density, hardness (Shore D), spectroscopic (Fourier transform infrared (FTIR) spectroscopy), morphological (Scanning electron microscopy (SEM)), mechanical, thermal (Differential Scanning Calorimetry (DSC), Heat Deflection Temperature (HDT) and Vicat softening temperature) analyses of OS filled LDPE composites were performed. As a result of the study, an increase in hardness and elastic modulus values of OS filled LDPE composites was observed, while no noticeable decrease in thermal properties was seen.Öğe Chemical foaming of polylactic acid/polypropylene and polylactic acid/polyamide 6: Evaluation of changes in their properties(SAGE Publications Ltd, 2024) Tuna, Sibel; Akkoyun Kurtlu, MeralMost of the polymers made from fossil fuels end up as waste material and this environment-damaging situation has revealed the need to take some precautions such as the use of eco-friendly, biodegradable materials obtained from renewable sources as an alternative. Biopolymers are being evaluated as alternatives to traditional polymers especially in the automotive industry due to their better-understood properties such as mechanical and physical behavior through the studies conducted. On the other hand, when the literature studies are evaluated, it can be seen that the production of foam materials, which are focused on lightness and carbon dioxide (CO2) emission limitations that are important and essential for the automotive sector, is an area that is also researched and studied for biopolymers. Several studies are carried out with both physical and chemical foaming agents on this subject in recent years. In this study, it is aimed to develop light, environmentally friendly, high-performance polylactic acid (PLA) based polymeric composite foams that can be used in the automotive industry by using twin screw extruder and compression molding methods. For this purpose, polyamide 6 (PA6) and polypropylene (PP) polymers were used with PLA and by adding 1 wt.%, 1.5 wt.% and 2 wt.% chemical blowing agents to the polymer mixtures, the physical, thermal, mechanical, morphological properties and changes in these properties were investigated. The most suitable chemical blowing agent ratio was found to be 1.5 wt.% for PLA/PP and PLA/PA6 mixtures. © The Author(s) 2023.Öğe Correlation Between Surface, Thermal, Mechanical and Morphological Properties of Polylactic Acid/Polypropylene and Polylactic Acid/Polyamide 6 Blends(Kırıkkale Üniversitesi, 2022) Tuna, Sibel; Akkoyun, MeralIn the automotive sector, which is one of the sectors where polymers are mostly used, their behaviour and compatibility in secondary processes such as painting and coating applications are important in the preference of polymers according to their usage areas as well as mechanical and thermal properties. In this context, it is known that surface wettability of a polymer material is of great importance for different application areas and it can be stated that wetting and non-wetting behaviours play an important role in the selection of polymers and their industrial applications. In this study, the contact angle properties of polypropylene (PP) and polyamide 6 (PA6), which are the most used polymers in the automotive sector and their polymer blends prepared by using polylactic acid (PLA) were examined. When PLA/PP and PLA/PA6 mixtures were compared, it was observed that there were significant differences in contact angle measurements and these properties detected in water contact angle measurements were attributed to changes in chemical structures, functional groups and morphology of related polymers. Surface analysis were supported by thermal, mechanical and morphological analysis and differences in static contact angle measurement results were explained.Öğe Development and characterization of polypropylene or polyamide 6 hybrid composites filled with magnetite and silicon carbide(Springer, 2025) Kurtlu, Meral Akkoyun; Tuncay, Beril; Tuna, SibelPolymers, which are becoming widespread day by day and find use in almost every domestic and industrial sectors, have many advantageous properties, on the other hand, their use in areas where thermal conductivity needed is limited due to their low thermal conductivity. To overcome this problem, the requirement for composite materials with high thermal conductivity is increasing and studies on this subject are becoming widespread. In this context, it is known that the thermal conductivity values of the polymer composite structure can be improved by adding fillers to the polymer structures that will augment the thermal conductivity. In this study, to improve the thermal conductivity of polypropylene (PP) and polyamide 6 (PA6), hybrid composites of PP or PA6, separately, filled with silicon carbide (SiC) and magnetite (Fe3O4) were prepared. For this purpose, PP/SiC/Fe3O4 and PA6/SiC/Fe3O4 composites were produced in 1:1 filler ratio with different filler contents (5, 10 and 20% by wts) by extrusion method and shaped by compression molding to determine the optimum amount of additives. Afterward, thermal conductivity, electrical conductivity, mechanical, molecular spectroscopic, and microstructure analyses were carried out for the characterization of all composites. When the study results were examined, it was seen that the PP/SiC/Fe3O4 composite structure containing the highest filler ratio of 20% (by wt) improved by 26% and a thermal conductivity value with a higher enhancement of 38% was obtained for PA6/SiC/Fe3O4 composite prepared at the same filler content compared to neat polymers.Öğe Development of Carboxymethyl Cellulose and Graphene Filled Polypropylene Composites: Hybridization of Natural and Nanofillers(Wiley-V C H Verlag Gmbh, 2025) Tuna, Sibel; Sen, IbrahimPolymeric composites have become important in materials engineering thanks to their advanced properties and potential for versatile applications. In this study, the effects of reinforcing polypropylene (PP), a widely used thermoplastic with carboxymethyl cellulose (CMC), a natural additive, and graphene (Gr), a nanoadditive on its performance were investigated. While CMC offers advantages such as lightness and biodegradability, the goal of Gr is to achieve high mechanical and thermal performance in the composite. Using maleic anhydride as a compatibilizing agent improves the compatibility between the fillers and the matrix. Physical, structural, thermal, mechanical and morphological characterization of the injection-moulded composite structures revealed slight increases in density and hardness values, as well as enhanced crystallization behavior, thermal stability, and degree of crystallinity. The tensile and flexural properties generally improved with increasing filler content and microstructural analysis confirmed the good distribution and high interaction of the fillers in the matrix. Overall, hybrid structures incorporating CMC/Gr fillers in a PP matrix were identified as a promising alternative for multifunctional and sustainable engineering applications.Öğe Effect of coupling agent on polylactic acid/polypropylene and polylactic acid/polyamide 6 foam composites(John Wiley and Sons Inc, 2024) Tuna, Sibel; Akkoyun Kurtlu, MeralThe main part of polymer materials generated from fossil fuels do not degrade after completing their usage life and then begin to be waste in the environment. This situation has led to the emphasis on environmentally friendly, biodegradable, and bio-based polymers obtained from renewable sources as an alternative. In recent years, several studies are concentrated on especially lightweight and carbon dioxide (CO2) emission limitations. In this work, the goal was to investigate at the same time environmentally friendly and lightweight polymer foam composites based on polylactic acid (PLA) polymer without lowering the performances of the materials. In this aim, polymer foam composites containing polypropylene (PP), polyamide 6 (PA6) and PLA were produced (PLA/PA6 (30:70) and PLA/PP (30:70)) with a chemical blowing agent (CBA) introduced at 1.5 wt.% to the polymer mixture. To improve the interpolymer compatibility and foaming activity maleic anhydride-grafted polylactic acid (PLA-g-MA) was utilized as coupling agent (CA) in different ratios (1, 3 and 5 wt.%). From the evaluation of the polymer mixtures in terms of their lightness, thermal and mechanical strength, the most appropriate CA ratios were determined as 1 wt.% for foamed PLA/PP (30:70) mixtures and 3 wt.% for foamed PLA/PA6 (30:70) mixtures. © 2023 Wiley Periodicals LLC.Öğe Effect of Olive Leaf Powder on Structural, Thermal, Mechanical, and Antioxidant Properties of Polylactic Acid Based Biocomposite Films(Wiley, 2025) Tuna, Sibel; Kizil, Demet; Sen, Ibrahim; Eroglu, MuratIn the present study, polylactic acid films containing olive leaves with different particle sizes and different additive ratios were characterized in terms of structural, thermal, mechanical, and antioxidant properties. XRD and SEM analyses showed that PLA films with olive leaf powder generally have an amorphous structure, whereas films with low filler ratios and fine particles exhibit higher crystallinity. Not so surprisingly, neither filler amount nor mixing time are making a big difference in the crystallinity or morphology of the surface. In the context of DSC analysis, a maximum variation of 2 degrees C in the glass transition temperature was observed. A comparable trend shift was observed between the Tg (glass transition temperature for DMA) values in the DMA analysis and the Tg (glass transition temperature for DSC) values in the DSC analysis. However, the change in the DMA analysis was more definitive. Antioxidant activity of the films was observed to increase with decreasing particle size of olive leaves added to polylactic acid and increasing additive ratio. Adding olive leaf powder to PLA and then looking at the effects on these aspects as mechanical, thermal, morphological, and antioxidant properties contributed to the evaluation of PLA as a potential additive for producing biodegradable polymers.Öğe Evaluation of the use and performance of natural filler based polypropylene/leonardite composites(Elsevier Sci Ltd, 2024) Sen, Ibrahim; Tuna, Sibel; Kurtlu, Meral AkkoyunThe use of polypropylene (PP), which has reached a considerably high level in the last century and is one of the polymers whose properties have been investigated and studied in much more detail with the use of various additives, can be obtained as composite structures with the use of both inorganic and organic additives, and the desired properties can be modified according to the desired purpose. In this study, it was aimed to evaluate the behavior of leonardite, a rich source of humic acid, with PP composite structures, whose performance with thermoplastic materials has never been investigated before, although there are studies on its use in different sectors. To evaluate the effects of different ratios of leonardite additives on PP polymer, the composites were prepared with a twin screw extruder, and the test specimens were produced using an injection molding device. Spectroscopic, density, microscopic, mechanical (tensile, impact, flexural), thermal and color analyses of composites containing leonardite at 0, 0.5, 1, 3, 5, and 10 wt% were carried out. As the amount of leonardite in the composite increased, a slight increase was observed in the density values of the composites, with a maximum of 4.7%. In microstructure analysis, a homogeneous distribution of the filler was observed in composites reinforced up to 1 wt%, while agglomeration occurred at higher rates. While the highest tensile strength and flexural strength values were found for the 5 wt% leonardite filled composite, it was observed that these values increased from 31.8 MPa to 32.7 MPa and from 32.84 MPa to 37.84 MPa compared to the pure PP, respectively. The highest Izod impact strength value was determined for the 10 wt% leonardite filled composite and an increase in this value was obtained from 2.47 kJ/m2 to 2.85 kJ/m2. The nucleation effect explains the decrease in supercooling temperature observed in the thermal analysis results. Furthermore, an increase of the thermal stability of PP/leonardite composite structures was demonstrated. When the color analysis results were examined, it was seen that the leonardite additive caused the color of the composite to darken, as expected.Öğe Impact of titanate coated magnetite nanoparticles on the properties of rigid polyurethane foams(2025) Yılmaz, Buse Fem; Kurtlu, Meral Akkoyun; Tuna, SibelClosed cell polyurethane-based materials represent more than 23% of all polyurethane manufacturing. Unlike to the use of closed cell polyurethane foams in a large variety of applications, these materials exhibit some drawbacks. Their limited mechanical strength and their limited thermal constancy hindering their usage in some areas can be given as examples. In the purpose to overcome and enhance the weaknesses of rigid polyurethane foams and at the same time enlarge the utilization areas of these materials, numerous studies were realized in the literature. The utilization of Fe?O? nanoparticles in various fields, including magnetic resonance, has gained significant attention in recent years. These additives can improve at the same time the thermal and mechanical properties of polyurethane foams. Nevertheless, the development of new methods concerning the surface modification of the nanoparticles is important. The improvement of the interfacial interactions at the polyurethane-filler interface was largely investigated with various agents such as silica, surfactants and precursor metals in the literature. However, the use of a titanate-based coupling agent was not yet researched. In this work, a surface coating of Fe3O4 nanoparticles with a titanate-based coupling agent (Ti-Fe3O4) was realized to produce Fe3O4 filled rigid polyurethane foam nanocomposites at different filler ratios. Microstructural, mechanical, thermal and electrical conductivity properties of all foam nanocomposites were characterized. The FTIR spectra exhibited only the presence of physical interactions. In addition, an increase of the crystallinity ratio with the increase of the filler content was observed. Concerning the electrical and thermal conductivity results, a noticeable improvement was detected from the pure rigid polyurethane foam to the 50 wt.% Ti-Fe3O4 filled nanocomposite. From the mechanical test results, a higher performance was observed for the rigid polyurethane foam nanocomposite produced at 12.5 wt.%.Öğe INVESTIGATION OF THE POLYETHYLENE GLYCOL AND CHERRY STEM WASTE RATIOS ON THE FINAL THERMAL, AND MECHANICAL PROPERTIES OF POLYVINYL ALCOHOL BASED COMPOSITE FILMS(2025) Tuna, Sibel“Green composites”, which are essentially composed of a biopolymer matrix and natural filler materials, have emerged as a significant alternative in the context of environmental pollution and sustainability studies in recent years. This study was designed to investigate the effects of polyethylene glycol (PEG) as a secondary polymer and cherry stem (CS) powder as a reinforcing phase on the thermal and mechanical performances of polyvinyl alcohol (PVA) based composite films. The composite films were produced using the solvent casting method. Taguchi optimization was performed to observe the effects of the PEG and CS ratios. The properties of the composite films were evaluated using Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing. It was determined that the use of PEG improves the thermal properties due to its high thermal stability, as well as improving the elongation at break values, while decreasing tensile strength due to its plasticizing effect. CS generally improves thermal properties and tensile strength by up to 5% but decreases by 10% due to agglomeration. Elongation at break decreases as the amount of CS increases.Öğe Manufacturing and Characterization of Three Modified Vegetable Oil-Added Polylactic Acid Composites(Wiley, 2024) Sen, Ibrahim; Atagur, Metehan; Tuna, Sibel; Eroglu, Murat; Kurtlu, Meral Akkoyun; Sever, KutlayPolylactic acid (PLA) was modified with three types of modified vegetable oils (MVOs), which are the epoxidized soybean oil (ESBO), maleinized sunflower oil (MSO), and maleinized olive oil (MOO), at different weight fractions. A corotating twin screw extruder was used to produce composite materials by the melt-mixing process. The effect of MVO content, from 2.5% to 10%, on the morphology, mechanical properties, density, and water absorption was investigated in detail. The addition of ESBO and maleinized vegetable oils leads to a slight decrease in the density of PLA from 1.252 to 1.231 g/cm3. As the concentration of MVO in PLA increases, the amount of water absorption also increases, and the highest water absorption value was observed in P10MSO. The FTIR spectra of all concentrations of the MOO and MSO have two peaks at 1781 and 1861 cm-1, attributed to the C=O stretching which is related to maleic acid copolymerization. In general, the elastic modulus (EM) was slightly changed by the addition of MVOs to PLA, while the tensile strength (TS) decreased. Due to the plasticizing effect of MVOs, an increase in the Izod impact strength was obtained.Öğe On the use of olive leaf powder to improve the performance of water-blown rigid polyurethane foam composites(Sage Publications Ltd, 2025) Tuna, Sibel; Kurtlu, Meral AkkoyunNowadays, polyurethane (PU) foams were preferred in a broad extent of applications particularly due to their lowest thermal conductivity values satisfying the demand for energy efficiency while their use as natural filler added foam composites can reduce the polymer content allowing a more environmentally friendly production. The purpose of this work was to research the impact of olive leaf powder of various particle sizes and weight ratios on the microstructure, thermal, and mechanical properties of rigid polyurethane foam composites. All results exhibited optimum mechanical, thermal, and microstructure properties for the finest particle sized and 3 wt% added foam composites. This foam composite demonstrated an enhancement by 54%, 41%, and 61% for the tensile strength, elongation at break, and compression strength values, respectively. The thermal degradation temperature of the foam composites was also improved in correlation with the reduction of the glass transition temperature of the soft segments while the glass transition of the hard segments increased. Concerning the thermal conductivity results, the highest reduction by 11% was observed for the finest particles filled at 5 wt%, compared to the pure rigid PU foam, in correlation with the cell size showing a maximum reduction by 18% for the same composite.Öğe Optimization of parameters on fig leaf powders added polylactic acid-based composite films using Taguchi method(Springer, 2025) Tuna, SibelThis study presents the effects of formulation and production parameters, which affect the performance of bio-based films that have been widely studied in recent years, using the Taguchi method. Since the demands for evaluating the effects of variables as a whole are important and meaningful to optimize the effects of the variables on material development studies in the bio-based packaging sector, the effects of the filler ratio, filler size and production temperatures, especially on mechanical and thermal properties, have been investigated. While fig tree leaves, which are considered agricultural waste, were used as filler at ratios of 3, 5 and 10%, the particle sizes of fig tree leaves were 33, 77 and 138 mu m. Film production was carried out at three different temperatures: 50, 60 and 70 degrees C. After produced films were characterized by spectroscopic, morphological, thermal and mechanical tests, important and unimportant factors were defined, especially in terms of mechanical and thermal properties. Accordingly, while the most effective factor on tensile strength was the filler ratio, the most effective factor on elongation at break was determined as filler size. When the factors that most affect the thermal properties were evaluated, this factor was determined as the filler ratio for the decomposition temperature of 50% of the film (T50) and the filler size for glass transition (Tg) temperature. The results obtained were analyzed with ANOVA. According to the results obtained, parameters can be determined according to the final purpose and application area in the films to be developed in future studies.Öğe Synergistic Effect of Blast Furnace Slag and Fly Ash on the Properties of Polyamide 6(Wiley, 2026) Akkoyun Kurtlu, Meral; Tuna, SibelThe use of waste products such as ground-granulated blast furnace slag (BFS) and fly ash (FA) as fillers in polymer matrices is a relatively new approach. Polymer composites prepared with BFS and FA can be suitable candidates for applications requiring electrical insulation properties due to their improved mechanical properties, wear resistance, and thermal resistance, as well as their low electrical conductivity. The aim of this work is to investigate the synergistic effects of BFS and FA on the final structural, thermal, mechanical, morphological, and electrical conductivity properties of polyamide 6 (PA6), a thermoplastic polymer widely used in the plastic industry. When BFS/FA-added PA6 composites prepared at ratios of 5, 10, 20, 30, and 40 wt.% using twin screw extruder and compression molding methods were characterized, the physical interactions were observed at the intermolecular level. A general decrease in tensile strength values with increasing BFS/FA content was obtained. BFS/FA particles were homogeneously dispersed in the PA6 matrix, but a weak interaction occurs at the filler-matrix interface. Concerning the electrical conductivity results, the use of BFS/FA fillers in PA6 composites improved the electrical conductivity values as intended, but the interfacial compatibility should be increased in applications requiring mechanical performance.Öğe Sıkıştırmalı kalıplama yöntemi ile PLA esaslı polimerik kompozit köpüklerinin üretimi ve özelliklerinin incelenmesi(Bursa Teknik Üniversitesi, 2022) Tuna, Sibel; Akkoyun, MeralBüyük çoğunluğu fosil yakıtlardan üretilen polimerler, kullanım ömürlerini tamamladıktan sonra bozunmaya uğramadıkları çevre ortamlarında atık haline gelmekte, her yeni hammadde üretim sürecinde gerek çevreye verilen zarar, gerekse sınırlı fosil yakıt kaynaklarının tüketimi bakımından benzer süreçler tekrarlanmaktadır. Ortaya çıkan bu kısır döngü son yıllarda yenilenebilir kaynaklardan elde edilen çevreci, biyo esaslı ve biyobozunur polimerlere ağırlık verilmesine neden olmuştur. Biyopolimerler, biyouyumlulukları ve biyobozunurlukları sebebiyle başlangıçta sadece biyomedikal uygulamalarda kullanım alanı bulsalar da yapılan çalışmalarla daha iyi anlaşılmaya başlanan fiziksel ve mekanik davranışları sebebiyle otomotiv uygulamalarında da petrol esaslı polimerlere alternatif olarak değerlendirilmeye başlanmıştır. Polilaktik asit (PLA), son yıllarda pek çok uygulama alanında kullanılabilirliği incelenen yüksek çekme dayanımı ve sertliği, kolay işlenebilirliği ile geleneksel petrol esaslı polimerler ile kıyaslanabilir özelliklere sahip olan alifatik bir polyesterdir. PLA kendisine avantaj sağlayan özelliklerinin yanı sıra yüksek maliyet, düşük tokluk, düşük ısıl direnç ve düşük kristalizasyon hızı gibi sınırlayıcı bir takım özelliklere de sahiptir. Ancak yapılan çalışmalarda bu sınırlamaların farklı polimerlerin, dolgu ve katkı sistemlerinin kullanılabildiği kompozit karışımların hazırlanmasıyla giderilebildiği görülmüştür. Literatür çalışmaları incelendiğinde özellikle otomotiv sektörü için önemli olan hafiflik ve karbon dioksit (CO2) emisyonu sınırlamaları sonucunda çalışmalarına ağırlık verilen köpük malzeme üretimlerinin biyopolimerler için de araştırılan ve üzerinde çalışılan bir alan olduğu, bu konuda hem fiziksel hem kimyasal köpürtme ajanları ile gerçekleştirilen çalışmalara son yıllarda ağırlık verildiği görülmektedir. Bu tez çalışmasında, otomotiv sektöründe kullanılabilecek hafif, çevreci, yüksek performanslı PLA esaslı polimerik kompozit köpüklerinin çift vidalı ekstrüder ve sıkıştırmalı kalıplama yöntemleri kullanılarak geliştirilmesi hedeflenmiştir. Bu amaçla, PLA ile birlikte poliamid 6 (PA6) ve polipropilen (PP) polimerleri kullanılarak, ilk aşamada polimer oranlarının belirlenmesi amacıyla 20:80, 30:70, 40:60 ve 70:30 oranlarında polimerik kompozit yapılar hazırlanmıştır. Sıkıştırmalı kalıplama yöntemi kullanılarak hazırlanan bu kompozit yapıların fiziksel, termal, mekanik ve morfolojik özellikleri ve bu özelliklerdeki değişimler incelenip en uygun polimer oranlarına karar verilmiştir. PLA/PP ve PLA/PA6 karışımları için en uygun polimer oranının 30:70 olduğu belirlenmiş, bu aşamadan sonraki çalışmalara bu oranlar ile hazırlanan karışımların kullanılarak devam edilmesi kararlaştırılmıştır. Ancak kimyasal köpürtücü ajan ve uyumlaştırıcı ajanın etkilerinin daha iyi anlaşılabilmesi için 30:70 oranı ile birlikte 70:30 oranı ile de çalışılmasına karar verilmiştir. Bu çalışmanın ikinci aşamasında, kimyasal köpürtücü ajan oranının belirlenmesi amacıyla ağırlıkça %1, %1,5 ve %2 oranlarında kimyasal köpürtücü ajan kullanılarak çift vidalı ekstrüder ve sıkıştırmalı kalıplama yöntemleri ile polimerik köpük yapılar hazırlanmıştır ve elde edilen numunelerin fiziksel, termal, mekanik ve morfolojik özellikleri ve kimyasal köpürtücü ajan oranına bağlı olarak bu özelliklerdeki değişimler değerlendirilmiştir. En uygun kimyasal köpürtücü ajan oranı PLA/PP ve PLA/PA6 karışımları için %1,5 olarak bulunmuştur. Son aşamada ise, köpürtülmüş ikili polimer sistemlerinde uyumsuzluğu gidermek amacıyla polimer oranları ve kimyasal köpürtücü ajan oranları belirlenen yapılar için son olarak en uygun uyumlaştırıcı ajan oranının belirlenmesi için çalışmalar gerçekleştirilmiştir. Uyumlaştırıcı ajan kullanımının fiziksel, termal, mekanik ve morfolojik özellikler üzerindeki etkilerinin değerlendirilmesi amacıyla ağırlıkça %1, %3 ve %5 oranlarında uyumlaştırıcı ajan içeren PLA/PP ve PLA/PA6 karışımları hazırlanarak analizleri gerçekleştirilmiştir. Köpük yapıdaki PLA/PP karışımları için en uygun uyumlaştırıcı ajan oranı ağırlıkça %1 olarak belirlenirken, bu oran köpük yapıdaki PLA/PA6 karışımları için ağırlıkça %3 olarak belirlenmiştir.
