A Novel Partially Biobased PAN-Lignin Blend as a Potential Carbon Fiber Precursor

Blends of polyacrylonitrile (PAN) and lignin were prepared with three different lignin types by solution blending and solution casting. Among three types of lignin, one type was chosen and different blend concentrations were prepared and casted. The casted blend films were characterized chemically with fourier transform infrared spectroscopy (FTIR), and thermally with thermogravimetric analysis (TGA). The mechanical properties of the blends were measured using dynamic mechanical analysis (DMA). FTIR analysis shows an excellent interaction of PAN and lignin. The interaction of the lignins and PAN was confirmed by TGA analysis. The DMA results reveal that the lignin enhance the mechanical properties of PAN at room temperature and elevated temperatures. The blend structure and morphology were observed using scanning electron microscopy (SEM). SEM images show that excellent polymer blends were prepared. The results show that it is possible to develop a new precursor material with a blend of lignin and PAN. These studies show that the side product of paper and cellulosic bioethanol industries, namely, lignin can be used for new application areas

Yüzeyi Fonksiyonelize Edilmiş Nanoparçacıklar ile Kararlı Nanoakışkan Hazırlanması ve Isıl İletkenlik Değişiminin Belirlenmesi

TÜBİTAK MAG Proje01.04.2019Çok çesitli uygulama alanına sahip olan nanoakıskanlar, ısı transferi sistemlerinde, kullanılanakıskanların ısıl iletkenlik katsayısını arttırmak amacıyla baz akıskanın içerisine, ısıl iletkenligiyüksek nano boyutlarda parçacıklar katılmasıyla üretilirler. Nanoakıskanların hazırlanması,hazırlanan nanoakıskanın ısıl iletkenliginin arttırılması her ne kadar basit görünse de çokkarmasık bir sistemdir. Nanoakıskanların ısıl iletkenliginin artması ve ısı transferiuygulamalarında kullanılabilirligi, hazırlanan nanoakıskanın kararlılıgından, viskozitesinekadar birçok önemli parametre ile baglantılıdır. Isıl iletim katsayısı ne kadar artmıs olursaolsun, kararlı olmayan nanoakıskanların kısa sürede çökmesi ve viskozitesinin baz akıskanagöre fazlaca artıs göstermesi, ısı transferi sistemlerinde basınç düsüsüne, korozyona vetıkanıklıklara neden olmaktadır. Tüm bunlar göz önüne alındıgında, hazırlanannanoakıskanların pratikte kullanımı için bu parametrelerin incelenmesi ve birbiri ile olanbaglantılarının ortaya konulması gerekmektedir. Bu projede kararlı nanoakıskanlarınhazırlanması ve ısıl iletkenliklerinin belirlenmesinin yanı sıra bu parametrelerin birbiri ilebaglantısının aydınlatılması hedeflenmistir.Baz akıskan olarak su, etilen glikol (EG) ve kompresör yagı kullanılan bu projede,nanoparçacık olarak farklı yüzey alanlarına sahip grafen nanoplateletler (GNP) ve tek duvarlıkarbon nanotüpler (SWCNT) kullanılmıstır. Nanoakıskan kararlılıgının saglanması amacıyla,polietilen glikol türevi polihedral oligomerik silseskuokzan (PEG-POSS) nanoakıskanlarda ilkkez yüzey aktif madde olarak bu projede kullanılmıstır. Ayrıca hazırlanan akıskanlarınkararlılıgının artması için pH ayarlaması yapılmıstır. SWCNT içeren su bazlı nanoakıskanlarınhazırlanmasında 50 dk ve 100 dk olmak üzere iki farklı ultrasonikasyon süresi kullanılarak ısıliletkenlige etkisi incelenmistir. Kararlılık degerlendirmesi için UV-Vis Spektrofotometrisi veZeta Potansiyeli ölçümleri yapılmıstır. Bu projede örneklerin santrifüj edilmesi gibi farklıislemler sayesinde nanoparçacık konsantrasyonunun zeta potansiyeline etkisi basarıylaincelenmistir. Isıl iletkenlik ölçümleri 3-omega yöntemiyle gerçeklestirilmistir. Ayrıca farklıyüzey alanlarına sahip nanoparçacıkların kullanılması, farklı konsantrasyonlarda yüzey aktifmadde kullanımı ve farklı baz akıskanlarla çalısılması; bu örneklerin reolojik davranısı, ısıliletkenlik ve yüzey gerilimi ile temas açısı gibi ısı transferi sistemlerinde önem tasıyanözelliklerinin belirlenmesi ve bu özellikleri etkileyen parametrelerin incelenmesi, bu projeyi çokyönlü ve basarılı bir çalısma haline getirmistir.Nanofluids, which have a wide range of applications, are produced by the addition of nanosizedparticles having high thermal conductivity to the base fluid to increase the thermalconductivity of the fluids used in heat transfer systems. Preparing the nanofluids andincreasing the thermal conductivity of the nanofluid are very complex process. The increase ofthermal conductivity of nanofluids and its usage in heat transfer applications are related withmany important parameters from the stability of the nanofluids to their viscosity. No matter howmuch the thermal conductivity is increased, the rapid sedimentation of unstable nanofluids andthe increase in viscosity of nanofluids over that of the base fluid lead to pressure drop,corrosion, and clogging in heat transfer systems. Considering all these, it is necessary toexamine these parameters and to make connections with each other for the practical use ofprepared nanofluids. In this project, it is aimed to prepare stable nanofluids and determine theirthermal conductivity and to clarify the connection of these parameters.Distilled water, ethylene glycol (EG), and compressor oil were used as base fluid. Graphenenanoplatelets (GNP) with different surface areas and single walled carbon nanotubes(SWCNT) were used as nanoparticles. Polyethylene glycol-derived polyhedral oligomericsilsesquioxane (PEG-POSS) was used for the first time in literature, as a surface active agentin nanofluids in order to ensure their stability. In addition, pH value was adjusted to increasethe stability of the nanofluids. In the preparation of water-based nanofluids containing SWCNT,the effect of two different ultrasonication times, 50 min and 100 min, on thermal conductivitywas investigated. UV-Vis Spectrophotometry and Zeta Potential analyses were performed forstability assessment. In this project, the effect of nanoparticle concentration on zeta potentialhas been studied successfully through different processes such as centrifugation and dilutionof samples. Thermal conductivity measurements were carried out by 3ω method. In additionto the usage of different carbon based nanoparticles, various concentrations of surface activeagent, and 3 different base fluids; studying the other factors (e.g. pH, ultrasonication time etc.)affecting the thermal, rheological, and surface properties of nanofluids in heat transfer systemhas made this project a multi-faceted and successful work.Key Words: GNP, SWCNT, nanofluids, 3ω thermal conductivity, viscosity

Preparation and characterization of polyurethane-hectorite nanocomposites

Bu çalışmada polimerler içerisinde üretim hacmi sürekli artan bir polimer olan poliüretan ve Türkiye’nin yerli kaynaklarından elde edilen doğal hektorit kili kullanılarak poliüretan nanokom-pozitleri hazırlanmıştır. Kimyasal ve mineralojik analizleri yapılan doğal hektorit kili saflaştırma işlemi yapılmadan ve herhangi bir organik yüzey aktif maddeyle modifiye edilmeden kullanılmıştır. Polimer nanokompozitlerin yapıları, X-ışınları kırınımı ve Fourier transform infrared spektroskopisi kullanılarak aydınlatılmıştır. Yapılan deneyler sonucunda hazırlanmış nanokompozitlerin çok başarılı şekilde hazırlandıkları X-ışınları kırınım yöntemiyle tespit edilmiştir. Fourier transform infrared sprektroskopisiyle de poliüretanın killere moleküler seviyede etkileşmesi sonucunda poliüretanın yapısının değiştiği ve kilin polimer yapısına çok iyi şekilde katıldığı tespit edilmiştir. Nanokompozitlerin ara yüzeyinin morfolojik özellikleri taramalı elektron mikroskobuyla incelenmiştir. Polimer nanokompozitindeki killerin tamamen delamine olmuş yapılarını gözlemlemek için geçirimli elektron mikroskobu kullanılmıştır. Yapılan çalışma sırasında geçirimli elektron mikroskobunda inceleme yapabilmek için çok yeni bir numune hazırlama yöntemi geliştirilmiştir. Nanokompozitlerin ısıl özellikleri ısıl ağırlık analizi ile karakterize edilmiştir. Hazırlanmış olan nanokompozitlerin viskoelastik özelliklerini ve mekanik özelliklerdeki sıcaklığa bağlı değişimini gözlemlemek için dinamik mekanik analiz çalışmaları yapılmıştır. Polimerin hidrofilik özelliğinin belirlenmesi için su temas açısı test yöntemi kullanılmıştır. Nanokompozitlerin çekme-uzama mukavemetlerini belirlemek için mekanik testler yapılmıştır. Yapılan çalışmalar sonucunda çok iyi delamine olmuş nanokompozit yapılar elde edilmiştir ve bunun da neticesinde poliüretanın mekanik özellikleri iyileştirilmiş ve ısıl kararlığı arttırılmıştır. Anahtar Kelimeler: Poliüretan, nanokompozit, kil, hektorit, mekanik özellikler, ısıl kararlılık. Polyurethanes are unique polymeric materials in terms of various applications such as biomedical, coatings, adhesives, thermoplastic elastomers and composite. Polyurethanes have a copolymer structure synthesized with the isocyanates and polyols forming the hard domains and soft domains as a consequence of the isocyanates and polyol part, respectively. The properties of the polyurethanes can be adjusted by two main routes. The first method is the chemical route changing the isocyanate/polyol ratio and using different amounts of chain extender. The second method is the materials route altering the properties of the polyurethanes with different fillers. The versatile types of these two main reactants (isocyanates and polyols), different ways to synthesize the polymer and finally the processing of the polymer change the  structure  and the properties of the polymer. The properties of the polyurethanes can be improved by using reinforcing material such as talc, mica and glass fiber in the form of polymer matrix composite material. The polymer composites prepared with glass fibers have been used since 1950s. They have been applied in the industrial scale as well. These materials increase the tensile strength and improve the mechanical properties but they sacrifice the elongation at break. Currently new composite materials are based on the reinforcing agents at the nano-scale enabling the increase in strength without loss in the elasticity of the material and even getting more tough materials. There are two other advantages of nanocomposites. The one is the increase of thermal properties and the other one is better optical properties. Within this context clays form important family of nano fillers. The clays used in the preparation of polymer nanocomposites are generally from the smectite family with well ordered crystalline structure. Clay mineral is abundant in nature. It is a very cheap raw material for preparation of industrial product, if it is used without any modification and purification. The clays can be found in the polymer matrix in three forms such as intercalated, flocculated or exfoliated structure. The best structure is the exfoliated structure due to the best dispersion of clay can be obtained in the polymer matrix and level of utilization for the reinforcement is  maximum. In this work, we have improved the properties of the polyurethanes with the materials route using the clays as the nano-scale reinforcing agent. In previous studies, the montmorillonite clay has always been examined to reinforce the polyurethane polymer. No work has been reported using the clay hectorite. In this work, we have investigated the effect of the hectorite content on the properties of the polyurethane. In some polymers such as polyethylene and starch, it has been observed that hectorite improves the mechanical properties of the matrix polymer. These led us to use the hectorite in the polyurethane matrix forming very novel nanocomposites. In this study, very novel polyurethane nanocomposites were prepared with the natural nanoclay hectorite without purification and organical modification. Generally, in the preparation of the polymer-clay nanocomposites, the organically modified clays have been used to create partial delamination before interacting with the polymer. In this study the exfoliated structures could be obtained without organic modification of the clays because of the hydrophilic nature of the polyurethane and swelling capacity of hectorite in the solvent, dimethylformamide. Exfoliated structures were identified using the X-ray diffraction analysis. Moreover the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to support the findings of the X-ray analysis. A novel sample preparation for transmission electron microscopy technique was used. With SEM, the clay particles could not be observed which shows the good dispersion of the clay platelets. With TEM, the individual layers of clay which could not be seen with SEM, were easily investigated with the thickness given in the pictures. Fourier infrared spectroscopy was used to determine the interactions at the molecular level. It was determined that the polyurethane and the clay interacted at the molecular level changing the structure of the polyurethane. Mechanical testing and thermal gravimetric tests were done for further investigations of the material. As a result of this successful nanocomposite preparation, the mechanical properties increased 113 wt % and thermal properties were also improved. Keywords: Polyurethane, nanocomposite, clay, hectorite, mechanical testing, thermal stability. 

The Use of Biodiesel Residues for Heat Insulating Biobased Polyurethane Foams

The commercial and biobased polyurethane foams (PUF) were produced and characterized in this study. Commercial polyether polyol, crude glycerol, methanol-free crude glycerol, and pure glycerol were used as polyols. Crude glycerol is byproduct of the biodiesel production, and it is a kind of biofuel residue. Polyol blends were prepared by mixing the glycerol types and the commercial polyol with different amounts, 10 wt%, 30 wt%, 50 wt%, and 80 wt%. All types of polyol blends were reacted with polymeric diphenyl methane diisocyanates (PMDI) for the production of rigid foams. Thermal properties of polyurethane foams are examined by thermogravimetric analysis (TGA) and thermal conductivity tests. The structures of polyurethane foams were examined by Fourier Transformed Infrared Spectroscopy (FTIR). Changes in morphology of foams were investigated by Scanning Electron Microscopy (SEM). Mechanical properties of polyurethane foams were determined by compression tests. This study identifies the critical aspects of polyurethane foam formation by the use of various polyols and furthermore offers new uses of crude glycerol and methanol-free crude glycerol which are byproducts of biodiesel industry

Preparation and Performance Testing of SBS Modified Bitumens Reinforced with Halloysite and Sepiolite Nanoclays

In this study, halloysite and sepiolite nanoclays were used to reinforce SBS modified bitumens. The nanoclays used are different from the materials in the literature and have properties such as easy to find, economical and available from local sources. The mixing parameters were determined before production process. The polymer additive SBS was added into base bitumen at 3% and 5%, while the nanoclay additives were added into polymer modified bitumen at 2% and 4% ratios. The morphological structures were investigated under fluorescence microscope. Physical and rheological properties of the samples were compared. The phase separation cases were investigated by storage stability test. Furthermore, rutting performance of samples was measured with zero shear viscosity (ZSV) and multi stress creep recovery (MSCR) test methods.&nbsp;</p