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

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

Uyumlaştırıcı Kimyasalla Güçlendirilmiş Nanoselüloz-Polipropilen Nanokompozitleri

Nanoselüloza olan talep giderek artmasıyla, bu önemli materyal uyumlaştırma kimyasallarıyla polipropilen matrikslerin güçlendirilmesinde kullanılmaktadır. Polipropilen (PP)-selüloz nanofibril (CNF) ve Fusabond Hibrit kompozitler çift vidalı ekstruder kullanılarak hazırlanmıştır. Ticari uyumlaştırıcı kimyasal PP/CNF kompozitlerinin mekanik özelliklerini iyileştirmek için kullanılmıştır. Buradaki esas zorluk, PP ve CNFs arasında uyumlu bağları oluşturmak ve polimer matriks içerisinde CNFs iyi bir dağılımını elde etmektir. Çeşitli oranlarda uyumlaştırma kimyasalı PP ve CNFs arasında yüzeyler arası bağlanmayı iyileştirmek için incelendi. Kompozitlerin FTIR karekterizasyonu polipropilen ve selüloz nanfibrilin yüzeyler arası yapışmasını belirlemek için gerçekleştirildi. Polipropilen/selüloz nanofibril kompozitlerinin mekanik ve morfolojik özellikleri üzerinde uyumlaştırıcı kimyasalın etkisi sırasıyla çekme testi, dinamik mekanik analiz ve SEM resimleriyle çalışıldı. En Kompozitlerin en iyi mekanik özellikleri, saf polipropilen (14.45 MPa, 0.570 GPa) ile karşılaştırıldığında 19.99 MPa (çekme direnci) ve yaklaşık %87 iyileşme gösteren 1.067 GPa (Young’s modülü) idi. Kırılma morfoloji incelemesi PP matriks içerisinde uyumlaştırıcı kimyasal ilavesi (0.1 wt%) durumunda CNFs’nin iyi dağılımı sağlandı. TGA sonuçları PP/CNF kompozitlerinin termal kararlılığını değiştirmediğini gösterdi, buna karşın muamelesiz PP/CNF Kompozitleriyle karşılaştırıldığında muamele edilmiş kompozitlerde hafif artış kaydedildi

Characterization of perlite powders from Izmir, Türkiye region

Perlite is an amorphous volcanic glass-type rock which is collected in open mines in various parts of the world. In this study, eight different perlite samples, supplied from the mines located in the Bergama, Izmir region, were used. The perlite samples were structurally, morphologically, and mineralogically characterized via a wide range of analytical techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) Surface Area Analysis, Optical Microscopy, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and a liquid pycnometer. Platelet shaped-like structures were observed in the SEM analysis of the expanded perlites in contrast to the images of spongy or cracked expanded perlites reported in literature. The O-H bending and Si-O-Si vibrations (both asymmetric and symmetric stretching) of perlite structures were confirmed by FTIR. Highly amorphous phases with a rather low percentage of crystalline phases were observed by XRD. In the BET surface area analysis, expanded perlite materials exhibited higher surface area compared to unexpanded ones. A detailed characterization of perlite structures is essential as there is a significant potential to use these minerals in various biocomposite applications and it is useful to explain structure-property relationships in this class of materials

Solvent impact on esterification and film formation ability of nanofibrillated cellulose

In this study we have manufactured nanofibrillar cellulose and modified the fibre surface with ester groups in order to hydrophobise the surface. Nanofibrillated cellulose was chosen to demonstrate the phenomena, since due to its high surface area the effects at issue are pronounced. The prepared NFC ester derivatives were butyrate, hexanoate, benzoate, naphtoate, diphenyl acetate, stearate and palmitate. X-ray photoelectron spectroscopy, solid state NMR and contact angle measurements were used to demonstrate the chemical changes taking place on the cellulose surface. NFC ester derivatives can be prepared after a careful solvent exchange to a water-free solvent medium has been carried out. Butyl and palmitoyl esters were chosen for film forming tests due to the difference in their carbon chain lengths, and their contact angles and water vapour and oxygen permeation rates were studied. The prepared nanocellulose esters show increased hydrophobicity even at very low levels of substitution and readily form films when the films are prepared from acetone dispersions. The permeation rates suggest a potential use as barrier materials