Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Mermer anıt yüzeylerinin polimer nanokompozit flimler ile korunması(2010) Tıhmınlıoğlu, Funda; Böke, Hasan; Sofuoğlu, Aysun; Ocak, Yılmaz; Oğuzlu, Hale; Akın, OkanMermer gibi kalsit içeren doğal taşlarla inşa edilmiş tarihi binalar ve anıtlarda artan hava kirliliğinin yarattığı problemler sonucu ortaya çıkan yüzey bozulmaları geçtiğimiz yüzyılda ivme kazanmıştır. Kükürt dioksit gazı mermerin yapısını oluşturan kalsit kristalleri ile reaksiyona girerek alçı taşını (CaSO4.2H2O) oluşturarak yüzeyi erozyona uğratmaktadır. Bu çalışmada hem geri dönüşebilen hem de koruyuculuk özelliği olan biyobozunur polimer nano kompozit kaplama geliştirilerek, koruyuculuk özelliklerinin belirlenmesi amaçlanmıştır. Bu amaçla silika ve kil nano partikülleri içeren biyobozunur polimerle hazırlanmış yüzey koruyucu kaplamalarının koruma potansiyelleri belirlenmiştir. Polilaktid bazlı nanokompozitlerin filmlerin kil dağılımı ve yapı XRD analizlenmiş, polilaktid-10A nanokompozitlerinde %7, polilaktid-93A nanokompozitlerinde ise %5 kil derişimine kadar eksfoliye ve interkale yapılar elde edilmiştir. Bununla birlikte nanoparçacıkların polimer matriksindeki dağılımına paralel olarak biyo-nanokompozitlerin geçirgenlik değerlerinde düşüş gözlenmiştir. Biyo-nanokompozitlerin bariyer özelliklerindeki değişim göz önüne alınarak mermer yüzey kaplamalarındaki nanoparçacık derişim aralıklarına karar verilmiştir.Article Citation - WoS: 34Citation - Scopus: 36Effects of Organo-Modified Clay Addition and Temperature on the Water Vapor Barrier Properties of Polyhydroxy Butyrate Homo and Copolymer Nanocomposite Films for Packaging Applications(Springer Verlag, 2018) Akın, Okan; Tıhmınlıoğlu, FundaPolymer nanocomposites, based on bacterial biodegradable thermoplastic polyester, poly(hydroxy-butyrate) (PHB), poly(hydroxyl-butyrate-co-hydroxy-valerate) (PHBHV), and commercial organo-modified montmorillonite (OMMT-Cloisite 10A) were prepared by solution casting method. This work aims to investigate the effect of Cloisite 10A type clay addition on the water vapour permeability properties of PHB/OMMT, and PHBHV/OMMT nanobiocomposite films. Temperature dependence of water vapor permeabilities of the films were also evaluated at various temperatures, and semi empirical permeability models were used to predict the permeability of polymer systems as a function of clay concentration and aspect ratio of nanoplates. Moreover, thermal, optical, and mechanical properties of the composites were examined by using varieties of techniques including differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and thin-film X-ray diffractometer (TF-XRD) respectively. Test results indicated that addition of highly intergallery swollen Cloisite 10A to the PHB/PHBHV, reduced the water vapor permeability up to 41 and 25% compared to native PHB and PHBHV films, respectively. Regarding the all mechanical properties measured, the maximum improvement was achieved for 3 wt% clay loaded samples for both PHB and PHBHV polymer composites. An increase of about 152 and 73% in tensile strength and of 77 and 18% in strain at break was achieved for PHB and PHBHV polymers, respectively. As a result of X-ray diffraction analysis, exfoliated structure was achieved at low clay loaded sample (1% w/w), however at higher concentration (3% w/w) the structure found as intercalated. Therefore, it is an evident that enhancement of characteristic properties highly depend on the dispersion level of clay particles in polymer matrix. The results obtained in this study show the feasibility of improvement of the properties of PHB based polymers with incorporation of nanoclay.Article Citation - WoS: 9Citation - Scopus: 10Novel Hybrid Process for the Conversion of Microcrystalline Cellulose To Value-Added Chemicals: Part 2: Effect of Constant Voltage on Product Selectivity(Springer Verlag, 2017) Akın, Okan; Yüksel, AslıIn this study, electrochemical degradation of microcrystalline cellulose (MCC) under hot-compressed water was investigated via application of constant voltage on reaction medium. Constant voltage ranges from 2.5 to 8.0 V was applied between anode (Titanium) and cathode (reactor wall). As an electrolyte and proton source 5–25 mM of H2SO4 was used. Reactions were carried out in a specially designed batch reactor (450 mL) made of T316 for 240 min at temperature of 200 °C.MCC decomposition products such as glucose, fructose, furfural, 5-HMF and levulinic acid were detected and quantified by High Performance Liquid Chromatography (HPLC). In the absence of electrolyte, applied voltage (2.5 and 4.0 V) decreased the total organic carbon (TOC) yield, in contrast at 8.0 V, TOC yield increased to 13%. Application of 8.0 V in hydrothermal conditions alter MCC decomposition pathway selectively to furfural (15%). Addition of electrolyte (5 mM, H2SO4) and application of 2.5 V potential increased TOC (54%) and changed the decomposition pathway in favor of 5-HMF (30%) and levulinic acid (21%). The structural changes in solid residues of electrochemically reacted MCC was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and found that MCC particles functionalized by carboxylic acid and sulfonated groups by the application of constant voltage to reaction medium. In the presence of electrolyte, under certain voltage (2.5 V), functionalization of solid particles became more obvious in FTIR spectrum results. Therefore, change in the selectivity values of degradation products were conducted with the functionalization of MCC particles due to applied voltage under sub-critical conditions.Article Citation - WoS: 11Citation - Scopus: 12Novel Hybrid Process for the Conversion of Microcrystalline Cellulose To Value-Added Chemicals: Part 1: Process Optimization(Springer Verlag, 2016) Akın, Okan; Yüksel, AslıIn this paper, a novel hybrid process for the treatment of microcrystalline cellulose (MCC) under hot-compressed water was investigated by applying constant direct current on the reaction medium. Constant current range from 1A to 2A was applied through a cylindrical anode made of titanium to the reactor wall. Reactions were conducted using a specially designed batch reactor (450 mL) made of SUS 316 stainless steel for 30–120 min of reaction time at temperature range of 170–230 °C. As a proton donor H2SO4 was used at concentrations of 1–50 mM. Main hydrolysis products of MCC degradation in HCW were detected as glucose, fructose, levulinic acid, 5-HMF, and furfural. For the quantification of these products, High Performance Liquid Chromatography (HPLC) and Gas Chromatography with Mass Spectroscopy (GC–MS) were used. A ½ fractional factorial design with 2-level of four factors; reaction time, temperature, H2SO4 concentration and applied current with 3 center points were built and responses were statistically analyzed. Response surface methodology was used for process optimization and it was found that introduction of 1A current at 200 °C to the reaction medium increased Total Organic Carbon (TOC) and cellulose conversions to 62 and 81 %, respectively. Moreover, application of current diminished the necessary reaction temperature and time to obtain high TOC and cellulose conversion values and hence decreased the energy required for cellulose hydrolysis to value added chemicals. Applied current had diverse effect on levulinic acid concentration (29.9 %) in the liquid product (230 °C, 120 min., 2 A, 50 mM H2SO4). © 2016, Springer Science+Business Media Dordrecht.