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    Microencapsulation of a fatty acid with Poly (melamine-urea-formaldehyde)
    (PERGAMON-ELSEVIER SCIENCE LTD, 2014) Konuklu, Yeliz; Paksoy, Halime O.; Unal, Murat; Konuklu, Suleyman
    The main purpose of this study is to obtain leakage-free, thermally stable decanoic acid microcapsules (microPCMs) for thermal energy storage applications. Decanoic acid (capric acid) is an environmentally friendly fatty acid since it is obtained from vegetable and animal oils. MicroPCMs were prepared with different capsule wall materials via a one-step in situ polymerization technique. The properties of microencapsulated PCMs have been analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA), Fourier transform infrared (FTIR) spectra analysis and particle size analyzer. The microPCMs prepared using Poly(urea-formaldehyde) (PUF) exhibit higher heat capacities and the microPCMs prepared using Poly(melamine-formaldehyde) (PMF) exhibit higher thermal stabilities. In order to obtain microPCMs with better properties such as suitable latent heat and better heat resistance at high temperatures, we microencapsulated decanoic acid with Poly (melamine-urea-formaldehyde) (PMUF). Furthermore, the effects of surfactants on microPCMs with PMUF were investigated by SEM, a particle size analyzer, DSC, and TGA. The results show that the binary surfactant system was a suitable emulsifier for this process. We determined that the melting temperature was close to 33 degrees C, the latent heat storage capacity was about 88 J/g, and the mean particle diameter was 0.28 mu m for microPCMs with PMUF. We recommend decanoic acid microencapsulated with PMUF for thermally stable and leakage-free applications above 95 degrees C. (C) 2014 Elsevier Ltd. All rights reserved.
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    Microencapsulation of caprylic acid with different wall materials as phase change material for thermal energy storage
    (ELSEVIER SCIENCE BV, 2014) Konuklu, Yeliz; Unal, Murat; Paksoy, Halime O.
    In this study, caprylic acid (octanoic acid) suitable for thermal energy storage applications was microencapsulated with different wall materials, including urea-formaldehyde resin, melamine-formaldehyde resin, urea+melamine-formaldehyde resin. Microcapsules were prepared using coacervation method. Hardening process of microencapsulated phase change material (PCM) was done with formaldehyde. The morphology and particle sizes of microencapsulated PCM were analyzed by scanning electron microscopy, (SEM). The latent heat storage capacities of caprylic acid and microencapsulated caprylic acid were determined with differential scanning calorimetry (DSC). The chemical characterization of microcapsules was determined by Fourier transformed infrared (FTIR) spectroscopy. It is concluded that urea-formaldehyde resin was the best capsule wall material for caprylic acid. Based on all results, it can be considered that the microcapsules were synthesized successfully and that, the phase change enthalpies of melting and freezing were about 93.9 J/g and 106.1 J/g, respectively, the particle diameter was 200 nm-1.5 mu m. (C) 2013 Elsevier B.V. All rights reserved.
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    Nanoencapsulation of n-alkanes with poly(styrene-co-ethylacrylate) shells for thermal energy storage
    (ELSEVIER SCI LTD, 2015) Konuklu, Yeliz; Paksoy, Halime O.; Unal, Murat
    In this work, we synthesized a series of four nanocapsules containing n-alkanes (CnH2n+2), namely tetradecane, pentadecane, hexadecane, and heptadecane, in poly(styrene-co-ethylacrylate) using an emulsion copolymerization method. The nanocapsules were characterized according to their geometric profiles, phase transition temperatures, phase transition heats, mean particle sizes, and chemical stabilities by means of scanning electron microscopy, differential scanning calorimetry, thermal gravimetric analysis and Fourier transform infrared spectroscopy. Furthermore, we also focused on the effect of the core/shell mass ratio on the phase change properties of the nanocapsules. We found that microcapsules were synthesized successfully and that the best core/shell mass ratio was 3:1 for this study. These results indicate that encapsulated n-alkanes with poly(styrene-co-ethylacrylate) have an excellent potential for energy storage. (C) 2014 Elsevier Ltd. All rights reserved.
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    Polystyrene-based caprylic acid microencapsulation for thermal energy storage
    (Elsevier Science Bv, 2017) Konuklu, Yeliz; Paksoy, Halime O.
    In this study, caprylic (octanoic) acid microcapsules were synthesized with polystyrene shell material using the emulsion polymerization method. The influence of the type and concentration of the cross linking agent on the phase-change properties of the microcapsules was examined. The structure and properties of the microcapsules have been characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). A second main contribution of this work is to investigate whether we could synthesize microcapsules with the same thermal properties during serial production. The effects of serial production on microencapsulated caprylic acid (microPCMs) have been investigated by thermal methods. The results show that reproducibility is an important parameter in the microencapsulation process. It was determined that when the synthesis amount is increased, we obtained lower efficiency in the microencapsulation of caprylic acid. (C) 2016 Elsevier B.V. All rights reserved.
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    Review on using microencapsulated phase change materials (PCM) in building applications
    (ELSEVIER SCIENCE SA, 2015) Konuklu, Yeliz; Ostry, Milan; Paksoy, Halime O.; Charvat, Pavel
    Energy demand for heating and cooling of buildings can be minimized through usage of thermal energy storage (TES) systems in building materials. TES in microencapsulated phase change materials provides a new solution to thermally regulated energy efficient buildings. This study summarizes the investigations and analysis of microencapsulated PCMs for building applications. Microencapsulated phase change materials (MPCMs) can be incorporated with many materials that are commonly used in building construction. This paper provides overview of various encapsulation techniques, test methods for MPCMs as well as applications of MPCMs in buildings. There are several micro-encapsulation methods by which the microcapsules of a wide range of sizes between 0.05 mu m and 5000 mu m can be produced. The MPCM incorporated with concrete, mortar, plaster and other materials have a significant potential to increase the thermal capacity of the mixture. Several authors reported testing of building materials with MPCM. Though the increase of thermal capacity with addition of MPCM is significant the decrease of mechanical properties, such as compressive strength, is relatively small. (C) 2015 Elsevier B.V. All rights reserved.
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    Synthesis and properties of microencapsulated phase change materials for thermal energy storage materials
    (Bulgarian Acad Science, 2016) Konuklu, Yeliz; Paksoy, Halime O.
    This work presents and discusses the microencapsulation of pentadecane in polystyrene shell as thermal energy storage materials. The emulsion polymerisation method was used for the microencapsulation process. Styrene (S) was used as monomer to obtain polystyrene (PS) and ethylene glycol dimethacrylate was used as crosslinking agents. The influence of the core: shell mass ratio on the encapsulation process and the physical properties of the resulting microcapsules have been studied. The surface morphologies of the microencapsulated phase change materials (microPCMs) were studied by scanning electron microscopy (SEM) and the thermal properties of the MicroPCMs were investigated by differential scanning calorimetry (DSC). SEM photographs showed that these microPCMs have relatively spherical profiles with diameter ranging from 10 to 80 mu m. It was determined that, the phase change enthalpies of melting and freezing were about 83.2 J/g and 81.8 J/g, respectively. The results show that pentadecane was microencapsulated successfully and its properties very suitable for thermal energy storage applications
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    The Preparation and Characterization of Chitosan-Gelatin Microcapsules and Microcomposites with Fatty Acids as Thermal Energy Storage Materials
    (WILEY-V C H VERLAG GMBH, 2015) Konuklu, Yeliz; Paksoy, Halime O.
    After cellulose, chitosan is the second-most-abundant natural resource and can be used as shell material during microencapsulation. In this study, chitosan-gelatin (CG) microcapsules and microcomposites containing either caprylic or decanoic acid were prepared according to the complex coacervation method and cross-linked by glutaraldehyde. To study the influence of the glutaraldehyde mass ratio upon encapsulation, as well as both the physical and thermal properties of the resulting microcapsules, the properties of microencapsulated phase-change materials (microPCMs) were analyzed by using scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show the successful synthesis of microPCMs and melting temperatures of approximately 11.5 and 24.2 degrees C with latent heat storage capacities of 79 and 73Jg(-1) for microPCMs containing caprylic acid and those containing decanoic acid, respectively.