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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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    Synthesis, electrochemical, and antibacterial activity of some novel N(4)O(2) ligand derivativies
    (MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008) Demir, Ibrahim; Sahmetlioglu, Ertugrul; Celik, Gokcen Y.; Unal, Murat
    A novel ligand has been synthesized by the condensation of 1,3-diaminoprophane (HL) with isonitroso-p-chloroacetophenone. The complexes of cobalt(II), nicel(II), cupper(II) and zinc(II) with HL were prepared. All compounds were characterized by spectroscopic techniques and its antibacterial activities were determined by the disc diffusion method used against to those gram-positive and-negative bacteria. All compounds were investigated by cyclic voltammetry at 25 degrees C. The voltammograms were recorded with a potential scan of 100 mV s(-1).
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    Thermal buffering effect of a packaging design with microencapsulated phase change material
    (Wiley, 2019) Unal, Murat; Konuklu, Yeliz; Paksoy, Halime
    Temperature fluctuations during storage and transportation are the most important factors affecting quality and shelf life of food products. Phase change materials (PCM) with their isothermal characteristics are used to control temperature in various thermal operations. In this study, octanoic acid as PCM candidate was used in a packaging material design for thermal control of a food product. The PCM candidate was microencapsulated in different shell materials in our laboratory. Among the synthesized microcapsules, microencapsulated PCM (mPCM) (Delta Hm = 42.9 J/g) with styrene polymer as the shell material was selected based on its properties of being cost effective and compatibility with human health. Thermal buffering effect of PCM in bulk and microencapsulated forms was tested in a packaging design with special PCM pockets. Results showed that packages with mPCM and bulk PCM provided 8.8 and 6 hours of thermal buffering effect for 160 g of chocolate compared with the package without PCM (reference package).