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ÇAKMAKÇI, EMRAH

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2012 - 201932020 - 20211
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Author: KAHRAMAN, MEMET VEZİR × Subject: COMPOSITES ×

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Now showing 1 - 4 of 4
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    Preparation and drug release properties of lignin-starch biodegradable films
    (WILEY-V C H VERLAG GMBH, 2012) OGAN, AYŞE; Calgeris, Ilker; Cakmakci, Emrah; Ogan, Ayse; Kahraman, M. Vezir; Kayaman-Apohan, Nilhan
    Starch is one of the most commonly available natural polymers which are obtained from agro-sources. It is renewable and abundant in nature. Unfortunately due to its poor mechanical properties and hygroscopic nature, there are some strong limitations to the development of starch-based products. Usually blends of starch are prepared and plasticized with glycerol to improve some of its properties. In this study, lignin was extracted from hazelnut shells and investigated as a potential additive for starch biofilms. The structural characterization of hazelnut lignin was performed by employing UV spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Lignin was blended with corn starch in different ratios to obtain biofilms. Mechanical and thermal properties of the biofilms were enhanced as the lignin amount was increased in the formulations. Water absorption tests were performed at pH 2.0, 4.0, and 6.0. The percent swelling values of the starch/lignin films increased as pH increased. Also, the biofilm exhibiting the best properties was chosen for the drug release studies. Biofilms showed a fast ciprofloxacin (CPF) release within an hour and then the drug release rate decreased. A pH dependent drug release mechanism was also observed according to KoshnerPeppas model. The drug release increased with a decrease in pH.
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    Preparation and Characterization of Thermally Conductive Thermoplastic Polyurethane/h-BN Nanocomposites
    (WILEY, 2014) ÇAKMAKÇI, EMRAH; Cakmakci, Emrah; Kocyigit, Ciler; Cakir, Selma; Durmus, Ali; Kahraman, M. Vezir
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    Thermally Stable Phosphonium Organoclay-Reinforced Polyimide Nanocomposites
    (TAYLOR & FRANCIS INC, 2017) ÇAKMAKÇI, EMRAH; Birtane, Hatice; Beyler-Cigil, Asli; Cakmakci, Emrah; Kahraman, Memet Vezir
    To prepare clay containing high-temperature processable polymer nanocomposites, new cation exchangeable agents with high thermal stability are required. In this work, we investigated the effect of a thermally stable phosphonium-modified organoclay on the properties of polyimides prepared from the reaction of 4,4-oxydianiline with 3,3,4,4-benzophenonetetracarboxylic dianhydride. The organoclay was prepared from the reaction of pristine clay with octyltriphenylphosphonium bromide. Phosphonium-modified clay displayed a negligible weight loss (<5%) below 300 degrees C. The thermal stability of the composites enhanced with the increasing amount of phosphonium-modified clay.
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    Autocatalytic reactive flame retardants for rigid polyurethane foams
    (ELSEVIER SCIENCE SA, 2021) ÇAKMAKÇI, EMRAH; Hamidov, Muradulla; Cakmakci, Emrah; Kahraman, Memet Vezir
    While technological progress is rapidly accelerating day by day, the demand for cutting-edge materials is also ever-growing. In terms of material chemistry, ingenious polymers and additives with superior properties are desired. To meet this need, in this study, we would like to present an innovative concept; autocatalytic reactive flame retardants (ACRFRs) for polyurethanes. In this work, we synthesized two different phosphorous and nitrogen containing flame retardants. They were characterized by FTIR and NMR techniques and were added into PUF formulations at different ratios (2.5, 5 and 10%). Their effects on the thermal, mechanical, flame retardancy and physical properties of the foams were investigated along with their catalytic performance. The synthesized ACRFRs displayed good catalytic activity, moderate flame retardancy (depending on the type and the concentration of the ACRFR). We believe more ACRFRs will be synthesized in future and find a place in industrial applications.