Browsing by Author "Pekcan, Önder"
Now showing items 21-40 of 91
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Elastic Properties of a Swollen PAAm-NIPA Copolymer with Various NIPA Contents
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Publisher and Date:(Taylor & Francis, 2014)Copolymer based on cross-linked polyacrylamide (PAAm) having N-isopropylacrylamide (NIPA) was prepared and their elastic properties were studied as a function of NIPA contents. NIPA content dependency of the shear modulus S of the PAAm-NIPA copolymers due to volume phase transition was measured using tensile testing technique at 30 degrees C. It was observed that its shear modulus and toughness were found to be strongly dependent on NIPA content. It is understood that the shear modulus was found ...
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Elasticity Study of PAAm-kappa C Composite Prepared in Various kappa C Content and Measured at Several Temperatures
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Publisher and Date:(Polish Acad Sciences Inst Physics, 2015)Polyacrylamide (PAAm)-kappa carrageenan (kappa C) composite gels were prepared via free radical crosslinking copolymerization with various (w/v) percentages of kappa C in the range between 0.5 and 3 (w/v)% of kappa C . Elasticity properties such as stress strain and compressive elastic modulus S of these composite gels were studied in various kappa C content and at several temperatures. The content and temperature dependence of the compressive elastic modulus S of the swollen PAAm-kappa C composite ...
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Electrical and optical percolations in PMMA/GNP composite films
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Publisher and Date:(Taylor & Francis Ltd, 2018)Effects of graphene nanoplatelet (GNP) addition on the electrical conductivity and optical absorbance of poly(methyl methacrylate)/graphene nanoplatelet (PMMA/GNP) composite films were studied. Optical absorbance and two point probe resistivity techniques were used to determine the variations of the optical and electrical properties of the composites respectively. Absorbance intensity A and surface resistivity R-s of the composite films were monitored as a function of GNP mass fraction (M) at room ...
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Electrical and optical percolations of polystyrene latex-multiwalled carbon nanotube composites
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Publisher and Date:(Academic Press Inc Elsevier Science, 2010)Electrical conductivity and optical transmittance properties of polystyrene (PS)-multiwalled carbon nanotube (MWCNT) composite films were investigated. Composite films were prepared by mixing of various mass fractions of MWCNT in PS-water dispersions. After water evaporates powder composite films were annealed at 175 degrees C above the glass transition of PS for 20 min. Photon transmission and two point probe resistivity techniques were employed to determine the variations of the optical and the ...
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Electrical optical and fluorescence percolations in P(VAc-co-BuA)/MWCNT composite films
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Publisher and Date:(Taylor & Francis Ltd, 2013)Effects of multiwall carbon nanotube (MWCNT) addition on the electrical conductivities optical transparencies and fluorescence emissions of poly(vinyl acetate-co-butyl acrylate) (P(VAc-co-BuA))/MWCNT composite films were studied. Optical transmission fluorescence emission and two point probe resistivity techniques were used to determine the variations of the optical fluorescence and electrical properties of the composites respectively. Transmitted photon intensity (I-tr) fluorescence emission ...
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Energy needs for drying of PAAm- kappa C composites prepared with various kappa C contents
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Publisher and Date:(European Polymer Federation, 2011)Various polyacrylamide (PAAm) - Kappa Carrageenan (kappa C) composite gels were prepared from acrylamide (AAm) N N'- methylenebisacrylamide (BIS) and different kappa C contents by free radical crosslinking copolymerization in water. Pyranine (P) was introduced as a fluorescence probe and scattered light I-sc and fluorescence intensities I from these gels were monitored during drying at different temperature. The fluorescence intensity of pyranine increased as drying time is increased for all ...
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Epidemic models for phase transitions: application to a physical gel
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Publisher and Date:(Taylor & Francis Ltd, 2017)Carrageenan gels are characterized by reversible sol-gel and gel-sol transitions under cooling and heating processes and these transitions are approximated by generalized logistic growth curves. We express the transitions of carrageenan-water system as a representative of reversible physical gels in terms of a modified Susceptible-Infected-Susceptible epidemic model as opposed to the Susceptible-Infected-Removed model used to represent the (irreversible) chemical gel formation in the previous work. ...
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Film Formation of Nano-Sized Hard Latex (PS) in Soft Polymer Matrix (PBA): An Excimer Study
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Publisher and Date:(John Wiley & Sons Inc, 2010)This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)labeled nano-sized polystyrene (PS) and poly(n-butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (T(g)) of polystyerene. Monomer (I(P)) and excimer (I(E)) ...
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Fluorescence quenching method for monitoring oxygen diffusion into PS/CNT composite films
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Publisher and Date:(Elsevier Science SA, 2013)Oxygen permeabilities of nanocomposite films consisting of multi wall carbon nanotubes (MWNT) and polystyrene (PS) were determined to investigate the oxygen diffusion depending on MWNT and temperature. A method which is based on quenching of an excited phosphorescent by oxygen was applied for the measurements. The composite films were prepared from mixtures of (MWNT) and surfactant-free pyrene (P)-labeled (PS) latexes of various compositions at room temperature. These films were then annealed at ...
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Fluorescence study of effect of particle size in PS latex/Al2O3 nanocomposite films
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Publisher and Date:(MANEY PUBLISHING, 2015)Steady state fluorescence and BioUV-Visible techniques were used to study film formation of polystyrene (PS) latex and Al2O3 composites depending on PS particles size and Al2O3 content. Two film series (SmPS/Al2O3 and LgPS/Al2O3) were prepared covering PS sphere (SmPS: 203 nm
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Fluorescence Study of Film Formation from PS Latex-TiO2 Composites: Effects of TiO2 Content Film Thickness and Particle Size
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Publisher and Date:(Amer Scientific Publishers, 2015)Steady-state fluorescence (SSF) technique in conjunction with UV-visible (UVV) technique atomic force microscope (AFM) and scanning electron microscope (SEM) is used for studying film formation from TiO2 covered polystyrene (PS) latex particles. The effects of TiO2 content film thickness and PS particle size on film formation and structure properties of PS/TiO2 composites are studied. For this purpose in the first part two different sets of PS films with thicknesses of 5 and 20 mu m were prepared ...
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Fluorescence study of film formation from PS/Al2O3 nanocomposites
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Publisher and Date:(Elsevier Science, 2014)Steady state fluorescence (SSF) and UV-vis (UVV) techniques were used to study the film formation behavior of pyrene (P) labeled polystyrene (PS) latex and Al2O3 (PS/Al2O3) composites depending on PS particles size and Al2O3 content. The close-packed arrays of PS spheres (SmPS: 203 nm ; LgPS: 382 nm) templates on clean glass substrates were covered with various layers of Al2O3 by dip-coating method. Two different film series (SmPS/Al2O3 and LgPS/Al2O3) were prepared in various Al2O3 layer content. ...
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Fluorescence study on drying of iota-carrageenan gels at different temperatures prepared with various CaCl2 content
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Publisher and Date:(Springer, 2011)The influence of temperature and salt content on drying was investigated by using steady-state fluorescence (SSF) technique. Supporting gravimetric and volumetric measurements were also carried out during drying of gels at various temperatures. iota-Carrageenan gels were prepared with various CaCl2 content. Pyranine was introduced as a fluorescence probe during gel preparation. Apparent fluorescence intensity I was measured during in situ drying process at each temperature and it was observed that ...
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Fluorescence technique for monitoring swelling of PAAm-kappa-carrageenan gel composites
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Publisher and Date:(Shaker Publishing, 2009)Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) gels with various content of kappa- carrageenan. Disc shaped composite gels were prepared by free-radical cross/inking copolymerization of acrylamide (AAm) with various amounts of kappa-carrageenan (kappa C) using N N'- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) initiator. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of ...
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Fractal dimension and phase transition of graphene oxide (GO) doped polyacrylamide
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Publisher and Date:(ELSEVIER SCI LTD, 2020)Graphene Oxide (GO)- Polyacrylamide composites prepared between 5 and 50 mu l GO were performed by Fluorescence Spectroscopy. The phase transition performed on the composites was measured by calculating the critical exponents, beta and gamma, respectively. In addition, fractal analysis of the composites was calculated by a fluorescence intensity of 427 nm. The geometrical distribution of GO in the composites was calculated based on the power law exponent values using scaling models. While the ...
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Fractal Dimensions of kappa-Carrageenan Gels during Gelation and Swelling
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Publisher and Date:(Taylor & Francis Inc, 2018)A photon scattering technique for research on the sol-gel and gel-sol transitions in kappa-carrageenan-water systems with various carrageenan contents (CC) was utilized for characterizing the fractal dimensions during gelation and swelling. It was observed that the scattered photon intensity I-sc increased at all temperatures with an increase in the CC when I-sc was monitored against temperature. Additionally the sol-gel transition temperatures were found to be much lower than the gel-sol transition ...
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Fractal Features and Structural Morphological Optical Characteristics of Sol-Gel Derived Silica Nanoparticled Thin Films
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Publisher and Date:(Polish Acad Sciences Inst Physics, 2018)Nanostructured silica films using a simple and effective sol-gel spin coating technique were synthesized and the influence of ammonia/sol ratios on the particle size and thickness of this film was investigated. In addition fractal dimensions of the prepared films were determined using the scattering response technique. The samples were characterized by atomic force microscopy and UV-vis spectroscopy. Comparing optical method and image analysis of atomic force microscopy micrographs the fractal ...
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Gelation electrical conductivity and elasticity of PAM- MWNT
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Publisher and Date:(Cambridge Univ Press, 2011)Polyacrylamide- Multiwalled carbonnanotube (PAM- MWNT) composites were prepared via free radical crosslinking copolymerization with different amounts of MWNT varying in the range between 0.1 and 15 wt. %. PAM- MWNT composite gels were characterized by fluorescence dielectric spectroscopy and the tensile testing technique. A small content of doped nanotubes dramatically changed gelation time conductivity and young modulus respectively. The gel fraction exponent ? of PAM- MWNT composite gels were ...
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Gelation of PAAm-PVP composites: A fluorescence study
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Publisher and Date:(World Scientific, 2014)Hybrid hydrogels are a new class of composite materials. Polyacrylamide (PAAm) hydrogels are mainly produced by free radical crosslinking copolymerization (FCC) of AAm in the presence of N N'-methylene bis (acrylamide) (BIS) as the crosslinker. Pyranine doped PAAm-poly (N-vinyl pyrrolidone) (PVP) composite were prepared with different amounts of PVP varying in the range between 0.0015 and 0.1 gr. It was observed that pyranine molecules as a fluoroprobe bind to AAm and PVP chains upon the initiation ...
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Group behaviour in physical chemical and biological systems
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Publisher and Date:(Indıan Acad Scıences, 2014)Groups exhibit properties that either are not perceived to exist or perhaps cannot exist at the individual level. Such 'emergent' properties depend on how individuals interact both among themselves and with their surroundings. The world of everyday objects consists of material entities. These are ultimately groups of elementary particles that organize themselves into atoms and molecules occupy space and so on. It turns out that an explanation of even the most commonplace features of this world ...
