Thermal decomposition behavior of oligo(4‐hydroxyquinoline)

In this study, the kinetic parameters and reaction mechanism of decomposition process of oligo(4‐hydroxyquinoline) synthesized by oxidative polymerization were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA‐derivative thermogravimetric analysis curves showed that the thermal decomposition occurred in two stages. The methods based on multiple heating rates such as Kissinger, Kim–Park, Tang, Flynn–Wall–Ozawa method (FWO), Friedman, and Kissinger–Akahira–Sunose (KAS) were used to calculate the kinetic parameters related to each decomposition stage of oligo(4‐hydroxyquinoline). The activation energies obtained by Kissinger, Kim–Park, Tang, KAS, FWO, and Friedman methods were found to be 153.80, 153.89, 153.06, 152.62, 151.25, and 157.14 kJ mol^?1 for the dehydration stage, 124.7, 124.71, 126.14, 123.75, 126.19, and 124.05 kJ mol^?1 for the thermal decomposition stage, respectively, in the conversion range studied. The decomposition mechanism and pre‐exponential factor of each decomposition stage were also determined using Coats–Redfern, van Krevelen, Horowitz–Metzger methods, and master plots. The analysis of the master plots and methods based on single heating rate showed that the mechanisms of dehydration and decomposition stage of oligo(4‐hydroxyquinoline) were best described by kinetic equations of A_n mechanism (nucleation and growth, n = 1) and D_n mechanism (dimensional diffusion, n = 6), respectively. POLYM. ENG. SCI., 54:992–1002, 2014. © 2013 Society of Plastics Engineers     

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225–250°C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water‐soluble crystallizable fraction and water‐insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and ¹H‐NMR analysis. Glycolysis product was used for synthesis of PET‐based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea‐formaldehyde and melamine‐formaldehyde resins for synthesis of epoxy ester–amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET‐based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino‐resin‐modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519–2525, 2015. © 2015 Society of Plastics Engineers     

Ring Opening of Epoxidized Soybean Oil with Compounds Containing Two Different Functional Groups

Epoxidized vegetable oils are desirable chemicals due to their eco‐friendly characteristics and their being a major source of many green products. Ring opening is one of the ways to convert these epoxidized oils to some new intermediates. The use of mono‐functional amines, alcohols, acid anhydrides and thioethers for epoxy ring opening has been reported in the literature. In this study, thioglycolic acid (TGA) bearing thiol and carboxylic acid as two different functional groups and methyl ester of thioglycolic acid (TGAME) were used. Currently, there is no reported literature describing epoxy ring opening using chemicals bearing two different functional groups simultaneously. In this way, two new polyols were synthesized, one with TGA (polyol 1) and one with TGAME (polyol 2). FTIR and ¹H‐ and ¹³C‐NMR spectroscopy confirmed that the ring was opened by the carboxylic acid group of TGA, and the thiol group was not involved in the ring opening whereas the ring was opened by the thiol group in the case of TGAME.     

Improvement of Palm Oil Biodiesel Filterability by Adsorption Methods

Palm oil biodiesel (POB) is characterized by a very high cold soak filtration time (CSFT), which places the acceptability of this biofuel at risk. Therefore, the effect of four adsorbents, namely diatomaceous earth, natural silicate (NS), neutral bleaching earth (NBE), and acid activated bleaching earth (AABE), at two levels of addition (1 and 5 wt%) or two temperatures (25 and 110 °C) on the precipitate content and CSFT of POB was investigated. The impact on total glycerin content, moisture content, and oxidative stability was also examined. All treatments significantly decreased the precipitate content, total glycerin content, and moisture content, but only treatments with NS, NBE, and AABE at 5 wt% and 25 °C achieved acceptable filterability. The OSI value was also decreased; however, it remained above the ASTM limit. Operational conditions of treatment with AABE were further optimized in a two‐factor, five‐level center composite design. The combination of 0.65 wt% AABE and 10 min at 25 °C decreased CSFT to below the ASTM limit. Lower adsorbent concentrations could be effective down to 0.44 wt%, given a corresponding increase in the contact time up to 30 min.     

Chemometric Studies on zNose™ and Machine Vision Technologies for Discrimination of Commercial Extra Virgin Olive Oils

The aim of this study was to classify Turkish commercial extra virgin olive oil (EVOO) samples according to geographical origins by using surface acoustic wave sensing electronic nose (zNose?) and machine vision system (MVS) analyses in combination with chemometric approaches. EVOO samples obtained from north and south Aegean region were used in the study. The data analyses were performed with principal component analysis class models, partial least squares‐discriminant analysis (PLS‐DA) and hierarchical cluster analysis (HCA). Based on the zNose? analysis, it was found that EVOO aroma profiles could be discriminated successfully according to geographical origin of the samples with the aid of the PLS‐DA method. Color analysis was conducted as an additional sensory quality parameter that is preferred by the consumers. The results of HCA and PLS‐DA methods demonstrated that color measurement alone was not an effective discriminative factor for classification of EVOO. However, PLS‐DA and HCA methods provided clear differentiation among the EVOO samples in terms of electronic nose and color measurements. This study is significant from the point of evaluating the potential of zNose? in combination with MVS as a rapid method for the classification of geographically different EVOO produced in industry.     

The synthesis,characterisation and molecular structure of a new hetarylazoindole dye studied by X‐ray diffraction,spectral analysis and density functional theory calculation

1,2‐Dimethyl‐3‐(5‐methylisoxazol‐3‐yldiazenyl)‐1H‐indole was obtained by coupling 3‐amino‐5‐methylisoxazole with diazotised 1,2‐dimethylindole. It was characterised by proton and carbon nuclear magentic resonance, ultraviolet–visible, infrared and Raman spectra, and the X‐ray single crystal diffraction method. On the theoretical side, the molecular geometry, chemical shifts and the fundamental vibrational frequencies were evaluated using density functional theory. Time‐dependent density functional theory was used to evaluate the electronic excitation spectra. In addition, the scaled quantum mechanical approach was used to study the total energy distributions of the vibrational modes of the molecule. The results showed that the general agreement between experimental and calculated geometric parameters, chemical shifts and λ_max values are good. Excellent agreement was found between the calculated and experimental vibrational frequencies.     

Comparison of melt extrusion and thermokinetic mixing methods in poly(ethylene terephthalate)/montmorillonite nanocomposites

The scope of this study consists in studying the effects of processing type on thermal stability of poly(ethylene terephthalate) (PET) and its nanocomposites prepared with organically modified clays. To achieve this goal, an intercalating agent was synthesized and montmorillonite type of clay modified with this intercalating agent was mixed with the PET by using melt extrusion and high‐shear thermokinetic mixing method. According to the results, manganese in the raw clay—though chemically bound—was found to be responsible for the decreased intrinsic viscosity (IV) values, i.e. decreased molecular weight in PET/organoclay nanocomposites. Besides, it was revealed that working on the thermokinetic mixer provided substantial contributions such as shorter processing times in comparison to the melt extrusion method, elimination of drying step before melt processing, which has been accepted as an inevitable process for PET so far, less thermal degradation because of short processing times, and more homogeneous and better dispersion of the clay particles in PET matrix phase. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Preparation of Gadolina Stabilized Bismuth Oxide Doped with Boron via Electrospinning Technique

In this study, boron doped and undoped poly (vinyl) alcohol/bismuth–gadolina acetate (PVA/Bi–Gd) nanofibers were prepared using electrospinning technique then calcinated at 800 °C for 2 h. The originality of this study is the addition of boron to metal acetates. The effects of boron doping were investigated in terms of solution properties, morphological changes and thermal characteristics. The characteristics of the fibers were investigated with FT-IR, XRD, SEM and BET. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively. The BET results showed that boron undoped and doped Bi₂O₃–La₂O₃ nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 59.72 and 39.80 m²/g, respectively.     

Leaching kinetics of colemanite in ammonium hydrogen sulphate solutions

The aim of the study was to investigate the dissolution kinetics of colemanite in ammonium hydrogen sulphate solutions in a mechanical agitation system and to declare an alternative reactant to produce boric acid. Reaction temperature, concentration of ammonium hydrogen sulphate, stirring speed, solid/liquid ratio and particle size were selected as parameters on the dissolution rate of colemanite. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for solid–fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio causes an increase the dissolution rate of colemanite. The dissolution extent is highly increased with increase the stirring speed rate between 100 and 500 rpm and the dissolution extent is slowly increased with increase the stirring speed between 500 and 700 rpm in experimental conditions. The activation energy was found to be 32.66 kJ/mol. The leaching of colemanite was controlled by diffusion through the ash or product layer. The rate expression associated with the dissolution rate of colemanite depending on the parameters chosen may be summarized as follows: 1 ? 3(1 ? X)^2/3 + 2(1 ? X) = 8.99 × C^1.08 × W^1.39 × D^?1.27 × (S/L)^?0.54 × e^(?32.66/RT)t.     

The effect of magnetic field on the impurity binding energy of shallow donor impurities in a Ga1?xInxNyAs1?y/GaAs quantum well

Using a variational approach, we have investigated the effects of the magnetic field, the impurity position, and the nitrogen and indium concentrations on impurity binding energy in a Ga_1−xIn_xN_yAs_1−y/GaAs quantum well. Our calculations have revealed the dependence of impurity binding on the applied magnetic field, the impurity position, and the nitrogen and indium concentrations.