Fluorescence study on drying of ι-carrageenan gels at different temperatures prepared with various CaCl<Subscript>2</Subscript> content

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. ι-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 fluorescence intensity values decreased for all gel samples. A simple model consisting of Case II diffusion was used to produce the packing constants, k ₀, for helixes. It was observed that k ₀ increased as the drying temperature was increased. On the other hand at each temperature, it was seen that k ₀ decreased as CaCl₂ content was increased. Packing energies for drying processes were obtained from fluorescence, volumetric, and gravimetric measurements separately.     

Zinc and tin xanthates in the coordination polymerization of propylene oxide

The polymerization of propylene oxide with zinc and tin xanthates was studied. Polymerization with both systems was found to be a zeroth‐order, nonterminating process, where the molecular weight was controlled by transfer reactions. It is discussed that these observations were consistent with a mechanism in which the rate‐determining step was the addition of monomer on the growing chain rather than the coordination of the monomer to active sites. These catalysts turned out to be quite stable, even under semiclosed conditions. With zinc isopropyl xanthate, high conversions in short polymerization times could be obtained. The product had a very broad molecular weight distribution and could be split into crystallizable and amorphous fractions. The crystallizable fractions consisted of stereoregular segments separated from each other by stereoirregularities or regioirregularities. The degrees of polymerization of stereoregular segments (S₁'s) were estimated from melting point measurements. It was found that the melting points and, hence, average S₁ values changed in different fractions. It was concluded that there was only one type of active center; however, the rates of wrong additions (e.g., head‐to‐head addition) of incoming monomer controlled the average S₁ value of the chain. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polythiophene/borax conducting composite II: Electrorheology and industrial applications

In this study, polythiophene (PT) and polythiophene/ borax conducting composite (PT/borax) were in‐situ synthesized using FeCl₃ as oxidizing agent containing 89.2% PT and 10.8% borax. The electrorheological (ER), creep‐recovery, and vibration damping characteristics of the PT/borax composite were investigated. A volume fraction series (φ = 5–25%) of the PT/borax/silicone oil dispersions were prepared and sedimentation stabilities were determined. An ER activity was observed from the samples, when subjected to external electric field strength thus, they were classified as smart materials. Some parameters affecting the ER properties of the dispersions such as volume fraction, shear rate, electric field strength, frequency and temperature were investigated. Creep tests were applied to the suspensions to investigate the viscoelastic behaviors and recoverable viscoelastic deformations observed. Finally, real time vibration damping experiment was carried out on a modified automobile shock absorber and a 68% vibration damping capacity determined for borax/SO suspension system under E = 0.3kV/mm condition. POLYM. COMPOS., 2011.© 2011 Society of Plastics Engineers     

SYNTHESIS OF ZSM-5 FROM MODIFIED CLINOPTILOLITE AND ITS CATALYTIC ACTIVITY IN ALKYLATION OF BENZENE TO ETHYLBENZENE

ZSM-5 catalysts were prepared by utilizing clinoptilolite found in Western Anatolia in abundant amounts as a type of natural zeolite. Hydrothermal reaction was conducted with HCl-treated clinoptilolite at 180°C. After characterizing the solid products obtained by this reaction as ZSM-5 by means of XRD, IR, TGA, surface area analyzer, and chemical analysis they were tested as catalysts in benzene alkylation reaction with ethylene leading to ethylbenzene. Catalytic performance of samples prepared in this study was investigated for benzene conversion, ethylbenzene yield, and selectivity. It was found that ZSM-5(A) sample showed performance similar to that of the reference sample (ZSM-5(C)) synthesized by using patented literature information in terms of benzene conversion. When the reaction temperature was increased from 400° to 425°C ethylbenzene yield and selectivity results of ZSM-5(A) sample were improved but coke formation increased. Catalyst test results indicated the possibility of using clinoptilolite as a raw material in the synthesis of ZSM-5 catalyst for alkylation of benzene with ethylene reaction.     

Effect of a carbon black surface treatment on the microwave properties of poly(ethylene terephthalate)/carbon black composites

A surface treatment was applied to carbon black to improve the electrical and microwave properties of poly(ethylene terephthalate) (PET)-based composites. Three different formamide solutions with 1, 2, and 3 wt % concentrations were prepared to modify the surface chemistry of carbon black. Microwave properties such as the absorption loss, return loss, insertion loss, and dielectric constant were measured in the frequency range of 8–12 GHz (X-band range). Composites containing formamide-treated carbon black exhibited enhancements in the electrical conductivity, electromagnetic interference (EMI) shielding effectiveness, and dielectric constant values when compared to composites with untreated carbon black. In addition, increases in the formamide solution concentration and carbon black content of composites resulted in an increase in the electrical conductivity, EMI shielding effectiveness, and dielectric constant values. The percolation threshold concentration of PET composites shifted from a 3 to 1.5 wt % carbon black composition with the surface treatment. The best EMI shielding effectiveness was around 27 dB, which was obtained with the composite containing 8 wt % carbon black treated with a 3 wt % formamide solution. Moreover, this composition gave the lowest electrical resistivity and the highest dielectric constant among the produced composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Purification and determination of inhibitory activity of recombinant soyacystatin for surimi application

A recombinant soyacystatin (r-soyacystatin) was tested for its inhibitory activity against cysteine proteinase of Pacific whiting and its activity was compared to that of egg white cystatin. A recombinant soyacystatin expressed in Escherichia coli was purified to electrophoretic homogeneity using phenyl-Sepharose and DEAE-Sepharose. Native egg white cystatin was purified by using affinity chromatography on CM-papain-Sepharose generated in our lab. Egg white cystatin and soyacystatin were tested for proteinase inhibitory activity against commercial papain and also cathepsin L purified from Pacific whiting muscle. The r-soyacystatin exhibited papain-like protease inhibition activity comparable to that of the egg white cystatin, which could inhibit papain and Pacific whiting cathepsin L. The r-soyacystatin subsequently inhibited the autolytic activity of Pacific whiting surimi.     

Exergetic sustainability indicators for a high pressure hydrogen production and storage system

This study examines the exergetic sustainability effect of PEM electrolyzer (PEME) integrated high pressure hydrogen gas storage system whose capacity is 3 kg/h. For this purpose, the indicators, previously used in the literature, are taken into account and their variations are parametrically studied as a function of the PEME operating pressure and storage pressure by considering i) PEME operating temperature at 70 °C, ii) PEME operating pressures at 10, 30, 50 and 100 bar, iii) hydrogen gas flow rate at 3 kg/h and iv) storage pressure between 200 and 900 bar. Consequently, the results from the parametric investigation indicate that, with the ascent of storage pressure from 200 to 900 bar at a constant PEME operating pressure (=50 bar), exergetic efficiency changes decreasingly between 0.612 and 0.607 while exergetic sustainability between 1.575 and 1.545. However, it is estimated that waste exergy ratio changes increasingly between 0.388 and 0.393 while environmental effect factor between 0.635 and 0.647. Additionally, it is said that the higher PEME outlet pressure causes the higher exergetic sustainability index, the lower environmental effect factor, the lower waste exergy output, the higher exergetic efficiency. However, the higher storage pressure causes the lower exergetic efficiency, the higher waste exergy output, the higher environmental effect factor and the lower exergetic sustainability index. Thus, it is recommended that this type of the system should be operated at higher PEME outlet pressure, and at an optimum hydrogen storage pressure.     

Saponins: properties, applications and processing

Saponins are a diverse group of compounds widely distributed in the plant kingdom, which are characterized by their structure containing a triterpene or steroid aglycone and one or more sugar chains. Consumer demand for natural products coupled with their physicochemical (surfactant) properties and mounting evidence on their biological activity (such as anticancer and anticholesterol activity) has led to the emergence of saponins as commercially significant compounds with expanding applications in food, cosmetics, and pharmaceutical sectors. The realization of their full commercial potential requires development of new processes/processing strategies to address the processing challenges posed by their complex nature. This review provides an update on the sources, properties, and applications of saponins with special focus on their extraction and purification. Also reviewed is the recent literature on the effect of processing on saponin structure/properties and the extraction and purification of sapogenins.