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Thermal
Kinds of Thermal Terms modified by Thermal Selected AbstractsTHERMAL AND HIGH-PRESSURE STABILITY OF PURIFIED PECTIN METHYLESTERASE FROM PLUMS (PRUNUS DOMESTICA)JOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2006CLÁUDIA S. NUNES ABSTRACT Pectin methylesterase (PME) from greengage plums (Prunus domestica) has been extracted and purified using affinity chromatography. Only one band on sodium dodecyl sulfate,polyacrylamide gel electrophoresis was obtained, with an estimated molecular weight of 31 kDa. On isoelectric focusing electrophoresis, two bands with neutral isoelectric points (6.8 and 7.0) were detected. The optimal pH and temperature for plum PME activity were 7.5 and 65C, respectively. A study of purified plum PME thermostability was performed at pH 7.5 and 4.0, indicating a higher thermostability at pH 7.5 than at pH 4.0. A biphasic inactivation behavior was observed for thermal treatments (54,70C), whereas its pressure inactivation could be described by a first-order kinetic model in a pressure range of 650,800 MPa at 25C. Purified plum PME was found to be relatively stable to thermal and pressure (,600 MPa) treatments, compared to PME from other fruits. [source] GEOMETRICAL, THERMAL AND MECHANICAL PROPERTIES OF OLIVE FRUITSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2010MOHAMAD I. AL-WIDYAN ABSTRACT In Mediterranean countries, olive trees play a significant economical role. Knowledge of olive fruits properties is essential for the efficient handling of the product and optimizing oil yield. The lack of such knowledge at the local level triggered this study in an attempt to report the fruit's chemical composition and some major engineering properties. Established procedures were followed in conducting the measurements and calculations on fruit samples. The study examined four major varieties of olive fruits, including Spanish, Black Spanish, improved Nabali and Nabali Baladi for their chemical composition and other properties, including geometrical, thermal and frictional properties. Thermal properties, including thermal conductivity, heat capacity and thermal diffusivity, ranged from 0.41 to 0.47 W/(m·K), 2.35 to 2.39 kJ/(kg·K) and 2.88 × 10,7to 2.779 × 10,7 m2/s, respectively. The geometrical properties of the Spanish and Black Spanish were quite similar except for roundness and sphericity. Similar results were found for improved Nabali and Nabali Baladi. The properties of weight, density and packing coefficient ranged from 2.22 to 8.60 g, 890 to 1,230 kg/m3 and 0.43 to 0.52, respectively. The fruit's static friction coefficient over mild steel, aluminum and softwood surfaces ranged from 0.20 to 0.30, 0.21 to 0.29 and 0.22 to 0.33, respectively. PRACTICAL APPLICATIONS In Jordan and other Mediterranean countries, olive fruits are produced in large quantities every season. They are very widely used as pickled fruits or are processed in mills to extract their oil. Despite the fact that fruit properties are a necessary prerequisite for the efficient handling and processing of fruits, literature search indicated the lack of a comprehensive study of scientific merit that reports on the engineering properties of olive fruits. In addition, it is established that knowledge of the fruit properties leads to optimized handling and processing and results in knowledge-based development of all processes and equipment that deal with the fruits. The practical merit of this study stems from the fact that it reports on the key properties of a major product (olive fruits) that has social, cultural and economical significance throughout a whole region and is expanding throughout the globe. [source] THERMAL AND RHEOLOGICAL PROPERTIES OF BRINE FROM FERMENTED AND SULFITE-PRESERVED CUCUMBERS,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2002O.O. FASINA ABSTRACT Pickling cucumbers may be temporarily preserved by fermentation in brine (6,8% NaCl) or without fermentation in salt-free, sulfite solution (300 ppm sulfite, pH 3.5). Brines obtained from preservation processes are often discarded. Due to environmental concerns, there is increasing consideration for further use of the brine solutions by recycling for use in bulk storage or filtration and incorporation into finished products. Thermal and rheological properties are fundamental to the reuse of the brine. The effect of temperature was determined on the rheological (5,45C) and thermal properties (5,75C) of brine. The properties of the brine samples were found to be significantly different (P < 0.05) from each other and from water. Salt content was the most important factor affecting the thermal and rheological properties of brine. At the same conditions, the values of the properties (thermal conductivity, specific heat, and thermal diffusivity, viscosity) were about 5 to 23% less than the corresponding values for water. [source] EFFECTS OF THERMAL AND ELECTROTHERMAL PRETREATMENTS ON HOT AIR DRYING RATE OF VEGETABLE TISSUEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2000WEI-CHI WANG ABSTRACT Cylindrical samples of carrot, potato and yam were dried in a hot-air dehydrator after preheating to 50C or 80C by three different heating methods (conventional, microwave and ohmic). The results showed that enhancement of drying rate increased with pretreatment temperature. Ohmic pretreatment increased the drying rate more than conventional and microwave heating. Desorption isotherms showed that in the low aw range, desorption data of preheated and raw materials were similar. However, the isotherms of preheated samples shifted when aw was high, which indicated that thermal pretreatments altered the structure, and apparently, the water distribution within these materials. For all samples, ohmic pretreatment showed stronger influences on isotherms than microwave heating, while the pretreatment effect of conventional heating was only observed for potato tissue. [source] THE EFFECTS OF THERMAL AND NONTHERMAL PROCESSING METHODS ON APPLE CIDER QUALITY AND CONSUMER ACCEPTABILITYJOURNAL OF FOOD QUALITY, Issue 1 2005LYNN H. CHOI ABSTRACT Due to increased concern about the safety of fruit, vegetable and juice products, the FDA has mandated that these must undergo a 5-log reduction in pathogens. The development of various processing methods for juice products has caused the need to determine the effects of these methods on said products. The effect of thermal pasteurization, UV irradiation and ozone treatment on apple cider quality and consumer acceptability was studied over 21 days. Thermally pasteurized samples were different in color and less preferred in all areas of consumer acceptability. UV-irradiated samples were lower in soluble solids for the first 7 days and showed no significant difference in consumer acceptability. Ozone-treated cider had greater sedimentation, lower sucrose content and a decrease in soluble solids by day 21. UV irradiation allows for a more cost-effective method to produce safe apple cider with minimal quality and consumer acceptability differences. [source] THE EFFECT OF SALTS ON THERMAL AND HYDRIC DILATATION OF POROUS BUILDING STONE*ARCHAEOMETRY, Issue 3 2009M. AL-NADDAF Fifteen desalinated sandstone drill core samples from Umm Ishrin Sandstone Formation in Petra (Cambrian age) were used for this study. The samples were mineralogically analysed using X-ray diffraction and their physical properties were also determined. Samples with similar physical properties and mineralogical composition were taken for further experimental work. After desalination, thermal and hydric dilatation coefficients were measured, then three types of salts (NaCl, KCl and Na2SO4·10H2O), which have high solubility and consequently are the most dangerous to building stone (and are also detected in the sandstone monuments in Petra), were introduced into the samples and their contents were calculated. The results show that salt crystallization in the pores of building stones can increase their thermal dilatation and decrease their hydric dilatation to varying extents, depending on the nature of the salt. The average increase in the thermal dilatation coefficient per unit mass of salt is the lowest for the Na2SO4·10H2O-salted samples with a value of 5.3%, while the NaCl-salted samples have the highest value with 7.8% per salt mass. The average percentage of the decrease of the hydric dilatation coefficient is 1061% for Na2SO4·10H2O-salted samples per mass of salt content; the NaCl-salted samples have a value of 1510% per mass of salt content, and the KCl-salted samples almost the same value. For the salt-free samples, it was found that in climatic conditions with a high temperature range, the deterioration of sandstone due to temperature fluctuation is more effective than that caused by change in the moisture content, while samples with high salt content suffer more from hydric dilatation. [source] Thermal and EPR investigations of thallium gallium disulphide single crystalCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2009M. Acikgoz Abstract In this research, the results of the differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) investigations of TlGaS2 single crystal are presented. Specific heat capacity (Cp) anomalies of layered TlGaS2 have been obtained by using a new DSC technique for such crystals. Remarkable heat capacity anomalies have been revealed at the temperatures of 137.7 K, 174.5 K and 238.5 K. It is found that the anomalies appear at maximum with a small deviation (by 3-4%) from the regular values, and Cp discontinuity amounted to approximately 5%. Additionally, EPR spectra of Fe doped TlGaS2 single crystals have been recorded at various temperatures down to 6 K for different orientations of the applied magnetic field. Transformations of present EPR spectra are not sufficient for the confirmation of structural phase transitions, in contrast to the cases in iso structural TlInS2 and TlGaSe2 compounds. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermal, phase transition and spectral studies in erythromycin pseudopolymorphs: dihydrate and acetone solvateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006Zhanzhong Wang Abstract The thermal, phase transition and spectral studies of erythromycin A dihydrate and acetone solvate were performed by Differential Scanning calorimetry (DSC), Thermo Gravimetry (TG-DTA), X-Ray Powder Diffraction (XRPD) and Fourier Transform Infra-Red (FTIR) spectrum. The non-thermal kinetic analysis of erythromycin A dihydrate was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The result showed that heating rate has substantial influence on the thermal behavior of erythromycin dihydrate. The Arrhenius parameters were estimated according to the Kissinger method. Corresponding to dehydration of dihydrate, melting of dehydrated dihydrate, phase transition from dehydrated dihydrate to anhydrate, and melting of anhydrate, the calculated activation energy were 39.60, 269.85, 261.23, and 582.16 kJmol,1, the pre-exponential factors were 3.46 × 103, 8.06 × 1032, 9.23 × 1030, and 7.29 × 1063 s,1, respectively. Ozawa method was used to compare activation energy values calculated by Kissinger method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato-Bridged Cobalt(II) ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2008Oluwatayo F. Ikotun Abstract The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(,-P2O7)}·6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 Å distance, and its conformation gives rise to intramolecular ,,, stacking interaction between adjacent phen ligands. Indeed, intermolecular ,,, stacking interactions between phen ligands from adjacent dinuclear complexes create a supramolecular 2D network in 1. Magnetic susceptibility measurements on a polycrystalline sample of 1 in the temperature range 1.9,295 K are typical of an overall antiferromagnetic coupling with a maximum of the magnetic susceptibility at 3.0 K. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = ,1.23 cm,1). The ability of the pyrophosphato ligand to mediate magnetic interactions between different first-row transition-metal ions when adopting the bis(bidentate) bridging mode is analyzed and discussed in the light of the small number of magneto-structural reports on this type of compound, bearing in mind the number of unpaired electrons and type of magnetic orbitals on each metal center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Influence of Al-Containing Interfacial Coatings on Carbon-Fiber/Bakelite Composite Thermal and Electrical Properties,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Zeljko Pajkic Polymer-matrix (Bakelite®) composites were produced with coated short carbon fibers as a filler material and characterized in terms of their thermal, electrical, and mechanical properties. The influence of thin, Al-containing ceramic coatings on the composite material's macroscopic properties is discussed, as the composites with interfacial coatings show improvements in some properties, as compared to the ones with uncoated fibers. [source] Photoswitchable Gas Permeation Membranes Based on Liquid CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Eric G, owacki Abstract We have fabricated switchable gas permeation membranes in which a photoswitchable low-molecular-weight liquid crystalline (LC) material acts as the active element. Liquid crystal mixtures are doped with mesogenic azo dyes and infused into commercially available track-etched membranes with regular cylindrical pores (0.40 to 10.0 ,m). Tunability of mass transfer can be achieved through a combination of (1) LC/mesogenic dye composition, (2) surface-induced alignment, and (3) reversible photoinduced LC-isotropic transitions. Photo-induced isothermal phase changes in the imbibed material afford large and fully reversible changes in the permeability of the membrane to nitrogen. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure relationship, but they show significant differences in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic,or vice versa , and can be further tuned by surface alignment. Permeability switching response times are 5 s, with alternating UV and >420-nm radiation at an intensity of 2 mW/cm2 being sufficient for complete and reversible switching. Thermal and kinetic properties of the confined LC materials are evaluated and correlated with the observed permeation properties. We demonstrate for the first time reversible permeation control of a membrane with light irradiation. [source] Carbon Nanotubes: (Thermal and Structural Characterizations of Individual Single-, Double-, and Multi-Walled Carbon Nanotubes) Adv.ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Funct. Here, M. T. Pettes and L. Shi report for the first time the thermal conductance, diameter, and chiral angle for a single single-walled carbon nanotube (SWCNT). A scanning electron micrograph of the suspended micro-thermometer device and transmission electron microscopy images used to determine the SWCNT's (22, 12) chirality are shown in this frontispiece image, along with the rendered unit cell. [source] Thermal and Structural Characterizations of Individual Single-, Double-, and Multi-Walled Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Michael T. Pettes Abstract Thermal conductance measurements of individual single- (S), double- (D), and multi- (M) walled (W) carbon nanotubes (CNTs) grown using thermal chemical vapor deposition between two suspended microthermometers are reported. The crystal structure of the measured CNT samples is characterized in detail using transmission electron microscopy (TEM). The thermal conductance, diameter, and chirality are all determined on the same individual SWCNT. The thermal contact resistance per unit length is obtained as 78,585,m,K,W,1 for three as-grown 10,14,nm diameter MWCNTs on rough Pt electrodes, and decreases by more than 2 times after the deposition of amorphous platinum,carbon composites at the contacts. The obtained intrinsic thermal conductivity of approximately 42,48, 178,336, and 269,343,W,m,1,K,1 at room-temperature for the three MWCNT samples correlates well with TEM-observed defects spaced approximately 13, 20, and 29,nm apart, respectively; whereas the effective thermal conductivity is found to be limited by the thermal contact resistance to be about 600,W,m,1,K,1 at room temperature for the as-grown DWCNT and SWCNT samples without the contact deposition. [source] A Stimuli-Responsive, Photoluminescent, Anthracene-Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical ProcessesADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yoshimitsu Sagara Abstract Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable,stable phase transition induced by external stimuli is prepared. A 2,6-diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6-diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid-crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic-columnar phase transition induced by heating or mechanical shearing for this 2,6-diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable,stable LC phase transition. [source] Synthesis and Processing of Monodisperse Oligo(fluorene- co -bithiophene)s into Oriented Films by Thermal and Solvent AnnealingADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Lichang Zeng Abstract A series of oligo(fluorene- co -bithiophene)s, OF2Ts, have been synthesized and characterized to investigate the effects of oligomer length and pendant aliphatic structure on glassy-nematic mesomorphism. The OF2Ts comprising more than one repeat unit and their polymer analogue, PF2T, carrying 52 number-average repeat units, possess the highest occupied molecular orbital energy level at ,5.3,±,0.2,eV, but the anisotropic field-effect mobilities increase with the oligomer length. Spin coating from high-boiling chlorobenzene with and without subsequent exposure to saturated chlorobenzene vapor constitute solvent-vapor annealing and quasi-solvent annealing, respectively. Solvent-vapor annealing yields monodomain glassy-nematic films in which OF2Ts are aligned as well as with thermal annealing across a 2,cm diameter. Quasi-solvent annealing, however, amounts to kinetically trapping a lower orientational order than solvent-vapor or thermal annealing. While amenable to thermal annealing at elevated temperatures, PF2T shows no alignment at all following either strategy of solvent annealing. [source] Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical PropertiesADVANCED MATERIALS, Issue 28 2009Chunyi Zhi Ultrathin boron nitride nanosheets are fabricated and detailed morphological and structural microscopic studies of are carried out. Polymeric composites containing BN nanosheets exhibit a remarkable reduction of the coefficient of thermal expansion (CTE) and possess enhanced elastic modulus and strength. [source] Thermal and mechanical numerical modelling of electric discharge machining processINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008Nizar Ben Salah Abstract In electric discharge machining (EDM), the heat gradients caused by the electric discharge create a non-uniform local thermal expansion on the level of the surface layers of machined materials from where genesis of thermal stresses takes place. These thermal stresses, if exceeding yield stress, can remain and become residual after the cooling of the part. The modelling of these phenomena, during the heating by the electric discharge and the cooling by the dielectric liquid, requires a heat transfer model, the material behaviour identification, a thermo-mechanical model for the thermal and the residual stress models. This paper presents numerical results concerning the temperature distribution, the thermal and residual stresses of a stable steel material (AISI316L) machined by EDM. Comparison of numerical results with experimental data and numerical results from the literature shows good agreement and is hence quite satisfactory. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermal flutter analysis of large-scale space structures based on finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2007Wei Li Abstract During the orbital day,night crossing period, the suddenly applied thermal loading is apt to introducing vibration on flexible appendages of large-scale space structures. This kind of thermally-induced vibration is a typical failure of modern spacecrafts. However, owing to the complexity of this problem, many earlier researches study only the vibration of simplified beam models, which can hardly describe the performance of practical structures. This paper aims at using the finite element method to analyse the non-linear vibration of practical thin-walled large-scale space structures subjected to suddenly applied thermal loading. In this study, the coupling effect between structural deformations and the incident normal solar heat flux is considered; the necessary condition of thermally-induced vibration is verified; and the criterion of thermal flutter is established. Copyright © 2006 John Wiley & Sons, Ltd. [source] 2D thermal/isothermal incompressible viscous flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2005Alfredo Nicolás Abstract 2D thermal and isothermal time-dependent incompressible viscous flows are presented in rectangular domains governed by the Boussinesq approximation and Navier,Stokes equations in the stream function,vorticity formulation. The results are obtained with a simple numerical scheme based on a fixed point iterative process applied to the non-linear elliptic systems that result after a second-order time discretization. The iterative process leads to the solution of uncoupled, well-conditioned, symmetric linear elliptic problems. Thermal and isothermal examples are associated with the unregularized, driven cavity problem and correspond to several aspect ratios of the cavity. Some results are presented as validation examples and others, to the best of our knowledge, are reported for the first time. The parameters involved in the numerical experiments are the Reynolds number Re, the Grashof number Gr and the aspect ratio. All the results shown correspond to steady state flows obtained from the unsteady problem. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of Bismuth Borate/LiF on the Sintering, Thermal, and Microwave Dielectric Properties of Ba6,3xSm8+2xTi18O54 (x=2/3) Solid SolutionINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008Narayana Iyer Santha Ba6,3xSm8+2xTi18O54 (x=2/3) (BST) was prepared by the solid-state method and the effect of bismuth borate (BB)/LiF on the sinterability, microstructure, and thermal and microwave dielectric properties were studied. BST+3.5 wt% BB+0.5 wt% LiF composite sintered at 1050°C has Q×f=4500 GHz, ,=52, and ,f=+6 ppm/°C. Raman spectrum of the composite was compared with that of BST and the structural changes were investigated. [source] Thermal and chemical contributions of added H2O and CO2 to major flame structures and NO emission characteristics in H2/N2 laminar diffusion flameINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2002Seung-Gon Kim Abstract Numerical simulation with detailed chemistry has been carried out to clearly discriminate the thermal and chemical contributions of added diluents (H2O and CO2) to major flame structures and NO emission characteristics in H2/N2 counterflow diffusion flame. The pertinence of GRI, Miller,Bowman, and their recent modified mechanisms are estimated for the combined fuel of H2, CO2, and N2. A virtual species X, which displaces the individual CO2 and H2O in the fuel sides, is introduced to separate chemical effects from thermal effects. In the case of H2O addition the chain branching reaction, H + O2 , O + OH is considerably augmented in comparison with that in the case of CO2 addition. It is also seen that there exists a chemically super-adiabatic effect in flame temperature due to the breakdown of H2O. The reaction path of CH2O,CH2OH,CH3 and the C1-branch reactions become predominant due to the breakdown of CO2. In NO emission behaviour super-equilibrium effects caused by the surplus chain carrier radicals due to the breakdown of added H2O are more superior to the enhanced effects of prompt NO with the breakdown of added CO2. Especially, it is noted that thermal NO emission is directly influenced by the chemical super-equilibrium effects of chain carrier radicals in the case of H2O addition. As a result the overall NO emission in the case of the addition of H2O is higher than that in the case of CO2 addition. Copyright © 2002 John Wiley & Sons, Ltd. [source] Original article: Thermal and light degradation kinetics of anthocyanin extracts from mangosteen peel (Garcinia mangostana L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2010Renan C. Chisté Summary The stability and half-life time of anthocyanin extracts from mangosteen peel were studied under controlled oxygen supply, undergoing the influence of light source (fluorescent, incandescent, infrared and ultraviolet) and storage temperature (5, 28, 40 and 50 °C). The kinetic parameters for anthocyanin degradation, under different illumination conditions fit the first-order reaction model, and the exposition under fluorescent light resulted in a higher half-life time (597 h), followed by incandescent (306 h), ultraviolet (177 h) and infrared (100 h). The kinetic behaviour for the storage in different temperatures also fit the first order, and at 5 °C the highest half-life time (4006 h) was found, followed by 28 °C (370 h), 40 °C (125 h) and 50 °C (93 h). The activation energy was 14.7 Kcal.mol,1, and Q10 values showed that at 5 °C the anthocyanin extracts were more sensitive to storage temperature changes compared to the other tested temperatures. [source] Improved Chiral Olefin Metathesis Catalysts: Increasing the Thermal and Solution Stability via Modification of a C1 -Symmetrical N-Heterocyclic Carbene LigandADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Jolaine Savoie Abstract Four new ruthenium-based olefin metathesis catalysts that possess an N-heterocyclic carbene (NHC) ligand with benzyl (Bn) or or n -propyl (n -Pr) N-alkyl groups have been prepared. The synthetic routes developed for the synthesis of the required dihydroimidazolium salts are general. Catalysts bearing larger NHC ligands with larger N-alkyl groups displayed improved thermal and solution state stability up to 80,°C. The reactivity of the new catalysts in ring-closing metathesis is directly related to the increased steric bulk of the NHC ligand. The new catalysts have been evaluated in desymmetrization reactions and the nature of the N-alkyl group of the NHC ligands has been shown to have an important effect on the observed enantioselectivities. [source] Thermal, catalytic, antimicrobial, and chelating aspects of phenolic resin and its polychelates with f-block elementsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008M. M. Patel Abstract The polymeric ligand (resin) was synthesized by condensation of 2-hydroxy-4-ethoxybenzophenone with ethane diol in the presence of polyphosphoric acid as a catalyst at 145°C for 10 h. The synthesized resin was used to study its ion exchange efficiency and to synthesize its polychelates with 4f-block elements. The resin and its polychelates were characterized on the basis of elemental analyses, electronic spectra, magnetic susceptibilities, IR, NMR, and thermogravimetric analyses. The molecular weight was determined using number,average molecular weight (Mn) by a vapor pressure osmometry (VPO) method. Ion-exchange studies at various concentrations of different electrolytes, pH, and rate have been carried out for f-block elements. Antimicrobial activity of all polychelates and catalytic activity of selected polychelates in organic synthesis have been studied. It is observed that resin can be used as an ion-exchanger and polychelates are found to be an efficient catalysts and antimicrobial agents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal and rheological properties of poly(vinyl alcohol) and water-soluble chitosan hydrogels prepared by a combination of ,-ray irradiation and freeze thawingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Xiaomin Yang Abstract Poly(vinyl alcohol) (PVA)/water-soluble chitosan (ws-chitosan) hydrogels were prepared by a combination of ,-irradiation and freeze thawing. The thermal and rheological properties of these hydrogels were compared with those of hydrogels prepared by pure irradiation and pure freeze thawing. Irradiation reduced the crystallinity of PVA, whereas freeze thawing increased it. Hydrogels made by freeze thawing followed by irradiation had higher degrees of crystallinity and higher melting temperatures than those made by irradiation followed by freeze thawing. ws-Chitosan disrupted the ordered association of PVA molecules and decreased the thermal stability of both physical blends and hydrogels. All the hydrogels showed shear-thinning behavior in the frequency range of 0.2,100 rad/s. Hydrogels made by freeze thawing dissolved into sol solutions at about 80°C, whereas those made by irradiation showed no temperature dependence up to 100°C. The chemical crosslinking density of the hydrogels made by irradiation followed by freeze thawing was much greater than that of hydrogels made by freeze thawing followed by irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal and dielectric properties of bismaleimide-triazine resins containing octa(maleimidophenyl)silsesquioxaneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Hongwei Cao Abstract Octa(maleimidophenyl)silsesquioxane (OMPS) was synthesized, characterized, and employed to modify the BT resin which composed of 4,4,-bismaleimidodiphenylmethane (BMI) and 2,2,-bis(4-cyanatophenyl)propane (BCE). The curing reaction between OMPS and BT resin was first investigated. It was found that OMPS accelerate the curing reaction of BCE, and the onset temperature of the cyclotrimerization was reduced up to 95.5°C (by DSC). As demonstrated by DSC and FTIR, there was no evidence that indicated the coreaction between maleimide and cyanate ester. 2,2,-diallyl bisphenol A (DBA) and diglycidyl ether of bisphenol A (E-51) (Wuxi Resin Factory, Jiangsu Province, China) were also used to enhance the toughness of BT resin, and the formulated BTA (containing DBA) and BTE (containing E-51) resins were obtained. The thermal properties of BT, BTA, and BTE resins incorporated with OMPS were then investigated. The results of DMA and TG showed that the BT, BTA, and BTE resins containing 1 wt % of OMPS exhibit enhanced thermal properties in comparison with their pristine resins respectively, while more contents of OMPS may impair the thermal properties of the polymer matrix, though the effect of OMPS was slight. Finally, the dielectric constant of these hybrid materials were detected, and their dielectric constant were distinctly reduced by the incorporation of OMPS, while overmuch contents of OMPS were disadvantageous for dielectric constant because of the aggregation of OMPS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Influence of fillers on the properties of a phenolic resin cured in acidic mediumJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008J. M. Laza Abstract The curing behavior of a phenolic resol resin in the presence of p -toluensulphonic acid is reported herein. The gel time of different systems has been determined by thermal scanning rheometry. Thermal and mechanical properties of the resin have been modified by the addition of varying amounts of fillers, talc, and kaolin. dynamic mechanical thermal analysis is used to determine the mechanical properties of the systems and the influence of the fillers and the postcuring. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal and dynamic mechanical properties of organic,inorganic hybrid composites of itaconate-containing poly(butylene succinate) and methacrylate-substituted polysilsesquioxaneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Takenori Sakuma Abstract Itaconate-unit-containing poly(butylene succinate) (PBSI) was synthesized by the reaction of 1,4-butanediol, succinic acid, and itaconic acid in a molar ratio of 2.0 : 1.0 : 1.0, and the obtained PBSI was reacted with methacryl-group-substituted polysilsesquioxane (ME-PSQ) in the presence of benzoyl peroxide (BPO) at 130°C to produce PBSI/ME-PSQ hybrid composites. The thermal and dynamic mechanical properties of the PBSI/ME-PSQ hybrid composites were investigated in comparison with those of PBSI cured at 130°C in the presence of BPO. As a result, the hybrid composites showed a much higher thermal degradation temperature and storage modulus in the rubbery state than the cured PBSI (C-PBSI). The thermal degradation temperature and storage modulus of the hybrid composites increased with increasing ME-PSQ content. The glass-transition temperature, measured by dynamic mechanical analysis of the hybrid composites, somewhat increased with increasing ME-PSQ content. However, the glass-transition temperatures of all the hybrid composites were lower than that of C-PBSI. Although the IR absorption peak related to CC groups was not detected for C-PBSI, some olefinic absorption peaks remained for all the hybrid composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007H. A. Khonakdar Abstract Uncrosslinked and chemically crosslinked binary blends of low- and high-density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt-mixing process using 0,3 wt % tert -butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation-at-break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co-continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261,3270, 2007 [source] THERMAL AND RHEOLOGICAL PROPERTIES OF BRINE FROM FERMENTED AND SULFITE-PRESERVED CUCUMBERS,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2002O.O. FASINA ABSTRACT Pickling cucumbers may be temporarily preserved by fermentation in brine (6,8% NaCl) or without fermentation in salt-free, sulfite solution (300 ppm sulfite, pH 3.5). Brines obtained from preservation processes are often discarded. Due to environmental concerns, there is increasing consideration for further use of the brine solutions by recycling for use in bulk storage or filtration and incorporation into finished products. Thermal and rheological properties are fundamental to the reuse of the brine. The effect of temperature was determined on the rheological (5,45C) and thermal properties (5,75C) of brine. The properties of the brine samples were found to be significantly different (P < 0.05) from each other and from water. Salt content was the most important factor affecting the thermal and rheological properties of brine. At the same conditions, the values of the properties (thermal conductivity, specific heat, and thermal diffusivity, viscosity) were about 5 to 23% less than the corresponding values for water. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||