Thermal Behaviour (thermal + behaviour)

Distribution by Scientific Domains


Selected Abstracts


1-D-Tin(II) Phenylchalcogenolato Complexes ,1[Sn(EPh)2] (E = S, Se, Te) , Synthesis, Structures, Quantum Chemical Studies and Thermal Behaviour

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2010
Andreas Eichhfer
Abstract A series of three 1-D-tin(II) phenylchalcogenolato complexes ,1[Sn(EPh)2] (E = S, Se, Te) were synthesized in yields > 80,% by reaction of SnCl2 with two equivalents of PhESiMe3 in organic solvents. In the crystal the molecules form two different types of one-dimensional chains. In ,1[Sn(SPh)2] the tin atoms are distorted trigonal pyramidal coordinated by sulfur atoms (two bonds within a monomer and one longer bond between neighbored monomers), while in ,1[Sn(EPh)2] (E = Se, Te) the tin atoms show contacts to two neighbored monomers leading to a fourfold coordination of the tin atoms by either selenium or tellurium atoms. The bond situation is discussed on the basis of density functional calculations. Thermal treatment mostly leads to the formation of the corresponding phase pure tin(II) chalcogenides however sublimation plays an increasing role ongoing from the tellurolato to the thiolato complex especially for the use of vacuum conditions. The investigation of the volatile cleavage products reveals the occurence of more complex reactions in the gas phase than the formal stoichiometric cleavage of EPh2 (E = S, Se, Te) with formation of SnE. [source]


Thermal Behaviour of Selected C10H16 Monoterpenes

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2006
Achim Stolle
Abstract The presented work investigates the thermal behaviour of selected monoterpenes under various reactor temperatures and residence times (carrier gas, reactor inserts). In addition to the analysis of the liquid products by capillary GC and GC-MS, chemical derivatisation techniques (Diels,Alder reaction, hydrogenation) were used to identify the liquid-phase products. A thermal conversion of ,-pinene (1), myrcene (2) and limonene (4) in a reaction network is presented and the experimental evidence for the formation of pyrolysis products by a biradical pathway is discussed. The reaction network was modified based on the identification of additional C10H16 terpene isomers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Investigation of the Thermal Behaviour of Non-metallic Curved-Face-Width Spur Gears

LUBRICATION SCIENCE, Issue 4 2004
L. Andrei
Abstract This paper describes a curved-face-width spur gear, specially designed for manufacture from non-metallic materials. The benefits of this gear are the higher contact ratio, bending and Hertzian contact resistance, and greater tooth stiffness compared to standard spur gears. A modified geometry is proposed for the gear tooth, the height of which varies along the gear face width. Due to the reduction in tooth height, in sections away from the gear centre, lower sliding friction is expected, with consequences for the gear's thermal behaviour. The complex gear geometry makes the design of a die difficult; therefore the gears were cut on a milling machine, using a special kinematic generation process and related equipment. The tooth flank profile, an involute or near involute in sections away from the gear half-width plane, as well as the flank surface quality determined by the single-cutter tool used for gear manufacture, influence the meshing condition, and can be detrimental to the thermal behaviour of the gear. Experimental tests were carried out to examine the influence of load and speed on the temperature of the curved-face-width spur gears with modified geometry. The measured temperature of the non-standard gear is further compared with the predicted temperature of plastic standard spur gears of the same specification. [source]


Synthesis, Characterization and Thermal Behaviour of Guanidinium-5-aminotetrazolate (GA) , A New Nitrogen-Rich Compound

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 4 2003
Jochen Neutz
Abstract This work describes the synthesis and the thermoanalytical characterization of guanidinium-5-aminotetrazolate (GA). GA is a new nitrogen-rich energetic material. It is not mentioned in the chemical literature so far. The molecular structure of the compound has been determined by IR, 1H-, 13C- and 15N-NMR spectroscopy. The thermal properties, the decomposition pathways and its volatile products were investigated by thermal analysis and are discussed. [source]


Thermal behaviour of cubic phases rich in 1-monooleoyl- rac -glycerol in the ternary system

FEBS JOURNAL, Issue 1 2003
- d -glucoside/water, 1-monooleoyl- rac -glycerol/n -octyl-
Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl- rac -glycerol (MO)/n -octyl-,- d -glucopyranoside (OG)/2H2O system with 58 or 45 wt % MO concentration and varying OG/2H2O contents. These MO contents correspond to a Pn3m cubic single-phase or a Pn3m cubic phase in excess water on the binary MO/water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG, while higher OG concentrations trigger a cubic-to-lamellar phase transition. Moreover, with increasing OG concentration the initial Pn3m structure is completely converted to an Ia3d structure prior to the L, phase being formed. Upon heating this effect is reversed, resulting in an Ia3d -to- Pn3m phase transition. For some samples additional peaks were observed in the diffractograms upon heating, resulting from the metastability notoriously shown by bicontinuous cubic phases. This judgement is supported by the fact that upon cooling these peaks were absent. Remarkably, both the Ia3d and the Pn3m cubic structures could be in equilibrium with excess water in this ternary system. A comparison is made with previous results on n -dodecyl-,- d -maltoside (DM), showing that cubic phases with OG have higher thermal and compositional stability than with DM. [source]


Thermal ecology of Zonocerus variegatus and its effects on biocontrol using pathogens

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2000
Simon Blanford
Summary 1 Thermal behaviour of the variegated grasshopper, Zonocerus variegatus, was investigated in the humid tropical zone of southern Benin, west Africa, in the dry seasons of 1996 and 1998. In 1998, investigations included studies of a population of grasshoppers sprayed with an oil-based formulation of the entomopathogenic fungus Metarhizium anisopliae var acridum. 2 Body temperature measurements and observations of thermal behaviour both in the field and on thermal gradients in the laboratory, suggest that Z. variegatus was not an active behavioural thermoregulator. Although it did show shade-seeking behaviour at high temperatures, no overt behavioural postures or microhabitat selection associated with heat gain and elevation of body temperatures was observed. Moreover, no alterations to thermal behaviour were found in response to infection by Metarhizium. 3 Body temperatures exhibited by Z. variegatus in the field will lengthen disease incubation of M. anisopliae var acridum compared with laboratory maintained, constant temperature conditions and may have a significant impact on pathogens with a lower thermal tolerance. 4 Habitat structure appeared to be an important factor determining the extent of body temperature elevation. The effect of habitat differences on infection and growth of M. anisopliae var acridum and other entomopathogenic fungi is discussed. [source]


Smectic phases of liquid crystals based on dinuclear palladium(II) complexes with carboxylato bridge

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2010
V. Crcu
Abstract In this paper we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear carboxylato bridge Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, IR and 1H NMR spectroscopy whereas the thermal behaviour was investigated by polarizing optical microscopy and differential scanning calorimetry. The monotropic smectic A phase displayed by these materials was identified by miscibility studies with a previously reported mesogen. It was found that the transition temperatures and the SmA mesophase stability depend on the alkyl chain length of the carboxylato bridge. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Imidazolium based ionic liquid crystals: structure, photophysical and thermal behaviour of [Cnmim]BrxH2O (n = 12, 14; x=0, 1)

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008
A. Getsis
Abstract The long chain imidazolium halides [Cnmim]BrxH2O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X-ray structure analyses of the monohydrates ([C12mim]BrH2O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, , = 81.89(5), , = 83.76(5), , = 78.102(5), 3523 unique reflections with Io > 2,(Io), R1 = 0.0263, wR2 = 0.0652, GooF = 1.037, T = 263(2) K; [C14mim]Br,H2O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, , = 94.86(2), , = 94.39(2), , = 101.83(2), 2063 unique reflections with Io > 2,(Io), R1 = 0.0429, wR2 = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (1,,1,*) and long lived (1,,3,*) transitions. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Crystal structure and thermal behaviour of (Rb,Cs)BSi2O6 solid solutions

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006
M. G. Krzhizhanovskaya
Abstract The crystal chemistry of Rb-Cs boroleucites has been studied by means of X-ray powder diffraction at room and elevated temperatures. The cubic I-43d , cubic Ia3d phase transition was investigated using a series of samples prepared by solid-state reaction along the pseudobinary system RbBSi2O6 - CsBSi2O6. The Rietveld refinement of the structures of Rb1-xCsxBSi2O6 solid solutions (x = 0.2, 0.4, 0.6, 0.8) demonstrates that the solutions with a high Rb content crystallise in the cubic I-43d space group, and the boroleucites with a considerable Cs content have Ia3d symmetry. Rb can substitute Cs in a wide range of compositions. Within a narrow range of x = 0.5 - 0.6 immiscibility was revealed. Under Rb-Cs substitution the cubic lattice parameter, the (Rb,Cs)-O distances, and the angles between tetrahedra of the I-43d phase change clearly, while those of the Ia3d phase change slightly. The HTXRD data shows that the I-43d phase transforms into a Ia3d phase on heating analogously to a change of the composition. As the Cs content increases the transition temperature decreases. The low temperature I-43d phase shows a higher thermal expansion than the high temperature Ia3d phase. 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source]


Thermal Behaviour of Selected C10H16 Monoterpenes

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2006
Achim Stolle
Abstract The presented work investigates the thermal behaviour of selected monoterpenes under various reactor temperatures and residence times (carrier gas, reactor inserts). In addition to the analysis of the liquid products by capillary GC and GC-MS, chemical derivatisation techniques (Diels,Alder reaction, hydrogenation) were used to identify the liquid-phase products. A thermal conversion of ,-pinene (1), myrcene (2) and limonene (4) in a reaction network is presented and the experimental evidence for the formation of pyrolysis products by a biradical pathway is discussed. The reaction network was modified based on the identification of additional C10H16 terpene isomers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Thermal behaviour of cubic phases rich in 1-monooleoyl- rac -glycerol in the ternary system

FEBS JOURNAL, Issue 1 2003
- d -glucoside/water, 1-monooleoyl- rac -glycerol/n -octyl-
Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl- rac -glycerol (MO)/n -octyl-,- d -glucopyranoside (OG)/2H2O system with 58 or 45 wt % MO concentration and varying OG/2H2O contents. These MO contents correspond to a Pn3m cubic single-phase or a Pn3m cubic phase in excess water on the binary MO/water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG, while higher OG concentrations trigger a cubic-to-lamellar phase transition. Moreover, with increasing OG concentration the initial Pn3m structure is completely converted to an Ia3d structure prior to the L, phase being formed. Upon heating this effect is reversed, resulting in an Ia3d -to- Pn3m phase transition. For some samples additional peaks were observed in the diffractograms upon heating, resulting from the metastability notoriously shown by bicontinuous cubic phases. This judgement is supported by the fact that upon cooling these peaks were absent. Remarkably, both the Ia3d and the Pn3m cubic structures could be in equilibrium with excess water in this ternary system. A comparison is made with previous results on n -dodecyl-,- d -maltoside (DM), showing that cubic phases with OG have higher thermal and compositional stability than with DM. [source]


Numerical parameter study of the thermal behaviour of a gypsum plaster board at fire temperatures

FIRE AND MATERIALS, Issue 2 2008
Luc Wullschleger
Abstract Based on a comparison between the measured and the calculated temperature evolutions within a gypsum plaster board subject to fire, a numerical parameter study regarding the material properties of gypsum at elevated temperatures has been carried out. This allowed quantifying the individual influence of different quantities and their deviations on the calculated thermal behaviour of this material. Copyright 2007 John Wiley & Sons, Ltd. [source]


Thermal properties of lightweight-framed construction components at elevated temperatures

FIRE AND MATERIALS, Issue 3 2005
Noureddine Bnichou
Abstract Fire resistance behaviour of lightweight-framed assemblies is determined by defining the thermal and structural performances of the assembly when exposed to fire. To adequately model thermal behaviour in a lightweight wood-framed assembly, thermal properties of the components of the assembly at elevated temperatures must be well defined. This paper presents results of measurements of thermal properties at elevated temperatures of construction materials commonly used to build lightweight wood-framed assemblies that were conducted at the National Research Council of Canada since 1990. The test results, in graphical form, are given as a function of temperature for thermal conductivity, specific heat, mass loss and thermal expansion/contraction for wood, gypsum and insulation. In addition, the effects of temperature on the thermal conductivity, specific heat, mass loss and thermal expansion/contraction of these materials are discussed. Finally, in addition to providing a resource of information, this paper also identifies the additional thermal property tests required to complete the matrix of information. Copyright 2005 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source]


Thermal properties of gypsum plasterboard at high temperatures

FIRE AND MATERIALS, Issue 1 2002
Geoff Thomas
Light timber frame wall and floor assemblies typically use gypsum-based boards as a lining to provide fire resistance. In order to model the thermal behaviour of such assemblies, the thermo-physical properties of gypsum plasterboard must be determined. The relevant literature and the chemistry of the two consecutive endothermic dehydration reactions that gypsum undergoes when heated are reviewed. The values determined for the thermo-physical properties are modified to create smooth enthalpy and thermal conductivity curves suitable for input into a finite element heat transfer model. These values are calibrated within a reasonable range and then validated using furnace and fire test data. The type of plasterboard used in these tests is an engineered product similar to the North American type C board. The temperature at which the second dehydration reaction occurs is altered to be consistent with later research with little apparent affect on the comparison with test results. Values for specific heat, mass loss rates and thermal conductivity for gypsum plasterboard that are suitable for use in finite element heat transfer modelling of light timber frame wall and floor assemblies are recommended. Copyright 2002 John Wiley & Sons, Ltd. [source]


Recent advances in stream and river temperature research

HYDROLOGICAL PROCESSES, Issue 7 2008
Bruce W. Webb
Abstract Research on stream and river temperatures is reviewed with particular attention being given to advances in understanding gained since 1990 and on investigations of fundamental controls on thermal behaviour, thermal heterogeneity at different spatial scales, the influence of human impacts and the nature of past and future trends. Copyright 2008 John Wiley & Sons, Ltd. [source]


Thermodynamic study of wet cooling tower performance

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2006
V. D. Papaefthimiou
Abstract An analytical model was developed to describe thermodynamically the water evaporation process inside a counter-flow wet cooling tower, where the air stream is in direct contact with the falling water, based on the implementation of the energy and mass balance between air and water stream describing thus, the rate of change of air temperature, humidity ratio, water temperature and evaporated water mass along tower height. The reliability of model predictions was ensured by comparisons made with pertinent experimental data, which were obtained from the literature. The paper elaborated the effect of atmospheric conditions, water mass flow rate and water inlet temperature on the variation of the thermodynamic properties of moist air inside the cooling tower and on its thermal performance characteristics. The analysis of the theoretical results revealed that the thermal performance of the cooling tower is sensitive to the degree of saturation of inlet air. Hence, the cooling capacity of the cooling tower increases with decreasing inlet air wet bulb temperature whereas the overall water temperature fall is curtailed with increasing water to air mass ratio. The change of inlet water temperature does not affect seriously the thermal behaviour of the cooling tower. Copyright 2005 John Wiley & Sons, Ltd. [source]


Effect of oil content and processing conditions on the thermal behaviour and physicochemical stability of oil-in-water emulsions

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2009
Megan Tippetts
Summary The destabilisation mechanism of oil-in-water (o/w) emulsions was studied as a function of oil content (20% and 40% o/w), homogenisation conditions and crystallisation temperatures (10, 5, 0, ,5 and ,10 C). A mixture of anhydrous milk fat and soya bean oil was used as the lipid phase and whey protein isolate (2 wt%) as emulsifier. Crystallisation and melting behaviours were analysed using differential scanning calorimetry. Physicochemical stability was measured with a vertical scan macroscopic analyser. Emulsions with 20% oil were found to be less stable than those with 40% oil. For 20% o/w emulsions, the crystallisation was delayed and inhibited in emulsions with smaller droplets and promoted in emulsions with larger droplets when compared with 40% o/w emulsions. Depending on the droplet sizes in the emulsion, the formation of lipid crystals (in combination with the emulsifier) either stabilises (small droplets) or destabilises (big droplets) the emulsion. [source]


Thermal ecology of Zonocerus variegatus and its effects on biocontrol using pathogens

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2000
Simon Blanford
Summary 1 Thermal behaviour of the variegated grasshopper, Zonocerus variegatus, was investigated in the humid tropical zone of southern Benin, west Africa, in the dry seasons of 1996 and 1998. In 1998, investigations included studies of a population of grasshoppers sprayed with an oil-based formulation of the entomopathogenic fungus Metarhizium anisopliae var acridum. 2 Body temperature measurements and observations of thermal behaviour both in the field and on thermal gradients in the laboratory, suggest that Z. variegatus was not an active behavioural thermoregulator. Although it did show shade-seeking behaviour at high temperatures, no overt behavioural postures or microhabitat selection associated with heat gain and elevation of body temperatures was observed. Moreover, no alterations to thermal behaviour were found in response to infection by Metarhizium. 3 Body temperatures exhibited by Z. variegatus in the field will lengthen disease incubation of M. anisopliae var acridum compared with laboratory maintained, constant temperature conditions and may have a significant impact on pathogens with a lower thermal tolerance. 4 Habitat structure appeared to be an important factor determining the extent of body temperature elevation. The effect of habitat differences on infection and growth of M. anisopliae var acridum and other entomopathogenic fungi is discussed. [source]


A RAPID METHOD OF QUANTIFYING THE RESOLUTION LIMITS OF HEAT-FLOW ESTIMATES IN BASIN MODELS

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2008
A. Beha
Deterministic forward models are commonly used to quantify the processes accompanying basin evolution. Here, we describe a workflow for the rapid calibration of palaeo heat-flow behaviour. The method determines the heat-flow history which best matches the observed data, such as vitrinite reflectance, which is used to indicate the thermal maturity of a sedimentary rock. A limiting factor in determining the heat-flow history is the ability of the algorithm used in the software for the maturity calculation to resolve information inherent in the measured data. Thermal maturation is controlled by the temperature gradient in the basin over time and is therefore greatly affected by maximum burial depth. Calibration, i.e. finding the thermal history model which best fits the observed data (e.g. vitrinite reflectance), can be a time-consuming exercise. To shorten this process, a simple pseudo-inverse model is used to convert the complex thermal behaviour obtained from a basin simulator into more simple behaviour, using a relatively simple equation. By comparing the calculated "simple" maturation trend with the observed data points using the suggested workflow, it becomes relatively straightforward to evaluate the range within which a best-fit model will be found. Reverse mapping from the simple model to the complex behaviour results in precise values for the heat-flow which can then be applied to the basin model. The goodness-of-fit between the modelled and observed data can be represented by the Mean Squared Residual (MSR) during the calibration process. This parameter shows the mean squared difference between all measured data and the respective predicted maturities. A minimum MSR value indicates the "best fit". Case studies are presented of two wells in the Horn Graben, Danish North Sea. In both wells calibrating the basin model using a constant heat-flow over time is not justified, and a more complex thermal history must be considered. The pseudo-inverse method was therefore applied iteratively to investigate more complex heat-flow histories. Neither in the observed maturity data nor in the recorded stratigraphy was there evidence for erosion which would have influenced the present-day thermal maturity pattern, and heat-flow and time were therefore the only variables investigated. The aim was to determine the simplest "best-fit" heat-flow history which could be resolved at the maximum resolution given by the measured maturity data. The conclusion was that basin models in which the predicted maturity of sedimentary rocks is calibrated solely against observed vitrinite reflectance data cannot provide information on the timing of anomalies in the heat-flow history. The pseudo inverse method, however, allowed the simplest heat-flow history that best fits the observed data to be found. [source]


Mechanistic understanding of the photochromism of a hybrid dithienylethene,naphthopyran system by NMR spectroscopy

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2007
S. Delbaere
Abstract Detailed 1H NMR kinetic investigations of the photochemical and thermal behaviour of a recently described poly-photochromic molecule including both dithienylethene and naphthopyran groups are reported. The combination of two photochromic moieties allows the selective controlled extension of the conjugated pi-electron system and the modulation of the absorption behaviour between ,380 to ,750,nm. It is shown that the two photochromic entities are coupled and do not behave independently. Copyright 2007 John Wiley & Sons, Ltd. [source]


Hyphenated techniques of thermal analysis for characterisation of soil humic substances

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 5 2003
Maria Teresa Dell'Abate
Abstract Our aim was to investigate the thermal behaviour of humic substances extracted from temperate and tropical soils by means of hyphenated techniques of thermal analysis (e. g. simultaneous thermal analysis DSC/TG coupled with mass spectrometry, MS, for the analysis of evolved gas, EGA) in order (i) to verify whether the chemical composition of isolated humic substances also reflected the differences in microbial parameters previously measured in related soil samples and (ii) to identify suitable indices of thermal stability. Our results show that the investigation of humic substances by thermal methods can provide information on soil organic matter dynamics. Differences in thermal behaviour between the two groups of soils were found. The indices of thermal stability here proposed, IR (index of thermal recalcitrance), and ID (index of thermal decomposability) clearly showed that in humic substances from tropical soils the thermally recalcitrant organic fraction dominated, whilst in temperate humic substances the opposite held. This agrees with previous results on the microbial dynamics and organic matter turnover of the respective soils and indicates that these indices of thermal stability could represent a useful tool in soil environmental quality investigations. [source]


Sunflower proteins: overview of their physicochemical, structural and functional properties

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2007
Sergio Gonzlez-Prez
Abstract There is increasing worldwide demand for proteins of both animal and plant origin. However, animal proteins are expensive in terms of both market price and environmental impact. Among alternative plant proteins, sunflower seeds are particularly interesting in view of their widespread availability in areas where soy is not or only sparsely produced. Compared with other sources of vegetable proteins, sunflower seeds have been reported to have a low content of antinutritional factors. Although the absence of these factors is important, the functionality of the protein preparations will mainly determine their applicability. This review provides detailed information about sunflower seed composition and processing, including processes to remove phenolic compounds from meals. The main part of the review concerns the structure and functionality of the two major protein fractions, helianthinin and 2S albumins. Regarding functionality, emphasis is on solubility, thermal behaviour and surface activity. Protein structure and functionality are discussed as a function of extrinsic factors such as pH, ionic strength, temperature and the presence of other seed components, particularly chlorogenic acid. In addition, sunflower proteins are compared from a structural and functional point of view with other plant proteins, particularly soy proteins. Copyright 2007 Society of Chemical Industry [source]


Fatty acid and triacylglycerol composition and thermal behaviour of fats from seeds of Brazilian Amazonian Theobroma species

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2002
M Victoria Gilabert-Escriv
Abstract Raw materials for cocoa butter substitutes, replacements or equivalents depend mostly on the unsteady supply from wild stands of plants, while there is no current supply of Neotropical origin. Seed fats from Theobroma species (T cacao, T bicolor, T grandiflorum, T obovatum, T subincanum, T speciosum, T sylvestre and T microcarpum, plus the closely related species Herrania mariae) were analysed for fatty acid and triacylglycerol composition by gas and liquid chromatography respectively, for iodine value, for melting point by open capillary tube and for solid fat content (SFC) by nuclear magnetic resonance. All Theobroma species had significantly lower palmitate levels than T cacao, except for T sylvestre and T speciosum, T microcarpum presented highly unsaturated fat (C18:2), while H mariae had high levels of arachidate. Fats from T sylvestre and T speciosum had a similar iodine value to T cacao and a higher melting point. No fat from the other species presented a similar melting profile to cocoa butter. T sylvestre and T bicolor were the most similar to T cacao but had a higher SFC at human body temperature. T sylvestre and T speciosum seed fats had more POP than cocoa butter. Fats from seeds of T speciosum, T sylvestre and T bicolor could be recommended as cocoa butter substitutes, while fats from species of the section Glossopetalum could be employed in products requiring fats with a lower melting point. 2002 Society of Chemical Industry [source]


Investigation of the Thermal Behaviour of Non-metallic Curved-Face-Width Spur Gears

LUBRICATION SCIENCE, Issue 4 2004
L. Andrei
Abstract This paper describes a curved-face-width spur gear, specially designed for manufacture from non-metallic materials. The benefits of this gear are the higher contact ratio, bending and Hertzian contact resistance, and greater tooth stiffness compared to standard spur gears. A modified geometry is proposed for the gear tooth, the height of which varies along the gear face width. Due to the reduction in tooth height, in sections away from the gear centre, lower sliding friction is expected, with consequences for the gear's thermal behaviour. The complex gear geometry makes the design of a die difficult; therefore the gears were cut on a milling machine, using a special kinematic generation process and related equipment. The tooth flank profile, an involute or near involute in sections away from the gear half-width plane, as well as the flank surface quality determined by the single-cutter tool used for gear manufacture, influence the meshing condition, and can be detrimental to the thermal behaviour of the gear. Experimental tests were carried out to examine the influence of load and speed on the temperature of the curved-face-width spur gears with modified geometry. The measured temperature of the non-standard gear is further compared with the predicted temperature of plastic standard spur gears of the same specification. [source]


Effect of eggshell powder as nucleating agent on the structure, morphology and functional properties of normal corn starch foams,

PACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2007
Yixiang Xu
Abstract Corn starch and eggshell powder (with particle sizes of 4,5m and 8,10m) composite foams were prepared by extrusion. Effects of eggshell on the structure, morphology, physical properties (unit density and expansion ratio), mechanical properties (spring index and compressibility) and thermal behaviour (thermal transition and stability) of the foams were investigated. Foam cell size decreased and cell population increased with addition of eggshell into starch matrix. The foam unit density, expansion ratio and compressibility decreased significantly (p < 0.05), while the spring index increased significantly (p < 0.05) as the eggshell content increased from 0 to 6wt%. Further increasing eggshell content to 10wt% increased the unit density and compressibility and decreased the expansion ratio and spring index. The thermal transition and stability increased with the addition of eggshell. The optimum eggshell content was 6wt% and the smaller-sized eggshell powder had a favourable effect on the functional properties of the foams. Copyright 2006 John Wiley & Sons, Ltd. [source]


Study of the thermal behaviour of alipharomatic polyesters around the glass,rubber transition region by thermomechanical analysis: the mobile and rigid amorphous fraction

POLYMER INTERNATIONAL, Issue 2 2007
George Karayannidis
Abstract The objective of this work was the study using thermomechanical analysis (TMA) of a peculiar behaviour, which was observed some years ago, around the glass,rubber transition region in some thermoplastic alipharomatic polyesters. For this purpose a series of nine alipharomatic polyesters was prepared by the two-stage melt polycondensation method in a glass batch reactor and subjected to TMA in both penetration and expansion mode. Differential scanning calorimetry (DSC) was additionally used and the results are discussed focusing mainly on the first derivative curve of TMA thermograms in the penetration mode. From this curve, which shows two distinct peaks, the first peak could be attributed to the glass transition temperature (Tg) of the mobile amorphous fraction, since the value coincides with that obtained from DSC and is due to the abrupt shrinkage of the amorphous part of the sample. The second peak (up to 40 C higher than Tg) is due most probably to the softening of the rigid amorphous fraction and the passage of the polymeric sample from the glass region to the cold crystallization region. When the sample is more crystalline than amorphous then the first peak is smaller or is completely absent. Copyright 2006 Society of Chemical Industry [source]


Synthesis and characterization of novel diimide,dinaphthols and resulting poly(urethane,imide)s

POLYMER INTERNATIONAL, Issue 9 2003
Shahram Mehdipour-Ataei
Abstract Novel diols containing imide groups were prepared via condensation of aromatic dianhydrides with 5-amino-1-naphthol. The diimide,dinaphthols prepared were characterized by conventional methods and used to synthesize new poly(urethane,imide)s (PUIs). All the polymers were characterized and their physical properties, such as solubility, solution viscosity, thermal stability, and thermal behaviour were studied. The polymers obtained showed more thermal stability than typical polyurethanes because of the presence of the imide groups. Copyright 2003 Society of Chemical Industry [source]


Thermal stability of some self-assembling hydrogen-bonded polymers and related model complexes,

POLYMER INTERNATIONAL, Issue 11 2002
Gordon Armstrong
Abstract The thermal stability of polymers is of fundamental importance both in processing and in many applications, eg, injection moulding, hot melts. As part of an investigation to determine the suitability of supramolecular polymers for novel applications in materials science, the thermal behaviour of two model compounds representing the principal classes of supramolecular polymer has been studied in some detail. p -Methoxybenzoic acid was complexed with 1,2-di(4-pyridyl)ethylene in 2:1 ratio as a model compound representing liquid,crystal association chain supramolecular polymers. It is proposed that the model compound degrades as a single species obeying first-order kinetics; the activation energy (Eact) of the degradation process was calculated to be 127,kJ,mol,1. A model ureidopyrimidinone dimer degraded in two steps, also following first order kinetics, with Eact,=,71.5,kJ,mol,1. The dimer was unaffected by annealing, suggesting that related polymers may be used at elevated temperatures. Polymer analogues of both model compounds were synthesized and their thermal behaviour was found to parallel that of the models. In light of these results, the implications for processing both supramolecular polymers are also considered. 2002 Society of Chemical Industry [source]


Electrochemical behaviour and electrochemical polymerization of fluoro-substituted anilines

POLYMER INTERNATIONAL, Issue 8 2002
Atilla Cihaner
Abstract The electrochemical behaviour of three fluoro-substituted aniline monomers, 2-fluoroaniline (2FAN), 3-fluoroaniline (3FAN) and 4-fluoroaniline (4FAN), was investigated in aqueous acidic and organic media by means of cyclic voltammetry (CV) studies. Constant potential electrolysis (CPE) of the monomers in acetonitrile,water mixture (1:1 by volume) using NaClO4 as supporting electrolyte yielded soluble polymers. The mechanism of electrochemical polymerization was investigated using in situ electron spin resonance (ESR) and in situ UV,VIS spectroscopic techniques for one of the monomers (4FAN). Both CV and in situ UV,VIS measurements indicated that the polymers obtained are in the emeraldine base form. In situ ESR studies indicated that electrochemical polymerization involves a radical-cation as an intermediate. Characterization of polymer products have been carried out using FTIR and NMR spectroscopic techniques, and thermal behaviour was studied using differential scanning calorimetry (DSC). It was found that conductivity can be imparted to as-synthesized polyfluoroanilines via iodine doping. 2002 Society of Chemical Industry [source]


3,3,6,6,9,9-Hexaethyl-1,2,4,5,7,8-hexaoxacyclononane at 296 K

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009
Jorge Cerna
The title molecule (diethyl ketone triperoxide, DEKTP), C15H30O6, is a cyclic triperoxide closely related to triacetone triperoxide (TATP), one of the most unstable explosives known. However, the stability of DEKTP is ca 20,50 times greater than that of TATP. DEKTP crystallizes with two molecules in the asymmetric unit, with virtually identical geometry. The cyclononane core is stabilized in a twisted boat,chair conformation (approximate D3 symmetry), very close to that previously described for TATP. The explanation for the safe thermal behaviour of DEKTP compared with TATP should thus not be sought in the molecular dimensions, but rather in the thermal decomposition kinetics. [source]