Thermal and hydrolytic degradation of electrospun fish gelatin membranes

The thermal and hydrolytic degradation of electrospun gelatin membranes cross-linked with glutaraldehyde in vapor phase has been studied. In vitro degradation of gelatin membranes was evaluated in phosphate buffer saline solution at 37 °C. After 15 days under these conditions, a weight loss of 68% was observed, attributed to solvation and depolymerization of the main polymeric chains. Thermal degradation kinetics of the gelatin raw material and as-spun electrospun membranes showed that the electrospinning processing conditions do not influence polymer degradation. However, for cross-linked samples a decrease in the activation energy was observed, associated with the effect of glutaraldehyde cross-linking reaction in the inter- and intra-molecular hydrogen bonds of the protein. It is also shown that the electrospinning process does not affect the formation of the helical structure of gelatin chains.     

Thermal behaviour of lignins extracted from different raw materials

The thermal degradation of lignins extracted from bagasse, rice straw, corn stalk and cotton stalk, have been investigated using the techniques of thermogravimetric analysis (TG) and differential thermal analysis (DTA), between room temperature and 600°C. The actual pyrolysis of all samples starts above 200°C and is slow. The results calculated from TG curves indicated that the activation energy, Efor thermal degradation for different lignins lies in the range 7.949–8.087 kJ mol^?1. The DTA of all studied lignins showed an endothermic tendency around 100°C. In the active pyrolysis temperature range, thermal degradation occurred via two exothermic process at about 320 and 480°C, and a large endothermic pyrolysis region between 375 and 450°C. The first exothermic peak represents the main oxidation and decomposition reaction, the endothermic effect represents completion of the decomposition and the final exothermic peak represents charring.     

Thermal properties of fats extracted from powdered baby formulas

The aim of this research was to analyse composition, fatty acids distribution and oxidative stability of fats extracted from four samples of baby formulas. The fats were oxidized in a differential scanning calorimeter (DSC) under polythermal (dynamic) conditions and at normal pressure. The DSC experiments were carried out in an oxygen flow atmosphere using different, linearly programmed, heating rates in the range of 4?C12.5?°C/min. The extrapolated onset temperatures were determined using DSC exotherms and used for the assessment of the thermal oxidative stabilities of the samples. Activation energies (E _a), pre-exponential factors (Z) and reaction rate constants (k) for oil oxidation under DSC conditions were calculated using the Ozawa?CFlynn?CWall method and the Arrhenius equation. The melting characteristics of the studied fats were obtained. The fats extracted from the agglomerated samples with higher onset temperatures were more stable than the fats extracted from the initial samples of baby formulas.     

Optical characteristics of an afterglow extracted from an inductively coupled plasma

An inductively coupled plasma is extracted into a quartz vacuum chamber through an orifice to observe optical characteristics of the extracted afterglow. The Mach disk, the barrel shock and the zone of silence, which are familiar in supersonic molecular beam experiments with neutral gases, are clearly observed. Axial profiles of the emission of various lines are measured with a photodiode array spectrometer. Intensities of ionic lines as well as atomic lines are stronger at the Mach disk than in the zone of silence. The location of the Mach disk with varying chamber presure is in conformity with an experimental equation obtained in supersonic molecular beam experiments.     

Thermal analysis of bitumens from black coal,extracted successively with different solvents

A successive extraction of bitumes from black coal was carried out using the following solvents: petroleum ether, petroleumether-benzene (11), benzene, benzene-ethyl ether (11), ethyl ether, ethyl ether ethanole (11), ethanol. These extract organic products as follows: 0.06, 0.16, 0.11, 0.21, 0.07, 0.29 and 0.70% respectively. The obtained by the above mentioned solvents chujniuds were compounds to the thermal and IR-spectral analysis.

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Zusammenfassung Mittels folgender Lösungsmittel wurde eine sukzessive Extraktion von Bitumen aus Steinkohle durchgeführt: Petrolether, Petrolether-Benzol (11), Benzol, Benzol-Ethylether (11), Ethylether, Ethylether-Ethanol (11), Ethanol. In dieser Reihenfolge konnten organische Produkte zu 0.06, 0.16, 0.11, 0.21, 0.07, 0.29 bzw. 0.70 % extrahiert werden. Die durch aufgeführte Lösungsmittel erhaltenen Verbindungen wurden einer Thermound einer IR-Analyse unterzogen.

     

Thermal properties of tannin extracted from Anacardium occidentale L. using TGA and FT-IR spectroscopy

The chemical nature of the polyphenols of cashew kernel testa has been determined. Testa contains tannins, which present large molecular complexity and has an ancient use as tanning agents. The use of tannins extracted from cashew testa, considered in many places as a waste, grants an extra value to the cashew. In this work we have analysed through high performance liquid chromatography, infrared spectroscopy (FT-IR) and thermo gravimetric analysis the average molecular weight, main functional groups and thermal properties of tannins extracted from Anacardium occidentale L. The results of these analyses are compared with the commercial grade tannic acid. The FT-IR spectra showed bands characteristic of C = C, C–C and OH bonds. This important bioactive compound present in the cashew nut kernel testa was suggested as an interesting economical source of antioxidants for use in the food and nutraceutical industry.     

Collagen-based scaffolds enriched with glycosaminoglycans isolated from skin of Salmo salar fish

In this study both collagen and glycosaminoglycans were isolated from biodegradable waste. Namely collagen was isolated from rat tail tendons and glycosaminoglycans (GAGs) from fish skin. Porous materials were then obtained based on the isolated collagen with 1 or 5% addition of GAGs by freeze-drying process. The scaffolds were studied by infrared spectroscopy, mechanical testing and examined for the porosity and density. The scaffolds structure was observed by scanning electron microscope. The adhesion and proliferation of human osteosarcoma SaOS-2 cells was examined on prepared scaffolds to assess their biocompability.The results showed that the addition of glycosaminoglycans improves the properties of collagen-based scaffolds. Mechanical strength was increased by GAGs addition as well as the porosity of studied materials. Each scaffold with and without GAGs displayed porous structure with interconnected regular shaped pores. The attachment of cells was better for pure collagen scaffold, however, GAGs additive promoted the cells proliferation on the scaffold.     

Thermal decomposition characteristics of humus horizons from culbin forest

Differential thermal analysis in an oxygen atmosphere and pyrolysis in vacuo combined with mass spectrometry have been used to follow the transformations occurring during the humification of vegetation. Two processes are indicated, one, apparently enhanced by liming consisting of oxidative degradation and the other corresponding to degradation of organic components with high thermal dissociation energies. At the base of some profiles the humus has characteristics close to those of translocated humus in freely drained soils.     

Chemical and physicochemical characteristics of humic acids extracted from compost, soil and amended soil

In order to gain understanding about how “HA-like substances” from organic amendments may change some properties in the soil solution, the knowledge of chemical and physicochemical characteristics (charge development, acid–base behavior and heterogeneity) should be known.

The aim of this research were (i) to study the elemental and functional composition, (ii) to determine charge behavior, acid–base properties (apparent dissociation constant and buffer capacity) and (iii) to evaluate heterogeneity of humic acids (HA) isolated from municipal solid waste compost (MWC) and from the corresponding MWC-amended soil, in comparison to those of the unamended soil HA using potentiometric titration and differential scanning potentiometry (DSP).

Potentiometric titration and the first derivative of −Q versus pH (negative charge development versus pH) curves could be used to determine proton-affinity distribution and the chemical heterogeneity of the HA as well as the average pK_app and buffer capacity in a wide range of pH.

Differential scanning potentiometry allows determination of the pK_app values in a narrower range of pH than potentiometric titrations and is another simple methodology to study acid–base behavior of HA.

DSP allows us to determine seven different pK_app values for HA-S and HA-E and four different pK_app for HA-C. Each one of these values corresponds to known acidic groups that can be present in the macromolecule of HA.     

Preparation of rapidly curable hydrogels from gelatin and poly (carboxylic acid) and their adhesion to skin

Papidly curable hydrogels were prepared through chemical crosslinking of gelatin with poly(carboxylic acid)s including poly (L-glutamic acid) (PLGA), hyaluronic acid (HA), and poly (acrylic acid) (PAA) by use of water-soluble carbodiimide (WSC). The effects of the nature of added poly (carboxylic acid)s on gelation of mixed gelatinpoly (carboxylic acid) aqueous solutions and adhesion of the resulting hydrogels to the mouse skin were evaluated. The addition of poly (carboxylic acid) s reduced the gelation time of gelatin aqueous solutions except for HA. Mixed gelatin-PLGA solutions were cured more rapidly than other mixed solutions and the gelation time was shortened with the increasing PLGA molecular weight. The resulting gelatin-PLGA hydrogels exhibited stronger adhesion to the mouse skin than gelatin-HA and gelatin-PAA hydrogels. The bonding strength increased with the increase in PLGA molecular weight up to 83,000 and thereafter decreased. The longer gelation time and lower adhesion of the gelatin-PAA hydrogels than the gelatin-PLGA hydrogels seem to be due to poorer compatibility of gelatin with PAA than with PLGA. The mixed gelatin-PLGA solution underwent phase separation when the concentration and molecular weight of PLGA became higher than a threshold. The insignificant or suppressive effect of HA addition might be ascribed to the HA-WSC reaction which was the least effective in hydrogel formation.     

Thermal and vibrational characterization of human skin

For a better understanding of the molecular and organizational changes in human dermis, biophysical methods were tested. The aim of this study was to find suitable and reproducible biomarkers for further clinical studies on intrinsic and extrinsic aging of dermis. Thermoporometry, hydric organization and thermal transitions of fresh and frozen skins were determined by differential scanning calorimetry (DSC). Fourier transform infrared spectroscopy (FTIR) was used to identify the absorption bands of the dermis especially in the 1800–1000 cm^?1 zone and to discriminate between the different secondary structures of proteins. A widening of the pore size distribution is evidenced with freezing, but there is no significant difference between the hydric organization and the endothermic collagen denaturation of fresh and frozen skins. The global FTIR spectra and the second derivative spectra in the scanned zone are also identical in fresh and frozen dermis, validating the storage protocol. DSC and FTIR are well-suited techniques to characterize human skin, giving accurate results with high reproducibility. The acquisition of thermal and vibrational biomarkers of the skin at the mesoscale and nanoscale contributes to its better knowledge and is promising for further studies on skin aging.     

Thermal transitions of gelatin evaluated using DSC sample pans of various seal integrities

Differential scanning calorimetry (DSC) has become a popular tool to investigate thermal transitions in food ingredients such as gelatin. Upon heating commercial gelatin samples beyond glass transition (T _g) and melting (T _m) temperatures, a relatively large endothermic transition (T _i) can be observed. We have observed that both the peak temperature and the enthalpy of the T _i transition are influenced by the integrity of the seal of the DSC pans used for the analysis. This study shows that escape of moisture from the DSC pan appears to be responsible for this effect. The effect of different types of DSC pans, as well as technique of sealing them on the T _i transition were evaluated using DSC, SDT, and TG–MS.     

Thermal characteristics of bitumen pyrolysis

The pyrolysis behavior of bitumen was investigated using a thermogravimetric analyzer–mass spectrometer system (TG–MS) and a differential scanning calorimeter (DSC) as well as a pyrolysis-gas chromatograph/mass spectrometer system (Py-GC/MS). TG results showed that there were three stages of weight loss during pyrolysis—less than 110, 110–380, and 380–600 °C. Using distributed activation energy model, the average activation energy of the thermal decomposition of bitumen was calculated at 79 kJ mol⁻¹. The evolved gas from the pyrolysis showed that organic species, such as alkane and alkene fragments had a peak maximum temperature of 130 and 480 °C, respectively. Benzene, toluene, and styrene released at 100 and 420 °C. Most of the inorganic compounds, such as H₂, H₂S, COS, and SO₂, released at about 380 °C while the CO₂ had the maximum temperature peaks at 400 and 540 °C, respectively. FTIR spectra were taken of the residues of the different stages, and the results showed that the C–H bond intensity decreased dramatically at 380 °C. Py-GC/MS confirmed the composition of the evolved gas. The DSC revealed the endothermic nature of the bitumen pyrolysis.     

Stability of anthocyanins extracted from grape skins

Summary The extractability and stability of anthocyanins from the skins ofVitis vinifera were determined at different pH values. Anthocyanins were extracted using acetone, partitioned with chloroform and pre-purified by solid-phase extraction (SPE). They were analysed by RP-HPLC, and the kinetic parameters of decomposition were calculated. The total monomeric anthocyanin content was determined by spectrophotometry. Anthocianins were well separated by RP-HPLC. The efficiency of extraction depended strongly on the pH of the extracting agent and on the character of the pigment to be extracted. The amount of anthocyanins decreased with increasing duration of storage, more so at elevated temperatures. Presented at Balaton Symposium '01 on High-Performance Separation Methods Siófok, Hungary, September 2–4, 2001.     

Thermal characteristics of synthetic sodium zeolites prepared with silica from rice-husk ash

The differential thermal analysis and thermogravimetric data on the synthetic sodium zeolite species NaX, P _c , HS, Z-21 and analcime, prepared with silica from rice-husk ash, are presented. The DTA curves revealed the presence of an initial endotherm for dehydration, followed by an exotherm at around 800 to 850°, representing the structural change and dissociation of all these species, except in the case of zeolite Z-21. For the latter, the initial endotherm was followed by an endotherm in the 900° region. The structural changes inferred on the basis of the DTA curves were confirmed by X-ray diffraction analysis.

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Zusammenfassung Differentialthermoanalytische und thermogravimetrische Daten von den synthetischen, unter Verwendung von Reisschalenasche als Siliciumdioxidquelle hergestellten Na-Zeolithen NaX, P _c , HS, Z-21 und Analcim werden angegeben. Die DTA-Kurven zeigen anfangs einen der Dehydratisierung zuzuschreibenden endothermen Peak, dem bei 800–850° ein exothermer folgt, der auf den Zusammenbruch der Zeolithstruktur zurückzuführen ist. Nur im Falle von Z-21 tritt dieser exotherme Peak erst bei 900° auf. Die mittels DTA festgestellten strukturellen Veränderungen wurden röntgendiffraktometrisch verifiziert.

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Study of the composition and gas-phase release characteristics of salt material extracted from MSW ash particles using STA

The ash material generated from the MSW incineration contains large amounts of alkali metals, heavy metals, chlorine and sulfur mainly deposited as inorganic salts and/or oxides on the surface of the Si-rich ash particles. In this work, the composition and gas-phase release characteristics of salt material extracted from MSW ash particles using a six-stage leaching process is studied using simultaneous thermal analysis (STA). The produced results provide useful information regarding the composition of the salt material and its melting behavior that is considered to play an important role to deposition and corrosion problems at MSW incinerators. The results may be used to model the deposition process and to the better understanding of the corrosion process during MSW incineration.     

Thermal decomposition of the solvent extracted molybdenum (VI) complexes from hydrochloric acid solutions with trioctylamine and trioctylmethylammonium chloride

The complexes of molybdenum(VI) with trioctylamine (TOA, R₃N) and trioctyl methylammonium chloride (TOMAC, R₃R'NCl) were prepared by drying in vacuo the organic solutions for the extraction of molybdenum(VI) from hydrochloric acid solutions at low and higher acidities, respectively, by TOA and TOMAC in benzene. The resulting complexes were examined by thermal analysis (TG and DTA) in air and under the atmosphere of nitrogen, and their thermally decomposed products such as volatile matters and residues by gas chlomatography, X-ray diffraction study and infrared spectrophotometry. It was found that their complexes decompose thermally to MoO₃ by cracking of alkyl groups combined with molybdenum(VI) ion. Accordingly the thermal decomposition process of those complexes is discussed and the probable structure of the complexes is proposed on the basis of the results obtained.

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Zusammenfassung Komplexe von Molybdän(VI) mit Trioktylamin (TOA, R₃N) und Trioktylmethylammoniumchlorid (TOMAC, R₃R'NCl) wurden hergestellt, mittels TG und DTA in Luft und in Stickstoffatmosphäre untersucht. Die thermischen Zersetzungsprodukte der Komplexe (flüchtige Substanzen und Rückstände) wurden mittels Gaschromatographie, Röntgendiffraktion und IR-Spektroskopie untersucht. Es wurde gezeigt, daß die Komplexe thermisch zu MoO₃ zerfallen, indem die an das Molybdän(VI)-Ion gebundenen Alkylgruppen abgekrackt werden. Die Ergebnisse der thermischen Zersetzungsprozesse wird diskutiert und auf der Basis der erhaltenen Ergebnisse die wahrscheinliche Struktur der Komplexe dargelegt.

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Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60^th birthday

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The author wishes to thank Dr. H. Watanabe and Mr. T. Takahashi for assistance with experimental work, and also the Koei Chemical Co., Ltd. for samples of TOA and TOMAC.     

Thermal characteristics of Cu-based oxygen carriers

Chemical looping combustion (CLC) is a novel combustion technology with the capability for segregation of exhaust products (i.e., carbon dioxide/H₂O or N₂/O₂). The combustion is performed in two interconnected reactors with a solid oxygen carrier circulating between them, transferring oxygen from the air to the fuel. The feasibility of a successful CLC system depends on the selection of an appropriate oxygen carrier. Cu-based oxygen carriers are good oxygen carriers due to high reactivity. However, it faces low melting point, agglomeration problems in fluidized bed. In this study, a circular reduction?Coxidation reaction simulated to the cyclic operation of the Cu-based oxygen carrier was conducted on the thermogravimetric analyzer (TG). The thermal behaviors of the potential Cu-based oxygen carrier were investigated by using an X-ray diffraction (XRD), scanning electron microscope (SEM), and surface analyzer. Multiple TG results show that the weight loss was 3.4%, indicating that the loading CuO amount was 17%. Moreover, the weight loss and weight gain was equal during 73 redox cycles, suggesting the good thermal stability of the oxygen carrier. The conversion rate of reduction and oxidation for each redox cycle remained constant even after 73 redox cycles. XRD results show the new phase formation of CuAl₂O₄ during redox cycles, which promotes the thermal stabilization of the oxygen carrier. The surface area of the oxygen carrier decreased from 105 to 13?m^2?g^?1 after 73 redox cycles and the particle size distribution shifted from 5?C15?nm to 15?C30?nm, suggesting that the micorpores were blocked or collapsed. However, the reactivity of the oxygen carrier didn??t decrease. SEM results show that CuO was evenly distributed on the surface of Al₂O₃ after 73 redox cycles. Overall, these results suggested that the Cu-based oxygen carrier was ready for fluidized bed tests.     

Structure of starches extracted from near-isogenic wheat lines

High-sensitivity differential scanning calorimetry (HSDSC) and small-angle X-ray scattering (SAXS) were used to investigate the structural characteristics of starch granules with different amylose content extracted from near-isogenic wheat lines with different combinations of active granule-bound starch synthase (GBSS I) isoforms. Paracrystalline diffraction model, ‘two-state’ model of starch melting and other physico-chemical approaches were used to estimate the sizes of amylopectin clusters, the thicknesses of crystalline lamellae and the structure of amylopectin defects for investigated wheat starches. The joint analysis of SAXS and DSC data has shown that the size of amylopectin cluster, the thickness of crystalline lamellae and the structure of amylopectin defects do not depend on the differences in combinations of active GBSS I isozymes. The data obtained supposed that the amylopectin cluster size and the thickness of crystalline lamellae are, generally, the universal structural parameters for wheat starches. Additionally, the data obtained suggest that increase of amylose content is accompanied by accumulation of both amylose tie-chains, located as defects in crystalline lamellae, and amylose chains oriented transversely to the lamella stack within amorphous lamellae. Disordered ends of amylopectin double helices and/or pre-existing double helices not participating in formation of crystals are considered as amylopectin defects arranged in crystalline lamellae. The relationship between structure of wheat starches extracted from near-isogenic lines and their thermodynamic properties was recognized.