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1.
The TG, DTG and DSC methods were used for investigation of the thermo-oxidative degradation in static air atmosphere and oxygen
flow of some sorts of lime tree wood (recent lime tree woods with different preparations, old lime tree woods extracted from
some Romanian historical and/or cultural objects). At the progressive heating in the mentioned atmospheres, all the investigated
materials exhibit three successive processes, associated with dehydration and two complex thermo-oxidative processes. Each
analyzed material has a characteristic thermogram (TG, DTG and/or DSC curve) that can be considered a material “fingerprint”.
It was pointed out that the following non-isothermal parameters can be used for distinction between a new and old lime tree
wood: mass loss in the first process of thermo-oxidation, ratio between the mass losses in the first and the second processes
of thermo-oxidation, the maximum rate of the first process of thermo-oxidation. Consequently, the certification of a patrimonial
object manufactured from lime tree wood could be performed by applying the thermal analysis methods. 相似文献
2.
The thermo-oxidative degradation of an epoxy resin obtained by curing of an industrially produced DGEBA mixture with 4,4′-methylene-dianiline (MDA) and used as electric insulator has been investigated by TG + DTG + DSC simultaneous analyses performed in static air atmosphere, at five heating rates. TG, DTG and DSC curves showed that, in the temperature range 25-900 °C, a glass transition followed by three thermo-oxidative processes occur. The processing of the non-isothermal data corresponding to the first process of thermo-oxidation was performed by using Netzsch Thermokinetics - A Software Module for Kinetic Analysis. The dependence of the activation energy, evaluated by isoconversional methods, on the conversion degree and the relative high standard deviations of this quantity show that the investigated process is a complex one. The mechanism and the corresponding kinetic parameters were determined by multivariate non-linear regression program and checked for quasi-isothermal data. It was pointed out that the first process of thermo-oxidation of the investigated resin consists in four steps, each step having a specific kinetic triplet. The obtained results were used for prediction of the thermal lifetime of the material corresponding to some temperatures of use and the end point criterion 5% and 10% mass loss. 相似文献
3.
Budrugeac P. Trandafir Viorica Albu Madalina Georgiana 《Journal of Thermal Analysis and Calorimetry》2003,72(2):581-585
The methods of the thermal analysis (TG, DTG and DTA) were used in order to investigate the effect of the hydration degree
on the thermal behaviour of some collageneous matrices. It was pointed out that the degradation of hydrated collagen in the
temperature range 20-400°C occurs through two successive processes accompanied by mass losses. The first process, consisting
in the collagen dehydration, is endothermic and takes place in the temperature range ≈25 - ≈125°C. The second process is exothermic
and consists in the decomposition and/or thermo-oxidation of dry collagen. The thermal parameters of both processes depend
on the hydration degree of collagen. The observed dependencies show that the hydrothermal and thermo-oxidative stability of
collagen are strongly correlated with its water content.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Thermal degradation of collagen-based materials that are supports of cultural and historical objects
Budrugeac P. Miu L. Bocu V. Wortman F. J. Popescu C. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):1057-1064
The thermal analysis methods (TG, DTG and DTA) were used for the investigation of the thermal degradation of some recent manufactured
tanned leathers, leathers that are supports of cultural or historical objects (leather from book covers (XVII-XIX centuries);
leather from an Austrian belt (Franz Joseph period), Cordoba leather (XVII century), lining leathers), recent and patrimonial
parchments and recent extracted collagen (sorts of collagen obtained from bovine leather at different pH-values, bovine collagen
with different hydration degree). At progressive heating, all investigated materials exhibit two main successive processes,
associated with the dehydration and thermo-oxidative degradation. Each analyzed material has a characteristic thermal analysis
curve (TG, DTG and DTA) that can be considered a material 'fingerprint'. This result suggests the use of the thermal analysis
methods to identify of leathers from which the patrimonial objects are manufactured. The rate of thermo-oxidation of recent
manufactured tanned leathers is substantially higher than the rate of the same process corresponding to naturally aged leathers
that exhibit values of the thermo-oxidation rate appropriate to those obtained for parchments and collagens. The rate of thermo-oxidation
of leather can thus be used as a criterion to distinguish between recent manufactured leather and patrimonial one.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
P. Budrugeac 《Journal of Thermal Analysis and Calorimetry》2009,97(2):443-451
The thermo-oxidative degradation of a parchment recent manufactured from a goat skin has been investigated by TG/DTG, DSC
simultaneous analysis performed in static air atmosphere, at six heating rates in the range 3–15 K min−1. At the progressive heating in air atmosphere, the investigated material exhibits three main successive processes occurring
with formation of volatile products, namely the dehydration followed by two thermo-oxidative processes. The processing of
the non-isothermal data corresponding to the first process of thermo-oxidation was performed by using Netzsch Thermokinetics—a
Software Module for Kinetic Analysis. The dependence of activation energy, evaluated by isoconversional methods suggested
by Friedman, and Ozawa, Flynn and Wall, on the conversion degree and the relative high standard deviations of this quantity
show that the investigated process is a complex one. The mechanism and the corresponding kinetic parameters were determined
by Multivariate Non-linear Regression program. Three mechanisms, one consisting in four successive steps and two others in
five successive steps, exhibit the best F-test Fit Quality for TG curves. It was also used the previously suggested criterion, according to which the most probable
process mechanism correspond to the best agreement between E
FR
= E
FR
(α) (E
FR
is the activation energy evaluated by isoconversional method suggested by Friedman; α is the conversion degree) obtained
from non-isothermal experimental data and activation energy values, E
iso
, obtained by applying the differential method to isothermal data simulated using non-isothermal kinetic parameters. According
to this last criterion, the most probable mechanism of parchment oxidation consists in four successive steps. The contribution
of the thermo-oxidation process in the parchment damage by natural aging is discussed. 相似文献
6.
P. Budrugeac Carmen Racles V. Cozan Maria Cazacu 《Journal of Thermal Analysis and Calorimetry》2008,92(1):263-269
Thermal and thermo-oxidative stability of some poly(siloxane-azomethine)s obtaining starting from bis(formyl-p-phenoxymethyl)tetramethyldisiloxane and different organic diamines have been investigated by TG+DTG+DSC simultaneous analyses
performed in argon flow and air static atmosphere, respectively. TG, DTG and DSC curves of each polymer showed three or four
successive degradation steps at different temperatures according to the composition of the sample and the gaseous atmosphere
in which the thermal analysis was performed. For each process, the following parameters were evaluated: total mass loss, temperature
corresponding to the maximum reaction rate, maximum reaction rate, temperature corresponding to certain mass loss. In order
to determine the thermal and thermo-oxidative stabilities of investigated polymers, the following values were determined:
T
x% — temperature corresponding to x% mass loss, and %Δm
T — mass loss at a given temperature T. The obtained orders of stability were correlated with the structure of investigated polymers. 相似文献
7.
Identification of collagen-based materials that are supports of cultural and historical objects 总被引:1,自引:0,他引:1
Budrugeac P. Miu L. Popescu C. Wortmann F.-J. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):975-985
The TG, DTG, DTA methods were used for investigation of the thermal degradation in static air atmosphere of some collagen-based
materials (some sorts of collagen, recent manufactured parchments and tanned leathers, patrimonial (historical) leathers).
At the progressive heating, all investigated materials exhibit two main successive processes, associated with the dehydration
and thermo-oxidative degradation. The patrimonial leathers were divided in two groups, namely: a group containing the majority
of the analyzed materials, for which the rates of the thermo-oxidation process are substantially lower than those corresponding
to the recent manufactured leathers, and a group for which the rates of thermo-oxidation process are closed to those corresponding
to the recent manufactured leathers. Consequently, if by the thermal analysis in air atmosphere of a leather sample, a value
of the rate of the thermo-oxidation process smaller than that corresponding to the recent manufactured leathers is obtained,
then the analyzed leather is a patrimonial one. The reciprocal statement of this qualitative criterion for distinction between
recent manufactured leather and patrimonial leather is not valid. The DSC analyses of collagen-based materials were performed
in air (DSC(air)) and in water (DSC(water)). The denaturation process takes place at lower temperatures in water than in air.
Unlike recent manufactured leathers and parchments, each patrimonial leather exhibits on DSC(water) plot 2-4 peaks. Consequently,
the number of peaks from DSC(water) curve could be another qualitative criterion for distinction between a recently manufactured
leather and a patrimonial leather.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Three types of acrylonitrile copolymers (acrylonitrile-styrene-butadiene copolymer (ABS1), acrylonitrile-styrene random copolymer (SAN2) and acrylonitrile-butadiene random copolymer (BAN3) were studied by thermogravimetry (TG/DTG4) and by pyrolysis in a semi-batch process at 450 °C in order to find structure–thermal behaviour relationships. The overlapped thermo-oxidative degradation processes were separated and the corresponding kinetic parameters were calculated. The TG/DTG studies have evidenced that the styrene-acrylonitrile interactions stabilize the nitrile groups reacting by chain scission rather than cyclization and destabilize the styrene units. Also, the cyclization of the acrylonitrile units in ABS is favoured by interactions with the styrene and butadiene units. The pyrolysis behaviour evidenced that the styrene-acrylonitrile interactions in SAN and ABS lead to the formation of 4-phenylbutyronitrile as the most important decomposition compound. ABS shows similar composition of the degradation oil with SAN copolymer therefore in the ABS the styrene-butadiene interactions are less important than those between styrene and acrylonitrile units. 相似文献
9.
Shashank Vummidi Lakshman Edward L. Dreizin Mirko Schoenitz 《Journal of Thermal Analysis and Calorimetry》2014,116(1):141-149
The scope of this work was the assessment of thermo-oxidative deterioration, hydrothermal stability, and crystalline zone deterioration of some bookbinding leathers from some religious books published in XVIII century stored in Romanian libraries. In this purpose, the following thermal analysis methods were employed: thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermo-oxidative damage of investigated leathers was characterized by the rate of the first thermo-oxidation process put in evidence in TG/DTG curves recorded in static air atmosphere. The hydrothermal stability was characterized by shrinkage temperature determined by DSC analysis of leathers in water excess. The damage of the crystalline zone of leathers was determined by DSC in nitrogen flow and DMA analyses. The qualitative damage for each leather and each kind of degradation was evaluated using the criteria resulted by thermal analysis of a large number of collagen-based materials (pure collagens, new and old parchments and leathers). The obtained results could be used for finding the best possible methods for preservation and/or restoration of the investigated bookbinding leathers. 相似文献
10.
Adriana Fuliaş Titus Vlase Gabriela Vlase Nicolae Doca 《Journal of Thermal Analysis and Calorimetry》2010,99(3):987-992
The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate,
starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min−1. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min−1. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears.
These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic
analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates:
5, 7, 10 and 12 °C min−1. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a
nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion
dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very
near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C). 相似文献
11.
Cheila G. Mothé Michelle G. Mothé Alan T. Riga Kenneth S. Alexander 《Journal of Thermal Analysis and Calorimetry》2011,106(3):637-642
Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative
thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration
of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds
of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were
similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties
were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited
by human skins’ samples, however, they presented different residue and constituents’ content. 相似文献
12.
Cs. Várhelyi Jr. G. Pokol Á. Gömöry A. Gănescu P. Sohár G. Liptay Cs. Várhelyi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):701-707
Fourteen
chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2:
various α-dioximes) have been studied by means of FTIR, NMR, MS data
and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic
parameters of the thermal decomposition of the complexes were also calculated
using Zsakó’s ‘nomogram method’. The mechanism of
the decomposition processes was characterised on the basis of mass spectra. 相似文献
13.
Mothé Filho H. F. Gonçalves M. L. A. Mothé C. G. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):381-389
Thermal degradation of granite and marble industry reject (GMIR), a red clay (RC)and their composites were studied by non-isothermal
thermogravimetry (TG/DTG) in nitrogen atmosphere, differential thermal analysis (DTA) and derivative thermogravimetry(DTG)
in air atmosphere. Measurements were made in the temperature range of 25–1000,25–1200 and 25–1400°C. The kinetic parameters
were determined by Flynn–Wall and Kissinger's methods. The results indicate the absent dominance of one mechanism of reaction,
and the composites show smaller values of kinetic parameters than GMIR or RC.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Zhou Bao-xue Zhong Wei-ke Zou Li-zhuang Wang Xiao-ling 《Journal of Thermal Analysis and Calorimetry》1996,47(3):815-820
Barium(II) tetraphenylborate, Ba(Bph4))2·4H2O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect. 相似文献
15.
Nicoleta Birta N. Doca Gabriela Vlase T. Vlase 《Journal of Thermal Analysis and Calorimetry》2008,92(2):635-638
The thermal behavior of sorbitol was studied under non-isothermal conditions, in both air and nitrogen atmosphere. The main
process is a deep and continuous dehydration.
For the kinetic analysis, the TG/DTG data obtained at five heating rates were processed by three different methods: Friedman,
Budrugeac-Segal and non-parametric kinetic, respectively. This analysis indicates a complex reaction with a preponderant chemical
process, described by a conversion function (1−α)3/2, accompanied by diffusion. 相似文献
16.
H. Sis 《Journal of Thermal Analysis and Calorimetry》2007,88(3):863-870
In this research, the relationship between particle size and combustion kinetics and combustion properties of lignite samples
was examined by utilizing the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. The lignite samples
separated into different size fractions were subjected to non-isothermal thermogravimetric analysis between ambient and 900°C
in the presence of 50 mL min−1 air flow rate. Activation energy (E) and Arrhenius constant (A
r) of combustion reaction of each size was evaluated by applying Arrhenius kinetic model to the resulting data. Combustion
properties of the samples were interpreted by careful examination of the curves. The apparent activation energies in major
combustion region were calculated as 41.03 and 53.11 kJ mol−1 for the largest size (−2360+2000 μm) and the finest size (−38 μm), respectively. 相似文献
17.
Adriana Fulias Gabriela Vlase Carmen Grigorie Ionuţ Ledeţi Paul Albu Mihai Bilanin Titus Vlase 《Journal of Thermal Analysis and Calorimetry》2013,113(1):265-271
The analysed substances, procaine and benzocaine, are two anaesthetic agents currently being administered in tablet form, also in the topical (cream, gel, balm) and injectable dosage forms. The TG/DTG/DTA curves were obtained in air at different heating rates. For determination of the heat effects, the DTA curves (in μV) were changed with the heat flow curves (in mW), so that the peak area corresponds to an energy in J g?1 or kJ mol?1. The non-isothermal experiments are preformed to investigate the thermal degradation process of these active substances, both as a solid and are performed in a dynamic atmosphere of air at different heating rates, by heating from room temperature to 500 °C. The kinetic analysis was performed using the TG data in air for the first step of substance’s decomposition at four heating rates: 7, 10, 12 and 15 °C min?1. The data were processed according to an appropriate strategy to the following kinetic methods: Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and NPK, to obtain realistic kinetic parameters, even if the decomposition process is a complex one. Thermal analysis was supplemented using Fourier Transform infrared spectroscopy coupled with the TG device to identify the anaesthetics with any products which may have formed (EGA—the evolved gas analysis). 相似文献
18.
The TG and DTA of a new series of Mn(II) and Cu(II) complexes with a number of newly prepared bisazo-dianil ligands were studied
in the temperature range (20-700°C). The TG and DTG curves display to main steps, the first one within the temperature range
(25-330°C) correspond to the elimination of water or and ethanol from the complexes. The second step within the range (350-625°C)
is due to the decomposition of the complexes yielding the metal oxides as the final product. The rate constants of the dehydration
and decomposition reactions were determined, from which some kinetic parameters were evaluated. The DTA curves show that the
dehydration of the metal complexes is an endothermic reaction. In all cases the anhydrous metal complexes undergo exothermic
decomposition reactions to give the metal oxide. The thermodynamic parameters (ΔE, ΔH, ΔS, ΔG) for the occurring processes
are calculated. The electrical conductivities of the solid complexes were measured and the activation energy of the complex
and its free ligand are also calculated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
K. E. Ozbas 《Journal of Thermal Analysis and Calorimetry》2008,93(2):641-649
In this study, the relationship between particle size and pyrolysis characteristics of Elbistan lignite was examined by using
the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. Lignite samples were separated into different
size fractions. Experiments were conducted at non-isothermal conditions with a heating rate of 10°C min−1 under nitrogen atmosphere up to 900°C. Pyrolysis regions, maximum pyrolysis rates and characteristic peak temperatures were
determined from TG/DTG curves. Thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics.
Apparent activation energy (E) and Arrhenius constant (A
r) of pyrolysis reaction of each particle size fraction were evaluated by applying Arrhenius kinetic model. The apparent activation
energies in the essential pyrolysis region were calculated as 27.36 and 28.81 kJ mol−1 for the largest (−2360+2000 μm) and finest (−38 μm) particle sizes, respectively. 相似文献
20.
Mihaela Dochia Dorina Chambre Simona Gavrilaş Cristian Moisă 《Journal of Thermal Analysis and Calorimetry》2018,132(3):1489-1498
The nature of the complexing agents used in the bioscouring process of cotton fabrics aiming to eliminate the non-cellulosic compounds (pectin, waxes, etc.) and to improve the hydrophilic and wetting properties influences the thermal behaviour and the FT-IR spectra of the textile materials. In this paper, we study the influence of the experimental conditions and complexing agent nature (sodium citrate or disodium EDTA salt) on the pectin elimination in bioscouring treatment of cotton fabric by FT-IR and TG/DTG/DTA analysis. The changes from FT-IR spectra of the specific bands (absorbance intensity at 2916, 2852, 1732 and 1640/1642 cm?1) were evaluated. The thermal behaviour of the investigated samples’ fabric by using TG/DTG/DTA analysis was studied at 30–600 °C temperature range, in air atmosphere. All samples showed three mass-loss steps due to the elimination of humidity, decomposition of the non-cellulosic and cellulosic components (main degradation stage of the samples) and thermo-oxidative decomposition of the formed degradation products. The Tonset values corresponding to the main decomposition step, the mass-loss values (%Δm) and the % residual mass (at 600 °C) were influenced by the complexing agent nature as well as the concentration and the action time of the commercial enzyme product. In addition, the calcium content of some samples treated with and without ultrasound was determined using atomic absorption spectroscopy method (AAS) in order to correlate the results with TG/DTG/DTA analysis. The obtained results have shown that the synergistic action of experimental conditions (enzyme concentration, pH, enzyme product action time, ultrasound) and the presence of sodium citrate as a biodegradable complexing agent led to the elimination of a higher amount of pectin from the cotton samples than that eliminated when using EDTA. 相似文献