Effect of accelerated thermal ageing on the thermal behaviour of the recently made parchments

To reveal the fire injuring of parchment, the changes in the thermal behaviour of some goat parchments, obtained from skins originating from different animals, as a result of thermal aging were determined by thermal analysis methods (DSC; simultaneous TG/DTG, DSC; micro hot table (MHT)). Thermal aging of parchments was revealed to bring about the decrease in shrinkage temperature, absolute value of enthalpy of denaturation in water and some changes in non-isothermal parameters characteristic for dehydration process in static air atmosphere. The results obtained by DSC analysis performed in N₂ and O₂ flows as well as those obtained by simultaneous TG/DTG, DSC analyses have shown that both softening (melting) process parameters and parameters of thermo-oxidative processes have not been changed by thermal ageing. The results obtained by thermal analysis methods were correlated with those obtained by microscopic investigation of parchment samples immersed in water and scanning electron microscopy (SEM). The application of these microscopic techniques has revealed the morphology changes in the investigated parchments as a result of thermal degradation.     

Non-destructive assessment of parchment deterioration by optical methods

A non-destructive and non-invasive method for quantitative characterization of parchment deterioration, based on spectral measurements, is proposed. Deterioration due to both natural aging (ancient parchments) and artificial aging (achieved by means of controlled UV irradiation and temperature treatment) was investigated. The effect of aging on parchment native fluorescence was correlated with its deterioration condition. Aging causes fluorescence intensity drop, spectral shift of the main peak, and an overall change in the fluorescence spectral features. Digital color imaging analysis based on visible reflectance from the parchment surface was also applied, and the correspondent color components (RGB) were successively correlated with the state of parchment deterioration/aging. The fluorescence and color imaging data were validated by analysis of historical parchments, aged between 50 and 2000 years and covering a large variety of states of deterioration. The samples were independently assessed by traditional microscopy methods. We conclude that the proposed optical method qualifies well as a non-destructive tool for rapid assessment of the stage of parchment deterioration.     

Characterisation and evaluation of the environmental impact on historical parchments by differential scanning calorimetry

Our recent developments concerning the assessment of parchments deterioration using DSC are reported. Measurements performed on samples in excess water conditions, in static air and gas flow provided qualitative and quantitative information on parchment ageing and deterioration at microscopic and mesoscopic level, when assembly of fibres/fibrils is weakened, partially and eventually completely lost, and at molecular level, when triple helix uncoiling occurs. A damage ranking scale based on a large collection of DSC parameters obtained by investigating artificially aged samples was set up. Deconvolution of the DSC thermal denaturation peaks in excess water enabled evaluating and discriminating stability of parchments with similar damage levels. Further experimental evidences such as softening of the crystalline fraction of collagen, thermal-oxidation and collagen gelatinisation were detected by DSC measurements in gas flow and static air, and related to specific deterioration patterns. DSC measurement of wet samples provided an objective and reliable method for evaluating parchment shrinkage temperature overcoming the limitations of conventional methods.     

Thermal Behavior of Sr(II) and Ba(II)‐Diclofenac Complexes in Solid State: Study of the Dehydration and Thermal Decomposition

Solid state compounds of general formula Sr(Diclof)₂·5.7H₂O and Ba(Diclof)₂·4.8H₂O were obtained. Thermogravimetry (TG), differential scanning calorimetry (DSC), X‐ray diffraction powder patterns and microscopy analysis were used to characterize these compounds. Details concerning the dehydration and thermal decomposition as well as data of kinetic parameters have been described here. The kinetic behaviors of these stages were evaluated from several heating rates with samples masses of 2 and 5 mg in open crucibles under a nitrogen atmosphere. The results of the present study improve the knowledge on these compounds including their dehydration and thermal stability. The obtained data depend on the mass of the sample which results in two kinetic behavior patterns.     

On the oximine complexes of transitionmetals

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.     

Thermal behavior of double salt schoenite

The thermal behavior of synthetic schoenite (K₂SO₄·MgSO₄·6H₂)) during heating has been studied by thermal methods. The temperatures of dehydration and decomposition of schoenite have also been determined by DTA, TG and DSC. The thermal reaction equations and the X-ray power diffraction results of the products have been given and the corresponding kinetic parameters have also been obtained.     

Application of non-isothermal cure kinetics on the interaction of poly(ethylene terephthalate) — Alkyd resin paints

Samples of paint (P), reused PET (PET-R) and paint/PET-R mixtures (PPET-R) were evaluated using DSC to verify their physical-chemical properties and thermal behavior. Films from paints and PPET-R are visually similar. It was possible to establish that the maximum amount of PET-R that can be added to paint without significantly altering its filming properties is 2%. The cure process (80–203°C) was identified through DSC curves. The kinetic parameters, activation energy (E _a) and Arrhenius parameters (A) for the samples containing 0.5 to 1% of PET-R, were calculated using the Flynn-Wall-Ozawa isoconversional method. It was observed that for greater amounts of PET-R added, there is a decrease in the E _a values for the cure process. A Kinetic compensation effect (KCE), represented by the equation InA=−2.70+0.31E _a was observed for all the samples. The most suitable kinetic model to describe this cure process is the autocatalytic Šesták-Berggreen, model applied to heterogeneous systems.     

Application of synchronous fluorescence to parchment characterization

A nondestructive method for quantitative parchment characterization and sensitive indication of its deterioration stage was developed. Synchronous fluorescence (SF) measurements were applied for the first time to parchment samples. The method provides detailed spectral features, which are useful for parchment characterization. The discrimination of parchment samples into groups (modern, historical, and artificially aged) was successfully performed. The SF spectra could be resolved into specific fluorophores, which were related to the parchment condition. The spectral data indicate a continuous change in the collagen-to-gelatin ratio during the aging process. Depth-resolved synchronous fluorescence spectra were also measured. The data indicate that parchments possess a layered structure, and the dominant fluorophore in the upper layer is different from those in the lower layers. Layer-resolved profiling allows for quantifying the contribution of each fluorophore in each given layer. This way, significant differences between modern, artificially aged, and historical samples can be observed.     

Thermal and electrical behavior of hybrid thermosets based on epoxy and maleimide resins cured with p-aminobenzoic acid

Two thermoset systems based on maleimides and diglycidyl ether of bisphenol A (DGEBA) cured with p-aminobenzoic acid were characterized in terms of thermal and electrical behavior. Thermal characterization has been undertaken by means of thermogravimetric analysis in nitrogen atmosphere up to 600°C using simultaneous thermogravimetric/Fourier transform infrared/mass spectrometry (TG/FT-IR/MS) analysis. In the first stage of thermal degradation, the global kinetic parameters [activation energy (E_a) and preexponential factor (log A₁ (s⁻¹))] were calculated using the isoconversional method of Friedman. The energies variation as well as the shape of the differential thermal analysis curves suggests that the thermal decomposition process occurred in multiple stages. The evolved gases analysis was conducted by simultaneous TG/FT-IR/MS coupled techniques. Dielectric relaxation spectroscopy characterization was also made.     

2，4，6-三硝基间苯二酚钡一水化合物的热分解动力学(英)

0IntroductionBarium2,4,6鄄trinitroresorecinatemonohydrate,Ba(TNR)·H2O,hasgooddetonatingpropertiesandissensitivetoflame.Itcanbeusedasinitiatingagent,igniterpowderordelaypowder.Itspreparation[1],pro鄄perties[1],crystalstructure[1]andthermalbehavior[2]haveb…     

Dynamic mechanical analysis (DMA), 13c solid state nmr and micro-thermomechanical studies of historical parchment

DMA and solid state ¹³C NMR techniques were used to measure historical parchment samples within the framework of the project (MAP) Micro Analysis of Parchment (EC contract No. SMT4-96-2101) in collaboration with the School of Conservation in Copenhagen. DMA was used in both thermal scan and creep modes. Thermal scans provided information on the transitions associated with the collagen polymer. Microthermal analysis was also used to obtain information on the topography and thermal conductivity of sample areas of 100 μm. Localised heating enabled measurements of softening transitions in the sample. This behaviour is influenced by the chemical composition of parchment. 13C NMR provided information on the carbon atoms associated with the polypeptide chains of the collagen in parchment. The behaviour of samples immersed in water and measured in DMA creep mode was used to measure the shrinkage behaviour of the parchment samples. The different but complementary techniques provided a means for characterising the physicochemical state of parchment samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Kinetic Study of the Dehydration of VOPO4.2H2O by Thermal Methods

The dehydration of VOPO₄.2H₂O hasbeen studied by thermogravimetric analysis (TGA),differential thermal analysis (DTA) and differentialscanning calorimetry (DSC). From the shift of the DTA,DTG, and DSC peaks, activation energies of thedehydration processes have been calculated based onKissinger's method. The most suitable kinetic modelsfor two-step dehydration have been found.     

Effect of previous thermal history on physical aging of amorphous poly (ethylene terephthalate)

Physical aging of amorphous PET, at aging temperatures (T_a) of 40 and 60°C and different aging times (t_a), has been studied by DSC using two kinds of samples with different thermal history: Liquid-Nitrogen-Quenched samples (LNQ) and DSC cooled samples at a controlled cooling rate of 60 K/min (CC). At T_a = 40°C, a sub-T_g peak appears in LNQ samples but is not clearly observed in the CC samples. At T_g = 60°C, a superposed peak to T_g is observed in both kinds of samples. This different behaviour can be explained considering the distribution of relaxation times in the polymer.     

Kinetic Analysis of the Thermal Decomposition of Synthetic Malachite by CRTA

The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO₂ and H₂O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO₂ and H₂O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermokinetic parameters and thermal hazard evaluation for three organic peroxides by DSC and TAM III

The thermokinetic parameters were investigated for cumene hydroperoxide (CHP), di-tert-butyl peroxide (DTBP), and tert-butyl peroxybenzoate (TBPB) by non-isothermal kinetic model and isothermal kinetic model by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III), respectively. The objective was to investigate the activation energy (E _a) of CHP, DTBP, and TBPB applied non-isothermal well-known kinetic equation to evaluate the thermokinetic parameters by DSC. We employed TAM III to assess the thermokinetic parameters of three liquid organic peroxides, obtained thermal runaway data, and then used the Arrhenius plot to obtain the E _a of liquid organic peroxides at various isothermal temperatures. In contrast, the results of non-isothermal kinetic algorithm and isothermal kinetic algorithm were acquired from a highly accurate procedure for receiving information on thermal decomposition characteristics and reaction hazard.     

差示扫描量热法测定食用油脂的热氧化稳定性及氧化寿命

利用差示扫描量热法（DSC）测定了四种食用花生油的热氧化稳定性,用Ozawa法和Kissinger法计算了四种食用花生油热氧化反应的动力学参数,推算了不同温度下的氧化寿命。     

Effect of thermal history on crystallization and melting behaviour of lldpe

In this paper two LLDPE samples with their own structural parameters were studied by means of DSC. Experimental results show that DSC was good for revealing slight structural difference between these two samples. Furthermore, the effect of thermal history on crystallization and melting behaviour of LLDPE was observed clearly through varying conditions of thermal treatment.

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Zusammenfassung Mittels DSC werden zwei LLDPE-Proben mit ihren eigenen Strukturparametern untersucht. Die Versuchsergebnisse zeigen, da\ sich DSC gut eignet, um gering fügige Unterschiede dieser zwei Proben nachzuweisen. Weiterhin wurde unter verschiedenen Bedingungen der Einflu\ der thermischen Vorgeschichte auf das Kristallisations-und Schmelzverhalten von LLDPE untersucht.

     

Comparative kinetic study of decomposition of some diazepine derivatives under isothermal and non-isothermal conditions

Thermal analysis is one of the most widely used methods for studying the solid state of pharmaceutical substances. TG/DTG and DSC curves provide important information regarding the physical properties of the pharmaceutical compounds (stability, compatibility, polymorphism, kinetic analysis, phase transitions etc.). The purpose of a kinetic investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the diazepam, nitrazepam and oxazepam thermal decomposition was performed, under non-isothermal and isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 483, 498, 523, 538 and 553 K. The TG/DTG data were processed by three methods: isothermal model-fitting, Friedman’s isothermal-isoconversional and Nomen-Sempere non-parametric kinetics. In the model-fitting methods the kinetic triplets (f(α), A and E _a) that defines a single reaction step resulted in being at variance with the multi-step nature of diazepines decomposition. The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation energies on the extent of conversion. It is very difficult to obtain an accord with the similar data which resulted under non-isothermal conditions from a previous work. The careful treatment of the kinetic parameters obtained in different thermal conditions was confirmed to be necessary, as well as a different strategy of experimental data processing.     

过氧化二异丙苯的热分解动力学研究

过氧化二异丙苯(DCP)是一种有广泛用途的过氧化物交联剂,具有高的交联效率和优良的交联性能.其分解温度较低,热分解速度较快,即使没有外界能量的作用,在自然储存的条件下也会发生化学反应,放出热量[1,2].