DSC characterisation of compression moulded PEEK-PTFE plaques

Thermal behaviour of substituted monoazo dyes I-XVI, have been investigated by means of differential thermal analysis (DTA) and thermogravimetry (TG). The thermal stabilities of these dyes have been determined using the DTA and TG curves and the influence of the substituents and intramolecular hydrogen bonds on the DTA and TG curves of the dyes together with the melting points were also examined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal analysis of hectorite. Part II. Differential thermal analysis

The thermal behavior of the SHCa-1 hectorite source clay specimen was studied by the technique of computerized differential thermal analysis (DTA) using dynamic nitrogen, dynamic air, dynamic carbon dioxide, and static air atmospheres. The atmospheric dependence of the DTA thermal curves was established. A series of samples heated in dynamic nitrogen purge was analyzed by X-ray diffraction spectrographic techniques to establish the high temperature phases of the SHCa-1 (carbonate-contaminated) hectorite specimen. Differential thermal analysis was also performed on a processed (carbonate-cleaned) hectorite specimen using dynamic nitrogen atmosphere. Additional TG-DTG thermal curves were included in this portion of the study.     

Synthesis and thermal decomposition of ditetrazol-5-ylamine

Ditetrazol-5-ylamine (DTA) was synthesized from cyanuric chloride in four steps. The thermal decomposition of DTA in the solid state was studied by thermogravimetry, volumetry, mass spectrometry, IR spectroscopy, and calorimetry. Under isothermal conditions at 200–242 °C, thermal decomposition obeys the first order autocatalytic kinetics. The kinetic and activation parameters of DTA decomposition were determined. The composition of gaseous reaction products and the structure of condensed residue were studied. The thermal effect of thermal DTA decomposition is 281.4 kJ mol⁻¹. The nitrogen content in a mixture of gaseous products formed by the reaction in a temperature interval of 200–242 °C exceeds 97 vol.%. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1660–1664, July, 2005.     

Formation of B-C-N Ceramics Investigated by Emanation Thermal Analysis, TG and DTA

Processes taking place during formation of B-C-N ceramics by thermal treatment of organic precursors were investigated using emanation thermal analysis (ETA), differential thermal analysis (DTA) and thermogravimetry (TG). An additional information about thermal behavior of precursors used for preparation of BC4N, BN and CNx ceramic systems by heating in argon up to 1100°C was obtained. The ETA enabled us to characterize microstructure changes in the samples at in situ conditions of thermal treatment. A good agreement of ETA, TG and DTA results was found. This revised version was published online in August 2006 with corrections to the Cover Date.     

LiNd(PO3)4晶体的热分析研究

对LiNd(PO₃)₄晶体分别在N₂气和空气下进行了TG和DTA热分析研究,给出TG和DTA曲线,讨论了LNP晶体在N₂气和空气下不同的热分解机理.得到分解产物分别为Nd₄(P₂O₇)₃和NdP₂O₇.     

α-三氢化铝的热分解动力学

用差热分析(DTA)研究了a-三氢化铝在氦气流下的热分解动力学。建立了A-E方程中动力学参数与DTA曲线的特征温度之间的关系式, 用序贯法对竞争模型进行最佳判别和参数估算, 确定a-三氢化铝的热分解曲线可用方程[-In(1-x)]~(1/4)=r_0e~(-E/RT_t)来描述, 表观活化能E为121.4±6.3 kJmoL~(-1), 指前因子r_0为8.1×10~(11±1)(sec-1), 模型计算结果与实验结果吻合较好。     

Correlation between thermal and mass spectral techniques for the characterization of allenylidene and carbene complexes

The fragmentation pathways of allenylidene and carbene complexes have been studied using FAB mass spectrometry in comparison with thermal analyses (TGA, DrTG and DTA). Both the decomposition modes are investigated and the possible fragmentation pathways are suggested. The use of mass and thermal analyses (TGA and DTA) in the analyses of allenylidene and carbene complexes allowed the characterization of the fragmentation pathways in MS. The major pathway includes successive loss of carbon monoxide followed by fragmentation of the organic part of the allenylidene or carbene molecules. This is also confirmed by thermogravimetric analysis (TGA) where the first step involves the loss of carbon monoxide followed by the organic ligand. The nature of each step; exothermic or endothermic, is also studied using DTA technique. The kinetic parameters of the thermal decomposition are also studied using the Coates-Redfern method.     

The thermal analysis of polymers at high pressures

The extension of two techniques of thermal analysis into the region high pressures (50–100 MPa) are discussed. One is the extension of dilatometry (thus becoming pressure-volume-temperature measurements, PVT). This technique has been well established over the past few years. Some results obtained on typical polymer systems are presented and discussed. The second is the extension of the differential thermal analysis (DTA) principle to high pressures, trying to maintain some of the advantages of the DTA technique when compared to the PVT method, such as small sample size and productivity. DTA determinations of the pressure dependence of the melting points of pure metals and polymers are presented and compared with results from the PVT technique. Satisfactory agreement is obtained. The advantages and limitations of our current high-pressure DTA method are discussed.We gratefully acknowledge the partial financial support of the high-pressure DTA development by Metler Instrumente AG, Switzerland.     

Thermal decomposition of chemotherapeutic preparations and expectorants

The thermal decomposition of 31 drugs containing sulphonamides, antituberculous agents, dyes, an oxidant, carboxylic acid derivatives and formaldehyde, expectorants and codeine phosphate has been studied by differential thermal analysis (DTA) and thermogravimetry (TG). The DTA, TG and differential TG curves have been used for identification of the drugs and their qualitative and quantitative analysis. The results for 18 of the drugs were in good agreement with those calculated from the formulation.     

Thermal Studies on Chlorinated Atactic Polypropylene

Thermal behavior of chlorinated atactic polypropylene (CAPP) obtained by thermal chlorination of atactic polypropylene was evaluated by thermogravimetric analysis and differential thermal analysis (DTA). It was found that the initial decomposition temperature, integral procedural decomposition temperature, activation energy, and char yield increase with an increase in chlorine content. The thermal stability of CAPP was found to be lower in air than in nitrogen. This has been ascribed to thermooxidative degradation in air. DTA study shows that onset decomposition temperature, glass transition temperature, and polymer melting temperature increase with increasing degree of chlorination. The possible reasons for the phenomena are discussed.     

On the method of bae for the determination of kinetic parameters from DTA curves

The mathematical error in the method proposed by Bae for the determination of kinetic parameters from DTA curves has been corrected. The proposed equation does not contain thermal constants of the apparatus, and can be applied to DTA curves by an iterative method. The results obtained by the application of this equation to experimental DTA curves for the decomposition of sodium bicarbonate compared well with those from isothermal measurements, even when the DTA sample holder assembly was of the isolated cup-type instead of the block-type assembly recommended by Bae.     

Etude sur le comportement thermique de quelques polymeres ignifugeants contenant du phosphore et des halogenes

The thermal behaviour a series of polyphosphonates was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The obtained data permitted the calculation of activation energies and reaction orders on decomposition zones by the Coats — Redfern method.     

Thermal Stability of Robust Unsymmetrical Copperporphyrins with Multiple Diphenylamino and Nitro Substituents

The syntheses and thermal stability properties of a series of amino and nitro substituted copperporphyrins are described. The thermal decomposition temperatures of the porphyrins were determined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The on-set thermal decomposition temperatures of the unsymmetrical porphyrins were found to be high in the range of 350 – 405 °C (DSC), 374 – 441 (TGA in air), 395 – 411 °C (TGA under nitrogen atmosphere), and 410 – 424 °C (DTA in air). Substituent dependent thermal stability trends were also studied. The trend is variable depending on the thermal analysis technique utilized. Possible reasons for such variation are discussed. These porphyrins are thermally robust even in the melamine-based sol-gel matrix. Containing 20% by weight of the substituted unsymmetrical copperporphyrin, melamine-based sol-gel showed no indication of decomposition until ?400 °C.     

Dynamic dielectric analysis. A new thermal analysis technique

Applications of dynamic dielectric analysis (DDA) in studies on the thermal decomposition and phase transformations of solid materials are discussed. Three illustrative examples are presented for (a) a system undergoing a chemical reaction or thermal alteration on application of heat, (b) a system undergoing a crystallographic transformation and (c) detection of moisture in naturally occurring materials. The advantages derived by applying a combination of DDA and a conventional thermal analysis technique such as DTA to studies on thermal processes are demonstrated. It is shown that the information obtained from techniques such as DTA or TG is limited in scope unless used in conjunction with a method which sheds light on the mechanistic aspects of the physical or chemical process of interest.     

Thermal studies on some reactions in the solid-state

The solid-state thermal reactions of 2,6-diamino-4-chloropyrimidine, 3,3-dimethoxybenzidine and of thiosemicarbazide with each of 2-hydroxy-1-naphthaldehyde and 2,4-dihydroxybenzaldehyde in a mole ratio of 1∶1 produced (1+1) condensation products (‘half units’). These solid state reactions have been studied by means of differential thermal analysis (DTA). The products of the reactions were identified using elemental analysis and IR spectroscopy. Some kinetic parameters such as orders and activation energies of the reactions were evaluated form the DTA curves.     

A DTA study of phenols

A comprehensive DTA study is reported of 17 halophenols and of the corresponding p-nitrobenzoylchloride 3,5-dinitrobenzoylchloride and p-phenylazobenzoylchloride derivatives, prepared “in-situ”by heating intimate mixtures of phenol and acid chloride in the DTA system. The thermal analysis data, in particular, the derivative formation temperatures, are interpreted in terms of the inductive, mesomeric and steric effects associated with the ring substituents of the phenol and acid chloride and the extent of inter- and intramolecular hydrogen-bonding existing in these systems. The DTA data collectively provide a reference base for the identification and characterization of halophenols via thermal analysis.     

Emanation thermal analysis

A high pressure differential thermal analysis (DTA) apparatus is described which is capable of operation in the pressure range up to 500 MPa and at temperatures from 25 to 300°C. The requirements for quantitative DTA are examined. The apparatus enables the determination of heat of transition under high pressure by using small samples.     

Thermal reactions by automated mass spectrometric thermal analysis

Combination of differential thermal analysis (DTA) with time-of-flight mass spectrometry and data storage on magnetic tape is used to study thermal decompositions.A modified Du Pont 900 DTA cell is used for reactions at atmospheric pressure with evolved gas sampling into a small time-of-flight spectrometer.For fast reactions a specially developed DTA cell is operated within the mass spectrometer and operates at high vacuum.A combination of both operational modes yields pressure dependencies of chemical decomposition.Examples studied include inorganic compounds and complexes, organometallics and organic chemicals such as fire retardants.The data are presented as intensity/temperature curves for each observed fragment, which not only yields decomposition temperatures but also—by the curve shapes—information on the mode of decomposition.     

DTA和XRD用于(14-x)SrCO3-xCaCO3-24CuO系统合成spin-ladder化合物Sr14-xCaxCu24O41的研究

The (14-x)SrCO3xCaCO324CuO system was investigated by means of differential thermal analysis (DTA) technique combined with the powder Xray diffraction (XRD) technique, and the relationship of its thermal behavior with the synthesis of spin-ladder compound Sr14-xCaxCu24O41 was first analyzed in detail. It is found that the DTA curve (x≤5.6) exhibits two endothermic peaks and could be divided into three reaction stages, corresponding to the solid state reaction to synthesize single-phase Sr14-xCaxCu24O41. The DTA curve (x≥8.4) shows three big endothermic peaks below 1000 ℃. The intensity and the position of the first endothermic peak around 800 ℃ is depending on the content of CaCO3 in the system, while the third endothermic peak is the crucial factor of the synthesis of single-phase compound.     

DTA curves and non-isothermal reaction rates

Differential thermal analysis (DTA) is an effective means for studying chemical reactions, but its application to reaction kinetics is handicapped by the involvement of temperature feedback from the reaction heat and by the solvent dependence of the thermal conductivity.General, empirical relationships are derived from digital computer application which allow to transform half width and shape index of a DTA curve of any first-order process in a uniformly temperated sample to the values of the corresponding rate curve at linearly increased temperature.The expressions are complemented by some new relationships for an n-order reaction and are useful for the kinetic study of complex processes.