Mechanism of thermal decomposition of thiourea derivatives

The thermal decomposition of a series of compounds has been studied by thermogravimetry, mass spectrometry, nuclear magnetic resonance and elemental analysis. The combined use of mass spectrometry and thermogravimetry (MS and TG) in the analysis of these compounds has allowed characterization of the fragmentation pattern which was the objective of this research. The gaseous products, volatile condensed products and solid residues were identified by NMR and MS. Based on the product of thermal decomposition, the mechanism of thermal decomposition has been derived.     

Thermal stability and flammability of butadiene- acrylonitrile rubber cross-linked with iodoform

Summary The paper discusses the results of thermal analysis and flammability of butadiene-acrylonitrile rubber, Perbunan NT 1845 of Bayer, cross-linked with iodoform. The properties of the iodoform vulcanizate have been compared with those of peroxide vulcanizate. The thermal analysis has been performed in air with use of a derivatograph under air and nitrogen atmosphere as well as dynamic scanning calorimetry (DSC). The flammability of vulcanizates has been determined by the method of oxygen index and in air. The toxicity of the thermal decomposition and combustion products of the vulcanizates under investigation has been also determined. Based on complementary examinations, DTA and DSC curves have been interpreted from the point of view of thermal transitions of the conventionally and non-conventionally cross-linked nitrile rubbers. The glass transition temperature of the cross-linked polymer both in cooling and heating has been determined.     

Thermal stability of cellulose acetate urethanes

The thermal degradation of isocyanate modified cellulose acetate has been studied by dynamic thermogravimetric analysis in air. The activation energy of decomposition of these modified polymers has also been determined from differential thermal analysis thermograms. The data indicate that the cellulose acetate urethane polymers are thermally stable.     

Thermal characterisation of Australian oil shales

There has been a significant research effort on the development of an oil industry based on Australian oil shales. However, to date the research has been based mainly on the processing aspects of oil shale. The thermal analyses of oil shales, while having been the subject of many studies, have been limited to some extent by instrumentation and analytical techniques. This paper reports on thermal analysis studies utilising traditional thermogravimetry/differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC). The application of modern thermal analysis techniques such as high resolution TG (HRTG) and modulated differential scanning calorimetry (MDSC) is also examined and compared to the traditional methods.     

Investigation of the thermal modification of asbestos wastes for potential use in ceramic formulation

Preliminary research has been carried out on the thermal modification of chrysotile asbestos. Destruction of the tubular structure of asbestos was achieved by calcination at 1000°C. In order to characterize the changes accompanying thermal modification both natural asbestos and calcined asbestos were subjected to thermogravimetric and differential thermal analysis, X-ray analysis and examination by scanning electron microscopy. The possibility of utilization of the calcined asbestos in the presence of a phosphate binder for the manufacture of refractory materials has been demonstrated.     

30 years of research in thermal analysis and calorimetry

The research in thermal analysis and calorimetry, conducted by the author over the period 1964 to 1993, is summarised and concisely reviewed. The major investigations have focussed on thermal analysis studies of coordination compounds, particularly the metal dithiocarbamate complexes. A significant solution calorimetric study of some metal dithiocarbamate complexes has also been undertaken. DSC has been applied to determine the sublimation enthalpies of many metal dithiocarbamate and metal pentane-2,4-dionate complexes and solution calorimetry has been applied to study the thermochemistry of the latter group of complexes. Thermal analysis investigations of several inorganic molten salt systems have been initiated. Thermometric titrimetry has been applied to study metal-macrocyclic ligand systems in aqueous media and particularly those systems of environmental significance. Temperature calibration standards for TMA have been proposed and TMA has been applied to study the mechanical properties of several common inorganic compounds. DTA has been applied to study a wide variety of phenols and has subsequently been applied as an analytical technique to determine the components of solid state phenol mixtures. Thermometric titrimetry has been applied to determine the phenolic content of wines. A comprehensive thermal analysis study of Australian brown coal has been undertaken, involving the DSC determination of coal specific energy, a TG/DTA study of the coal pyrolysis and combustion processes and a TG/DTA and EGA study of the cation catalytic effect on the coal pyrolysis process. Thermal analysis and calorimetric techniques have been extensively publicised and promoted by the publication of specialist reviews, the presentation of symposia review papers and the oral presentation of short courses, particularly in the SE Asian region. This review essentially reveals the diversity of possible application of thermal analysis and calorimetric techniques and the primary significance of thermodynamic data in the fundamental rationalisation of chemical phenomena.     

Infrared and thermal studies of strontium zirconyl oxalate hexahydrate

Strontium zirconyl oxalate hexahydrate (SZO) is prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition studies have been made using thermogravimetry (TG) and differential thermal analysis (DTA). The decomposition has been found to proceed through three major steps (i) a three stage dehydration, (ii) decomposition of the oxalate and (iii) decomposition of carbonate to strontium zirconate. Carbon dioxide is found to be trapped in the solid during the decomposition of the oxalate. The identification of residues at various stages has been done by IR spectra and chemical analysis.     

Synthesis and study of structure and physicochemical properties of dicopper(II) (diaqua)benzene-1,2,4,5-tetracarboxylate

Layered complexes of copper(II) with benzene-1,2,4,5-tetracarboxylic acid has been prepared for the first time. The data of elemental analysis, X-ray diffraction analysis, IR spectroscopy, and differential thermal analysis have confirmed the purity of the complex compound. Its chemical composition has been elucidated, and thermal decomposition has been studied. The prepared complex contained no water molecules, and the polymeric layered structure has been retained.     

Self‐Assembly Studies of a Chiral Bisurea‐Based Superhydrogelator

A chiral bisurea‐based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mM is reported. This soft material has been characterized by thermal studies, rheology, X‐ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy‐driven self‐assembly process. These particular thermal characteristics make these materials easy to handle for soft‐application technologies.     

Intercalation compounds between nicotine and a high surface area Saponite

The retention of nicotine by a high surface area saponite has been studied using two methods: (1) in repose at room temperature, and (2) heating at 70 °C under reflux. Different contact times were considered for each method. The intercalation compounds obtained were studied by chemical analysis, X-ray diffraction, infrared spectroscopy and thermal analysis. Nicotine is retained both in the interlayer region and at the edge of clay particles. The amount of nicotine retained in the interlayer region has been calculated from thermal analysis and CHN measurements.     

Evaluation of the degree of hydration of synthetic alites by quantitative differential thermal analysis

The degree of hydration of synthetic alites has been determined by quantitative differential thermal analysis, using strong signals related to the polymorphic transformations of alites. The conditions suitable for noting the various reference signals, obtained with maximum apparatus sensibility, have been described and the data derived from differential thermal test with those obtained by analysis of the liquid phase in contact with the hydrating solid are correlated.     

Combined kinetic analysis of thermal degradation of polymeric materials under any thermal pathway

Combined kinetic analysis has been applied for the first time to the thermal degradation of polymeric materials. The combined kinetic analysis allows the determination of the kinetic parameters from the simultaneous analysis of a set of experimental curves recorded under any thermal schedule. The method does not make any assumptions about the kinetic model or activation energy and allows analysis even when the process does not follow one of the ideal kinetic models already proposed in the literature. In the present paper the kinetics of the thermal degradation of both polytetrafluoroethylene (PTFE) and polyethylene (PE) have been analysed. It has been concluded, without previous assumptions on the kinetic model, that the thermal degradation of PTFE obeys a first order kinetic law, while the thermal degradation of PE follows a diffusion-controlled kinetic model.     

The thermal decomposition of metal formates. II. Solid state thermal decomposition studies on magnesium formate dihydrate

Magnesium formate dihydrate has been synthesized by the action of formic acid on anhydrous magnesium oxide. This product analysed as Mg(COOH)₂ · 2H₂O. Its mode of thermal decomposition has been studied by thermal methods of analysis including simultaneous DTA/mass spectrometry. Nitrogen adsorption surface area of the solid products at various stages of its decomposition have been obtained. X-Ray diffraction and scanning electron micrographs have also been used to interpret the results. The decomposition of magnesium formate took place in three stages, which includes a phase change, at 265°C. The endotherm at 430°C changed to an exotherm in the presence of air; it corresponded to the decomposition of a new anhydrous phase of magnesium formate. The effect of the sample holder and changing atmospheres on the DSC analysis has been investigated. A scheme is presented for the thermal decomposition.     

四氯·两个二(2-乙基已基)硫醚合铂(IV)配合物的合成及其分子结构

用萃取法合成了[Pt(DEHS)_2Cl_4],对配合物进行了元素分析,摩尔电导,差热一热重和红外光谱等测试并经X射线单晶结构分析确定了配合物的结构。     

Non-isothermal Kinetics of the First-stage Decomposition Reaction of Cobalt Oxalate Dihydrate

Introduction Solid state kinetics has been extensively studied by means of thermal analysis methods[1]. The aim of the study is to determine the mechanism function f(α) , the activation energy E and the pre-exponential factor A. In recent years there have been many methods of processing thermal analysis kinetic data[2-11].     

Chicken Bone as a Bioresource for the Bioceramic (Hydroxyapatite)

Natural hydroxyapatite (HAP) is isolated from waste chicken bone by thermal calcinations at different temperatures in the range of 200 °C to 1000 °C. The isolated HAP has been characterized using thermo gravimetric analysis (TG) and differential thermal analysis (DTA), Fourier Transformed Infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission electron microscope (FE-SEM), and energy dispersive X-ray (EDX). The XRD results showed that the enhanced crystallinity of HAP phase by thermal calcination above 600 °C and the crystal size has been found to increase with increasing temperature of thermal calcinations due to agglomeration. Value addition for the waste chicken bone is given by the isolation of useful bioceramics (HAP) and the optimum temperature for the thermal calcination is found to be 600 °C. The isolated HAP has been characterized as carbonated HAP of B type with the hexagonal structure. These results will not only make the chicken bone as an important bioresource for the HAP but will also reduce the environmental pollution caused by dumping of the waste chicken bone.     

Preparation, crystal structure, and thermolysis of phenylenediammonium diperchlorate salts

Three salts of phenylenediammonium diperchlorate have been prepared and characterized by X-ray crystallography. Their thermal decomposition has been studied by thermogravimetry (TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal decomposition was evaluated by model fitting and isoconversional methods using TG data. The oxidation-reduction reactions near the surface of thermolysing perchlorates may be responsible for the decomposition followed by explosion. The possible pathways of thermolysis have also been proposed.     

New Adventures in Thermal Analysis

This paper describes recent advances in thermal analysis instrumentation which combine the high resolution imaging capabilities of the atomic force microscope with physical characterisation by thermal analysis. Images of the surface may be obtained according to the specimen's thermal conductivity and thermal expansivity differences in addition to the usual topographic relief. Localised equivalents of modulated temperature differential scanning calorimetry, thermomechanical and dynamic mechanical analysis have been developed with a spatial resolution of a few micrometres. A form of localised thermogravimetry-evolved gas analysis has also been demonstrated. The same instrument configuration can be adapted to allow IR microspectrometry at a resolution better than the optical diffraction limit. This revised version was published online in August 2006 with corrections to the Cover Date.     

DSC study of chlorosulphonated polyethylene

The results of thermal analysis of speciality elastomers CSM with different chlorine and sulphur contents is presented in the article. The thermal curves obtained under the atmosphere of inert gas have been interpreted from the point of view of phase transitions and chemical reactions of the examined polymers during their heating. It has been stated that from among the investigated chlorosulphonated polyethylenes, only CSM24, which has the lowest chlorine content, contains a crystalline phase, clearly influences on its T _g temperature. Results of the thermal analysis obtained under inert gas atmosphere have been compared with results obtained under termooxidative atmosphere. Irrespective of the research atmosphere, the thermal decomposition of investigated CSM takes place in three stages. The maximum rate of thermal destruction of modified by heating elastomers, dm/dt, decreases with the increase in chlorine content in the sample having been heated.     

一次热解吸直接进样浓缩方法的研究--室内大气中挥发性有机化合物的分析

研制了新型的一次热解吸直接进样热解析仪．考察了新型热解吸仪热解吸定量的重复性、准确性、热解析率、线性等性能．通过实际采样分析证明,该方法提高了浓缩倍数,操作简单,易于掌握,定量重复性好、准确度高,分析结果可靠．适合大批量样品的分析测试．