Showing papers on "Thermogravimetric analysis published in 1981"

Thermal decomposition of ferrous oxalate dihydrate studied by direct current electrical conductivity measurements

Abstract: The feasibility of the use of direct current electrical conductivity,σ, measurements in the study of solid-state reactions involved in the synthesis ofγ-Fe2O3 from ferrous oxalate dihydrate has been reported. The study has been carried out in static air, dynamic air, dry nitrogen and dynamic air + water vapour environments. The conductivity data determined in static air are quite complex; nevertheless, the formation of Fe3O4 andα-Fe2O3 with the probable intermediate formation ofγ-Fe2O3 has been indicated. In dry nitrogen the step corresponding to dehydration is well resolved in the temperature region 145–220° C; the formation of FeO and Fe3O4 is also well characterized. In dry dynamic air the reaction further proceeds to the formation ofα-Fe2O3. In dynamic air containing water vapour there are definite indications of the formation ofγ-Fe2O3 prior to the formation ofα-Fe2O3. Definite experimental conditions have been determined for the formation ofγ-Fe2O3 in dynamic air containing water vapour. The conductivity measurements have been supplemented with infra-red spectroscopy and X-ray diffraction pattern measurements. The electrical conductivity measurements were found to give additional information on the solid-state reaction to that obtained from conventional thermal analytical techniques (such as differential thermal, thermogravimetric and differential thermogravimetric analyses).γFe2O3, obtained from the decomposition of FeC2O4 · 2H2O in dynamic air + water was found to have a coercive force of 3.142 A m−1, a saturation magnetization value of 7.1 T kg−1 and a ratio of remanence to saturation magnetization of 0.64.

Chemistry of miscible polycarbonate–copolyester blends

Abstract: Blends of polycarbonate and the copolyester based on 1,4-cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids are known to be completely miscible. This study was concerned with various chemical events which may occur in this system, particularly during melt processing. Degradation reactions were studied by both TGA and dilute viscometry techniques, and some indications of component interaction were noted. The residual titanium catalyst from the copolyester formation was found to produce color formation by interaction with phenolic end groups in the polycarbonate and to promote interchange reactions. Both events could be suppressed by deactivation of the residual catalyst with appropriate additives. An indication of the extent of interchange reactions was obtained by following the crystallizability of the copolyester component using differential scanning calorimetry.

Aromatic polyamides. II. Thermal degradation of some aromatic polyamides and their model diamides

Abstract: Thermal degradation behavior of poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) was investigated with the aid of some appropriate model compounds. The pyrolysis products of these materials were identified by gas chromatography (GC), gas chromatography/Fourier transform infrared spectroscopy (GC/FT-IR), and gas chromatography/mass spectrometry (GC/MS). The residual chars were characterized by IR spectroscopy. Thermogravimetric analysis (TGA) was applied to study the effect of end-group concentration on the degradation characteristics of the two polyamides. Kinetic parameters that describe the thermal degradation of the polyamides were also evaluated by TGA. The results of this investigation suggest that the thermal decomposition of these aromatic polyamides involves homolytic as well as hydrolytic cleavages of the amide units.

Infrared and thermogravimetric studies of the thermal degradation of chrysotile asbestos fibers: evidence for matrix effects

Abstract: Thermal decomposition of short chrysotile asbestos fibers under static heating has been studied by infrared spectroscopy and thermogravimetry. The spectral changes were monitored at room temperatur...

Crystallization of iron phosphate glasses

Abstract: Differential thermal analysis (DTA), thermogravimetric analysis (TG), X-ray diffraction and Mossbauer spectroscopy were employed in the investigation of crystalline products of FeOx-P2O5 glasses generated by various heat treatments. In glasses with a high value of α=Fe2+/(Fe2+ + Fe3+), absorption of oxygen occurs in a broad temperature range identified by TG. Depending on the value of α, two exotherms appear in the DTA curves, the low-temperature one corresponding to crystallization of the Fe3(PO4)2 type regions, and the high-temperature one being related to various phases with dominating FePO4. Each exotherm has its own transformation region, identical in absolute value. The Mossbauer spectra of glasses which underwent thermal treatment at higher temperatures exhibit some indication of phases of the types Fe3(PO4)2 · xH2O and FePO4 · xH2O.

Assessment of the adhesive bond properties of allyl 2-cyanoacrylate

Abstract: The adhesive bond of allyl 2-cyanoacrylate between steel substrates has been analyzed and compared to that of ethyl 2-cyanoacrylate. Mechanical strength as well as thermomechanical, calorimetric, thermogravimetric, and dynamic mechanical response was observed. It was demonstrated that the allyl 2-cyanoacrylate bonds exhibit improved temperature resistance owing to the formation of heat-induced crosslinks in the adhesive layer, resulting in much improved lap-shear strengths. Scanning electron microscopy of the fracture surfaces showed that plastic deformation occurred in the allyl 2-cyanoacrylate adhesive after thermal aging, while interfacial and brittle failure dominated all other cases.

The formation energy of crystallographic shear planes in TinO2n-1

Abstract: The electrostatic contributions to the formation energies of Ti n O 2 n ─1 (4≼ n ≼ 9) have been obtained by calculating the electrostatic energy difference due to the introduction of crystallographic shear planes (c. s. p.) into rutile. Difference sums converge rapidly without the need for both real and reciprocal space summations. Short-range repulsive energy changes have also been estimated. Inclusion of elastic strain energy, required to expand the ideal c. s. structure to the observed cell parameters, and relaxation energy, released by the local displacements of individual atoms, allows the formation energies of Ti n O 2 n ─1 to be quantitatively assessed for the first time. Theoretical predictions for the internal energy are then compared with values deduced from thermogravimetric measurements.

Studies of Some Newer Polyhydrazides Containing Amide Linkages. Part 1

Abstract: An attempt has been made to prepare some new polyamide hydrazides of high thermal stability with different dicarboxylic acid chlorides by the solution polymerization technique. The polymerization was carried out at -20°C. Amide linkage was present in each polymer unit. Results of thermal degradation and thermogravimetric analysis indicate that these polymers melt or decompose above 350°C, and the steep weight loss of the polymer takes place in the range 360–390°C. Most of the polyhydrazides are soluble in organic solvents.

Kinetic analysis of thermogravimetric data XVI: Thermal decomposition of some complexes of the type [Co(niox · H)2(amine)2]X

Abstract: The influence of the sample weight and the heating rate upon the thermal deamination of [Co(niox · H)2(pyridine)2]I(I), [Co(niox · H)2(aniline)2]I (II) and [Co(niox · H)2 (pyridine)2] NCS · 1.5 H2O (III) and upon the dehydration of (III) has been studied (niox · H2 stands for nioxime: 1,2-cyclohexanedione dioxime). Kinetic parametersn, E andZ have been derived by means of the authors' three computerized integral methods. Analysis of the results shows method 1 to be equivalent to method 2 with respect to the numerical values obtained, but it needs a tenfold computer time. Method 3 gives better results due to the better choice of input data. The influence of the working conditions and of the chemical constitution upon the kinetic parameters, as well as the kinetic compensation effect, are discussed.RésuméOn a étudié l'influence du poids de l'échantillon et de la vitesse de chauffage sur la désamination thermique de [Co(niox · H)2(pyridine)2]I (I), [Co(niox · H)2(aniline)2]I (II) et [Co(niox · H)2(pyridine)2]NCS · 1.5 H2O (III) ainsi que sur la déshydratation de (III) (niox · · H2 représente la nioxime: 1,2-cyclohexanedione dioxime). A l'aide des trois méthodes d'intégration sur ordinateur des auteurs, les paramètres cinétiquesn, E et Z ont pu Être déduits. L'analyse des résultats montre que la méthode est équivalente à la méthode 2 quant aux valeurs numériques obtenues; elle exige cependant dix fois plus de temps d'ordinateur. La méthode 3 donne de meilleurs résultats en raison de la meilleure sélection des données d'entrée. On discute l'influence des conditions de travail et de la structure chimique sur les paramètres cinétiques ainsi que l'effet de compensation cinétique.ZusammenfassungDer Einfluss des Probengewichts und der Aufheizgeschwindigkeit auf die thermische Desaminierung von [Co(niox · H)2(pyridin)2]I (I), [Co(niox · H)2(anilin)2]I (II) und [Co(niox · H)2(pyridin)2]NCS · 1.5 H2O (III) sowie auf die Dehydratisierung von (III) wurde untersucht (niox · H2 bedeutet Nioxim: 1,2-cyclohexandion-dioxim). Die kinetischen Parametern, E undZ wurden mit Hilfe der drei komputerisierten Integralmethoden der Autoren abgeleitet. Die Analyse der Ergebnisse zeigt, da\\ Methode 1 der Methode 2 hinsichtlich der erhaltenen numerischen Werte ebenbürtig ist, doch eine zehnfache Rechenzeit beansprucht. Methode 3 ergibt bessere Resultate dank der besseren Wahl der eingegebenen Daten. Der Einfluss der Arbeutsbedingungen und der chemischen Struktur auf die kinetischen Parameter, sowie der kinetische Kompensationseffekt werden diskutiert.РЕжУМЕИжУЧЕНО ВлИьНИЕ ВЕсА ОБРАжцА И скОРОстИ НАгРЕВА НА тЕРМИЧЕск ОЕ ДЕАМИНИРОВАНИЕ кОМплЕксОВ [сО(НИОкс. Н)2 (пИРИДИНУ I (I), [сО(НИОкс. Н)2 (АНИлИН)2] I (II) И [Co(НИОкс.Н)2 (пИРИДИНУ NCS. 1.5 H2O (III), гДЕ (НИОк с.Н)2 — НИОксИМ: ДИОксИМ 1.2-цИклОгЕксАНДИОНА. Дль пОслЕДНЕгО Иж УкА жАННых сОЕДИНЕНИИ Иж УЧЕНА тАкжЕ ДЕгИДРАтАцИь. с пОМОЩ ьУ тРЕх ИНтЕгРАльНых, Вы ЧИслИтЕльНых МЕтОДО В, пРЕДлОжЕННых АВтОРА МИ, ВыЧИслЕНы кИНЕтИЧЕскИЕ пАРАМЕ тРып, EИ.Z. АНАлИж РЕжУл ьтАтОВ пОкАжАл, ЧтО МЕтОД 1 ЁкВ ИВАлЕНтНыИ МЕтОДУ 2 В ОтНОшЕНИИ пО лУЧЕННых ЧИслОВых жН АЧЕНИИ, НО тРЕБУЕт В ДЕсьть РАж Б ОльшЕ МАшИННОгО ВРЕМЕНИ. МЕ тОД 3 ДАЕт лУЧшИЕ РЕжУл ьтАты, ЧтО ОБУслОВлЕНО лУЧшИМ п ОДБОРОМ ВВОДНых ДАННых. ОБсУж ДЕНО ВлИьНИЕ ЁкспЕРИ МЕНтАльНых УслОВИИ И хИМИЧЕскОг О сОстАВА сОЕДИНЕНИИ НА кИНЕтИ ЧЕскИЕ пАРАМЕтРы, сОВ МЕстНО с кИНЕтИЧЕскИМ кОМпЕН сАцИОННыМ ЁФФЕктОМ.

Identification of Thermal Degradation Products of Titanium Polyethers Using Coupled Thermogravimetric Analysis-Mass Spectroscopy: Development and Evaluation of Instrumentation

Abstract: The construction and evaluation of a coupled Thermogravimetric Analyzer-Mass Spectrometer (TG-MS) instrument, capable of heating samples as small as one milligram to temperatures as high as 1200°C, while continuously monitoring the gaseous effluents using mass spectrometry, is described. Degradation of titanium polyethers was studied to assess the performance of the TG-MS.

Thermal degradation of methyl and ethyl cyanoacrylate oligomers

Abstract: Thermal degradation of methyl and ethyl cyanoacrylate polymers of number-average molecular weights 370–1350 is shown to proceed by depolymerisation at temperatures in the range 140°–180°C. Under the conditions of the thermogravimetric analysis technique employed, weight loss kinetics appear to be governed by diffusion of monomer vapour through the liquid sample. A mathematical model of this process is postulated.

Spectral, Thermal, and Magnetic Properties of Chelate Polymers

Abstract: Polychelates of VO(II), Mn(II), Zn(II), Cr(III), and Fe(III) with the bis-oxime of 5, 5′-methylene-bis-salicylaldehyde have been prepared and are characterized on the basis of their elemental analyses, IR, diffuse reflectance spectra, magnetic moments, and thermogravimetric analyses. Except for VO(II), the other metal ions form octahedral polychelates. VO(II) forms a square-pyramidal coordination polymer. The Zn(II) poly-chelate has the highest thermal stability.