Showing papers on "Thermogravimetric analysis published in 1968"

Infrared spectra and thermal decompositions of metal acetates and dicarboxylates

Abstract: The infrared spectra of rare earth acetates have been studied to examine the metal-acetate bonding. The thermal decomposition of rare earth acetates as well as lead and copper acetates have been investigated in detail by employing thermogravimetric analysis and differential thermal analysis. Thermal decomposition of calcium dicarboxylates (malonate to sebacate) have been studied employing t.g.a. and d.t.a. Infrared spectra of the dicarboxylates have also been studied. Preliminary results on the products of decomposition of dicarboxylates have been reported.

Thermogravimetric analysis of cellulose

Abstract: An application of TGA technique to elucidate the chain reaction mechanism of cellulose pyrolysis is discussed. The mathematical expressions for isothermal kinetics are modified for use with temperature-programmed kinetics. It is shown that in temperature-programmed kinetics, the initial reaction should theoretically be a pseudo zero-order type, whereas the latter part should be a pseudo first-order type. Experimental data from the present study and from the literature are in good agreement with the theory. Energies of activation for the initiation and the propagation steps of cellulose pyrolytic reactions are analyzed from TG data. Various cellulose samples, such as adsorbent cotton, vibratory ball-milled absorbent cotton, mercerized commercial yarn, mercerized and treated commercial yarn, dewaxed-kiered cotton, and microcrystalline cellulose are included in this study. A basic problem which is associated with all thermogravimetric kinetic expressions is also discussed.

Oxidation Characteristics of MoS2 and Other Solid Lubricants

Abstract: Thermogravimetric oxidation data are presented for fifteen refractory metal dichalcogenides. Interpretation of these data is supported by oxidation thermograms of the chalcogens and the refractory metals and by X-ray diffraction analysis of the oxidized products. The effects of humidity, heating rate, and particle size on oxidation of the dichalcogenides are presented. Thermogravimetric analysis is shown to be helpful in detecting impurities, such as unreacted elements, in commercial samples. Some dichalcogenides are shown to retain the same relative oxidation stability, when bonded in thin films with a ceramic, as for pure powder samples. A table is presented summarizing these oxidation characteristics together with information from the literature on crystal structures, electrical resistivities, and densities. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Chicago, Illinois, October 17–19, 1967.

Vaporization of Lead Zirconate-Lead Titanate Materials: II, Hot-Pressed Compositions at Near Theoretical Density*

Abstract: The vaporization of lead monoxide from lead zirconate-lead titanate materials was studied by thermogravimetric techniques in vacuum with hot-pressed pellets of near theoretical density. The initial step of the complex, two-step vaporization observed in cold-pressed pellets in an earlier investigation is absent. The rate-determining step for both the porous, cold-pressed, and pore-free, hot-pressed materials is the bulk diffusion of lead across a thickening lead-depleted layer at the surface of the pellet and results in a parabolic time dependence. Although parabolic rate constants are slightly lower overall for the dense materials, the activation energies for the weight loss process remain approximately 38.5 and 35 kcal/mole for the pure and Bi-doped Pb(Zr0.65Ti0.35)O3 compositions, respectively. Vaporization mechanisms and rates were unchanged under nitrogen or oxygen pressures up to 50 torr at 1000°C. Alumina Knudsen cells were used to study the equilibrium vapor above a powdered, hot-pressed Pb(Zr0.65.Ti0.35)O3 composition. Mass spectrometric analysis of the vapor at 950°C showed that the vapor species and their relative abundances were the same as the equilibrium vapor species above pure lead monoxide. Continuous weight loss data from these cells gave an apparent vapor pressure that was 2% of the vapor pressure of pure lead monoxide at a given temperature, but gave the same second law enthalpy of vaporization. The overall vaporization process can be represented by the reversible equilibria: the diffusion of Pb2+ and O2- to the surface through a lead-depleted region whose phases and compositions are determined by the subsolidus phase relations in the PbO-ZrO2-TiO2 ternary system, the reaction at or near the surface to form PbO, and the subsequent vaporization of PbO.

Thermal degradation studies of several Pyrrone films

Abstract: Thermal degradation of polyimidazopyrrolone /pyrrone/ films in air and vacuum, using thermogravimetric analysis

Extraction of Meaningful Kinetic Parameters from Thermogravimetric Analysis

Abstract: MUCH effort is being devoted to thermo-analytical techniques such as thermogravimetric analysis (TGA)1–3, differential thermal analysis (DTA)4–6 and differential enthalpic analysis (DEA)7, in order to evaluate kinetic parameters for solid state decompositions of the generic type It is generally accepted8,9 that such reactions, which are often characteristic of polymer degradations and the decomposition of inorganic complexes and minerals, begin at certain discrete regions, called nucleus-forming sites, on the surface of the reactant. Further chemical reaction is localized at the interface between the nuclei and the reactant matrix, so that the nuclei grow in size as the reaction proceeds. For a complete kinetic description of the decomposition of a solid it is therefore necessary to know the rate of formation and spatial distribution of the nuclei; the rate of growth of the nuclei (which will, in general, vary with crystallographic direction); and the size and shape of the parent particle(s). Hence the full mathematical formulation of the rate process must, in general, be expressed10 in terms of both spatial and time coordinates.

Thermal Degradation Spectrum; Instrumentation to Record Thermogravimetric Results

Abstract: Simple modification of conventional temperature-programmed thermogravimetric apparatus permits direct recording of the thermal degradation spectrum (TDS) of polymers and the rate of weight loss with rising temperature. The effect of heating rate on the TDS of poly(methyl methacrylate) is discussed.

Metal coordination polymers. I. Synthesis and thermogravimetric analysis of beryllium phosphinate polymers

Abstract: The preparation, properties, infrared, DTA, and TGA data are given for beryllium dimethyl-, tetramethylene-, di-n-butyl-, di-n-pentyl-, di-n-heptyl-, methylphenyl-, diphenyl-, and bispentafluorophenylphosphinates. Synthesis of dimeric beryllium acetylacetonyl phenyl-[o-methylcarboranyl (B10)] phosphinate is reported. The beryllium phosphinates were prepared by the reaction of beryllium acetylacetonate with the appropriate phosphinic acid.

Thermal degradation of nadic methyl anhydride‐crosslinked novolac epoxy resin

Abstract: The physicochemical high-temperature reactions of a nadic methyl anhydride-cross-linked novolac epoxy resin were investigated by means of differential thermal analysis, thermogravimetric analysis, and by other analytical procedures. The thermogravimetric study revealed that decomposition involving weight loss occurred in two stages. Chemical analysis showed that the major gaseous products formed during weight loss were 2-methylcyclopentadiene, carbon dioxide, and carbon monoxide. The formation of a fine mist of solid particles was observed during the second stage of degradation. Changing various experimental parameters affected the degradation processes. The kinetics of degradation were also investigated. The method of Freeman and Carroll was used to find that a zero-order rate law was followed at the beginning of both first and second stages of reaction. The activation energy associated with the major portion of the first stage of weight loss was 15 kcal/mole. There was good agreement between the observed reaction rates and the reaction rates calculated from a theoretical model which depended on desorption as the rate-controlling step. The activation energy for the beginning of the second stage of weight loss was 24 kcal/mole. By using DTA, the heat of exothermal reaction during this latter phase of decomposition was evaluated as 65 cal/g.

Changes in valency state of ions in CuMn2O4 at high temperatures

Abstract: Thin films of copper manganite with three different molar ratios of Cu∶Mn viz 1∶1, 1∶2 and 1∶3 have been deposited on quartz plates. The electrical conductivity of these thin films has been studied as a function of temperature. The energy of activation for electrical conduction in these compounds is found to increase from 0.20 eV to about 0.62 eV above 600° K. Differential thermal analysis of bulk sample of copper manganite also shows a small endothermic change at 600° K, while thermogravimetric analysis does not show any change in weight. It has been concluded from these results that the stable form of the ionic configuration of copper manganite at low temperatures, i.e. Cu1+[Mn3+Mn4+]O4 changes at high temperatures to Cu2+[Mn23+]O4

The Use of Dynamic Differential Calorimetry for Ascertaining the Thermal Stability of Polymers

Abstract: The use of thermal analytical methods for the study of the thermal stability (and/or the thermal oxidative stability) of high polymeric materials has enjoyed increasing popularity Traditionally, thermogravimetric analysis (TGA) or differential thermal analysis (DTA) have been used either separately or in complementary studies1–3

The nature and properties of manganese violet

Abstract: A new method for the preparation of manganese violet is reported and the formula confirmed as manganese(III) ammonium pyrophosphate by wet analysis, X-ray powder diffraction, infrared spectroscopy, thin-layer chromatography, and magnetic measurements. The thermal decomposition has been studied and thermogravimetric curves obtained. Using the above techniques, the products have been identified as either manganese(II) trimetaphosphate, or a mixture of manganese(II) tri- and tetra-metaphosphates depending on the temperature and duration of heating.

Preparation of poly(diphenyl phosphazene)

Abstract: The preparation of substituted polyphosphazenes has been briefly surveyed. A method of synthesis of a fully substituted poly(diphenyl phosphazene) has been investigated. The product has been characterized and thermogravimetric analysis carried out. The volative products of pyrolysis have been identified and the hydrolytic stability of the polymer tested.

Thermal Degradation of Polymers. V. Derivation of Thermogravimetric and Kinetic Data from Mass Spectrometric Thermal Analysis

Abstract: Derivation of kinetic and thermogravimetric data from mass spectrometric thermal analyses of polytetrafluoroethylene and silicone resins has been achieved using a new method of data treatment applicable to the entire temperature range in which degradation occurs, even at relatively high heating rates (66 to 118°C/min). For heating rates to 300°C/min, the method of Ozawa relating activation energy to the slope of a graph of log (heating rate) vs. reciprocal temperature of the MTA maximum was employed to estimate an activation energy for polytetrafluoroethylene. Both methods give data in satisfactory agreement with results obtained by other methods.

Thermal stability of modified poly(vinyl chloride) by TGA

Abstract: The stability of poly(vinyl chloride), as measured by thermogravimetric analysis, is significantly different from that of other thermoplastics. It is shown that the onset of weight loss can be correlated with the development of color in a processed resin. It is further shown that the ingredients within a rigid polyvinyl chloride compound drastically alter its thermal behavior. The effect of lubricant and stabilizer on the degradation of poly(vinyl chloride) is stressed.

Synthesis and thermogravimetric analysis of diol‐linked tetrameric hexaphenyldichlorophosphonitrile polymers

Abstract: Several high molecular weight polymers have been prepared from the reactions of hexaphenyldichlorophosphonitrile tetramer with p,p′-biphenol, 4,4′-oxydiphenol, resorcinol, and benzidine. A simple fractionation procedure yielded samples of the biphenol-linked polymer with molecular weights of approximately 500,000. DTA and TGA studies of this polymer in a variety of environments indicate thermal degradation is initiated in the phosphonitrile ring.

Some properties of poly-α-piperidone

Abstract: The high molecular weight polymer of α-piperidone, which had been unobtainable with the use of alkali metal, trialkyl aluminum, or Grignard reagent as catalyst, was prepared with M–AlEt3, (where M is alkali metal), MAlEt4 or KAlEt3 (piperidone) as catalyst and N-acyl-α-piperidone as initiator. From the determination of the behavior of the solution viscosity of poly-α-piperidone in m-cresol at 30°C. the value of 0.27 for the Huggins constant was obtained. Examination of the correlation between the number-average molecular weight, determined by endgroup titration, and the intrinsic viscosity gave a somewhat small value for the endgroup COOH. This may be considered due to the consumption of N-acyl-α-piperidone by a propagating polymer in the course of polymerization. The thermal stabilities of the polyamides, nylons 4, 5, and 6, was in the order nylons 6 > 5 > 4 according to differential thermal and thermogravimetric analyses, Poly-α-piperidone, which has a reduced viscosity of 0.7, shows a melting point of 270°C.. which was expected from the zigzag pattern of the correlation between melting points and numbers of CH2 groups for polyamino-acid polymers.