Showing papers on "Thermogravimetric analysis published in 1979"
TL;DR: In this paper, nylons 6 and 11 have been plasticized with anhydrous ammonia and subsequently were solid-state coextruded below the melting point by a temporary disruption of the strong hydrogen bonding between amide groups of adjacent nylon chains.
Abstract: Reversible plasticization of nylons with anhydrous ammonia is a new concept. In the present studies, nylons 6 and 11 have been plasticized with anhydrous ammonia and subsequently were solid-state coextruded below the melting point. The plasticization is attained by a temporary disruption of the strong hydrogen bonding between amide groups of adjacent nylon chains. Thermogravimetric and infrared analysis show that for the nylons 6 and 11 the amount of ammonia absorbed is 18% and 10% of the weight of the dry samples, respectively. The ammonia incorporation to preformed nylon ribbons prior to extrusion alleviated significantly the processing difficulties encountered with untreated nylons and aided the rapid extrusion of highly oriented states (EDR 12). The extent of orientation is documented by the high total birefringence values (8.25 × 10−2 for nylon 6 and 5.8 × 10−2 for nylon 11), by the significant increase in crystallinity (23.5%–53% for nylon 6 and 25.7%–40% for nylon 11), and by the enhanced tensile moduli (13 GPa for nylon 6 and 4 GPa for nylon 11).
43 citations
TL;DR: In this article, the first two stages of the thermal decomposition of calcium oxalate monohydrate have been established from non-isothermal thermogravimetric studies, and the rate-controlling processes are phase boundary reactions; the dehydration step assumes spherical symmetry whereas the decomposition step follows cylindrical symmetry.
38 citations
TL;DR: EPR spectra of spin-labelled cuticle indicate that the epicuticular lipids are very mobile at ambient temperature, with the translational diffusion coefficient being about 5 × 10−6 cm2 sec at 22 C, and that the low-temperature transition is associated with an increase in mobility of the hydrocarbon chains of the Epicuticular Lipids.
35 citations
TL;DR: In this article, the authors investigated the relationship between crosslinking, cyclization, and depolymerization in polybutadienes (PBDs) decomposition.
30 citations
TL;DR: In this article, two polyimides were taken as examples demonstrating the possibilites of combining the methods of thermal analysis (TGA, DTA and TVA) for studying the transformations of polyamic acids and polyimide over the temperature range 20-800°.
23 citations
TL;DR: In this article, the thermal decomposition of three commercial samples of carboxy-terminated polybutadiene (PBCT) resins was studied by thermogravimetric analysis (TGA) at heating rates varying from 2° to 100°C/min.
Abstract: The thermal decomposition of three commercial samples of carboxy-terminated polybutadiene (PBCT) resins was studied by thermogravimetric analysis (TGA) at heating rates varying from 2° to 100°C/min. Kinetic parameters of the decomposition process at different heating rates were evaluated by means of the Fuoss method.1 The decomposition process and the activation energy values are found to be dependent on heating rate. Mass-spectrometric analysis of the decomposition products shows that the pyrolysis products of PBCT resins are mainly low molecular weight hydrocarbons: ethylene, acetylene, butadiene, propadiene, vinylcyclohexene, etc. The rates of evolution of these hydrocarbon products vary with the carboxy content of the PBCT resin. Based on this, a carbonium ion mechanism has been suggested for the thermal decomposition. The data generated from this work are of importance for a consideration of the mechanism of combustion of composite solid propellants based on PBCT binders.
21 citations
TL;DR: In this article, the authors compared the results of the Achar, Brindley and Sharp (ABS) and the integral one of Coats and Redfern (CR) for the thermal decomposition of Pb(SCN)2 at the lowest heating rate.
Abstract: Abstract The \"differential\" method of Achar, Brindley and Sharp (ABS) and the \"integral\" one of Coats and Redfern (CR) are applied to the dehydration of BaBr2-H20 and HCOOLi-H20 and to the thermal decomposition of Pb(SCN)2, and the kinetic parameters so obtained are compared with those deduced isothermally. The results of the ABS method, at the lowest heating rate (q = 1.2 K min — '), agree well with the isothermal ones, whereas the CR method leads to satisfactory results only for the Pb(SCN)2 thermal decomposition (q = 1.2 K min~*). A possible explanation is given.
20 citations
TL;DR: In this paper, seven new complexes of Pd(II) with methionine were synthesized and characterized by elementary analysis, thermogravimetry, UV and IR spectra.
19 citations
TL;DR: In this article, a phase transition for NH 4 H 2 PO 4 (ADP) was observed in the region from 400 to 500 cm −1 of the infrared spectra in the temperature range of 138-174° C.
19 citations
TL;DR: In this article, a method is suggested for the kinetic consideration of a differential thermal analysis (DTA) or thermogravimetric (TG) curve which is based on a relation for the first-order reaction rate and Arrhenius's equation.
17 citations
TL;DR: In this paper, the shape of the weight and temperature curves expected in quasi-isothermal analysis for different controlling mechanisms is discussed, and a method is given for calculating the activation energies from these curves.
TL;DR: In this article, the physical properties of poly(N-aryl maleimide polymers have been studied and some of their physical properties have been characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), and programmed thermogravimetric analysis.
Abstract: Poly(N-aryl maleimide)s of characteristic structures have been synthesized and some of their physical properties studied. The polymerization of N-(fluoro phenyl) maleimides by free-radical initiation in bulk or in solution and by anionic catalyst have been studied to compare the characteristics of polymerization by ..gamma..-ray irradiation with that by free-radical initiation. The polymers were characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), programmed thermogravimetric analysis, and x-ray diffraction. Spectra of polymers prepared by radiation and anionic polymerization were nearly identical with those of polymers prepared by free-radical polymerization initiated by azobisisobutyronitrile in bulk or in solution and by the self-initiated thermal polymerization. A variety of reaction conditions were tried, but all attempts to change the molecular structure of the polymers were unsuccessful. Rates of thermal degradation for poly(N-(fluoro phenyl) maleimide)s have been analyzed by using a multiple-heating-rate procedure. Overall activation energy, order of reaction, and frequency factor have been evaluated. 6 figures, 8 tables.
TL;DR: In this paper, a technique for preparing sorbents was developed based on polyethylene glycols of different molecular weights and the solid support Chromaton NAW DMCS, which can be used for the gas chromatographic analysis of C3-C20 free fatty acids.
TL;DR: In this paper, the thermal stability of the polymer prepared by substituting poly(dichlorophosphazene) with an excess of a 64/36 mole-% mixture of the sodium salts of 2,2,2-trifluoroethanol/2.5 octafluoropentanol were studied by thermogravimetric and gel permeation chromatography techniques.
Abstract: The thermal stability of the polymer prepared by substituting poly(dichlorophosphazene) with an excess of a 64/36 mole-% mixture of the sodium salts of 2,2,2-trifluoroethanol/2,2,3,3,4,4,5,5-octafluoropentanol were studied by thermogravimetric and gel permeation chromatography techniques. The primary mode of degradation of this polymer was shown to be via random scission. The overall degradation reaction corresponds to quasi-zero-order kinetics.
TL;DR: In this paper, the authors used differential scanning calorimetric, thermogravimetric and mass spectrometric techniques to study double-base propellants in air and vacuum.
Abstract: Thermal decomposition studies on double-base propellants have been carried out in air and vacuum using differential scanning calorimetric, thermogravimetric and mass spectrometric techniques. Low temperature (90 degree C-170 degree C) decomposition seems to involve diffusion controlled process, the mechanism in air and vacuum being different. High temperature (170 degree -205 degree C) decomposition involves bond breakage.
TL;DR: In this paper, a polymerization reaction was carried out in aqueous medium and in methanol-water mixture at 40/sup 0/C using sodium bisulfite as initiator.
Abstract: Poly(methyl methacrylate)--lead silicate composites were prepared with different amounts of crystalline or amorphous PbO--SiO/sub 2/ binary composition (70 mole % PbO). The polymerization reaction was carried out in aqueous medium and in methanol--water mixture at 40/sup 0/C using sodium bisulfite as initiator. The presence of lead silicate was found to increase the molecular weight of the poly(methyl methacrylate). The prepared composites were characterized by studying their shielding properties to ..gamma.. radiation, mechanical hardness, dielectric constant, and thermal stability. It was found that lead silicate increases the absorbing power of the composites to ..gamma.. radiation. This behavior was found to be dependent on the amount and the type of lead silicate (amorphous or crystalline). Gamma irradiation of the composites was found to cause chemical degradation of the poly(methyl methacrylate) leading to a decrease in mechanical hardness. Molecular weights of the poly(methyl methacrylate) for some of the composites were determined before and after irradiation viscosimetrically. Dielectric constants for some of the composites were determined at two different temperatures. The thermal stability of the composites was studied by means of an automatic thermogravimetric analyzer. 2 figures, 5 tables.
TL;DR: In this article, an anion exchange membrane having a backbone of polyethylene and a sidechain of sulfonamide amine and the water sorbed on this membrane have been studied by infrared spectroscopy and thermogravimetric measurements.
TL;DR: In this paper, the stability of chromium (III) sulfate in the temperature range from 880 to 1040 K was determined by employing a dynamic gas-solid equilibration technique.
Abstract: The stability of chromium (III) sulfate in the temperature range from 880 to 1040 K was determined by employing a dynamic gas-solid equilibration technique. The solid chromium sulfate was equilibrated in a gas stream of controlled SO3 potential. Thermogravimetric and differential thermal analyses were used to follow the decomposition of chromium sulfate. Over the temperature range studied, the change in the Gibbs’ free energy of formation of chromium sulfate Cr2O3(s) + 3SO3(g) → Cr2(SO4)3(s) can be expressed as ΔG0 = •143,078 + 129.6T (±300) cal mole•1 ΔG0 = •598,350 + 542T (±1250) J mole•1. X-ray diffraction analysis indicated that the decomposition product was crystalline Cr2O3 and that the mutual solubility between Cr2(SO4)3 and Cr2O3 was negligible. Over the temperature range investigated, the decomposition pressures were significantly high so that chromium sulfate is not expected to form on commercial alloys containing chromium when exposed to gaseous environments containing oxygen and sulfur (such as those encountered in coal gasification).
TL;DR: In this paper, two methods for the polymerization of acrolein are proposed: suspension polymerization in water with the redox system K2S2O8:AgNO3 = 1:0.1 with respect to the monomer and a static method with the system K 2S2 O8:PA-SO2 adduct.
Abstract: Two methods for the polymerization of acrolein are proposed: suspension polymerization in water with the redox system K2S2O8:AgNO3 = 1:0.1 with respect to the monomer and a static method with the system K2S2O8:PA–SO2 adduct. The dependencies of yield, molecular weight, and structure of polyacrolein under investigation on the following factors: the amount and the ratio of the initiator components, the pH of the medium, and the monomer:solvent ratio were investigated. The structure of polyacrolein was studied by infrared spectroscopy, thermogravimetric analysis, and chemical functional analysis. The molecular weight distribution of samples of static and suspension polyacroleins modified under identical conditions was determined by gel permeation chromatography.
TL;DR: In this paper, a method for obtaining V6O13 from NH4VO3 by heating it at 500 − 550 ˚ in a stream of purified nitrogen was proposed.
Abstract: Based on thermogravimetric studies of thermal decomposition of NH4VO3 a method is proposed for obtaining V6O13 from NH4VO3 by heating it at 500– 550‡ in a stream of purified nitrogen.
01 Jan 1979
TL;DR: In this article, the surface area, pore volume and average pore size increased with pH of precipitation, and an estimate of the grain boundary area as a function of calcination temperature was obtained from the crystallite and BET surface areas.
Abstract: Zirconia gels, precipitated at pH4, 6, 8 and 10 from zirconyl chloride solutions, have been calcined at temperatures up to 1200/sup 0/C and the products investigated by nitrogen adsorption and thermogravimetric, DTA and X-ray diffraction techniques. The apparent surface area, pore volume and average pore size increased with pH of precipitation. Crystallization occurred at 390 to 420/sup 0/C yielding the monoclinic phase (pH 10 sample), the metastable tetragonal phase (pH 4 sample) or a mixture of the two (pH 6 and 8 samples). There was no relationship between the average crystallite size and the existence of the metastable phase. Increasing the calcination temperature of the pH 10 gel brought about a decrease in the surface area, resulting largely from the extensive crystallite growth, and an increase in the average size of the intercrystallite pores. Sintering of the crystallites also occurred, however, and an estimate of the grain boundary area as a function of calcination temperature was obtained from the crystallite and BET surface areas.
Journal Article•
TL;DR: In this article, various polymeric materials, including synthetic polymers and cellulosic materials, were evaluated at different temperatures, heating rates and air flow rates for thermophysical and toxicological responses.
Abstract: Various polymeric materials, including synthetic polymers and cellulosic materials, were evaluated at different temperatures, heating rates and air flow rates for thermophysical and toxicological responses. It is shown that char yields appeared to be a function of air access as much as of the chemical structure of the material. It is stated that the sensitivity of the apparent thermal stability of some materials to air access is so marked that thermogravimetric studies in oxygen-free atmospheres may be a consistently misleading approach to comparing synthetic polymers intended to increase fire safety. Toxicity also appeared to be a function of temperature and air access as much as of the chemical structure of the material. Toxicity of the gases evolved seemed to increase with increasing char yield for some polymers.
TL;DR: In this article, the thermal analysis of acrylic fibres is discussed and a procedure for the characterisation of 28 commercial fibres by thermogravimetry and derivative thermograves is described.
TL;DR: In this paper, thermal stability of a polymer system consisting of styrene, acrylonitrile and trimethylolpropane trimethacrylate was evaluated using both dynamic and isothermal TGA and IR analysis.
Abstract: Thermogravimetric (TGA) and infrared (IR) analyses were used to determine the thermal stability of a polymer system consisting of styrene--acrylonitrile--acrylamide--trimethylolpropane trimethacrylate. This study indicates that increases in curing temperature and the use of two initiators with different activities decreases the percentages of unreacted monomers. This increases the thermal stability of the polymer. To prove this, dynamic and isothermal TGA were used. The change in typical functional groups found by IR spectra also confirms this observation. 7 figures, 2 tables.
TL;DR: In this article, pyropolycarboranes, nondeformable thermally stable cross-linked polymeric materials obtained by pyrolysis of carborane-containing polymers, were investigated.
Abstract: This paper reports the results of an investigation of pyropolycarboranes, nondeformable thermally stable cross-linked polymeric materials obtained by pyrolysis of carborane-containing polymers. Carborane-containing polyamides and polyesters were heated in air under pressure and analyzed by thermomechanical and thermogravimetric methods. Moreover, the friction properties of the filled materials have been investigated. The effect of hydrogen liberation on the friction of filled pyropolycarboranes at elevated temperatures was used in developing self-lubricating materials with friction coefficients at 300–400°C.