Showing papers on "Thermogravimetric analysis published in 1969"
TL;DR: In this paper, the first success in using carbon dioxide as a direct starting material for synthesizing high polymers was reported, which was confirmed with the aid of IR, NMR and elemental analysis.
Abstract: Attempts to copolymerize carbon dioxide with epoxide led us to the first success in using carbon dioxide as a direct starting material for synthesizing high polymers. Some organometallic catalyst systems were found to catalyze the alternate copolymerization of carbon dioxide and epoxide, resulting in the formation of polycarbonates, the structures of which were confirmed with the aid of IR, NMR and elemental analysis. Diethylzinc-water system produced a methanol insoluble aliphatic polycarbonate of much higher molecular weight than that produced by polycondensation. Thermal properties of the methanol insoluble polycarbonate were studied by differential thermal analysis and thermogravimetric analysis.
521 citations
282 citations
TL;DR: In this paper, the authors show that in vacuo, PDMS fractions depolymerize to cyclic dimethylsiloxanes and low molecular weight linear residues by a randomly initiated mechanism which, it is postulated, involves the formation of an intramolecular, cyclic, four-centered transition state followed by siloxane bond rearrangement.
Abstract: Thermogravimetric analyses (TGA) of catalyst-free polydimethylsiloxanes (PDMS) have been carried out in controlled atmospheres and a kinetic analysis of the results has enabled the various decomposition processes to be separated and identified. The calculated activation energy for thermal depolymerization is 42 ± 3 kcal/mole, while thermo-oxidation has an apparent activation energy of 30 ± 2 kcal/mole. Quantitative analyses of the major degradation products and molecular weight distribution studies of the residues from degradation studies under isothermal conditions have shown that in vacuo, PDMS fractions depolymerize to cyclic dimethylsiloxanes and low molecular weight linear residues by a randomly initiated mechanism which, it is postulated, involves the formation of an intramolecular, cyclic, four-centered transition state followed by siloxane bond rearrangement. This mechanism is a basic property of linear PDMS fractions and is independent of molecular weight. Molecular weight distribution (MWD) changes observed from further isothermal investigations on hydroxy endblocked PDMS fractions, have shown the presence of a chain-lengthening process in vacuo below the depolymerization temperature. This process, with an apparent activation energy of 8.6 ± 1 kcal/mole, is attributed to the intermolecular condensation of terminal hydroxyl groups.
240 citations
TL;DR: In this paper, the authors proposed a trial-and-error method for the determination of the g(α) and p(x) functions fitting the equation and thus an estimation of the probable mechanism of the reaction and other kinetic parameters (activation energy and frequency factor).
Abstract: According to Doyle, the thermogravimetric curve of a decomposition reaction can be expressed by the equation log g(α)–log p(x) = B. The variable x depends on the temperature Tα, at which the fraction of the initial compound decomposed is α. Both g(α) and p(x) depend on temperature; however, B is independent of temperature. The trial-and-error method allows, for a given thermogravimetric curve, the determination of the g(α) and p(x) functions fitting the equation and thus an estimation of the probable mechanism of the reaction and of other kinetic parameters (activation energy and frequency factor). To facilitate the analysis of experimental data, a table of log g(α) values for various decomposition mechanisms and a plot of-log p(x) vs T for various activation energies are presented. The use of the table and the diagram is described.
140 citations
TL;DR: In this paper, a novel polyimide forming reaction was reported, where pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt-fusion conditions to give polydiphenyl methanepyromellitimide (II) and carbon dioxide.
Abstract: A novel polyimide forming reaction is reported. Pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt-fusion conditions to give polydiphenylmethanepyromellitimide (II) and carbon dioxide. Polymer II was characterized by inherent viscosity, infrared spectrum, and thermogravimetric analysis. An intermediate Polymer I was isolated which appeared to contain seven-membered rings in the backbone. It is postulated that these rings eliminate carbon dioxide to form polyimide II.
75 citations
TL;DR: In this paper, the pyrolysis of acrylic fiber up to 400°C in an inert atmosphere at 1° and 6°C/min was studied by means of thermogravimetric and differential thermal analysis.
Abstract: The pyrolysis of acrylic fiber up to 400°C in an inert atmosphere at 1° and 6°C/min was studied by means of thermogravimetric and differential thermal analysis. The exothermic reaction occuring at 180–300°C was shown to be due to the reaction of nitrile groups by comparing the extent of exotherm with the number of nitrile groups present, determined by infrared spectroscopy. In addition, results of single-fiber tensile measurements, density, and elemental analysis of the pyrolyzed fibers are interpreted in terms of possible molecular structures. The gases evolved on pyrolysis were analyzed for both ammonia and hydrogen cyanide and the liberation of ammonia was attributed to a termination reaction of the polymerization of nitrile groups. The critical conditions necessary for the production of high strength and modulus carbon fiber are discussed briefly in ralation to the chemical changes occurring on pyrolysis.
58 citations
01 Jan 1969
38 citations
TL;DR: In this article, the reduction of a catalyst based on Fe2O3MoO3 with N 2 H 2 and N 2 NH 3 as reducing mixtures has been studied by a thermogravimetric method.
32 citations
TL;DR: In this article, the apparent kinetic parameters of the pyrolysis reaction have been derived by means of the modified Doyle method, which do not characterize the purely chemical reaction, but the complex heterogeneous process as a whole.
Abstract: Thermal decomposition of 21 complexes of the type [Co(DH)2(amine)2]NCS has been studied under the conditions of thermogravimetric analysis, by using different heating rates. From the thermogravimetric curves apparent kinetic parameters of the pyrolysis reaction have been derived by means of the modified Doyle method. Apparent reaction order increases and apparent activation energy decreases with increasing heating rate. Thus, the obtained kinetic parameters do not characterize the purely chemical reaction, but the complex heterogeneous process as a whole. The explanation of the observed effect is discussed. Results are compared with those obtained with other analogous complexes.
29 citations
28 citations
TL;DR: In this article, the oxidation of 304L stainless steel was measured in steam and in air in the temperature range from 1000 to 1375 C (1832 to 2507 F) using a thermogravimetric technique.
Abstract: The oxidation of 304L stainless steel has been measured in steam and in air in the temperature range from 1000 to 1375 C (1832 to 2507 F) using a thermogravimetric technique. This temperat...
TL;DR: The initial mode of decomposition varied within the copper group as discussed by the authors, and the iodides, bromides, and chlorides all decomposed via dehydroxylation and in this way resembled the Cd and Zn basic halides.
Abstract: Copper basic halide compounds have been studied by thermogravimetric and differential thermal analyses. This study reveals the general pattern of thermal stability observed for cadmium and zinc basic halides.The initial mode of decomposition varied within the copper group. The iodides, bromides, and chlorides all decomposed via dehydroxylation and in this way resembled the Cd and Zn basic halides. The copper basic fluorides, on the other hand, decomposed by simultaneous dehydroxylation and dehydrofluorination which is in distinct contrast to the Cd and Zn basic fluorides.
TL;DR: The beryllium chelates of 2-trifluoroacetylphenol and 2-hydroxyisobutyrophenone in addition to the above o-acylphenols were synthesized in this paper.
Abstract: The beryllium chelates of 2-hydroxy-3-methylacetophenone, 2-hydroxy-3-isopropylisobutyrophenone and 2-hydroxyacetophenone, and the copper- and nickel chelates of the ketimine derivatives of 2-trifluoroacetylphenol and 2-hydroxyisobutyrophenone in addition to the above o-acylphenols were synthesized. The thermal stability and relative volatility of these chelate compounds, measured by means of a thermogravimetric method, were found to be strongly increased by introduction of bulky alkyl or trifluoromethyl groups.
TL;DR: In this article, the decomposition of cellulose in the absence and presence of additives was studied in a combined DTA-TGA (differential thermal analysis - thermogravimetric analysis) system, in which both determinations were carried out simultaneously and on the same sample.
Abstract: The decomposition of cellulose, in the absence and presence of additives, has been studied in a combined DTA-TGA (differential thermal analysis — thermogravimetric analysis) system, in which both determinations were carried out simultaneously and on the same sample. The overall process was found to be endothermic in untreated cellulose and in the presence of acidic catalysts, but changed into an exothermal one in the presence of strong bases.
TL;DR: In this paper, a range of block copolymers of styrene and methacrylic acid has been prepared by the suspension method involving migration of a growing radical across a phase boundary, and two methods, involving calculation from solubility data and thermogravimetric analysis respectively, have been used to give an estimate of the length and composition of the blocks.
Abstract: A range of block copolymers of styrene and methacrylic acid has been prepared by the suspension method involving migration of a growing radical across a phase boundary. The way in which copolymer composition varies with change in the amount of the two monomers in the reaction mixture has been studied, and explanations are suggested to account for these variations. Two methods, involving calculation from solubility data and thermogravimetric analysis respectively, have been used to give an estimate of the length and composition of the blocks.
TL;DR: In this article, the effect of amino, substituted amino, and hydroxy groupings on the thermal stability of poly(m-aminostyrene) homopolymers and copolymers with styrene was investigated.
Abstract: Thermogravimetric and differential thermal analysis have been employed to study the effect on the thermal degradation pattern in static air of the molecular weight of poly(m-aminostyrene) homopolymers and copolymers with styrene. Related substituted styrene polymers and copolymers with styrene have also been studied in order to assess the effect of introduction of amino, substituted amino, and hydroxy groupings into a polystyrene main chain. The effect of these groupings on the thermal stability of the polymers as compared with polystyrene suggests that the inherent antioxidant characteristics of the subtituent grouping plays the major role in stabilization. A molecular weight effect has been shown to be operative for m-aminostyrene, p-N,N-dimethylaminostyrene, and m-hydroxystyrene polymers. This manifests itself in terms of different thermograms rather than by significantly influencing the procedural decomposition temperatures, although a trend is seen.
TL;DR: In this article, it was shown that the Fries rearrangement takes place in the aromatic polyesters in the presence of the Friedel-Crafts catalysts and on ultraviolet irradiation as well.
Abstract: Self-protective polyesters were synthesized in two ways: by polymer analog transformations on polymers obtained and by introduction of inhibiting groups into the polymer during synthesis. It is shown that the Fries rearrangement takes place in the aromatic polyesters in the presence of the Friedel-Crafts catalysts and on ultraviolet irradiation as well. Thermogravimetric analysis of the rearranged polymers and investigations of the influence of the ultraviolet irradiation on their properties show that the rearrangement markedly increases the photochemical and thermal stability of the polymers. Photostabilization may also be accomplished by the introduction of inhibiting groups, such as hydroxyl, sulfur, or phosphorus into the polymer molecule.
TL;DR: In this paper, simple aromatic amines have been polymerized by use of ferric chloride as a combined Friedel-Crafts catalyst and oxidant to yield polymers which are both thermally and oxidatively stable.
Abstract: Simple aromatic amines have been polymerized by use of ferric chloride as a combined Friedel-Crafts catalyst and oxidant to yield polymers which are both thermally and oxidatively stable. Under certain reaction conditions a polydiphenylamine was prepared which was stable in air up to 465°C as shown by thermogravimetric analysis. This polymer has a softening point of ca. 80–100°C and is soluble in some organic solvents. Such a polydiphenylamine and other polymers with similar properties are regarded as useful for conversion to thermally stable Phillips-type resins by crosslinking with conventional difunctional agents.
TL;DR: In this article, structural assignments were made based on elemental and infrared analyses and neutralization equivalents and thermal gravimetric analysis, where appropriate, neutralization equivalence equivalents were used.
Abstract: m-Bisaccharin and a number of its derivatives have been synthesized. Structural assignments were based on elemental and infrared analyses and, where appropriate, neutralization equivalents and thermal gravimetric analysis.
TL;DR: Temperatureogravimetric studies of the products have been used to determine the optimum temperature range of ignition of potassium thiocarbonate as a complexing and precipitating agent for gravimetric estimations.
01 Jan 1969
TL;DR: In this paper, the development of a high-heating-rate thermogravimetric analyzer for use with ablative plastics is described, and data are presented for the decomposition of a nylon-phenolic ablator.
Abstract: The development of a high-heating-rate thermogravimetric analyzer for use with ablative plastics is described. Data are presented for the decomposition of a nylon-phenolic ablator.
TL;DR: In this article, the properties of a series of polymers based upon various aromatic diamines and several isomeric diketones were investigated and compared in air and under a nitrogen atmosphere.
Abstract: This investigation was undertaken to determine the properties of a series of polymers based upon various aromatic diamines and several isomeric diketones. Consequently, six isomeric polymers were synthesized by the acid-catalyzed polycondensation of p- and m-dibenzoylbenzene with o-, p-, and m-phenylenediamine. Two fluorine-containing, isomeric polymers were also synthesized by condensing m-dibenzoylbenzene with tetrafluoro-m-phenylenediamine and tetrafluoro-p-phenylenediamine. Comparative thermal stabilities of the products both in air and under a nitrogen atmosphere were investigated by thermogravimetric analysis. Several of the polymers exhibited a high degree of thermal stability and all of the polymers exhibited essentially the same resistance to initial thermal decomposition in the oxidative as well as the nonoxidative atmosphere. A correlation of molecular structure and geometry with thermal stability and solubility is discussed and a mechanism for initial thermal decomposition of some of ...
TL;DR: In this article, the thermal decomposition of MgCO3⋅3H2O was studied using T. G. A. and X-ray powder diffraction.
Abstract: The thermal decomposition of MgCO3⋅3H2O was studied using T. G. A. and X-ray powder diffraction.Calculation of thermogravimetric curves showed that the decomposition processes consisted of four stages. The dehydration processes were superimposed in part, but each of the effects were separated by calculation. The energy of activation and the order of reaction were derived as, X-ray patterns of heated samples showed the intermediate phase of the dehydration process to be MgCO3⋅2H2O and coincided with T. G. A. data.
01 Jan 1969
01 Jan 1969
TL;DR: In this paper, a combined mass spectrometric and thermogravimetric analysis was used to estimate the thermal degradation of polymeric materials using a combination of MS-TGA and TGA.
Abstract: Polymeric materials thermal degradation kinetic parameters using combined mass spectrometric and thermogravimetric analysis /MS-TGA/
TL;DR: In this article, the authors propose a method to find the optimal weight for a 3mg/cm2G drug using a modified version of the BLEU algorithm, which is shown to be effective.
Abstract: 加圧下における物性変化測定の一つとして,熱重量分析を行なうために高圧熱天びんを試作した.この装置は圧力0～100気圧,温度0～1000℃の範囲で使用できる.加圧下で熱重量変化を測定する場合には,ふんい気ガスの温度変化および試料の体積変化に伴う浮力の変化によって生ずる見かけの重量変化が最も大きな問題となる.この装置では,浮力の変化を電気的に演算する回路を用いて見かけの重量変化を補正した.補正後の重量変化測定の誤差は試料1000mgに対しアルゴン加圧下80kg/cm2G,温度0～800℃で±3mg以下である.この装置を用い,炭酸マンガンおよびシュウ酸カルシウムの加圧下熱分解反応について熱重量測定を行なった.
01 Oct 1969
TL;DR: The method of mathematical treatment of thermogravimetric curves obtained under a constant rate of heating that has been used in the present study makes it possible to determine the principal kinetic parameters (n, E, and K/sub 0/) of thermal decomposition of coals.
Abstract: Thermal decomposition of coals is not satisfactorily described by first- or second-order kinetic equations. The method of mathematical treatment of thermogravimetric curves obtained under a constant rate of heating that has been used in the present study makes it possible to determine the principal kinetic parameters (n, E, and K/sub 0/) of thermal decomposition of coals. Thermal decomposition of coals is a complex process consisting of a number of parallel and consecutive reactions, as indicated by the kinetic order of the process. 17 references.
TL;DR: In this article, copolymers of tetrafluoroethylene with perfluoroalkenes were prepared by emulsion and y-irradiation techniques and their compositions were determined by pyrolysis-g.l.c.