Showing papers on "Thermogravimetric analysis published in 1988"
TL;DR: In this paper, three important thermal properties of polylactides have been measured and discussed: glass transition temperature, melting temperature, and degradation behavior, and they have been found to be highly sensitive to heat, especially at temperatures higher than 190°C.
636 citations
TL;DR: In this article, a new method for preparation of high-specific-surface (60-400 m2/g) SiC is described, which consists of the attack of high specific-surface activated carbon by SiO vapor generated by the high-temperature reaction of Si and SiO2.
214 citations
TL;DR: A straightforward and generalizable synthesis of metal-free and metal (Cu, Co, Ni, or Fe) derivatives of a symmetrically tetrasubstituted phthalocyanine derived from 15,16-dicyano-2,3,5,6,8,9,11,12-octahydro-benzo[1,4,7,10,13]pentaoxacyclopentadecine is described as mentioned in this paper.
Abstract: A straightforward and generalizable synthesis of metal-free and metal (Cu, Co, Ni, or Fe) derivatives of a symmetrically tetrasubstituted phthalocyanine derived from 15,16-dicyano-2,3,5,6,8,9,11,12-octahydro-benzo[1,4,7,10,13]pentaoxacyclopentadecine is described. The new compounds have been characterized by elemental analyses, and i.r., 1H n.m.r., u.v.–visible, and fast atom bombardment mass spectra. The alkali metal ions (sodium and potassium) bound to crown ether groups of the metal complexes force dimerization of the phthalocyanine units in solution as observed in the electronic spectra by the broadening of the Q-band transition at ca. 630 nm. The solubilities of the metal phthalocyaninates in chloroform were determined to be ca. 10–3 mol dm–3. The thermal stabilities of the compounds were determined by thermogravimetric and differential thermal analysis. The high affinity of the cobalt(II) derivative for the potassium ion was observed in solvent extraction experiments.
124 citations
TL;DR: In this paper, the effect of Al concentration on the strength of acid sites was examined using temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA).
104 citations
TL;DR: In this paper, the influence of the starting aluminum salt (chloride, nitrate, or sulfate) and the pretreatment temperature (773-1273 K) on textural properties, crystal structure, and surface acidity of AlPO4 (Al P = 1 ) catalysts was studied in order to learn how preparation conditions affect catalyst activity in organocationic reactions.
63 citations
TL;DR: In this article, the corrosion of Si3N4 under thin films of Na2CO3 was investigated at 1000°C. Thermogravimetric analysis and morphology observations lead to the following detailed reaction mechanism: (I) decomposition of Na 2CO3 and formation of NaSiO3, (II) rapid oxidation, and (III) formation of a protective silica layer below the silicate and a slowing of the reaction.
Abstract: Corrosion of Si3N4 under thin films of Na2CO3 was investigated at 1000°C. Pure Si3N4 and Si3N4 with various additives were examined. Thermogravimetric analysis and morphology observations lead to the following detailed reaction mechanism: (I) decomposition of Na2CO3 and formation of Na2SiO3, (II) rapid oxidation, and (III) formation of a protective silica layer below the silicate and a slowing of the reaction. For Si3N4 with Y2O3 additions, preferential attack of the grain-boundary phase occurred. The corrosion of pure Si and SiC was also studied for comparison to Si3N4. The corrosion mechanism generally applies to all three materials. Silicon reacted substantially faster than Si3N4 and SiC.
60 citations
TL;DR: In this article, the structural changes which occur during the calcination (250-1000°C) and subsequent reduction of precursors to Ni/MgO catalysts were made.
48 citations
TL;DR: In this article, a thermogravimetric/mass spectrometric (TG/MS) system was used to characterize the thermolysis reactions of (4-O-methyl-D-glucurono)-D-xylan.
Abstract: A thermogravimetric/mass spectrometric (TG/MS) system was used to characterize the thermolysis reactions of (4-O-methyl-D-glucurono)-D-xylan. The mass spectrometric peaks, measured as function of time, were attributed to water, methanol, carbon monoxide, carbon dioxide, formaldehyde, formic acid, acetic acid, acetone, acrolein, 2-furaldehyde, and 3-hydroxy-2-penteno-1,5-lactone. The time derivative of the thermogravimetric curve (DTG) consisted of two partially overlapping peaks, indicating a multistep mechanism. The mass spectrometric intensities of the peaks assigned to methanol and 2-furaldehyde coincided with the first DTG peak, suggesting that the first DTG peak represents both dehydration and fragmentation pathways. Methanol, water, formyl group, and carbon dioxide contributed to both of the DTG peaks. This indicates that the dehydration, decarboxylation, and decarbonylation took place in two steps. The compounds observed only in the second DTG peak and later (acetone, formic acid, formaldehyde, acrolein, acetic acid, and 3-hydroxy-2-penteno-1,5-lactone) are probably products of reactions which occur after the collapse of the original polysaccharide structure.
48 citations
TL;DR: Oxygen nonstoichiometry of the YBa2Cu3O7-x phase has been determined for between 200 to 850°C and oxygen partial pressure of 10 to 30×10-4 atm by thermogravimetric measurements.
Abstract: Oxygen nonstoichiometry of the YBa2Cu3O7-x phase has been determined for between 200 to 850°C and oxygen partial pressure of 10 to 30×10-4 atm by thermogravimetric measurements Values of the partial molar enthalpy of oxygen were estimated The stable region of the orthorhombic phase was suggested to expand at lower temperatures
44 citations
TL;DR: In this paper, the system (La,Sr)2CuO4-CuO has been investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and slow-cooling flux growth experiments.
36 citations
TL;DR: In this paper, the reactivity of amorphous copper manganese oxides (Hopcalite) with respect to thermal treatments has been investigated, showing complex bulk and surface changes upon heating in vacuum, air, oxygen and carbon monoxide.
TL;DR: In this article, a thermogravimetric investigation of the reaction of pyrite with water vapour has been completed, showing that the reaction occurs in two stages to produce magnetite via pyrrhotite.
TL;DR: In this paper, the mechanical, thermal, and surface properties of poly(dimethylsiloxane)-poly(methyl methacrylate) block copolymers (PDMS-b-PMMA) prepared by the use of poly siloxane(azobiscyanopentanamide)s were intensively investigated.
Abstract: Mechanical, thermal, and surface properties of poly(dimethylsiloxane)–poly(methyl methacrylate) block copolymers (PDMS-b-PMMA) prepared by the use of polysiloxane(azobiscyanopentanamide)s were intensively investigated. The mechanical strength of block copolymers was found to decrease with an increase of siloxane contents. Dynamic mechanical analysis (DMA) of block copolymers having long siloxane chain length (SCL) and high siloxane content revealed the existence of two glass transitions attributable to microphase separation of two segments. Differential scanning calorimetry (DSC) also gave some evidence of microphase separation supporting the DMA results. It was observed that the incorporation of PDMS segments in block copolymers improved thermal stability of PMMA, as confirmed by thermogravimetric analysis. Surface analysis of the block copolymers films cast from several solutions indicated surface accumulation of PDMS segments, as revealed by water contact angle and ESCA measurements.
TL;DR: In situ thermogravimetric analysis during the synthesis of Ba 1− x K x BiO 3− y shows the various processes occurring as a function of temperature and the gas composition of the ambient atmosphere as discussed by the authors.
Abstract: In situ thermogravimetric analysis during the synthesis of Ba 1− x K x BiO 3− y shows the various processes occurring as a function of temperature and the gas composition of the ambient atmosphere. This allows the synthesis procedure to be optimized. Single-phase material can be produced with the metal-ion stoichiometry of the starting oxide mixture.
TL;DR: In this article, 2,6-di(4-hydroxystyryl)pyridine (DHSP) with terephthaloyl or adipoyl chloride was used to synthesize new polyesters.
TL;DR: In this article, the properties of 8-quinolyl acrylate with transition metal bromides and uranyl acetate have been characterized by elemental analyses, electronic and vibration spectroscopic studies and magnetic moments.
TL;DR: In this paper, heat-resistant polymers were obtained by thermal polymerization of several bismaleimides or their substituted derivatives by adding imidized benzophenone tetracarboxylic dianhydride between the maleimide rings.
Abstract: Heat-resistant polymers were obtained by thermal polymerization of several bismaleimides or their substituted derivatives. The chain of the polymer precursors was extended by incorporation of imidized benzophenone tetracarboxylic dianhydride between the maleimide rings in order to impart a degree of flexibility in the polymers. The bismaleimides and their corresponding tetraamic acids were characterized by infrared (IR) and proton nuclear magnetic resonance ('H-NMR) spectroscopy. The differential thermal analysis (DTA) thermograms of the monomers showed exotherms at 200-340°C attributed to the thermally induced polymerization reactions. The influence of different substituents in the maleic double bond on the curing temperature was investigated. The thermal stability of the cured resins was evaluated by thermogravimetric analysis (=A) and isothermal gravimetric analysis (IGA). They were stable up to 367-433°C both in nitrogen and air atmosphere and afforded 57768% char yield at 800°C under anaerobic conditions. The structure of the aromatic and aliphatic diamines utilized for imidization was correlated with the thermal stability of the cured resins. The bismaleimide derived from p-phenylenediamine gave the most heat-resistant resin because of its higher rigidity.
TL;DR: In this paper, the thermal decomposition of ammonium paratungstate (NH 4 ) 10 (H 2 W 12 O 42 ) · 7H 2 O was studied using thermogravimetric and differential thermal analyses.
TL;DR: The influence of heating rates and environment conditions on the thermal behavior of two cobalt basic salts, β-Co2(OH)3Cl and Co5(O)85Cl15 · 25H2O, have been studied using thermogravimetric and differential thermal analysis, X-ray diffraction, and infrared spectroscopy as mentioned in this paper.
Abstract: The influence of heating rates and environment conditions on the thermal behaviour of two cobalt basic salts,β-Co2(OH)3Cl and Co5(OH)85Cl15 · 25H2O, have been studied The processes were followed using thermogravimetric and differential thermal analysis, X-ray diffraction, and infrared spectroscopy When decomposition reactions are carried out in a nitrogen atmosphere, Co3O4 is always formed in quantities that seem to depend on the heating rates When decomposition processes are carried out in an X-ray high-temperature diffraction chamber, pure cobalt is obtained at 750° C as the final product Green cobalt hydroxychloride, the composition of which determined from chemical analysis seems to correspond to the formula Co5(OH)85Cl15 · 25H2O or alternatively 4Co(OH)2 CoCl15(OH)05 · 25H2O, has been isolated as a stable compound and the evolution of this material during the ageing process has been followed by X-ray diffraction, electron microscopy and BET surface-area determination
TL;DR: In this paper, the authors used a thermogravimetric technique in exposure atmospheres of air, a low-\(p_{O_2 } \) gas mixture, and low-''O''2'' gas mixtures with several levels of sulfur.
Abstract: Oxidation-sulfidation studies were conducted on sheet samples of nickel aluminide, containing 23.5 at. % Al, 0.5 at. % Hf, and 0.2 at. % B in an annealed condition and after preoxidation treatments. Continuous weight-change measurements were made by a thermogravimetric technique in exposure atmospheres of air, a low-\(p_{O_2 } \) gas mixture, and low-\(p_{O_2 } \) gas mixtures with several levels of sulfur. Detailed scanning electron microscopy (SEM), X-ray, and electron microprobe analyses of the corrosion product scale layers were performed. The air-exposed specimens developed predominantly nickel oxide; the specimen exposed to a low-\(p_{O_2 } \).
TL;DR: In this article, an increase in the heating rate of thermogravimetric analysis from 5°C to 150°C min −1 displaced the integral curves towards higher temperature depending on the amount of residual non-cellulosic polysaccharides present along with the fibre cellulose.
TL;DR: The physicochemical properties of the polyazulene-bromine complex were characterized by elemental and thermogravimetric analyses, infrared and ultraviolet-visible absorption spectroscopy, cyclic voltammetry and gel permeation chromatography as discussed by the authors.
Abstract: Simultaneous chemical oxidation and polymerization of azulene by iodine and bromine were carried out. The polyazulene-bromine complex is electrically conductive and partially soluble in organic solvents whereas the polyazulene-iodine complex is much less conductive and insoluble. The physicochemical properties of the polyazulene-bromine complex were characterized by elemental and thermogravimetric analyses, infrared and ultraviolet-visible absorption spectroscopy, cyclic voltammetry and gel permeation chromatography. Experimental evidences suggest that the soluble fraction of the complex consists mainly of azulene oligomers.
TL;DR: In this paper, phosphorus-containing homopolyurethanes were synthesized by reacting various diisocyanates such as tolylene diisOCyanate, methylenebis(4-phenylisocynate) and hexamethylene-1,6-diisOCynet with 1,4-bis[(dialkoxyphosphinyl)hydroxymethyl]benzene (BDAB).
Abstract: New phosphorus-containing homopolyurethanes were synthesized by reacting various diisocyanates such as tolylene diisocyanate, methylenebis(4-phenylisocyanate) and hexamethylene-1,6-diisocyanate with 1,4-bis[(dialkoxyphosphinyl)hydroxymethyl]benzene (BDAB). In addition, copolyurethanes containing approximately 3% phosphorus were prepared by copolymerization of these diisocyanates with an equimolar amount of BDAB—hydroquinone mixture. BDAB was less reactive towards diisocyanates than hydroquinone due to the electron-withdrawing inductive effect of the phosphinyl groups. The polymers synthesized were characterized by inherent viscosity measurements as well as by proton nuclear magnetic resonance (1H-NMR) and infrared (IR) spectroscopy. The spectroscopic examination of polymers did not provide evidence for crosslinking by allophanate groups. Differential thermal analysis (DTA) studies of polymers revealed that the incorporation of BDAB in polyurethanes altered their thermal decomposition mode by increasing the exothermicity due to pyrolysis. Thermogravimetric analysis (TGA) of polymers showed that the phosphorus-containing homopolyurethanes and copolyurethanes were thermally less stable than the corresponding common polyurethanes but afforded higher char yields. Determination of the limiting oxygen index (LOI) values showed that the phosphorus-containing copolyurethanes exhibited a higher fire resistance than that of common polyurethanes.
TL;DR: In this paper, the surface area retention of the alumina-montmorillonites after thermal and hydrothermal treatment increased with increasing temperature of the aluminum chlorohydrate solution used in the preparation of the materials.
TL;DR: In a cooperative testing of polymer blends of polycarbonate (PC) and linear low-density polyethylene (LLDPE), 17 laboratories from six countries contributed measurements of differential scanning calorimetry (DSC) or differential thermal analysis (DTA) and of thermogravimetric analysis (TGA) as discussed by the authors.
Abstract: In a cooperative testing of polymer blends of polycarbonate (PC) and linear low-density polyethylene (LLDPE), 17 laboratories from six countries contributed measurements of differential scanning calorimetry (DSC) or differential thermal analysis (DTA) and of thermogravimetric analysis (TGA). This work is part of the activity of the VAMAS* Technical Working Party–Polymer Blends (TWP–PB), which provided the samples and coordinated the tests. Thermal analysis proved to be a, rapid means of assessing the miscibility of polymers using small samples. The system PC/LLDPE investigated in this test is found immiscible. The results of this cooperative test are a basis to elaborate a standard procedure for the characterization of polymer blends.
TL;DR: In this paper, a temperature-programmed decomposition of a highly characterized system of silica-immobilized heteropoly complexes containing Cu(II) and M(III) was investigated.
TL;DR: In this paper, the authors describe experiments to determine the level of water absorption in polymeric materials under different conditions of relative humidity and temperature using thermogravimetric analysis, including the glass fibre-epoxide resin laminates used in printed circuit board manufacture.
Abstract: Water absorption is a serious problem in all polymeric materials, including the glass fibre‐epoxide resin laminates used in printed circuit board manufacture. This paper describes experiments to determine the level of water absorption in these materials under different conditions of relative humidity and temperature using thermogravimetric analysis.
TL;DR: In this article, the thermal decomposition kinetics of three pesticides with different chemical structures: pirimicarb (carbamate), trichlorphon (organophosphorus) and chloridazon (heterocyclic) have been studied by thermogravimetric analysis.
TL;DR: In this paper, the thermogravimetric properties of PPS and PEEK resins and carbon fiber reinforced composites are presented, the addition of carbon fiber and the effects of environment on the thermal stability are presented.
Abstract: Polyphenylene sulfide (PPS) and Polyetherether ketone are high performance engineering thermoplastics with a unique combination of excellent thermal, mechanical and environmental properties. This paper presents the thermogravimetric properties of PPS and PEEK resins and carbon fiber reinforced composites. The addition of carbon fiber and the effects of environment on the thermal stability are presented. The way in which crosslinking of Polyphenylene sulfide in air enhances thermal stability is discussed. PEEK resin and its composite show higher thermal stability than PPS by 70 C to 100 C and this is also described. 16 references.