Search Results
Abstract
Results on the preparation and thermoanalytical investigation of aliphatic bismaleamic acids and bismaleimides are presented. Correlations were established between the chemical structure and the thermal properties. The melting point and the thermal stability of the bismaleimides decrease as the number of carbon atoms in the structure increases. Chemically imidized samples have significantly higher thermal stability, which is almost independent of the chemical structure. Thermal polymerization begins just after the melting of the materials. A thermal fragmentation scheme is proposed, based on the results of mass spectrometry.
Abstract
The crystalline solvates containing fullerenes and (di)methylnaphthalenes were investigated by thermal analyses and X-ray diffraction methods. It was found that C60 with (di)methylnaphthalenes forms two types of stable solvates: either at the molar ratio 1:2 decomposing at temperatures close to 100C or at 1:1 molar ratio decomposing in the temperature range 120–214C. Crystalline lattice and thermal stability of the solvates depends on the structure of the solvent molecules. The strong solute-solvent interaction is also manifested by the modification of the C60 absorption spectra in solution. The results are discussed using semiempirical quantum chemistry methods.
Abstract
Thermal stability of silica-polyvinylsiloxane systems with different ratio of hydrophilic and hydrophobic components and its forms with adsorbed dyes were studied using thermochemical method. It was shown that the maximum of endoeffect relating to dehydroxylation of sorbents surface is observed at 325C. The maximum temperature of the second endoeffect depends on the organosilica sorbents composition and increases with a decrease of hydrophilic and hydrophobic sites ratio. It was found that the values of the summary thermal effect lowers upon the raise of the quantity of silanol groups. It was shown that thermal stability of composition materials is higher in comparison with initial organosilica sorbents.
Abstract
The boundary of the ‘analytical’ thermal stability of a phenol-formaldehyde-urea binder was determined, assuming the lack of nitrogen losses as a criterion of thermal stability.
References 1 ‘ Thermal Stability Analysis of HAN-Based Liquid Gun Propellants ' by Oxley , J. C. , Smith , J. L. , Askins , J. A. , Gilson , N. S. , Feng , H. , Banks , M. , (NMIMT
Abstract
Thermogravimetry technique is useful to determine the thermal stability of vegetable oils. In this paper some vegetable oils obtained from brazilian Cerrado native plants were studied based on their high oleic acid content. Amburana, baru and pequi pulp oils presented higher yield of extraction compared to soybean oil. The thermal stability of oils in nitrogen was very close hence their fatty acid composition was very similar. Amburana and baru oils have major amount of unsaturated fatty acids, especially linoleic acid and pequi pulp oil has the highest short chain fatty acid content which can explain its lowest thermal stability in synthetic air.
Abstract
Results of studies dealing with an effect of polymers (selected kinds) and plasticizer on thermal stability of coal-tar pitch were presented. Factors being decisive in miscibility of composition constituents and instability of bitumen-polymer-plasyticizer mixtures were determined.
Abstract
New oxyfluoride glasses based on the system ZrO2-Pr2O3-ZrF4-BaF2 were obtained, and the glass forming ability of this system was evaluated. The effects of glass composition on both thermal stability and the crystalline phases formed upon heat treatment were determined by the DSC and XRD methods, respectively. The composition with higher thermal stability and better glass forming ability contained 2 mol% of oxides.
Abstract
In this study, the thermal stability of sisal in cycle process was investigated between room temperatures and 600°C in various conditions (in air, in composites, in argon) by thermogravimetry and mechanical testing measurement. The results indicated that the thermal stability of sisal was worse in air before five times of thermal cycles, but after the five times thermal stability of sisal in composites was better. In different conditions of same cycles process, the thermal stability of sisal was different. With increasing of thermal cycles times, the max. load (is the maximum strength in stress-strain curve) of sisal fiber showed downtendency in different conditions and decreased most obviously in composites.
Abstract
Thermal analysis of fusion and decomposition processes were carried out on recently synthetized pharmaceutical compounds in order to establish thermal stability criteria. This study was carried out using thermogravimetry, TG, and differential scanning calorimetry, DSC. Degradation and fusion temperatures have been produced as thermal data with the aim of to study the thermal stability of the compounds. Relationship is found among stability and a series of effects of structure of the compounds. The compounds which present an amide functional group in the central molecule are more stable because they have a comparatively higher fusion and degradation temperature. In addition, the stability of this type of compounds depends on the position of the electrophilic substitution (in ortho, meta or para). Likewise, the groups linked to the aromatic ring with high electronic density give stability, and therefore are able to delocalize the charge in a greater spacial interval. Therefore, criteria for the selection of substituents have established that improve the stability of compounds
