Application of heat conduction calorimetry to high explosives

This paper describes some thermal analysis experiments conducted on high explosive samples. These employ differential scanning calorimetry to monitor thermal effects at elevated temperatures (around 200 °C) and heat conduction calorimetry to record thermal effects at much lower temperatures (below 100 °C).The work shows that, due to the generally high thermal stability of many high explosive compositions, heat generation rates are very low, if detectable at all, at normal storage temperatures, even when using a very sensitive instrument. The sensitivity and reproducibility of this technique has been investigated in detail by Wilker et al. [S. Wilker, U. Ticmanis, G. Pantel, Detailed investigation of sensitivity and reproducibility of heat flow calorimetry, in: Proceedings of the 11th Symposium on Chemical Problems Connected with the Stability of Explosives, Sweden, 1998] and shown to be capable of recording heat generation rates of less than a microwatt. This allows continuous measurement of decomposition processes in nitrate ester based propellants at temperatures as low as 40 °C. However, the measurement of very low levels of heat generation is difficult, time consuming and therefore expensive. If the assumption is made that the life limiting process is invariably the slow decomposition of the energetic component, this will frequently lead to very long service lifetime predictions.A number of possible complications are identified. Firstly, due to its low detection threshold, a heat conduction calorimeter may detect other reactions which will not lead to failure, but which may still dominate the heat flow signal. Secondly, the true failure process may generate little energy and be overlooked. In view of these considerations, at present it seems unwise to rely on heat conduction microcalorimetry as the only tool for the assessment of the life of high explosive energetic systems.Based on examples of life terminating processes in high explosives during storage and use, it is clear that decomposition of the energetic material is not invariably the cause of system failure. It is also by no means the only reaction that may take place in, and be observed by, a heat conduction calorimeter.     

双马来酰亚胺增韧研究Ⅱ.链扩展双马来酰亚胺及其树脂的合成及表征

合成了一系列结构不同和链长短不一的双马来酰亚胺，并对其结构和性能作了表征，同时研究了它们的固化反应和固化产物的性能。用双马来酰亚胺和二烯丙基化合物反应制造了增韧树脂，研究了该树脂的固化和热稳定性。     

Kinetic determination of microamounts of some sulphur-containing ligands

Some sulphur-containing ligands have been shown to inhibit the Hg(II)-catalysed substitution of p-nitrosodiphenylamine (p-NDA) for cyanide in hexacyanoferrate(II), by binding the mercury(II). This effect is used for determination of microamounts of cysteine, thioglycollic acid and thiosulphate. The reactions are followed spectrophotometrically at 640 nm (lambda(max) of [Fe(CN)(5).p-NDA](3-)). The determination range depends on the amount of mercury(II) added and the stability of the Hg(II)-ligand complex. Under specified conditions, the detection limits are: thioglycollic acid 1 x 10(-7)M, cysteine 1 x 10(-6)M and thiosulphate 4 x 10(-7)M.     

载体γ-Al2O3和钐对非晶态NiB合金热稳定性的影响

用化学还原法制备了NiB、NiB/Al2O3和NiBSm/Al2O3三种催化剂，它们都呈非晶结构.用等离子耦合发射光谱仪(ICP)对催化剂组分进行了分析，采用差示扫描量热法（DSC）对三种催化剂进行了热稳定性分析.结果表明，载体的引入使非晶态NiB合金的体相组成中B的含量降低.将非晶态NiB合金负载到γ-Al2O3上,可以明显改善非晶态合金的热稳定性，少量Sm可以进一步提高晶化温度.晶化激活能数据亦表明了载体和Sm对非晶结构具有良好的稳定作用.载体和Sm可能通过不同的作用提高了非晶态合金的热稳定性.     

The use of glass capillary columns for the analysis of polar natural products

Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence.     

A simplified integral equation for adsorption of gas mixtures on heterogeneous surfaces

Summary The multiple integral representing the overall isotherm for adsorption of gas mixtures on heterogeneous surfaces is transformed to a single integral, which is promising for predicting the mixed-gas adsorption by means of single-gas adsorption parameters. This transformation is possible when the adsorption energies of components for various adsorption sites show a certain type of correlation.

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Eine vereinfachte Integralgleichung für die Adsorption von Gasmischungen auf heterogenen Oberflächen

Zusammenfassung Das multiple Integral, das die Adsorption von Gasmischungen auf heterogenen Oberflächen darstellt, wurde zu einem einfachen Integral transformiert, das zur Voraussage der Adsorption von Gasgemischen mittels der Einzelgas-Adsorptionsparameter geeignet sein sollte. Diese Transformation ist dann möglich, wenn die Adsorptionsenergien der Komponenten einem bestimmten Korrelationstyp angehören.

     

The composition of the evolved gases from the thermal decomposition of certain metal sulfates

By the use of TG—MS, the thermal dissociation of anhydrous CuSO₄ and Al₂(S0₄)₃ was found to proceed according to the reactions:

followed by the reactions:

No SO₃ was indicated in the dissociation of alunite. The sulfate ion appears to dissociate by at least two different mechanisms although the parameter which controls the mechanisms has not been elucidated.     

Multiparametric curve fitting-VII Determination of the number of complex species by factor analysis of potentiometric data

The number of complex species in solution may be determined by a computer-assisted factor analysis of a set of potentiometric titration curves, by finding the rank of the normalized data matrix. An application of the program SPECIES is demonstrated for some examples of titration data. The method is limited in that it can discriminate only between species with differing degrees of polymerization.     

Effect of the reaction state on the polymerization of p-xylenesulfonium salts

1,4-Phenylenebis(methylene) sulfonium salts were polymerized under different conditions to yield p-xylylene sulfonium salt polyelectrolytes in a broad range of molecular weights. The aqueous reaction mixture formed a reversible gel at initial monomer concentrations higher than 1.0M, but at lower concentrations it remained as an emulsion until reaction completion. The effect of reaction time on intrinsic viscosities and polymer yields for both the emulsion and the gel state is discussed. The higher yields obtained when the reaction was carried out in the presence of a water-immiscible organic solvent were apparently due to the effect of this solvent on increasing the concentration of the reactive intermediate that led to the polyelectrolyte. Both the addition of an organic solvent and the variation of the initial monomer concentrations allowed some control over the molecular weight of the polyelectrolyte formed.     

Long-range dispersion coefficients for like centrosymmetric linear molecules and an application to H2-H2

The real spherical tensor theory of long-range intermolecular coefficients developed in previous papers is applied to derive explicit formulae for the first three dispersion coefficients for like centrosymmetric linear molecules. The expansion of angle-dependent coefficients in associated Legendre polynomials allows one to identify the isotropic and anisotropic components of the dispersion interaction in terms of London dispersion constants, the treatment of higher coefficients being simplified by the coupling of the elementary (l, l′)-polarizations to resultant angular momenta L_A and L_B onto each molecule. The contributions from all coupling schemes are given explicitly for C₆, C₈, C₁₀, and numerical results are presented for H₂-H₂ using two-term reduced spectra values from the Kaiserlautern group.