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Abstract  

A new pressure DSC module (Mettler DSC27HP) and its abilities for vapor pressure determination in the range of subambient pressure to 7 MPa are presented. To compare the new to an established method, vapor pressures of caffeine, naphthalene and o-phenacetin have been determined both by pressure DSC and the Knudsen effusion cell method. These results, including the derived heats of evaporation and heats of sublimation, are compared to literature values.

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Abstract  

In this paper the temperature calibration of a Mettler Toledo DSC27HP high-pressure DSC for measurements in an ammonia atmosphere is described. Measurements were performed on the melting process of three reference substances in golden crucibles: indium, tin and lead. The procedure described by the German Society for Thermal Analysis and Calorimetry, GEFTA, was applied: to correct for temperature gradients in the DSC-cel extrapolated onset temperatures of the endothermic melting peaks were measured as a function of heating rate to find by extrapolation the extrapolated onset temperature at zero heating rate, which should be a temperature corrected for temperature gradients. However, measurements performed at different pressures (between 1.5 and 8.4 bar) showed that the evaluated extrapolated onset temperatures at zero heating rate decreased with increasing pressure. This observation cannot be explained by the known dependence of melting temperatures on pressure. Therefore pressure dependence of the extrapolated onset temperatures must be caused by experimental issues. It is assumed that, although the results were extrapolated to zero heating rate, results are still influenced by temperature gradients in the DSC-cell. As a mean value, the extrapolated onset temperatures at zero heating rate decreased by 0.053�C when the pressure was raised by 1 bar. Since the software package does not allow for the pressure dependence of calibration parameters, measurement results must be corrected manually for this effect.

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Abstract  

The influence of pressure on the polycondensation reaction between novolac resin (N) present in commercially available moulding compounds and hexamethylenetetramine (HMTA) was studied up to 80 bars under air and in an inert atmosphere. For a low HMTA content (N/HMTA=98/2 mass ratio) high pressure enables the detection of two successive curing reactions. With increasing HMTA content the peak due to the first curing reaction becomes less pronounced at high pressure, while the enthalpy of the second increases. In an inert atmosphere both curing reactions are well observable even at ambient pressure and for lower HMTA content take place at lower temperatures, as expected. For the sample with N/HMTA=98/2 the curing reaction was followed using TG-MS.

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Abstract  

Pressurised differential scanning calorimeter (PDSC) has been used to obtain information on the pyrolysis and combustion characteristics of oil shales. Two distinct exothermic peaks were identified in combustion experiments known as low temperature oxidation (LTO) and high temperature oxidation (HTO) reaction regions. The pyrolysis process of all studied oil shale samples showed one exothermic effect at each total pressure studied. Kinetic data were analysed by Roger & Morris and Arrhenius methods and the results are discussed.

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Abstract  

The eutectic binary phase diagrams of volatilizable energetic material 1,3,3-trinitroazetidine (TNAZ) with 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 1-methyl-2,4-dinitroimidazole (MDNI) have been investigated by high pressure differential scanning calorimeter (PDSC), respectively. The liquefying and melting processes of TNAZ/RDX and TNAZ/MDNI volatilizable systems have been studied. On the basis of the data of apparent fusion heat and liquefying temperature, the phase diagrams of apparent fusion heat (H) with composition (X) and liquefying temperature (T) with composition (X) were constructed, respectively. The results showed that the gasification or volatilization of easy volatile energetic materials could be efficiently restrained by high pressure atmosphere, and the perfect and ideal phase diagrams can be constructed. The eutectic temperatures for TNAZ/RDX and TNAZ/MDNI are measured to be 95.5 and 82.3 °C, respectively. The eutectic compositions of mole ratios for the two systems are obtained to be 93.55/6.45 (TX method), 93.79/6.21 (H–X method) and 62.25/37.75 (TX method), 63.29/33.71 (HX method), respectively.

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Abstract  

A micro DSC analyzer fitted with special high-pressure vessels was used to investigate the kinetics of methane hydrate formation in the water phase dispersed as a stable emulsion in deep offshore drilling fluids. At high sub-cooling conditions, the peak of hydrate formation is perfectly visible and regular-shaped, and could be fitted by a Gaussian law. The average time for hydrate crystallization of the water droplets’ population was represented as a logarithmic function of the inverse of absolute temperature. At low sub-cooling conditions, the formation appears confused with the baseline; the amount of hydrate formed was thus measured from its enthalpy of dissociation, after periods of formation of variable duration.

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Journal of Thermal Analysis and Calorimetry
Authors: Lin-Quan Liao, Hong-Jian Wei, Ji-Zhen Li, Xue-Zhong Fan, Ya Zheng, Yue-Ping Ji, Xiao-Long Fu, Ya-Jun Zhang, and Fang-Li Liu

is to investigate the interactions and compatibilities between PNIMMO with some common and new energetic materials under the non-isothermal condition by means of pressure DSC technique [ 11 – 17 ]. Experimental

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Summary The influence of the atmospheric conditions such as the oxygen concentration and its pressure on the spontaneous ignition behaviour of activated carbon was investigated with high pressure DSC (HP-DSC), TG-DTA and SIT (spontaneous ignition test). The onset temperature with HP-DSC lowered with the increase of the oxygen concentration and the onset temperature could be predicted with the oxygen concentration. From the adiabatic self-heating profiles observed by SIT the onset temperature lowered with the increase of the oxygen concentration and the activation energy of induction period of exothermic reaction was determined as 28~39 kJ mol-1.

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