High pressure crucible

An optional high-pressure crucible (Fig. 8 1) may be used for chemical reactions in solutions with an inherent vapor pressure of up to 100 atmospheres. The crucible is equipped with a centering pin for exact positioning on the measuring sensor. 

As an example, one may consider that a DSC operated at 4 or 5 Kmin-1 with high pressure crucibles presents a detection limit of lOWkg 1. For extrapolation towards lower temperatures, a low activation energy must be chosen, for example, 50kjmor (Figure 11.6). This delivers conservative, that is, high values for the extrapolated heat release rate. 

Figure 12.12 Dynamic DSC thermogram of 12.3 mg concentrate in a gold plated high pressure crucible. The scan rate is 4Kmin l. The energy is 500JgT Temperature in °C, heat release rate in WkgT...

Figure 12.13 Isothermal DSC thermograms recorded with 25.2mg sample at 240°C and 23.4mg at 250°C in gold plated high pressure crucibles. For both experiments, the energy was close to 500JgT Time in hours and heat release rate in Wkg ...

Approximately 7- to 10-mg samples of this resin were weighed in sealed-glass, high-pressure crucibles. Pressure cells were used to contain any volatile, reactive... 

Fig. 2.14 Controlled high pressure crucible with the Calvet t5tpe DSC...

To our knowledge, the question of the standard state corrections in DSC experiments has never been addressed. These corrections may in general be negligible, because most studies only involve condensed phases and are performed at pressures not too far from atmospheric. This may not be the case if, for example, a decomposition reaction of a solid compound that generates a gas is studied in a hermetically closed crucible, or high pressures are applied to the sample and reference cells. The strategies for the calculation of standard state corrections in calorimetric experiments have been illustrated in chapter 7 for combustion calorimetry. 

Photopolymerization 0,5 g silica II vras mixed with 2 ml of the liquid monomer or its solution in ethanol in a flat shaped weighing tottle (35 x 30, 15 ml). The photopolymerization was performed in the presence of air by irradiating the mixture for a certain time (3 minutes in a typical experiment) with a high pressure mercury lamp (TQ 105, Heraeus) at a distance of 5 cm without agitation at room temperature. The solid material III (with silica gel shape) was collected quantitatively by filtration, washed with 100 ml ethanol on the filter crucible and dried overnight in vacuo. The weight increase of the sample corresponds well with the polymer formation on the materials III calculated from the results of the elemental analysis. (All experiments were performed twice to control the experimental error.)... 

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