(81ax) 100% Adiabaticity: Realized with the Differential Accelerating Rate Calorimeter

The major shortcoming of conventional adiabatic calorimeters, such as the accelerating rate calorimeter, is that a large portion of the heat released is absorbed by the sample container which acts as a heat sink, and causes misleading results under some conditions. By definition, a true adiabatic calorimeter should eliminate sample heat losses to both the environment and the sample container. By carefully managing a well-controlled temperature environment, the heat loss from sample to environment can be minimized. However, the heat loss from the sample to the sample container, the so-called thermal dilution effect, has long been considered ?inevitable and inherent.?

Although the heat capacity correction, i.e. phi-factor correction, has been used for some simple reaction systems, this approach falls short of providing real-world, time-resolved temperature and pressure curves. Also, because of the damped temperature rise, the scenarios of decomposition reactions that occur at high temperatures may never be observed, and a simple phi-factor correction can not be used to reinstate the temperature and pressure rate information.

Using the differential adiabatic heat compensating technique, the heat-sink or phi effect of the sample container is totally eliminated in real-time, resulting in an undistorted, true adiabatic process gaining the highest adiabatic temperature rise that matches the theoretical value and the experimentally measured true TMRad. Because of the elimination of the container heat-sink effect, no temperature gradient is developed in the sample. Therefore, a homogeneous adiabatic environment, critical for testing unstirred liquids, semi-solids and powdery samples, remains.

Also, because of the elimination of the container heat capacity effect, the time-resolved temperature and temperature rate data become sample/vessel mass-independent. Since temperature is an intensive value, this mass-independent nature of the calorimeter simplifies the test operation by eliminating all sample and vessel weighing procedures. The advantage of this ?containerless? effect, is that runaway reaction experiments can be carried out in real-world process conditions, and parameters obtained are readily scalable (i.e., instrument-independent), and the theoretical time-temperature and time-pressure rises and rates can now be obtained experimentally.

A number of typical reaction systems have been investigated on this novel differential adiabatic calorimeter, including the thermal decomposition of di-tertiary-butyl-peroxide (DTPB), the polymerization and decomposition of dicyclopentadiene (DCPD), and the acetic anhydride hydrolysis reaction. The theoretical importance is that this true adiabatic calorimeter successfully eliminates all heat losses to the environment and to the sample container, experimentally achieving the theoretical state of 100% true adiabaticity and the true TMRad.