The Thermodynamics and Kinetics of Explosives Thomas M. Jerant Cindy D. Spangler

TNAZ 1,1,3 Trinitroazetidine is more powerful, but less-sensitive than other explosives. Can be melted and moulded Thermally stable above its melting point TNAZ has approximately 30% more energy than TNT

Power Compensated DSC Both the sample and the reference are kept at the same temperature while electrical power used by the heaters is monitored Small samples are used to insure that thermal equilibration will occur fast The sample and reference are located above the heaters and the temperatures are monitored using electronic temperature sensors located just beneath the samples. The output of the differential temperature control circuit is used to generate the DSC curve

DSC Curve

Determination of Kinetics Finding the accuracy of activation energy evaluations using the isoconversional method A single step kinetic equation is usually used for solid state decompositions; given by Where α is the extent of conversion and f(α) is the reaction model Isoconversional Method is when the same amount of the same is converted: ie: same percentage.

Determination of Kinetics To find α, it requires differentiation of experimental measurements but produces unacceptably noisy data So the integral form is used The integral of the reaction model can have useful approximations used in it in order to lead to simple linear equations and estimation of Arrhenius parameters

Reaction Model Importance The activation energy depends on the choice of reaction model Model is usually chosen based on statistics; however within a confidence level, models can be statistically equivalent -Table 1 is a type of kinetic analysis that is applied to a model. They are fitting the reaction models to a single heating rate data set -R based max is usually the determining factor on which model is the best: R=10, but using Fisher’s transformaion it allows the R values for 10 11 12 to be statistically the same within 95% confidence level. -Compare model 10 with model 11/12, This is the uncertainty in estimating the activation energy: choosing the model based off only a single heating rate data set

Statistical Procedure Validation Used five heating rates and nine independent sets of experimental measurements at each rate to determine the activation energies