Simulation of the Minor Heat Release during Aging of Energetic Materials using AdvancedKinetic Elaboration of HFC Signals

摘要

High energetic materials can slowly decompose during storage or transport particularly atelevated temperatures which may result in reduced performance and correct functionality. Even verylow decomposition progress of the exothermic reaction resulting in minor heat release can significantlychange the properties of the propellants leading to shortening of the service life-time. The reactionprogress influencing already the behaviour of the samples can be in the range of ca. 1-2% of the totaldecomposition degree. There are the literature reports showing that the amount of the evolved heatduring decomposition as low as ca. 40 J/g can alter the material properties. Monitoring such a minor heatrelease requires very sensitive techniques as Heat Flow Calorimetry (HFC).Proposed method for simulation of the amount of heat evolved during aging of the energetic materialswhich allows predicting the thermal behaviour of the samples is based on the elaboration of thedifference between the HFC signals recorded for the unaged and differently altered samples. Thesamples aged in furnaces at 50, 60 and 70°C were investigated by HFC technique at 80°C and obtainedsignals were compared with the traces of the unaged sample recorded during 10 days also at 80°C.Observed changes of the recorded heat flows as a function of time at 80°C for the differently agedsamples related to the heat flow of the unaged sample allowed the determination of the kineticparameters of the decomposition process. They were determined by the differential isoconversionalmethod applying the principle of the compensation effects widely used in the kinetics of the solidheterogeneous reactions. The knowledge of the kinetics of the early stage of the process allowed theprecise prediction of the reaction rate at any temperature mode. It allowed also the simulation ofarbitrarily chosen cumulative heat release (e.g. 40 J/g) at any temperature profile such as storageconditions depicted in STANAG 2895 or A1 cycles “extreme hot climate” with daily temperaturefluctuations between 32 and 71°C.The application of the proposed advanced kinetic method of the elaboration of the HFC signalssignificantly shortens the time of the experiments: note that the required information is gained from theHFC experiments carried out at relatively high temperature of 80°C.