ADVANCED SIMULATION OF THE LIFETIME OF ENERGETIC MATERIALS BASED ON HFC SIGNALS
1 AKTS AG Advanced Kinetics and Technology Solutions, http://www.akts.com, TECHNOArk 3, 3960 Siders,
Switzerland
2 PB Clermont s.a., http://www.pbclermont.be, Rue de Clermont 176, 4480 Engis, Belgium
3 Bundeswehr Institute for Materials (WIWEB), Grosses Cent, 53913 Swisttal-Heimerzheim, Germany
4 armasuisse, Science and Technology, http://www.armasuisse.ch, 3602 Thun, Switzerland
5 Nitrochemie Wimmis AG, http://www.nitrochemie.com, 3752 Wimmis, Switzerland
Abstract
The prediction of the shelf life of energetic materials requires the precise determination of the
kinetics of their decomposition. Due to the fact that energetic materials decompose with the evolution
of heat, the thermoanalytical methods such as Differential Scanning Calorimetry (DSC) and Heat
Flow Calorimetry (HFC) are often used for the monitoring the reaction rate and the evaluation of the
kinetic parameters of these reactions. In the present paper we describe the precise, advanced method of
the evaluation of the kinetic parameters from HFC signals. Proposed method was applied for the
kinetic evaluation of the decomposition process of two spherical double base and one EI® propellants
type, all for small calibre used in defence applications. The kinetic parameters were determined from
the experiments carried out between 50-100°C. The very good description of the low temperature data
by the kinetic parameters determined at higher temperatures indicates the constancy of the
decomposition mechanism between 50 and 100°C. The experimental data collected during more than
7 years by means of HFC (at 50°C) were well simulated by the kinetic parameters derived from the
high temperature HFC signals. Such a possibility enables e.g. the precise prediction of the shelf life of
the energetic materials at any temperature mode in the range of 50-10°C, at different climatic
categories proposed by STANAG 2895 [1] and, more generally, the precise simulation of the reaction
at any temperature profile close to the ambient temperature.
View publication: ADVANCED SIMULATION OF THE LIFETIME OF ENERGETIC MATERIALS BASED ON HFC SIGNALS (pdf, 594 KB)
Prediction of the thermal behaviour of energetic materials by advanced kinetic modelling of HFC and DSC signals
1AKTS AG Advanced Kinetics and Technology Solutions, http://www.akts.com, TECHNOArk 3, 3960 Siders, Switzerland
2armasuisse, Science and Technology Centre, http://www.armasuisse.ch, 3602 Thun, Switzerland
3Nitrochemie Wimmis AG, http://www.nitrochemie.com, 3752 Wimmis, Switzerland
Abstract
High energetic materials can slowly decompose during storage or transport particularly at
elevated temperatures which may result in reduced performance and correct functionality. Even very
low decomposition progress of the exothermic reaction resulting in minor heat release can
significantly change the properties of the propellants leading to shortening of the service life-time. The
reaction progress influencing already the behaviour of the samples can be in the range of ca. 1-2% of
the total decomposition degree. There are the literature reports showing that the amount of the evolved
heat during decomposition as low as ca. 40 J/g can alter the material properties. Monitoring such a
minor heat release requires very sensitive techniques as Heat Flow Calorimetry (HFC).
Proposed method for simulation of the amount of heat evolved during aging of the energetic
materials which allows predicting the thermal behaviour of the samples is based on the elaboration of
the difference between the HFC signals recorded for the unaged and differently altered samples. The
samples aged in furnaces at 50, 60 and 70°C were investigated by HFC technique at 80°C and
obtained signals 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
aged samples related to the heat flow of the unaged sample allowed the determination of the kinetic
parameters of the decomposition process. They were determined by the differential isoconversional
method applying the principle of the compensation effects widely used in the kinetics of the solid
heterogeneous reactions. The knowledge of the kinetics of the early stage of the process allowed the
precise prediction of the reaction rate at any temperature mode. It allowed also the simulation of
arbitrarily chosen cumulative heat release (e.g. 40 J/g) at any temperature profile such as storage
conditions depicted in STANAG 2895 or A1 cycles “extreme hot climate” with daily temperature
fluctuations between 32 and 71°C.
The application of the proposed advanced kinetic method of the elaboration of the HFC
signals significantly shortens the time of the experiments: note that the required information is gained
from the HFC experiments carried out at relatively high temperature of 80°C.
Computational aspects of kinetic analysis.
The ICTAC Kinetics Project - numerical techniques and kinetics of solid state processes
1 AKTS AG Advanced Kinetics and Technology Solutions, http://www.akts.com, TECHNOArk 1, 3960 Siders, Switzerland
Abstract
This is Part E of a series of papers that present the kinetic results computed for a hypothetical simulated process and experimental data for the thermal decompositions of calcium carbonate and ammonium perchlorate. The results show that model-fitting techniques are successful in correctly describing the decomposition of solids when assuming multi-step kinetic models. The multi-heating rate data should be used for the kinetic calculations because the application of the single-heating rate data may fail to disclose the complexity of the process. The comparison of the kinetic parameters obtained from isothermal and non-isothermal experiments is presented and discussed. The results indicate that the proper consideration of the experimental conditions at which the reaction has been investigated should be taken into account for a correct interpretation of kinetic data of solid-gas reactions.
Influence of mass transfer on interaction between thermoanalytical and mass spectrometric curves measured in combined thermoanalyser-mass spectrometer systems
a Department of Chemical Engineering and Industrial Chemistry, Swiss Federal Institute of Technology, ETH-Zentrum, CH-8092 Zurich, Switzerland
b Department of Chemical and Process Engineering, Warsaw Universit 3, of Technology; PL-00-645 Warsaw, Poland
Abstract
The convective and diffusional mass transfer occurring in combined thermoanalyser-mass spectrometer systems can cause significant deviation between measured thermoanalytical and mass spectrometric curves. Based on experimental studies of the decomposition of CaCO3, a model has been developed which allows to interrelate the thermoanalytical (DTG) and mass spectrometric curves and provides a criterion defining under which conditions (carrier gas-flow rate and diffusivity of evolved gas) the disguising mass-transfer influences can be neglected. The criterion relates the total residence time Ttot of the gas in the experimental system to the characteristic time tN of the gravimetrically recorded decomposition process and allows to quantify the agreement between the thermoanalytical and mass spectrometric curves.
Influence of experimental conditions on the kinetic parameters of gas-solid reactions - parametric sensitivity of thermal analysis
Abstract
The influence of experimental conditions on the kinetic parameters of gas-solid reactions has been investigated using the reduction of nickel oxide by hydrogen as a model reaction. The experimental parameter studied were heating rate, sample mass, total gas flow and hydrogen concentration.
For arbitrarily chosen "standard conditions" the kinetic parameters best describing the course of the reaction were calculated using the global cruves analysis method. Experiments were carried out with different heating reates, in the range 1.3-10.6 K min-1. Twenty two kinetic models of solid-state reactions proposed in the literature were tested using numeric integration methods.
The confidence space, in which the kinetic parameters, calculated for "standard conditions", fit the kinetics of NiO reduction properly, was calculated taking into account the influence of all investigated variables.
The results illustrate the great influence of the experimental conditions on the measured thermoanalytic curves ("parametric sensitivity") and demonstrate the limited validity of kinetic data calculated from experiments carried out under arbitrary chosen conditions.
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