Technical comments
Determination of SADT and Cook-Off Ignition Temperature by Advanced Kinetic Elaboration of DSC Data
The exothermic decomposition parameters of a single-base propellant were obtained using differential scanning calorimeter (DSC) tests conducted at various heating rates. The DSC signals were processed using the Friedman isoconversional method to compute activation energy as a function of conversion. There was excellent agreement between the experimental and the simulation plots, which confirms the validity of the kinetic model used to describe the propellant’s exothermic decomposition. The kinetic parameters and heat balance were subsequently analyzed and used for a simulation of cookoff experiments conducted at different experimental rates (heating rates 3.3 – 1.0 K/h and a heat-wait-search mode) …
Prediction of the Thermal Behaviour of Energetic Materials by Advanced Kinetic Modelling of HFC and DSC Signals
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 …
Prediction of the Ageing of Rubber using the Chemiluminescence Approach and Isoconversional Kinetics
A common scepticism towards the application of many product formulations results from the fact that their long-term stability is difficult to predict. In the present study we report on a new approach of kinetic analysis of the oxidation reactions of natural rubbers with and without stabiliser in an oxygen atmosphere at moderate temperatures using CL measurements carried out on a newly-developed instrumentation. The kinetic parameters of the oxidation process, calculated from the chemiluminescence’s signals by means of the differential isoconversional method of Friedman, were subsequently applied for the simulation of the rubber aging under different temperature profiles …
The Simulation of the Thermal Behavior of Energetic Materials based on DSC and HFC Signals
Two small calibre and four medium calibre types of propellants were investigated non-isothermally (0.25-4 K min-1) by differential scanning calorimetry (DSC) in the range of RT-260-C and isothermally (60-100°C) by heat flow calorimetry (HFC). The data obtained from both techniques were used for the calculation and comparison of the kinetic parameters of the decomposition process. The application of HFC allowed to determine the kinetic parameters of the very early stage of the reaction (reaction progress below 0.02) what, in turn, made possible the precise prediction of the reaction progress under temperature mode corresponding to real atmospheric changes according to STANAG 2895 …
Evaluating SADT by Advanced Kinetics-based Simulation Approach
Present study depicts the extension of the method of the application of the advanced kinetic description of the energetic materials decomposition by its combination with the exact heat balance carried out by numerical analysis and the determination of the Self-Accelerating Decomposition Temperature (SADT). Moreover, the additional parameters such as thermal conductivity of the self-reactive substances, the type of containers and insulation layers, and different temperature profiles of the surrounding environment were taken into consideration …
Advanced Kinetics-based Simulation of Time to Maximum Rate under Adiabatic Conditions
An adiabatic calorimeter is very often used for the investigation of runaway of exothermic reactions. However the ideal adiabatic environment is a theoretical state which during laboratory scale testing cannot be obtained but may only be approached. Deviation from the fully adiabatic state comes from (i) the thermal inertia of the test system or heat lost into the sample container and (ii) the loss of heat from the container itself to the environment that reflects the ‘operational adiabaticity’ of the instrument…
Advanced Simulation of the Lifetime of Energetic Materials based on HFC Signals
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 …
Prediction of Thermal Stability of Fresh and Aged Parchment
The hyphenated thermal analysis-mass spectrometry technique (TA-MS) was applied for the investigation of the thermal behavior of reference and aged parchment samples. The kinetic parameters of the process were calculated independently from all recorded TA and MS signals. The kinetic analysis showed the distinct dependence of the activation energy on the reaction progress. Such behavior is characteristic for the multistage mechanism of the reaction …
Up-Scaling of DSC Data of High Energetic Materials
Differential scanning calorimetry (DSC) carried out with few heating rates was applied in the studies of the thermal properties of four energetic materials: EI® propellant, high explosive PBXW-17, pyrotechnic mixtures with composition B/KNO3 (50:50) and B/KNO3 (30:70). DSC signals, after optimization of the baseline, were used for the calculation of the kinetic parameters (KP) of the decomposition process applying advanced kinetic software designed by AKTS. The determination of the kinetic parameters was based on the differential iso-conversional method of Friedman. The correctness of the estimation of KP was checked by the comparison of the experimental and predicted courses of the decomposition …
The Prediction of Thermal Stability of Self-Reactive Chemicals
An advanced study on the thermal behaviour of double base (boost and sustain propellant) rocket motor used in a ground to air missile has been carried out by differential scanning calorimetry (DSC). The presence of two propellants as well as the different experimental conditions (open vs. closed crucibles) influence the relative thermal stability of the energetic materials. Several methods have been presented for predictions of the reaction progress of exothermic reactions under adiabatic conditions. However, because decomposition reactions usually have a multi-step nature, the accurate determination of the kinetic characteristics strongly influences the ability to correctly describe the progress of the reaction …