OPTIMIZATION OF MODELING OF PROPELLANTS AGING INVESTIGATED ACCORDING TO NATO AOP-48 ED.2 TEST PROCEDURE

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1 OPTIMIZATION OF MODELING OF PROPELLANTS AGING INVESTIGATED ACCORDING TO NATO AOP-48 ED. TEST PROCEDURE Bertrand Roduit, Marco Hartmann, Patrick Folly, Alexandre Sarbach, Pierre Guillaume, Laurence Jeunieau 4 AKTS AG, TECHNOArk, 96 Siders, Switzerland, b.roduit@akts.com armasuisse, Science and Technology Centre, 6 Thun, Switzerland PB Clermont s.a., Rue de Clermont 76, 448 Engis, Belgium 4 Royal Military Academy, Avenue de la Renaissance, Bruxelles, Belgium Thermal degradation of high energetic materials Nitrocellulose-based propellants decompose slowly even at ambient temperatures. Decrease of the chemical stability. To prevent this undesired process stabilizers are introduced to the propellants to react with the degradation products.

2 Thermal degradation of high energetic materials Experimental observation of propellant decomposition is difficult due to its very low rate at room temperature. Immeasurable physicochemical changes. Common investigation of the aging processes is based on the experiments carried out at higher temperatures when the reaction rates are significantly higher. Stability test procedure % < α < % reaction progress Kinetics Experiments temperature T T T? Predictions days < t < months time 5 C < T < C 4

3 Stability test procedure : NATO AOP-48 Ed- Common stability test procedure is described in NATO Allied Ordnance Publication AOP-48 Ed. 5 Stability test procedure : NATO AOP-48 Ed- Kinetic analysis for determination of the thermal stability of solid materials Three major steps: Experimental collection of data Computation of kinetic parameters Prediction of the reaction progress for required temperature profiles applying determined kinetic parameters. 6

4 Stability test procedure : NATO AOP-48 Ed- Following NATO AOP-48 Ed. test procedure: Monitoring stabilizer depletion can be carried out by High Performance Liquid Chromatography (HPLC). Stabilizer depletion requires the set of aging experiments performed at least three temperatures, generally 6, 7 and 8 C. Computation of kinetic parameters assuming certain kinetic reaction model i.e. Reaction-Order (Fn) model: n f ( α) = ( α ) Prediction of the reaction progress for required temperature profiles applying determined kinetic t α parameters. dα n dα = k( α) ta = dt dt = n k( α) α 7 NATO AOP-48 Ed- : Fn model Following NATO AOP-48 Ed. test procedure: Thermal aging T Arrhenius Model 8

5 Common kinetic analysis 9 Common kinetic analysis

6 Common kinetic analysis Can Fn describe PT? NO Universal kinetic model The aim of the present paper is to: Propose another more universal kinetic model

7 Common kinetic analysis Can Fn describe PT? NO Common kinetic analysis m= Can PT describe Fn? Yes 4

8 Common kinetic analysis 5 Common kinetic analysis n m Can PT describe Pn, An, Rn, D, D? Yes (*) with A =A c or f(α)=c(-α)nα^m (*) L.A. Perez-Maqueda, J.M. Criado, P.E. Sanchez-Jimenez, Combined kinetic analysis of solid-state reactions: a powerful tool for the simultaneous determination of kinetic parameters and the kinetic model without previous assumptions on the reaction mechanism, J. Phys. Chem. A (6)

9 Common kinetic analysis (*) L.A. Perez-Maqueda, J.M. Criado, P.E. Sanchez-Jimenez, Combined kinetic analysis of solid-state reactions: a powerful tool for the simultaneous determination of kinetic parameters and the kinetic model without previous assumptions on the reaction mechanism, J. Phys. Chem. A (6) NATO AOP-48 Ed- : Fn model Following NATO AOP-48 Ed. test procedure: Thermal aging T Arrhenius Model 8

10 More universal model : PT model More universal kinetic model Thermal aging T Arrhenius Model 9 More universal model : PT model More universal kinetic model Set 7 points generated for three temperatures: 6, 7 and 8 C kj/mol =.5 = = = 5E sec - Fitting experimental or generated data by Fn and PT models T Prediction of reaction progress by Fn and PT models

11 Mathematical validation Data collected in 5 months Fitting by Fn and PT models Prediction: Storage time at 5 C for stabilizer depletion of 5%. 4 Time (month) Time (year) 5 6 Difference between Fn and PT-models results in relative error of prediction (.7-.9)/.9 =.8% Mathematical validation points collected at 5 C are taken into considerations Data collected in 6 months Time (month) Fitting by Fn and PT models 5 C Prediction: Storage time at 5 C for stabilizer depletion of 5% Time (year) 5 6 Difference between Fn and PT-models results in relative error of prediction (9.-.9)/.9 = 9.7%

12 Mathematical validation points collected at 5 C are taken into considerations Data collected in 6 months Time (month) Fitting by Fn and PT models 5 C Prediction: Storage time at 5 C for stabilizer depletion of 5% Time (year) 5 6 Difference between Fn and PT-models results in relative error of prediction (9.-.9)/.9 = 9.7% Mathematical validation Data collected in month Data collected in one month only! Time (month) 5 6 4

13 Mathematical validation Data collected in month Data collected in one month only! Time (month).5 6 Fitting by Fn and PT models Time (year) 8.9 Prediction: Storage time at 5 C for stabilizer depletion of 5%. 4 6 Difference between Fn and PT-models results in relative error of prediction (8.9-.9)/.9 = 87%! 5 Mathematical validation Application of more universal PT model Significant decrease of points required for kinetic analysis i.e. Significant reduction of experimental time for the data collection. Correct stability prediction 6

14 Experimental verification Summary of the kinetic analysis of all propellants: kinetic parameters derived during fitting experimental data by Fn and PT models, t 5 - i.e. the storage time at 5 C after which a stabilizer depletion of 5 % is reached 7 Experimental verification 8

15 Mathematical and experimental verification Application of more universal PT model Significant decrease of points required for kinetic analysis i.e. Significant reduction of experimental time for the data collection. Correct stability prediction Mathematical considerations confirmed by the evaluation of the stability of single- and double based propellants (= experimental verification). 9 NATO AOP-48 Ed- : Fn model Following NATO AOP-48 Ed. test procedure: Thermal aging T Arrhenius Model

16 More universal model : PT model More universal kinetic model Thermal aging T Arrhenius Model Conclusion The correct kinetic analysis applying more universal PT-model can be successfully carried out even if the number of experimental data is significantly smaller than those required by NATO-AOP 48 Ed. test procedure.

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