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Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants

Jonathan Lavoie Catalin-Florin Petre, Pierre-Yves Paradis, Charles Dubois DRDC – Valcartier Research Centre

Bibliographic information: Propellants, Explosive, Pyrotechnics, Wiley online library, 2017, 42: 149–157.

Date of Publication from External Publisher: February 2017

Defence Research and Development Canada External Literature (P) DRDC-RDDC-2018-P012 February 2018

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IMPORTANT INFORMATIVE STATEMENTS

Disclaimer: This document is not published by the Editorial Office of Defence Research and Development Canada, an agency of the Department of National Defence of Canada, but is to be catalogued in the Canadian Defence Information System (CANDIS), the national repository for Defence S&T documents. Her Majesty the Queen in Right of Canada (Department of National Defence) makes no representations or warranties, expressed or implied, of any kind whatsoever, and assumes no liability for the accuracy, reliability, completeness, currency or usefulness of any information, product, process or material included in this document. Nothing in this document should be interpreted as an endorsement for the specific use of any tool, technique or process examined in it. Any reliance on, or use of, any information, product, process or material included in this document is at the sole risk of the person so using it or relying on it. Canada does not assume any liability in respect of any damages or losses arising out of or in connection with the use of, or reliance on, any information, product, process or material included in this document.

This document was reviewed for Controlled Goods by Defence Research and Development Canada (DRDC) using the Schedule to the Defence Production Act.

© Her Majesty the Queen in Right of Canada (Department of National Defence), 2017 © Sa Majesté la Reine en droit du Canada (Ministère de la Défense nationale), 2017

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DOI: 10.1002/prep.201((full DOI will be filled in by the editorial staff)) Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants Jonathan Lavoie[a], Catalin-Florin Petre[b], Pierre-Yves Paradis[c], Charles Dubois*[a] Abstract: The influence of two selected bistetrazoles, 5,5’-bis-(1H-tetrazolyl)-amine (BTA) and 5,5’-hydrazinebistetrazole (HBT), on the combustion behaviour of a typical triple-base propellant was investigated. Seven propellant formulations, one reference and six others incorporating respectively, 5%, 15% and 25% of either HBT or BTA compounds were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93% higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT-containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25% HBT. The thermal behaviour of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen-rich materials, indicating that the two compounds probably react readily with the –ONO2 groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds.

Keywords: Bistetrazole, Burning Rate, High Nitrogen, Nitrogen Rich, Propellant

formulations. The formulations based on materials 1 Introduction containing the triaminoguanidnium cation presented tremendously fast burning rates as well as increased There are multiple challenges nowadays in the field of pressure exponents. On the other hand, formulations chemical propulsion. They range from increasing the incorporating BTATz showed lower pressure performance, lowering the vulnerability, reducing the dependency, but high burning rates (at least 40% environmental impact, and minimizing the erosivity of higher). Similarly, investigations of DAATO3.5 and the propellants, to name but a few. In recent years, a BTATz as monopropellants for micro-thruster new family of energetic materials that has the potential applications also showed low pressure exponents and to tackle these challenges has emerged in the form of high burning rates [13]. With one exception (Damse et nitrogen-rich molecules. These are often designated al. [8]), the burn rate characterization of the nitrogen- as nitrogen-rich materials due to their high nitrogen rich propellants was conducted on low pressure content, which can exceed 80% of the total weight of ranges more suited to rocket propellants, that is on the the molecule. This shifts the source of the energy order of 0.1 to 10 MPa which greatly differs from gun produced in the molecule from the oxidation of the propellants where the pressure can reach upwards of carbon backbone to the production of nitrogen gas 100 MPa while the combustion is still ongoing. from materials with high enthalpies of formation. On The past work on the burning behavior of the other hand, most of the current research has nitrogen-rich materials demonstrated their potential focused on the synthesis of these new nitrogen-rich usefulness as burn rate modifiers, which could also compounds, the characterisation of their come with additional benefits, such as lower molecular physicochemical properties and their explosive weight combustion gases and lower flame performance, with little to no research on their effects temperature. It should however be noted that the when incorporated in actual propellants [1-3]. As an amount of nitrogen-rich materials tested under such example, there has been some insight for the circumstances is fairly limited. The literature works determination of the burn rates of some of the earlier previously performed also showed that the effects of nitrogen-rich materials, in their pure form, such as 3,6- such materials vary greatly from one nitrogen-rich dihydrazino-s-tetrazine (DHT), 3,6-bis(1H-1,2,3,4- material to another. tetrazol-5-ylamino)-s-tetrazine (BTATz), More recently, the number of nitrogen-rich triaminoguanidinium-5,5’-azobis(1H-tetrazolate) materials based on the tetrazole ring that have been (TAGzT), etc., under various pressure conditions [4-7]. synthesized and characterized has significantly Those works showcased high burn rates accompanied increased and they have shown desirable energetic by very variable pressure exponents and linear burn content as well as fairly acceptable sensitivities. rate coefficients. Tetrazoles are of particular interest as they strike the The limited amount of work from the literature right balance between stability, nitrogen content and on nitrogen rich materials incorporated into gun energy content through high enthalpies of formation. propellants has focused on the effects of Among these materials, 5,5’-bis-(1H-tetrazolyl)-amine triaminoguanidinium nitrates (TAGN) and (BTA) and 5,5’-hydrazinebistetrazole (HBT), shown in triaminoguanidinium azide (TAGAZ) [8], BTATz [9, 10] Figure 1, have demonstrated a great potential, as their and TAGzT [6, 11, 12] on nitramine based performance has been successfully compared to that

1 Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine sensitivity is still better than that of many energetic (HMX) and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), materials used in low vulnerability ammunitions, such two components often used in low vulnerability as RDX and HMX (see Table 1). However, HBT propellants [1, 2]. The synthesis of the precursor of proved to be much more sensitive to friction than HBT has successfully been scaled up to the multi- anticipated based on the values reported in the kilogram scale [14]. Care was taken to choose nitrogen literature. The 1H and 13C NMR performed on the rich molecules for which the synthesis could be scaled HBT revealed no impurities to which the increase in up with relative ease and with a small number of sensitivity could be attributed. However, impurities intermediaries. below the detection threshold of NMR would not have been detected. Both HBT and BTA were not recrystallized either. The sensitivity results are in accordance with the testing previously done on HBT synthesized in much smaller quantities at our facilities. BTA is less sensitive to friction than HBT and similarly sensitive to impact. Conversely, while BTA has proven to be more sensitive than previously Figure 1. Chemical Structure of HBT and BTA reported (30 J, >360 N) [1], it still has lower sensitivity than materials with similar detonation parameters such This work is concerned by the characterization as HMX (see Table 1). Both nitrogen-rich materials of the effects of incorporating either BTA or HBT in a had slightly lower density than previously reported [1, typical nitrocellulose-based triple base propellant. The 2], however, this could be attributed to the method burning performances of the resulted propellants were used to calculate the density. Values previously characterized via closed vessel tests. The thermal reported in the literature were of 1.84 g/cm3 and 1.86 behavior of these propellants and their nitrogen-rich g/cm3 for HBT and respectively BTA and were constituents has been investigated through differential measured through XRD. On the contrary, the density scanning calorimetry (DSC) experiments. Furthermore, measurements in this work were obtained by some of the properties of the bistetrazole molecules performing gas pycnometry on the dry powders. used, such as the sensitivity and density are also presented. 2.2 Thermochemical Data A total of seven (7) propellant formulations were 2 Results and Discussion manufactured, starting with the reference formulation containing no nitrogen-rich components and followed 2.1 Bistetrazoles by three formulations for each bistetrazole compound. Due to safety concerns associated with the handling of The reference propellant was composed of 53% energetic materials, the sensitivities to impact and nitrocellulose, 39% trimethylolethane trinitrate friction of the synthesised bistetrazole compounds (TMETN), 7% triethylene glycol dinitrate (TEGDN) and were tested prior to mixing the propellant formulations. 1% stabilizer. Ethyl centralite was used as the Similarly, in order to provide accurate calculations of stabilizer. The plasticizers were chosen after multiple the thermochemical properties of the propellant CHEETAH calculations, which demonstrated that in formulations, the density of the materials was order to maintain performance only a minimum amount measured through gas (helium) pycnometry. These of oxygen was required in the propellant. To obtain the values are reported in Table 1. Some differences were bistetrazole propellants, parts of the reference observed between the properties previously reported propellant constituents were replaced by, respectively, in the literature and the properties measured trough 5%, 15% and 25% of bistetrazoles on a mass basis experimentation. and in such a way that the nitrocellulose to plasticizer ratio remained the same for all formulations. The Table 1. Selected Properties of the Nitrogen Rich calculated thermochemical properties of the resulted Materials, RDX and HMX propellant formulations are presented in Table 2. 3 a a ρ (g/cm ) Impact (J) Friction (N) Table 2. Thermochemical Properties of the Gun HBT 1.78 10 20 Propellants BTA 1.84 10 120 Ref. 5% 15% 25% 5% 15% 25% RDX 1.82 4 96 HBT HBT HBT BTA BTA BTA F (J/g) 1138 1121 1084 1040 1138 1137 1134 HMX 1.91 4 120 T (K) 3224 3137 2954 2763 3187 3111 3032 a All sensitivity data was obtained using the same Pmax 211 209 204 197 212 214 215 testing apparatus and methodology. (MPa) Mg 23.6 23.3 22.7 22.1 23.3 22.8 22.2 (g/mol) HBT proved to be much more sensitive than RF 100 99.0 96.4 93.2 100 101 107 previously reported in the literature, as the reported (%) sensitivities were greater than 30 J for impact and greater than 108 N for friction [2]. The impact The thermochemical data provides some interesting insight as to the changes incurred from the

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  Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants that while HBT doesn’t play a part in initiating the propellants [10] where BTATZ presents a s-tetrazine decomposition of the propellant, it still reacts with the between two tetrazole rings rather than an amine or other constituents and causes the propellant to hydrazine group. This approach could be an undergo faster decomposition. From the safety alternative to the use of ionic nitrogen-rich compounds concerns and thermal stability standpoints, HBT where the various cations and anions are generally proved to be the most interesting of the two tested used to change the burning properties and the molecules. composition of the resulting molecule. Of course, both Given the similarity between the two approaches can be used in conjunction, with a good bistetrazole compounds, one can conclude that the example being the use of salts of bistetrazole and chemical group present between the tetrazole cycles, azotetrazole. in this case amine for BTA and hydrazine for HBT, has a direct effect on the thermal stability of the 3 Experimental propellants. A similar trend can be observed with the activation energies of the main decomposition of the HBT and BTA were synthesized according the propellants. The activation energy for the HBT- procedures previously described by Klapötke et al. [1, containing propellants increases with the increase of 2]. The purity of all materials was verified through the HBT content, which corroborates with the high hydrogen, carbon and nitrogen nuclear magnetic thermal stability provided by HBT. On the contrary, for resonance spectroscopy (1H-NMR and 13C-NMR). 1 the BTA-containing propellants due to their lower BTA: H NMR (400 MHz, DMSO-d6, 25°C) = 11.92 13 thermal stability, the calculated energy of activation ppm (s, 3 H, NH) C NMR (400 MHz, DMSO-d6, 25°C) 1 was found to decrease with the increase of the BTA = 154.16 (s, 2 C, CN3). HBT: H NMR (400 MHz, 13 content (see Table 4), which is also in agreement with DMSO-d6, 25°C) = 9.67 ppm (s, 4 H, NH) C NMR the measured lower onset temperature of these (400 MHz, DMSO-d6, 25°C) 159.48 ppm (s, 2 C, CN3). propellants. All materials were synthesized with high yields as well For the cases of the propellants containing as good purity. Precursors for the synthesis of these 15% and 25% HBT, a second decomposition peak can materials were procured from Sigma-Aldrich and used be observed at higher temperatures (Figure 5). This as is with the exception of sodium 5-5’-azobis(1H- peak is very small for the propellant containing 15% tetrazolate) (Na2zT) which was synthesized on site HBT, but becomes significant for the propellant according to the procedure described by Radack et al. containing 25% HBT. This second peak cannot be [14]. In the case of HBT and its azotetrazolate attributed to the decomposition of unreacted pure HBT. precursor, the syntheses were performed at higher HBT’s decomposition peak generally occurs at lower concentrations than reported in the literature in order temperatures (226oC) than the decomposition peaks to reduce the reactor volume required, the other observed in Figure 5 (237oC). On the contrary, the experimental conditions remained the same as those propellants containing BTA do not show any additional reported in the literature. Grade C nitrocellulose, decomposition peaks, except maybe for a very small nitrogen content of 13.25%, wetted with ethanol was peak at 25% concentration. It is likely that multiple used as the polymeric binder and as an energetic decomposition reactions also occur for the propellants component. containing BTA, but they occur simultaneously rather The propellant manufacturing facility was than sequentially. Once again, the difference in the previously described in detail by Petre et al. [15].The decomposition mechanisms can be attributed to the propellants were mixed in a sigma blade mixer using different chemical groups lodged between the two the solvent incorporation method until a dough judged tetrazole rings. to be adequate for extrusion was obtained. The dough While the exact decomposition mechanisms was subsequently extruded, cut in cylindrical resulting from the addition of HBT and BTA remain geometries with no perforations and dried until the unknown for now, a difference between the weight loss due to solvent evaporation was negligible. decomposition of the two bistetrazole compounds in Closed vessel tests were conducted on the the condensed phase can be observed through the propellant grains to evaluate their burning DSC experiments. One interesting fact is that the characteristics. For this study, a RARDE (model CV21, decomposition mechanisms of bistetrazole containing V=700 cm3) closed pressure vessel was used with an propellants can be easily influenced by the presence internal metallic sleeve in order to bring the volume or absence of certain chemical groups present down to ~188 cm3. The closed vessel can be operated between two tetrazole rings. This also suggests that at pressures up to 248 MPa. A piezoelectric pressure the decomposition pathways of both compounds are transducer was used to measure the pressure-time probably different. As a result, the burning properties relationship for each sample. Ignition of the propellants of bistetrazole containing propellants could be altered was achieved using an electric match and a small to a certain extent through the use of different quantity of black powder. All formulations were fired at chemical groups linking the two tetrazole rings, while a loading density of 0.155 g/cm3. The use of the the nitrogen and energetic content still remains high. sleeve increased the heat loss in the vessel to an This could also explain the difference observed in the estimated 30%-35% for all firings. The burning rate burning behavior of HBT and BTA containing coefficient (β) and pressure exponent (α) as well as propellants compared to that of BTATz containing the dynamic vivacity were calculated from the

6 Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants pressure-time data recorded in the closed vessel and that HBT itself was found to be more sensitive than its the use of the impetus and flame temperature data counterpart, which in turn provided a greater increase simulated through the use of the CHEETAH of burning rate properties. It is also important to note thermochemical code using the virial equation of state that the compatibility of the materials used in the (BLAKE compatibility). The BRLCB v3.0 computer propellant formulations was summarily evaluated. No code was used to perform the burning rate short term compatibility issues were observed; regressions. The closed vessel temperature was however long term stability was not investigated. maintained at 21oC through the use of a jacket where Finally, the DSC experiments brought to light cold water was circulated. that, despite their similarities, both bistetrazole lead to The sensitivity of the nitrogen rich materials different decomposition mechanisms when was assessed using a Julius-Peters BAM friction incorporated into the same propellant formulation. apparatus and impact sensitivity was evaluated using However, more work is needed in order to determine a Julius-Peters drop hammer. The sensitivity threshold the exact decomposition pathways favored by these for both materials was defined as the force or energy two molecules. where no reaction, be it smoke, crackling, spark or other occurred for six consecutive tests. Acknowledgements Differential Scanning Calorimetry was carried out using a TA Instruments Q2000 DSC with auto The authors would like to thank ARDEC, sampler and aluminium hermetic pans at various MITACS and NSERC for providing the funding heating rates under a nitrogen flow of 50 mL/min. necessary to this work. The authors would also like to thank M. Charles Nicole and M. Pascal 4 Conclusions Beland from DRDC-Valcartier for helping with the propellant manufacturing and testing. Finally, we Both bistetrazole compounds tested in this work (BTA and HBT) have shown high potential as burn rate would like to thank M. Étienne Comtois from modifiers, even when only small quantities were added General-Dynamics-OTS Valleyfield and Dr. to the propellant. In addition, both bistetrazoles studied Daniel Chamberland from DRDC-Valcartier for here can easily be synthesized from commercially many inspired discussions. available materials with good yields and purity which will be helpful in scaling up the synthesis if desired. References Furthermore, the synthesis of the precursor of HBT was successfully scaled up to the multi-kilogram scale [1] T. M. Klapotke, P. Mayer, J. Stierstorfer, and J. J. [14]. Weigand, Bistetrazolylamines-synthesis and By adding 5% of HBT or BTA to the triple base characterization, J. Mater. Chem. 2008, 18, 5248- propellant formulation used in this work, the relative 5258, 2008. quickness was found to increase with 10% and 18%, respectively. Furthermore, by adding 15% of either [2] T. M. Klapotke and C. M. Sabate, Bistetrazoles: HBT or BTA the relative quickness increased with 42% nitrogen-rich, high-performing, insensitive and 59%, respectively. On the contrary, at higher energetic compounds, Chem. Mater. 2008, 20, 67- concentrations (>15%), the burn rate modification 75. effects slowed down and it is probable that, for this [3] R. E. Kaczmarek, M. S. Firebaugh, B. M. Rice, T. particular propellant formulation, higher concentrations of bistetrazoles will only yield small increases of the M. Klapötke, J. M. Short, R. D. Lynch, et al., burning rate. While the increase in burning rates may Topics in Energetics Research and Development, not be as significant at high concentrations, other ESPC Press, 2013. advantages such as lower flame temperature and less [4] S. F. Son, H. L. Berghout, C. A. Bolme, D. E. erosive combustion gases for similar relative force can Chavez, D. Naud, and M. A. Hiskey, Burn rate be obtained with the use of these nitrogen-rich molecules. This could be especially expected for HBT, where a sensibly lower flame temperature and a higher [a] J. Lavoie, C. Dubois amount of nitrogen gas produced could lead to Chemical Engineering Department interesting reduction in gun barrel wear, with no École Polytechnique de Montréal significant performance losses. Montréal, H3C 3A7 (Canada) The main disadvantage of the two chosen E-mail: [email protected] bistetrazoles is probably their effect on the pressure [b] C.-F. Petre dependency of the burning rates. The presence of Defense Research & Development Canada Valcartier these materials was found to increase the pressure Valcartier G1X 3J5 (Canada) exponent (α) by a non-negligible amount and this is not [b] P.-Y. Paradis desirable as it could yield combustion instabilities. General Dynamics-OTS Canada Valleyfield Of the two bistetrazole, HBT provided the Valleyfield J6S 4V9 (Canada) better thermal stability to the resulting propellant. This Supporting information for this article is available on in turn could result in safer propellants, despite the fact the WWW under http://www.pep.wiley-vch.de or from the author.

7 Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants measurements of HMX, TATB, DHT, DAAF, and Meeting, Salt Lake city, UT, USA, November 4-9 BTATz 28th International Symposium on 2007. Combustion, Edinburgh, UK July 30 - August 4, [15] C. F. Petre, F. Paquet, C. Nicole, and S. Brochu, 2000, p. 919-924. Optimization of the Mechanical and Combustion [5] D. E. Chavez and B. C. Tappan, Synthesis and Properties of a New Green and Insensitive Gun Characteristics of Novel High-Nitrogen Material, Propellant Using Design of Experiments, Int. J. Int. J. Energ. Mater. Chem. Prop. 2013, 12, 173- Energ. Mater. Chem. Prop. 2011, 10, 437-453. 182. [16] I. A. Johnston, Understanding and Predicting Gun [6] D. E. Chavez, B. C. Tappan, B. A. Mason, and D. Barrel Erosion, Report DSTO-TR-1757, Weapons Parrish, Synthesis and energetic properties of bis- Systems Division - Defence Science and (triaminoguanidinium) 3,3-dinitro-5,5-azo-1,2,4- Technology Organisation, Edinburgh, Australia, triazolate (TAGDNAT): A new high-nitrogen 2005. material, Propellants, Explos., Pyrotech. 2009, 34, [17] N. Kubota, Propellants and Explosives 475-479 Thermochemical Aspects of Combustion: Wiley- [7] B. C. Tappan, S. F. Son, A. N. Ali, D. E. Chavez, VCH, 2007. and M. A. Hiskey, Decomposition and [18] R. S. Damse and A. K. Sikder, Suitability of performance of new high nitrogen propellants and nitrogen rich compounds for gun propellant explosives, 6th International Symposium on formulations, J. Hazard. Mater. 2009, 166, 967- Special Topics in Chemical Propulsion: 971. Advancements in Energetic Materials and [19] U. S. Department of Defense, "MIL-STD-286C," Chemical Propulsion, Santiago, Chile, 2005, p. . ed, 1991. [8] R. S. Damse, N. H. Naik, M. Ghosh, and A. K. [20] J. H. Flynn and L. A. Wall, General Treatment of Sikder, Thermoanalytical screening of nitrogen- the Thermogravimetry of Polymers, J. Res. Natl. rich compounds for ballistic requirements of gun Bur. Stand. (U. S.) 1966, 70A, 487-523. propellant, J. Propul. Power 2009, 25, 249-256. [21] ASTM, Standard Test Method for Arrhenius [9] J.-H. Yi, F.-Q. Zhao, Y.-H. Ren, B.-Z. Wang, C. Kinetic Constants for Thermally Unstable Zhou, X.-N. Ren, et al., "BTATz-CMDB Materials Using Differential Scanning Calorimetry propellants: High-pressure thermal properties and and the Flynn/Wall/Ozawa Method Standard their correlation with burning rates," J. of Therm. E698-11, Conshohocken, PA: ASTM International, Anal. and Calorim. 2011, 104, 1029-1036. 2011. [10] J.-H. Yi, F.-Q. Zhao, B.-Z. Wang, Q. Liu, C. Zhou, R.-Z. Hu, et al., Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety Received: ((will be filled in by the editorial staff)) and burning rates of BTATz-CMDB propellant, J. Revised: ((will be filled in by the editorial staff)) Hazard. Mater. 2010, 181, 432-439. [11] N. Kumbhakarna, S. T. Thynell, A. Chowdhury, and P. Lin, Analysis of RDX-TAGzT pseudo- propellant combustion with detailed chemical kinetics, Combust. Theory Modell. 2011, 15, 933- 956. [12] B. A. Mason, J. M. Lloyd, S. F. Son, and B. C. Tappan, Burning rate studies of bis- triaminoguanidinium azotetrazolate (TAGzT) and hexahydro-1,3, 5-trinitro-1, 3, 5-triazeve (RDX) mixtures, Int. J. Energ. Mater. Chem. Prop. 2009, 8, 31-8. [13] A. N. Ali, S. F. Son, M. A. Hiskey, and D. L. Naud, Novel High Nitrogen Propellant Use in Solid Fuel Micropropulsion, J. Propul. Power 2004, 20, 120- 126. [14] C. Radack, J. Salan, and L. Shelly, Bis Triaminoguanidinium Azotetrazolate (TAGzT) Scale Up And Production, AIChE 2007 Annual

8 Full Paper J . L a v o i e , C.-F.Petre, P,-Y. Paradis, C. Dubois

9 1.2 y = -9306.8x + 20.452 R² = 0.9987 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.08E-03 2.10E-03 2.12E-03 2.14E-03 2.16E-03 2.18E-03 T-1 (K-1)

Arrhenius plot of the reference propellant

1.2 y = -8091.6x + 18.186 R² = 0.9952 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.12E-03 2.14E-03 2.16E-03 2.18E-03 2.20E-03 2.22E-03 T-1 (K-1)

Arrhenius plot of the propellant containing 5% BTA 1.2 y = -9508.2x + 20.998 R² = 0.9883 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.10E-03 2.12E-03 2.14E-03 2.16E-03 2.18E-03 2.20E-03 T-1 (K-1)

Arrhenius plot of the propellant containing 5% HBT

1.2 y = -7774.1x + 17.613 R² = 0.999 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.13E-03 2.15E-03 2.17E-03 2.19E-03 2.21E-03 2.23E-03 T-1 (K-1)

Arrhenius plot of the propellant containing 15% BTA 1.2 y = -10728x + 23.729 R² = 0.9976 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.10E-03 2.12E-03 2.14E-03 2.16E-03 2.18E-03 2.20E-03 T-1 (K-1)

Arrhenius plot of the propellant containing 15% HBT

1.2 y = -17176x + 38.141 R² = 0.9794 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.16E-03 2.18E-03 2.20E-03 2.22E-03 T-1 (K-1)

Arrhenius plot of the propellant containing 25% BTA 1.2 y = -11570x + 25.543 R² = 0.9629 1.0

0.8

β 0.6 log

0.4

0.2

0.0 2.10E-03 2.12E-03 2.14E-03 2.16E-03 2.18E-03 2.20E-03 T-1 K(-1)

Arrhenius plot of the propellant containing 25% HBT

DSC of the pure nitrogen rich materials

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3. TITLE (The complete document title as indicated on the title page. Its classification should be indicated by the appropriate abbreviation (S, C or U) in parentheses after the title.)

Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants

4. AUTHORS (last name, followed by initials – ranks, titles, etc., not to be used) Lavoie, J.; Petre, C.-F.; Paradis, P.-Y.;Dubois, C.

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11b. FUTURE DISTRIBUTION OUTSIDE CANADA (Any limitations on further dissemination of the document, other than those imposed by security classification.) 12. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual.) The influence of two selected bistetrazoles, 5,5’-bis-(1H-tetrazolyl)-amine (BTA) and 5,5’- hydrazinebistetrazole (HBT), on the combustion behaviour of a typical triple-base propellant was investigated. Seven propellant formulations, one reference and six others incorporating respectively, 5%, 15% and 25% of either HBT or BTA compounds were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93% higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT-containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25% HBT. The thermal behaviour of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen-rich materials, indicating that the two compounds probably react readily with the –ONO2 groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds. ______13. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g., Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.)

Bistetrazole, Burning Rate, High Nitrogen, Nitrogen Rich, Propellant