The effect of polymer matrices on the thermal hazard properties of RDX-based PBXs by using model-free and combined kinetic analysis

Abstract

Abstract:In this paper, the decomposition reaction models and thermal hazard properties of 1,3,5-trinitro-1,3,5-triazinane (RDX) and its PBXs bonded by Formex P1, Semtex 1A, C4, Viton A and Fluorel polymer matrices have been investigated based on isoconversional and combined kinetic analysis methods. The established kinetic triplets are used to predict the constant decomposition rate temperature profiles, the critical radius for thermal explosion and isotherms under a low temperature. It has been found that isoconversional and combined kinetic methods could yield equivalent reliable kinetic triplets, whereas it's easier to use the latter one to determine reaction models of energetic materials. The effect of the polymer matrices on the decomposition mechanism of RDX is significant, where Formex P1, Semtex and C4 could make initial decomposition of RDX follow a phase boundary controlled reaction mechanism, while under the effect of Viton A and Fluorel, its reaction model shifts to a random two dimensional nucleation and growth model. It has also been shown that the energetic materials that have longer induction period on constant reaction rate curves would have greater impact energy. According to isothermal simulations, the threshold cookoff time until loss of functionality at 82 °C for RDX-C4 and RDX-FM are less than 500 days, while it is more than 700 days for the others. Unlike simulated isothermal curves, when considering the charge properties and heat of decomposition, RDX-FM and RDX-C4 are better than RDX-SE in storage safty at arbitrary surrounding temperature.

The mechanisms for desensitization effect of synthetic polymers on BCHMX: Physical models and decomposition pathways

“…Firstly, the master plots method has been used for determination of the kinetic models on the basis of characterized shape function z(˛) and y(˛) [34][35][36]. The authors have summarized and interpreted this method elsewhere before [11,30] and in this paper only the Johnson-Mehl-Avrami (JMA, Eq. (1)) and autocatalytic (AC, Eq.…”

“…Here a modifiedŠesták-Berggren equation (SB, Eq. (2)) has been used to fit the experimental data [30,39,40]. Eq.…”

“…As it could be seen, the shape of the model curves obtained by these two methods is actually very close to each other even they have different parameters. It means that both of the methods yield equivalent kinetic models, which was also the case for RDX and CL-20 based PBXs [29,30]. Since the shapes (inherent mechanisms) of physical models obtained by these two methods are equivalent, one could select any one of them to reconstruct the experimental curves for the sake of reliability.…”

“…However, the decomposition physical models for most of the BCHMX based PBXs are not known from the literature, and hence first this paper is principally concerned with the determination and interpretation of the physical models. Then the temperature profiles for their constant rate decomposition are predicted, which may have some connections with the impact initiation processes [30]. In order to clarify the chemical processes for impact initiation, the detailed thermolysis pathways under fast heating (300 K ps −1 ) are further obtained from the MD trajectories using a reactive force field code (ReaxFFlg), which enable to directly probe the condensed phase chemistry under extreme conditions of temperature and pressure, identifying the key bimolecular radical reactions responsible for the low activation routes [31].…”

Probing the compatibility and interaction of energetic binders based on 3,3‐bis(azidomethyl)oxetane with some explosives: thermal, interfacial and simulation studies

“…[1][2][3] Polymer binders are substances added to propellants and explosives to give them appropriate mechanical and forming properties. 4,5 Besides that, they can provide combustible elements as part of the fuel, so the binders also affect the energy level of the formulations.…”