Formulation and Characterization of a New Nitroglycerin- Free Double Base Propellant

Double base propellants composed of nitrocellulose (NC) and nitroglycerin (NG) have been used in rocket and gun applications since the late 1800s [1] . Such propellants offer several benefits over their more modern composite counterparts, including simple formulation, high modulus and strength, and chlorine-free minimum smoke exhaust products [2,3] . Nevertheless, double base propellants are plagued with several drawbacks. The majority of these issues stem from the inclusion of NG as a major energetic ingredient. Like all nitrate esters, NG is capable of autocatalytic decomposition under certain storage conditions, and its tendency to migrate during propellant processing and storage has been widely observed and studied [4–6]. Additionally, due to the low melting point of NG (287 K), its quantity in propellants must be limited to prevent excessive degradation of grain strength, thus placing an upper bound on the performance of NG-based propellants. In an effort to overcome these issues, one might consider a room temperature-solid nitrate ester as a replacement. Pentaerythritol tetranitrate (PETN) is the standard bearer of this family, in wide manufacture and use since the 1930s [7] , however its low oxygen balance ( 10%), high sensitivity to friction and impact, and poor deflagration at atmospheric pressure make it an inferior prospective propellant ingredient. In 2008, Chavez et al. [8] reported the synthesis of a new solid nitrate ester, 1,4-dinitrato-2,3-dinitro-2,3bis(nitratomethylene)butane (colloquially, SMX). SMX has a better oxygen balance (0%, CO2 balanced) than PETN while surpassing it in density (1.917 gcm ). Its sensitivity to various initiating stimuli is similar to that of PETN [8]. Additionally, as a room temperature solid, SMX offers the potential for reduced migration and improved propellant physical properties at high concentrations. As such, SMX may have the combination of performance and stability to serve as a viable replacement for NG. Though fielded double base propellants have changed little in the past few decades, recent work by Wolszakiewicz et al. [9] with 2,4-dinitrotoluene and related compounds reported the formation of an energetic solid-phase solution by combining a solid nitrate ester compound with nitrocellulose. Such a process would be ideal for the incorporation of SMX into an NC-based system, thus forming a new class of double base propellants.