Effect of anionic carboxymethyl cellulose acetate butyrate on recrystallization and surface modification of energetic ion salt TKX-50 crystal

Abstract

The energetic ion salt, TKX-50, has attracted great interests in the field of energetic materials due to its advantages of high enthalpy of formation, low sensitivity and low toxicity. However, the large aspect ratio and poor surface adhesion performance of its crystal are inconducive to the safe use and interfacial bonding for the preparation of composite energetic materials. To solve these problems, we introduced an anionic polymer, carboxymethyl cellulose acetate butyrate (CMCAB), as the crystal control agent and surface modifier for the recrystallization of TKX-50 by the anti-solvent method. The effects of CMCAB on the morphology, internal structure, surface elemental composition, mechanical sensitivity, specific heat capacity (Cp) and thermal stability of TKX-50 were investigated. It was found that the morphologies of the TKX-50 recrystallized in the anti-solvents containing CMCAB were better with lower aspect ratios and narrower particle size distributions. A discontinuous CMCAB coating layer was formed on the crystal surfaces due to the electrostatic interaction between CMCAB and TKX-50, resulting in the CMCAB@TKX-50 complex. The coating degree and surface modification were more significant with the increase of CMCAB concentration. The CMCAB coating reduced the friction sensitivity of TKX-50 by 12–38%, meanwhile, the impact sensitivities of CMCAB@TKX-50 prepared at different CMCAB concentrations remained at the low levels of 4–12%. The DSC analysis revealed that the Cp of CMCAB@TKX-50 was generally higher than that of TKX-50. The bigger the crystals of CMCAB@TKX-50, the greater the Cp and the higher the thermal stability. The peak decomposition temperature of the first stage, the activation energy (Ea) and pre-exponential factor (A) of CMCAB@TKX-50 were generally higher than those of TKX-50, suggesting better thermal stability and safety of CMCAB@TKX-50 than TKX-50. The CMCAB@TKX-50 prepared in our work not only shows superior safety performance, but also is well compatible with the traditional binder, cellulose acetate butyrate (CAB). The good dissolution properties of CMCAB make CMCAB@TKX-50 more suitable for the preparation of polymer-bonded explosives (PBX), which can promote the application of TKX-50 in PBX.