Preparation and performance optimization of core@double-shell structured energetic composite materials

A suitable binder system is critical to ensure the energy properties, safety properties, formability, and mechanical properties of an energetic composite material (ECM). The energetic ionic salt, 5,5′-bistetrazole-1,1′-diolate (TKX-50), has attracted extensive attentions due to its low sensitivity and high energy properties. Its composition with the high energy explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) can construct ECMs with high energies and low sensitivities. However, the poor interfacial adhesions between TKX-50 and conventional binders greatly limit its application to such purpose. In this work, the interaction forces between cellulose acetate butyrate (CAB) and its anion derivative, carboxymethyl cellulose acetate butyrate (CMCAB), and two explosives, TKX-50 and HMX, were compared by using the molecular dynamics (MD) software. The effects of the binder systems including CAB, CMCAB and CMCAB@CAB on the bonding and coating of the mixtures of TKX-50 and HMX were compared by SEM and binder component analysis. And then CMCAB@CAB was selected to prepare a series of core-double-shell ECMs at different TKX-50:HMX mass ratios. The effects of the binder systems and TKX-50 content on the morphology and mechanical sensitivity of the ECMs were evaluated using a SEM and sensitivity apparatuses. The thermal conductivities (λ) and specific heat capacities (C_p) of the ECMs were determined using a thermal conductivity meter and DSC, respectively. The thermal decomposition properties of ECMs in open and adiabatic environments were characterized by a DSC and accelerating rate calorimeter (ARC), respectively, and the thermal decomposition mechanism was discussed. It is revealed that the good coating effects of CMCAB@CAB on TKX-50/HMX mixture enable the good formability of ECMs. The obtained ECMs show excellent mechanical sensitivities and thermal safety. Our work has provided a new approaching to the application of TKX-50 and the preparation of new high-energy and insensitive energetic composites.