Microfluidic strategy for coating and modification of polymer-bonded nano-HNS explosives.

• A new microfluidic strategy was used for modification and coating of HNS based PBX. • The PBX has narrow particle size distribution due to the uniform crystallization environment. • The mechanism of coating PBX was analyzed based on the rapid screening function. • The effects of micro-mixing conditions on PBX were studied from micro-scale growth. • The PBX breaks the limitation that HNS cannot resist high overload. Polymer bonded explosives (PBXs) have the characteristics of high energy density, and excellent safety and mechanical performances. In this work, a microfluidic crystallization system (MCS) based on microscale chaotic advection is proposed to control and optimize the crystallization environment of PBXs. Comparison with the macroscale method not only verifies the feasibility of the MSC in the preparation of PBXs, but it also boasts a narrower particle size distribution, regular morphology, and high crystal quality. Furthermore, based on the advantages of the rapid and simple preparation of the MCS, the suitable polymer-coated explosive composite system can be quickly screened out. Four typical binders were selected by the MCS to coat the nano-hexanitrostilbene (nano- HNS), and their properties were analyzed. On this basis, the surface modification and coating mechanism of the binder on HNS crystals and the effect of micro mixing conditions on PBXs crystal growth were studied. Finally, the anti-overload performance of four different PBXs was evaluated through air gun experiments. The results show that all four PBXs can maintain the stability of the charge under strong external dynamic load conditions. This study provides an efficient route to prepare PBXs with narrow particle size distribution, high crystal quality and resistant high overload. This work serves those studying the composite system of crystals and polymers, as well as polymer-coated crystals. [ABSTRACT FROM AUTHOR]