Interfacial reinforcement of core-shell HMX@energetic polymer composites featuring enhanced thermal and safety performance

Abstract

The weak interface interaction and solid-solid phase transition have long been a conundrum for 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX)-based polymer-bonded explosives (PBX). A two-step strategy that involves the pretreatment of HMX to endow –OH groups on the surface via polyalcohol bonding agent modification and in situ coating with nitrate ester-containing polymer, was proposed to address the problem. Two types of energetic polyether—glycidyl azide polymer (GAP) and nitrate modified GAP (GNP) were grafted onto HMX crystal based on isocyanate addition reaction bridged through neutral polymeric bonding agent (NPBA) layer. The morphology and structure of the HMX-based composites were characterized in detail and the core-shell structure was validated. The grafted polymers obviously enhanced the adhesion force between HMX crystals and fluoropolymer (F2314) binder. Due to the interfacial reinforcement among the components, the two HMX-based composites exhibited a remarkable increment of phase transition peak temperature by 10.2°C and 19.6°C with no more than 1.5% shell content, respectively. Furthermore, the impact and friction sensitivity of the composites decreased significantly as a result of the barrier produced by the grafted polymers. These findings will enhance the future prospects for the interface design of energetic composites aiming to solve the weak interface and safety concerns.

Keywords

• HMX crystals
• Polyalcohol bonding agent
• Energetic polymer
• Core-shell structure
• Interfacial reinforcement