Hierarchical synergistic surface construction towards high-efficiency interfacial and mechanical enhancement in energetic polymer composites

As important parts in weapon systems, polymer bonded explosives (PBX) are often subjected to different external stimuli, e.g. compression, tension and impact during manufacturing, transportation and handling. Hence, sufficient mechanical property is necessary to ensure the security and reliability. However, weak interfacial interactions always restrict and weaken the properties of the PBX, especially for the mechanical property. Conventional surface modifications can hardly achieve a desired result, due to the inadequacy for solving the low surface energy, smooth and poor adhesive performance of high-quality explosives. To solve this problem, herein, we reported a novel multi-scale surface modification strategy of explosive crystals to strengthen interfacial properties. The surface of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was in-situ grafted by a crosslinked high-strength polymer network consisting of hyperbranched polyurethane (HBPU) and graphene oxide (GO), which significantly improved the interfacial bonding, interlocking and mechanical strength of interface layer itself. Beneficial from this multi-scale surface modification, a high-efficiency mechanical enhancement of PBX was achieved. With only 0.5 wt% network content, the maximum tensile and compressive strength PBX composites were both significantly improved, which were 59% and 26% higher than those of pure PBX, respectively. This approach of constructing multi-scale surfaces aiming at low surface wettability and weak interface of explosives potentially provided a creative opportunity for design and fabrication of high performance PBX, and might raise potential of interest to the communities in energetic materials.