Novel urea-thiourea copolymers for TATB-based PBXs: Design, synthesis and mechanical performance enhancement

The mechanical properties of PBXs are critical to weapon system safety and reliability. In this work, two novel urea-thiourea copolymers (DADO-IPDI and DADO-HMDI) were designed and synthesized via a mild two-step reaction, as alternative binders of fluoropolymer-based TATB-PBXs. These copolymers integrate urea, thiourea and ether linkages, with favorable thermal stability ( T d, 5% >200 °C) and processable glass transition temperatures (76.3 °C and 60.3 °C). Compared with conventional fluoropolymers, they exhibit higher surface energy and polar components, improving wettability and adhesion to TATB crystals. Results demonstrate that the mechanical properties of PBX-1 and PBX-2 based on DADO-HMDI and DADO-IPDI are significantly enhanced. In particular, PBX-2 achieves an exceptional Brazilian tensile strength up to 8.77 MPa, which is 53% higher than that of fluoropolymer-based PBX-F (5.75 MPa). The compressive strengths of both PBX-1 and PBX-2 exceed 52 MPa, representing an improvement of more than 82% compared with PBX-F (28.16 MPa). Meanwhile, PBX-2 presents a low maximum creep strain of 5.1 × 10 −5  at 60 °C and 7 MPa, a 74.5% reduction relative to PBX-F (2.0 × 10 −5 ). The performance enhancement arises from the dense multiple hydrogen-bonding interactions at the binder–TATB interface, which enable efficient stress transfer, suppress interfacial debonding, and result in a dominant transgranular fracture mode. This study validates the efficacy of the newly developed binders for PBX reinforcement, and provides a promising strategy for advancing the mechanical properties of high-solid-loading energetic composites.