Position effects of nitrile groups on the thermal and oxidative stability of benzoxazines for defense applications

This paper focuses on the development of thermosetting resins with lightweight, excellent thermal stability and oxidation resistance. Specifically, the curing behavior and thermal properties of benzoxazines incorporating nitrile groups at the ortho, meta, and para positions of amine moiety were systematically evaluated to identify the most favorable chemical structures. Furthermore, thermal stability analysis revealed that C2-abn exhibited a high char yield of 68.49% at 800 °C. Flame exposure tests and EDS analysis indicated that C2-abn showed superior oxidation resistance with a low oxygen content of 18%. This paper provides insights into how nitrile positioning influences polymer network formation, crosslinking, and thermal performance. Also, the design and performance of high-performance benzoxazines emphasize their potential for application, which can contribute to the advancement of defense materials technology. • Benzoxazine monomers with nitrile groups at different positions were successfully synthesized. • Nitrile position significantly influenced curing behavior and crosslinking density. • Ortho-nitrile benzoxazine exhibited enhanced Mannich bridge formation and higher curing temperature. • Poly(C2-abn) achieved an exceptionally high char yield of 68.49% at 800 °C. • Dense and crack-free char layer provided superior thermal and oxidative stability.