Design and synthesis of fluorine/benzoxazole ring-modified bismaleimide resin and its reinforcement for PBO paper

The rapid development of radar systems has led to a surge in demand for low-dielectricity specialty paper’s mechanical, dielectric, and heat-resistant property. Poly (p-phenylene benzobisoxazole) (PBO) fiber is highly promising for the production of low-dielectricity specialty paper due to its excellent mechanical, heat-resistant and low dielectric property. The surface modification and nanosizing of PBO fiber have been applied to the reinforcement of PBO paper, however, these techniques have potential drawbacks, including lengthy preparation cycles and harsh conditions. Resin reinforcement is the simplest way, but suffers from weak interfacial strength. In this work, we creatively introduced the fluorine and benzoxazole ring into the bismaleimide (BMI) resin, based on the idea of homogenous reinforcement, to enhance the interaction between the PBO fiber and the resin. With the strong interfacial interaction and stable chemical structure, the composite paper has outstanding mechanical and heat-resistant property, its tensile strength and T_d reach 78.8 MPa and 389 °C, respectively. Furthermore, the dielectric constant (ε) and dielectric loss (tan δ) of the composite paper are as low as 1.66 and 0.004 at 10⁶ Hz, respectively. We anticipate that this work will offer a viable approach to PBO paper preparation.

Graphical Abstract