Optimization of PBO fibers/cyanate ester wave-transparent laminated composites via incorporation of a fluoride-containing linear interfacial compatibilizer

Bisphenol A dicyanate ester (BADCy) was utilized as the matrix, poly (p-phenylene-2, 6-benzobisoxazole) (PBO) fibers as the reinforcement, and synthesized fluorine-containing linear PBO precursor (preFLPBO) as the interfacial compatibilizer to prepare PBO fibers/FLPBO-m-BADCy wave-transparent laminated composites. The fluorine groups and PBO-like structures could respectively improve the dielectric properties of BADCy matrix and the interfacial compatibility between the BADCy matrix and PBO fibers. Additionally, the partly interpenetrating network formed between preFLPBO and BADCy could significantly improve the mechanical properties. PBO fibers/FLPBO-m-BADCy wave-transparent laminated composites with 7 wt% preFLPBO displayed the optimal comprehensive performances. Dielectric constant (ε) and dielectric loss (tanδ) were respectively 2.90 and 0.0042, and the corresponding theoretical wave-transmittance (|T|²) at 1 MHz was 93.3%, higher than that of PBO fibers/BADCy wave-transparent laminated composites. The minimum percentage of simulated electromagnetic wave-transparent energy (E_{T (simulation)}) of the PBO fibers/FLPBO-m-BADCy (1 mm) wave-transparent laminated composites at 0.3~40 GHz was 87.3%, also better than PBO fibers/BADCy wave-transparent laminated composites (85.9%). The flexural and interlaminar shear strength (ILSS) of PBO fibers/FLPBO-m-BADCy wave-transparent laminated composites were increased from 587.4 and 36.7 MPa to 628.0 and 44.8 MPa, respectively. In addition, the corresponding volume resistivity and breakdown voltage were 2.7 × 10¹⁵ Ω·cm and 19.12 kV/mm, respectively.