PBO fibers/fluorine-containing liquid crystal compound modified cyanate ester wave-transparent laminated composites with excellent mechanical and flame retardance properties

Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound (LCFE) are applied as polymer matrix (LCFE-BADCy), poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers as reinforcements, and fluorine/adamantane PBO precursor (preFABPBO) as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites. LCFE could improve the order degree of BADCy cured network, in favor of enhancing the wave-transparent performance, mechanical properties, and intrinsic thermal conductivity. The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature (25–200 °C) and frequency (10⁴–10⁷ Hz and 8.2–12.4 GHz) stable with the value of 2.49 and 0.003 under 10⁶ Hz at 25 °C, and the corresponding wave transmission efficiency is 95.0%, higher than that of 92.5% for PBO fibers/BADCy composites. The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa, 38.1% and 16.2% higher than those of PBO fibers/BADCy composites. Besides, the volume resistivity, breakdown voltage, heat resistance index, glass transition temperature, flame retardant grade, and ultimate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3 × 10¹⁵ Ω cm, 29.75 kV/mm, 217.2 °C, 245.7 °C, V-1 grade, and 33.6%, expected to be performed as a new generation of “lightweight/loading/wave-transparent” electromagnetic window materials in advanced military weapons and civil communication base station.