Improving the comprehensive properties of PBO fibres/cyanate ester composites using a hyperbranched fluorine and epoxy containing PBO precursor

Hyperbranched fluorine and epoxy containing PBO precursor (epoxy- pre FHBPBO) was synthesized and utilized as interface compatibilizer to synchronously improve the mechanical and dielectric properties of poly( p -phenylene-2, 6-benzobisoxazole) (PBO) fibres reinforced bisphenol A dicyanate ester (BADCy) resins (PBO fibres/FHBPBO- co -BADCy) laminated composites. 1 H NMR, 13 C NMR, and FTIR analyses confirmed the successful preparation of epoxy- pre FHBPBO. The introduction of hyperbranched structure and fluorine groups significantly improved the mechanical properties and wave-transparent performance. Compared with PBO fibres/BADCy, the flexural strength and interlaminar shear strength of PBO fibres/FHBPBO- co -BADCy composites with 7 wt% epoxy- pre FHBPBO were respectively enhanced to 634.9 and 46.9 MPa, increased by 8.1% and 27.8%. The corresponding dielectric constant and dielectric loss were 2.65 and 0.003, respectively, lower than those of PBO fibres/BADCy (3.06 and 0.006) composites. Meanwhile, the corresponding volume resistivity and breakdown strength were 4.93 × 10 15 Ω•cm and 25.38 kV/mm, higher than PBO fibres/BADCy resins composites (2.2 × 10 15 Ω•cm and 17.69 kV/mm).