Branched Fluorine/Adamantane Interfacial Compatibilizer for PBO Fibers/Cyanate Ester Wave-Transparent Laminated Composites

Branched fluorine/adamantane PBO precursor (preFABPBO), synthesized via random co-condensation between 2,2-bis(3-amino- 4-hydroxyphenyl)hexafluoro propane, 1,3-adamantanedicarbonyl dichloride, and trimesoyl chloride, is performed as interfacial compatibilizer, bisphenol A dicyanate ester (BADCy) resin as polymer matrix, and poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers as reinforcements to prepare PBO fibers/FABPBO-BADCy wave-transparent laminated composites by high temperature molding. The mechanical properties, wave-transparent performances, and heat resistances of PBO fibers/BADCy composites are simultaneously improved by the addition of preFABPBO. The interlaminar shear strength (ILSS) and flexural strength of PBO fibers/FABPBO-BADCy composites are 48.9 and 665.3 MPa, respectively, increased by 33.2% and 13.3% compared to those of PBO fibers/BADCy composites (36.7 and 587.4 MPa). The dielectric constant and dielectric loss values at 10⁶ Hz are 2.53 and 0.003, respectively, lower than those of PBO fibers/BADCy composites (3.06 and 0.006), and the corresponding wave transmission efficiency is 94.8%, which also presents excellent stability over the wide temperature (25—200 °C) and frequency range (10³—10⁷ Hz and 8.2—12.4 GHz). Meanwhile, the heat resistance index and glass transition temperature are 229.9 °C and 247.5 °C, also better than those of PBO fibers/BADCy composites (229.6 °C and 247.1 °C).