Fluorine/adamantane modified cyanate resins with wonderful interfacial bonding strength with PBO fibers

Abstract

Novel compound (AEAF) with both cage-type adamantanes and fluorine-containing structures was synthesized from bisphenol AF, 1-adamantyl chloride and epichlorohydrin through successive esterification and O-alkylation reaction, which was then introduced into the curing networks of bisphenol A cyanate ester (BADCy) resins through copolymerization, to obtain AEAF-co-BADCy resins. AEAF presented low polarizability & dipole density, rigid cage adamantane, and stable CF3 group. When the mass fraction of AEAF was 6 wt%, AEAF-co-BADCy resins displayed the minimum real part (ε′r), imaginary part (ε”r) of complex permittivity, and dielectric loss tangent (tanδ) values, which were 2.49, 0.012, and 0.0048, respectively. And the corresponding wave transmission efficiency (T) was 92.3%, significantly higher than that of pure BADCy (86.6%). AEAF-co-BADCy resins also possessed excellent mechanical properties and better interfacial compatibilities with poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. The corresponding flexural strength (126.5 MPa) and impact strength (15.2 kJ m−2) were increased by 16.6% and 47.6%, in comparison to pure BADCy (flexural strength of 108.5 MPa and impact strength of 10.3 kJ m−2). Meantime, the single fiber pull-out strength of PBO fibers/AEAF-co-BADCy (6 wt% AEAF) micro-composites also displayed an increase from 3.1 MPa (PBO fibers/BADCy) to 3.4 MPa.