Facile method for fabricating low dielectric constant polyimide fibers with hyperbranched polysiloxane

Abstract

High-performance fibers with a low dielectric constant and good mechanical properties as well as excellent thermal stability are in demand for the next generation of advanced radar-wave-transparent composites. In this study, an effective method is proposed to prepare amine-functionalized hyperbranched polysiloxane (NH₂-HBPSi) reinforced polyimide (PI) composite fibers with exceptional dielectric behavior, mechanical and thermal properties. The amino-functionalized NH₂-HBPSi were grafted to PI chains during in situ polymerization, promoting the uniform dispersion of the NH₂-HBPSi nanoparticles and forming strong interfacial interactions between NH₂-HBPSi and the PI matrix. The composite fiber containing 10 wt% NH₂-HBPSi exhibited a 10% and 26% increase in tensile strength and modulus compared to the pure PI fiber. Owing to the dielectric confinement effect from NH₂-HBPSi, the dielectric constants of the NH₂-HBPSi/PI composites were reduced drastically and the value could reach as low as 2.2 at 10⁸ Hz. The composite fiber demonstrated better specific strength, specific modulus and lower dielectric constant than the commonly used E-glass, S-glass and quartz fibers. These results provide useful information for designing molecular architecture and fabricating high-performance reinforcing fibers in the future radomes.