Microstructure and electrical properties of polyimide-based composites reinforced by high-aspect-ratio titanium oxide nanowires

Due to the unbalance between dielectric and insulation, the low dielectric constant and short corona aging life limit the application of the pure polyimide (PI). To achieve high dielectric constant and long corona aging life of polyimide-based composites simultaneously, the titanium oxide nanowires (TNWs) with high aspect ratio (20 nm in diameter, 10 μm in length and the aspect ratio is about 500) were reinforced into PI matrix by using in-situ polymerization in this study. The microstructure and electrical properties of PI/TNWs nanocomposite films with different mass fractions were investigated. The synchrotron radiation small angle X-ray scattering (SAXS) was carried out to explore how the interface structure affects the properties of PI/TNWs nanocomposite films. The results showed that the hybrid of TNWs not only make the structure of the composite films loose, but also increase the interfacial thickness of the PI matrix and TNWs. The dielectric constants of PI/TNWs nanocomposite films are increased dramatically up to 10.6 (about 3 times that of PI) with a only dielectric loss tangent of 0.03 at 101 Hz and the corona aging lifetime of 5 wt% PI/TNWs is closed to 28 h (about 9 times that of PI). In addition, the thermal stability of PI/TNWs nanocomposite films is also improved obviously. The resulted composites have a great potential application in the field of electrical insulation and electronic packaging.