Preparation and characteristics of polyimide/CaMoO₄ nanocomposites with enhanced dielectric performance and thermal stability

The polyimide/CaMoO₄ nanocomposites were successfully prepared by ex-situ polymerization. (3-Aminopropyl) triethoxysilane (KH550) was used as coupling agent to disperse the CaMoO₄ nanoparticles in polyimide matrix homogeneously. To characterize the structure and properties of the obtained nanocomposites, Scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, dielectric properties and thermal stability were studied. It was observed that the CaMoO₄ nanoparticles were dispersed homogeneously in the polyimide matrix without obvious aggregation. The results show that nano-sized CaMoO₄ will improve dielectric constant and decrease dielectric loss of the nanocomposites in the relatively high-frequency region (>10 kHz). And the nanocomposite with excellent dielectric properties of ε = 3.04, δ = 8.0 × 10⁻³ was obtained after doping 2.5 wt% nano-sized CaMoO₄ into polyimides. Dielectric loss of the nanocomposites is reduced in low frequency domain (<10 kHz) and enhanced in high frequency domain (>10 kHz). In addition, the thermal stability of the nanocomposites was enhanced from 544 to 651 °C compared to pure polyimide.