Effect of alumina shapes on dielectric properties of UV-cured epoxy acrylic composite with alumina

Polymer-based composites with the advantages of ceramics and polymers exhibit high dielectric constant, good processing properties and low dielectric loss. The composites with a varied content of irregular alumina (i-Al₂O₃) filler were prepared by UV-cured epoxy acrylic (EA). Spherical alumina (s-Al₂O₃) was used as a filler to further investigate the effect of alumina (Al₂O₃) shapes on dielectric properties of composites in the frequency range of 50 Hz-1 MHz. Fourier transform infrared spectroscopy proved that the UV-cured epoxy acrylic/ alumina (Al₂O₃/EA) composites were successfully fabricated. Scanning electron microscopy demonstrated that i-Al₂O₃ particles have superior homodispersion in the matrix. Through testing, for all samples, with the addition of Al₂O₃, the relative permittivity of composites increased as expected, and the dielectric loss decreased accordingly. These data show that the incorporation of i-Al₂O₃ particles presents better properties when compared with s-Al₂O₃/EA, which indicates that i-Al₂O₃ particles have more influence on the dielectric properties of the composites than those of s-Al₂O₃ particles. According to Weibull distribution, the characteristic breakdown strength of the Al₂O₃/EA composites was obtained and the results suggested that the composites of i-Al₂O₃/EA exhibited better breakdown performance.