Preparation and properties of hollow ceramic spheres-epoxy dielectric composites

High strength hollow ceramic spheres are incorporated into epoxy resin to prepare insulating composite materials. The characterization shows simultaneous enhancement in thermal conductivity, mechanical strength and dielectric permittivity. A thermal conductivity of 1.36 W/(m center dot K) (7.5 times of that of pure epoxy) is measured from the sample prepared from hollow spheres with high alumina content. The compressive strength and impact strength measured from the same sample are 104.04 MPa and 3.61 kJ/m(2), corresponding to an increase of 18.3 and 31.4 %, respectively, from pure epoxy. The permittivity of the sample measured at low frequency is 9.85 which decreases slightly as frequency increased to 10(6) Hz. The electrical breakdown data are analyzed with Weibull model and the decreased breakdown strength is explained.