Impact of a silane-coating of hollow glass microspheres on the electrical properties of syntactic foam

Syntactic foam is a solid insulation material, featuring a foam-like structure. It's a composition of hollow microspheres and a polymeric matrix material. In this study it consists of glass microspheres and an epoxy resin matrix. The present paper deals with the influence of modified inner interfaces (achieved by silane-coated glass microspheres in order to improve the adhesion quality between the glass microspheres and the epoxy resin matrix) on the electrical properties of the material. The experiments show that the silane-coating (also known as silanization) has a positive influence on the breakdown field strength under electrical ac and dc short term stress. The experiments are conducted for different degrees of filling of the glass microspheres (10 vol.% ... 50 vol.%). It is shown, that the influence of the silanization becomes more significant with higher degree of filling. The life time of the material under electrical ac as well as dc stress can also be improved by a silanization. The dielectric properties (loss factor and relative permittivity) are not influenced by a silanization. Measurements of the viscosity of syntactic foam verify that a silanization reduces the viscosity of the uncured, liquid material during the manufacturing process. Hereby, an improvement of the material's production quality can be achieved at high microspheres' filling degrees.