On the Effect of a Thixotropic Agent on the Dielectric Properties of Epoxy Resin-based Syntactic Foams

Deformations of magnetic cores of inductive medium-voltage instrument transformers can lead to measurement errors and therefore require elastic compensation layers. These deformations occur due to manufacturing-related mechanical stresses of epoxy resin-based insulating systems. Alternatively, compressible gas-filled polymer hollow microspheres can be embedded in the epoxy resin matrix to increase elasticity. By using this composite material known as syntactic foam, costly cushioning layers can be avoided. However, current laboratory-scale manufacturing processes require of a complex mold rotation to prevent sedimentation of the hollow microspheres in the cured material. In order to make syntactic foam more accessible for industrial applications, the effect of a thixotropic agent to homogenize the distribution of hollow microspheres was investigated. Specimens using both manufacturing processes (mold rotation and thixotropic agent) with varying filling degrees were prepared and compared on the basis of their hollow microspheres’ distribution and dielectric properties. Given the minor differences of measurement results and the simplified manufacturing process, the use of thixotropic agents for avoiding sedimentation in epoxy resin-based syntactic foams is recommended.