Electrical-insulation behavior of cellular polymer foams in comparison to their piezoelectret properties

Polymer foams are widely used in daily life for thermal insulation, shock and sound absorption, packaging, etc. A more recent development is the emergence of so-called ferroelectrets (or piezoelectrets). They are completely non-polar polymer foams that exhibit piezoelectricity after internal charging of the cavities by means of a series of dielectric barrier discharges (DBDs). The internally charged cavities are considered as macroscopic dipoles, which - in combination with the heterogenous mechanical properties of the material - induce the piezoelectricity. The piezoelectric properties of ferroelectrets and their dependence on material structures have been extensively studied in recent years. Polymer materials are often used for electrical insulation e.g. in electronic devices or in AC and DC power transmission and distribution systems. Due to their unique microstructure, polymer foams possess specific electrical and functional properties and are promising for a wide range of electrical applications. Here, we comparatively study piezoelectric and electrical insulation properties of polymer foams and their dependence on material structures.