At the present, electrical insulation is widely based on synthetic polymers which have largely superseded traditional insulation materials such as paper and ceramics. Polymer composite materials incorporating various amounts of inorganic filler particles are often used to improve the properties and to reduce the cost of the composite. During the last years, a considerable interest has risen towards dielectric polymer nanocomposites which incorporate low mass amounts of inorganic filler particles with one or more dimension in the nanometric scale. Due to the large interfacial area between the nanoparticles and the surrounding polymer matrix, improved material properties may be achieved. Regarding to dielectric properties, improvements in e.g. dielectric strength and permittivity as well as reduction of dielectric losses may be achieved, all of which would be desirable for capacitor applications.

In the NANOPOWER –project (Novel Polymer Nanocomposites for Power Capacitors), funded mainly by the Finnish funding agency for technology and innovation (TEKES), the application possibilities of novel dielectric polymer nanocomposites in power capacitors are studied. This thesis was done as a part of the NANOPOWER-project with the focus on metallized film capacitors which incorporate thin electrodes directly evaporated on dielectric polymer film instead of separate sheets of aluminium foil traditionally used in film capacitors. Although metallized film capacitors already enable high energy density and high reliability, demands for even higher energy density, better reliability and longer life-time exist. It may be possible to fulfil these demands by utilizing nanodielectric films and thus, metallized film capacitor technology offers an interesting platform for further research and development.

The main objective of this thesis is to study the application possibilities of polypropylene nanocomposites in metallized film capacitors. The subject is approached by performing an extensive literature research on polymers, dielectric polymer nanocomposites and metallized film capacitors. In the empirical part, a measurement system which could be used in the future to conduct various DC tests on single metallized nanocomposite film samples is planned, constructed and tested. The studied electrical properties included dielectric strength, maximum permissible electric field stress and self-healing capability of the film. In addition, the dependency of these properties on external pressure was studied with the measurement setup. /Kir11