Innovative nanostructured epoxy composites for enhanced high voltage insulation systems

In order to cope with the growing demand in electricity, operating voltages and power ratings have seen an increase in the past years. This means that electro-thermal stresses on the existing electrical insulation systems have increased concomitantly. However, polymeric materials used for high voltage insulation are prone to degradation due to electrical discharges and commonly boast rather low thermal conductivities, which is why there is an impelling need for a new generation of insulating materials with improved dielectric and thermal performances. During the last decades, attention was drawn towards a novel class of dielectric materials: polymer nanocomposites or nanodielectrics. These dielectrics feature nanometric filler particles instead of micrometric particles, which can lead to significantly enhanced performances - such as improved dielectric breakdown strengths - already at very low contents, thus indicating their great potential for application in HV insulation systems. Nevertheless, such nanodielectrics only unfold their full potential when a good dispersion and distribution of those filler particles within the polymer matrix are achieved. Albeit, clusters of nanoparticles with submicrometric or micrometric dimensions are often found, which is due to the incompatibility of inorganic particles with the organic polymer. Such agglomerations will subsequently cancel the beneficial effect seen for well dispersed nanoparticles. In order to enhance the interaction between inorganic filler particles and organic matrix, and hence, improve the dispersion of such particles in polymers, the functionalization of nanofillers has become rather common. Still, little is known about the long-term stability of such functionalizers under electro-thermal stresses, which poses a drawback to their broad industrial use in high voltage engineering. The objective of the presented thesis was to develop innovative, nanostructured époxy composites that reveal enhanced dielectric and thermal performances, and to evaluate their applicability for high voltage insulation systems. In order to achieve an original contribution to the field of nanodielectrics, a novel approach was explored by using functional nanometric additives, so-called polyhedral oligomeric silsesquioxanes (POSS) instead of applying surface functionalization for the filler particles used. Even more, multifunctional nanostructured composites were to be designed, involving functional POSS additives along with