Polymer nanodielectrics: materials with enhanced electrical properties

Nanotechnologies have provided recently many possible applications in several fields, from electronics to bioengineering, from materials engineering to electrical engineering, thanks to the availability of cheaper and cheaper nanofillers which allow nanostructured materials to be manufactured at affordable costs. Nanostructured materials have been studied during the last two decades with the aim of improving mechanical and thermal properties of materials, but only recently applications in the field of high voltage insulation are being devised. Most of the past literature, in fact, focuses on mechanical and high-temperature behavior of organic materials filled by inorganic nanoadditives. However, several new contributions start to deal with electrical properties of insulating materials, showing for example better resistance to partial discharge activity, surface discharges, lower space charge accumulation, longer life. The advantage of using nanofillers consists of maximization of the surface/volume ratio of the filler. This brings to obtain completely new materials, showing different properties from the base material even with a relatively small weight percentage of the nano-filler (typically ranging from 1% to 10%). Let us note that the improvement of electric properties is sometimes harder to be reached than the improvement of mechanical/thermal properties. In fact, electric properties can be affected significantly by several factors during material manufacturing. The compatibilization process between matrix and filler can leave often contaminants if the final material is not properly cleaned, thus worsening electrical properties (e.g., electric strength, endurance, etc.) with respect to the base material, particularly if a DC field is applied. This may occur particularly for those fillers that need a compatibilization process which can introduce extra ionic species in the matrix. Another kind of material contamination is relevant to the water absorbed by hydrophilic nanofillers that can be present in the final nanocomposite (NC) and affect dramatically electrical properties. Both phenomena should be considered because their impact on insulating material choice and insulation system manufacturing can be extremely important for the potentiality of applications of such new technology. For example, the need to dry the nanofiller and/or protect the NC from humid environment might discourage applications such as cable insulation or increase noticeably the cost of a nanostructured material.