• Virtanen, Suvi

Abstract

A constant need for the development of new and superior materials is always present; for example, a better electrical insulator would enable more efficient use of electrical power. Polymeric nanocomposites, i.e. nanodielectrics, are thought to have unique electrical properties. The basic chemical constitution of a material alone fails to provide an understanding of how desired properties of a material originate or predict the long term behavior of a material. We need to define the structure behind the functionality of a material. To do that, the structure of the material must be studied on several scales. This research was part of the Finnish Funding Agency for Technology and Innovation (TEKES) consortium projects NANOCOM and NANOPOWER. The general objective of these projects was to create truly new theoretical, experimental and practical knowledge of novel polymer nanocomposites to be further developed and finally used both in electrical and electronics insulation technology, as well as in other fields of technology.<br/><br/>Raman imaging was found to be a good tool for studying the structure of the materials: it provides information on the chemical species as well as dispersion of the filler. Alongside traditional confocal Raman imaging, which gives detailed information even at the submicron scale, coarse Raman imaging was used allowing the screening of a large area from a sample which is important for quality control of the composites to be used in industrial scale. <br/><br/>A new synthetic approach was used to afford well-dispersed silica particles with electroactive core functionalization in epoxy in order to study the effect of the charge layer at the interface of nanoparticle and polymer matrix. If the achieved distribution of particles was dense enough, the dielectric breakdown strength (DBS) increased considerably. The demonstrated increase in DBS and permittivity of the material leads to an increase of up to 125% in theoretical capacitive energy storage capability, and this is promising for future applications. These changes in properties are achieved with only 2 wt-% filler loading. Dielectric losses in the frequency range critical to the planned application stayed at the level of unfilled epoxy. This work is the first step towards new type functionalization of filler that offers good dispersion of nanoparticles without using harsh mixing conditions. These preliminary results indicate that the charge layer in the nanoparticle core, alongside a sufficiently dense enough distribution of particles at nanoscale, could be one way to improve dielectric properties of polymer materials.

Topics

• nanoparticle
• nanocomposite
• impedance spectroscopy
• dispersion
• polymer
• strength
• functionalization
• dielectric breakdown strength