Influence of the physical and chemical surface structure on the water adsorption characteristics of insulation materials

Recent work is indicating, that the insulation characteristics of insulation material surfaces are influenced by the relative humidity in a greatly differing extent. This work has demonstrated, that this influence mainly depends on the physical and chemical surface structures of insulation materials. Additives such as hardeners and fillers, which are added in different amounts to the respective base material, have an important influence on the surface roughness and the chemical compound of insulation materials. This leads to a different behaviour of insulation material surfaces with respect to the adsorption of water molecules. Therefore in this paper we try to clarify the influence of physical and chemical properties of insulation material surfaces on their water adsorption characteristics. In order to describe the physical structure of insulation material surfaces we performed the REM spectroscopy and we determined the specific surface area. Additionally, the energy disperse X-ray (EDX) analysis has been applied in order to investigate the chemical compound of the test specimen. All investigations have been carried out on the test specimen consisting of two different glass fibre reinforced resins (epoxy and polyester resin). Furthermore, a laminate consisting of presspan and polyester foil has been investigated. The achieved test results show, that the laminate consisting of presspan and polyester foil shows the best insulation characteristics of the investigated insulation materials under high humidity, although it has the largest specific surface area and therefore-as we will show-is the most hydrophilic material