Influence of Microorganisms on the Electrical Conductivity of Composite Materials Under Extreme Conditions

Abstract

It has been established that the variation in the conductance of insulation made with materials of various chemical nature and physical structure (polyvinyl chloride plastic compound and varnished cambric) with a short-term exposure to a mold fungus has an S-shaped character. The unambiguous correlation of the induction period, the stage of rapid increase and the time to reach the quasi-stationary level of conductance with the induction period, the stage of rapid growth, the time to reach the maximum amount of biomass on the surface of the material is due to the sorption by isolation of the metabolic products of the mold fungus. The variation in conductance at short times of exposure to microorganisms (~ 1 month) is reversible. Removal of microorganisms from the surface leads to a decrease in conductance to its original level. With their longer exposure (~ 1 year), the change in conductance may become irreversible as a result of the biochemical decomposition of insulation components, in particular, dialkyl phthalates - polyvinyl chloride plasticizers. Features of the processes of changes in conductance are due to the duration of the growth of microorganisms, the nature of materials and their components. The growth of microorganisms depends primarily on temperature and humidity conditions. For materials with high water absorption (varnished cambric), the most important external factor is temperature, and for materials with low water absorption (polyvinyl chloride) – relative humidity.