Variation of the dielectric properties of a multilayer stack of dry kraft paper with air pressure, mechanical pressure, temperature and time duration

The dielectric properties of a multilayer stack of kraft paper depend on the frequency, the temperature, the mechanical pressure and its dwell time, and the air temperature. It takes over 3000 hours for the dielectric loss factor to attain a new steady value after a change in air pressure, and over 20 hours to reach a steady value after a change in temperature. These long-term effects are probably due to the slow diffusion of ions through the stack, particularly those held at the interfaces between sheets