To Örebro University

In this study we investigated the complex dielectric permittivity of cardboard with different water contents using a coaxial transmission/reflection technique from 10 MHz to 1.5 GHz. A relaxation process was analyzed to identify the bonding forms that exist in cardboard; this analysis was accompanied by a selective direct thermo-coulometric method. Two different types of bonding of water are found in cardboard (free and bound water) and both can be eliminated at 105 degrees C. The novelty of this work is the experimental correlation between the relaxation frequency situated in the radio-frequency band and the fraction of bound water in cardboard with a low water content.