The New Measurement Method of the Adsorbed Moisture Distribution in the Porous Materials

Abstract

Moisture absorption by porous materials with mesopores and micropores is generally evaluated by measurement of the water adsorption isotherm and analysis of the pore distribution by the nitrogen adsorption method using completely dry samples. In practical use, however, the adsorbent contains some water depending on the environmental conditions. To evaluate the pore distribution accompanied by the water adsorption, the nitrogen adsorption method was modified by using a frozen sample, which was dipped into liquid nitrogen after the water adsorption had reached equilibrium. Water adsorption was found to proceed from the smaller to the larger pores as relative humidity increased. The pore distribution at the relative humidity above which pores were completely occupied by absorbed water was shown visually on a histogram.