To develop a humidity-control building-material, adsorbed water of four kinds of sepiolite were investigated by the differential thermogravimetory (DTG), differential scanning calorimetory (DSC), and water vapor adsorption and desorption isotherm analysis. Following results were obtained;
1) By the DTG analysis, two dehydration peaks at 30°C and 55°C were observed. The intensity ratio of 55°C/30°C peaks were in the order of the sepiolite from USA (39%)< Turkey (45%)< Spain (50%)< China (67%). The DSC analysis also showed two endothermic peaks at 60°C and 90°C, and the intensity ratio 90°C/60°C were in the order of the sepiolite from USA (37%)< Turkey (43%)< Spain (50%)< China (67%). The amount of the water vapor adsorption at the relative humidity of 90% were in the order of the sepiolite from Turkey (28%)> Spain (24%)=USA (23%)> China (10%).
2) Even after the elimination of the impurity mineral effect on the amount of the water vapor adsorption, significant differences remained in the water vapor adsorption. But the order of the adsorption at P/P0=0.9changed like that of DTG and DSC; the sepiolites from USA (31%)> Turkey (29%)> Spain (25%)> China (20%).
3) Those differences were attributed to the difference in the ratio of micropore to total pore volume, which will be affected by the mean diameter of sepiolite fibers indicated by the crystallite size calculated by a peak width of X-ray diffraction and electron microscopy.
4) Pore size distribution curves calculated by the nitrogen and water vapor adsorption isotherms supported the above estimation.
