Moisture regulation 175 SILICA GEL Moisture adsorption rate and capacity 25'C and 20, 40, 80% RH MTI@80%RH·MII@40%RH·MII@20% Fig 9.2 Adsorption rate and capacity at 20, 40, and 80% RH 9.3.2 Capacity and conditions of use Mined clay is activated for use through careful drying. Adsorption capacities are in the range of 25-30% of dry weight at normal room temperature and below Above 35C clay will begin to desorb moisture. As a result the utility of clay is greatest under temperate conditions 9.3.3 Adsorption/desorption Adsorptive capacity varies with composition and the source. Fig. 9.3 illustrates the adsorptive characteristics of clay from a particular mine located in Oklahoma known as Oklahoma 1. Adsorption of moisture by clay is relatively rapid even at low relative humidity. As can be seen in Fig. 9.3 clay will adsorb its full complement of moisture in a matter of hours 034P2: P choice for many industrial and particu山时yh applications. Packaging may be in adhesive coated, reinforced kraft paper, non- wovens, or perforated film laminates. Larger sized packages of lkg or more may be in fabric bags, filled, then sewn closed. As noted above, the adsorption of moisture is more rapid than necessary for some applications. For operational expediency and to permit more open or working time, a package material with somewhat restricted permeability may be chosen In order to account for the differences between one source of desiccant clay and nother and indeed from one desiccant to another, the US military established a standard unit of adsorption. In November 1963, the Department of Defence9.3.2 Capacity and conditions of use Mined clay is activated for use through careful drying. Adsorption capacities are in the range of 25–30% of dry weight at normal room temperature and below. Above 35ºC clay will begin to desorb moisture. As a result the utility of clay is greatest under temperate conditions. 9.3.3 Adsorption/desorption Adsorptive capacity varies with composition and the source. Fig. 9.3 illustrates the adsorptive characteristics of clay from a particular mine located in Oklahoma known as Oklahoma 1. Adsorption of moisture by clay is relatively rapid even at low relative humidity. As can be seen in Fig. 9.3 clay will adsorb its full complement of moisture in a matter of hours. 9.3.4 Packaging and applications Clay is the desiccant of choice for many industrial and particularly bulk applications. Packaging may be in adhesive coated, reinforced kraft paper, non￾wovens, or perforated film laminates. Larger sized packages of 1kg or more may be in fabric bags, filled, then sewn closed. As noted above, the adsorption of moisture is more rapid than necessary for some applications. For operational expediency and to permit more open or working time, a package material with somewhat restricted permeability may be chosen. In order to account for the differences between one source of desiccant clay and another and indeed from one desiccant to another, the US military established a standard unit of adsorption. In November 1963, the Department of Defence Fig. 9.2 Adsorption rate and capacity at 20, 40, and 80% RH. Moisture regulation 175