Desiccants

Contents

Clay desiccants:
Clay desiccants are non-hazardous, moisture adsorbent substances created by the controlled drying of a calcium (bentonite) aluminosilicate clay. This naturally occuring montmorillonite clay has a special affinity for moisture and is chemically inert and non-corrosive. The layered structure of clay desiccant attracts and adsorbs moisture onto its surface and between its layers. Desi Pak sachets will protect the contents of a properly sealed container during shipping and storage.
Clay is the least expensive of all desiccants and highly effective within normal temperature and relative humidity ranges. It is used in most industrial applications requiring humidity control. Clay can adsorb up to 28% of its weight in water vapor at 77°F (25°C) and 80% relative humidity. At full moisture vapor capacity, Desi Pak remains dry and free-flowing. There is no apparent change in size, shape, or texture of the desiccant.
Clay works satisfactorily below 120°F (49°C). Above 120°F (49°C), there is a possibility that the clay will give up moisture rather than pull it in (silica gel or molecular sieve are suitable for such temperatures). Accordingly, anticipated storage and transportation conditions should be considered when deciding whether or not to use clay.

Silica gel desiccants:
Silica gel is silicon dioxide (SiO2), an amorphous form of silica which is manufactured from sodium silicate and sulfuric acid. It is a naturally occuring mineral that is purified and processed into beaded or granular form. Like clay desiccant, silica gel is also non-corrosive and chemically inert. Much like a sponge, silica gel's interconnected pores form a vast surface area that will attract and hold water by adsorption and capillary condensation, allowing silica gel to adsorb about 40% of its weight in water vapor at 100% humidity.
As a desiccant, silica gel has an average pore size of 24 angstroms. Silica gel will pull in moisture at temperatures up to 220°F (104°C). As temperatures increase above 100°F (38°C) the rate of moisture pick-up will slow down, but the silica gel will still work. Silica gel performs best at room temperatures between 70°F to 90°F (21°C to 32°C) and at high humidity between 60% to 90% relative humidity.