Features of Silica Gel Packaging Desiccants:
- Pore opening size ranges a magnitude up and down from a billionth of a meter (nano-meter). The pores create a huge surface area which will bind water through surface adsorption and capillary action.
- Silica gels are available in different qualities, which have different absorption characteristics. In general a particular silica gel will have a maximum absorbance at a particular relative humidity and the absorbance will fall off at either direction from this point.
- Under optimal conditions silica gel will adsorb up to 40% of its own weight, but under practical conditions usually much less.
- The adsorption ability falls at temperatures above 30-40C. Although some moisture can be adsorbed at temperatures up to 80C, the risk of re-evaporation of already adsorbed moisture make silica gel unsuitable for use in an environment where temperatures of above 40C may occur even temporarily.
- Silica gel is not suitable as a container desiccant, but is good for use in packages where the risk of high temperature is small.