Desiccants, How to Best Use!
Desiccants will only be effective when used in a closed moisture barrier package or a rigid, sealed container. This needs to be in a controlled environment to allow for optimal adsorption of the trapped vapors inside. If additional moisture from outside gets inside the packaging, then these moisture control products cannot guarantee the same results. For optimum humidity control, it is best to use desiccants in conjunction with a Humidity Control Card, which can be placed inside the package to monitor humidity levels. When the card shows a reaction, it is time to replace the desiccant.
There are various moisture control products, so it is important to pick the right desiccant. The type and quantity of desiccant will depend on the type of packaging being used and the volume of the container. With this, it is possible to determine which desiccants can work with a Desiccant Requirement Chart. From these options, it is critical to then consider the amount of moisture that needs to be adsorbed and the rate at which the process must occur. Overall shipping and storage conditions have an impact as well, with temperature and humidity goals affecting the final decision.
In general, the material of the desiccant can greatly impact its cost and absorption rate capacity. On the low end is Clay Moderate, with an absorption rate capacity by weight of 28%. Silica Gel Moderate offers medium capacity by weight at 38%, while Molecular Sieve Fast has a high absorption rate capacity by weight of 20%.
Desiccant Material Comparison Chart
|Property||Molecular Sieve||Silica Gel||Clay|
|Adsorptive Capacity at low H20 Concentrations||Excellent||Poor||Fair|
|Rate of Adsorption||Excellent||Good||Good|
|Capacity for Water @77° F, 40% RH||High||Medium||Medium|
|Adsorptive Capacity at Elevated Temperatures||Yes||No||No|
|Separation by Molecular Sizes||Excellent||Poor||Poor|