Desiccant Performance Data
Activated Clay
Moisture
Adsorbent
Clay desiccant is a
chemically inert, non-corrosive, calcium aluminosilicate clay. The internal
structure of this calcium-rich montmorillonite is a layer structure which
attracts and adsorbs moisture onto its surface and between its layers. At full
moisture vapor capacity, Clay remains dry and free-flowing. There is no
apparent change in size, shape or texture of the desiccant. At 70% RH and 75°F,
Clay adsorbs over 20% of its weight in water. This is accomplished in
approximately 6 hours. (Refer to Exhibits 1 and 2).
Silica Gel
Moisture Adsorbent
Silica Gel is
made from amorphous silicate. It is a hard, translucent material with an
extremely high capacity for moisture at temperatures below 75° and at humidity
levels above 40%.
Silica Gel is designed to control moisture levels within
packaged products. The function of Silica Gel when controlling moisture is like a
tiny sponge with millions of microscopic pores. Under very low humidity
conditions, a small amount of water vapor will be adsorbed in the smallest
pores. As humidity increases, the larger pores will begin to fill. For example,
at 20% RH and 75°F, Silica Gel can adsorb 12% of its weight in water. At 80% RH and
75°F, it can adsorb 35% of its weight in water (see Exhibit 3). Unlike a sponge,
however, Silica Gel remains dry even at maximum capacity. In addition to adsorbing
more at higher humidity levels, Silica Gel will also adsorb more as the time period
increases. For example, at 70% RH and 75°F, Silica Gel can adsorb 15% of its weight
in water within two hours and reach adsorption capacity within eight hours (see
Exhibit 4).
NOTE: Clay and Silica Gel desiccants by
Poly Lam Products Corp. are qualified under Mil D-3464
Type I and II for use in Method II Packaging Mil P-116. Through our
Manufacturing Partners (Certificate of
compliance furnished upon request).
Activated Carbon
Odor/Gas Adsorbent
Getter® consists of activated
carbon and is used in controlling objectionable odors and gases within packaged
products. These odors and gases are removed through the process of adsorption.
Many products contain gas and odor molecules of an
objectionable nature. These molecules are readily adsorbed by Activated Carbon because:
- They are heavier than most other types of
molecules.
- Their chemical nature draws them to the activated
carbon located within the Getter Package.
Through adsorption, Getter protects several types of
products ranging from pharmaceuticals to electronics. Exhibit 5 illustrates the
percent pick-up of Carbon Tetrachloride versus time, using Getter at
75°F.
Molecular Sieve
Moisture/Gas Adsorbent
Molecular sieves
originating from zeolite compounds are synthetically produced crystalline metal
alumino-silicates used for adsorption. They are unique to other adsorbents
because:
- They adsorb molecules on the basis of polarity
differences due to electrostatic attraction.
- They have a uniform pore structure which enables
them to separate molecules by size.
Water molecules, for example, are adsorbed strongly
by Molecular sieves because they possess a higher degree of polarity and have the proper
molecular size for entrance into the sieves' pores.
The structure of Molecular sieves provides a higher capacity
for water adsorption than either silica gel or clay at low humidity levels.
Exhibit 6 compares the adsorption capacity of Molecular sieves with silica gel and clay
at varying humidity levels.
Molecular sieves also retains a higher percent of moisture
capacity than either silica gel or clay as temperature levels increase. Exhibit
7 compares this relationship.
2-in-1TM
Moisture and Odor/Gas
Adsorbent
2-in-1 is a combination of silica gel and activated
carbon packaged together for use in controlling moisture, gas and odor within
packaged products.
As a moisture adsorbent, 2-in-1 attracts the excess
water vapor that is present within the package. Under even very low humidity
conditions, a small amount of water vapor will settle in its sponge-like pores.
As humidity increases, the larger pores will begin to fill and adsorb the
remaining moisture.
Simultaneously, 2-in-1 will adsorb gas and odor
molecules. These molecules are readily adsorbed because:
- Gas and odor molecules are heavier than most other
molecules.
- They are chemically attracted to the carbon located
within the 2-in-1 package.
