Frequently Asked Question?
1. What size desiccant do I need?
It depends. The answer to the size of desiccant needed depends on the size of the air space to be desiccated, the nature of the material in the package, the moisture barrier surrounding the package, the type of desiccant being used, the desired shelf life, the atmosphere conditions where the package is sealed, the type of seal on the package, etc. When we receive a call from someone looking for a desiccant, we will ask a number of questions to determine this information so we can calculate which size desiccant will work best in a particular application.
2. What types of desiccant are there?
Zettapac deals mostly with three types of desiccant and occasionally with a fourth. The most commonly used desiccant are clay, silica gel, container dry and molecular sieve. Occasionally we run into an application that calls for calcium chloride with better absorption ability.
3. What is a clay desiccant?
Clay desiccant are made from montmorillonite clay which has a special affinity for moisture. Clay is a good basic desiccant that works satisfactorily below 120℉ (approximately 50℃). Above 120℉, there is possibility that the clay will give up moisture rather than pulling it in, so anticipated storage and transportation conditions should be considered. The upside to clay is that it is normally the least expensive desiccant per pound. Its appearance is that small grey pallet.
4. What is Silica Gel?
Silica gel is silicon dioxide (SiO2).It is a naturally occurring mineral that is purified and processed into either granular or beaded form. As a desiccant, it has an average pore size of 24 angstroms and has a strong affinity for moisture molecules. The silica gel will pull in moisture at temperature up to 220℉ (150℃). As temperature goes above 100℉, the rate of moisture pick-up will slow down but the silica gel will drop the relative humidity in a container down to around 40% Rh. In the United State, silica gel commonly use in food and pharmaceutical applications as only silica gel has been approved by the FDA for direct contact with these items.
5. What is indicating Silica gel?
Indicating silica gel is a silica gel bead or granule that has been washed with a concentration of cobalt chloride (a heavy metal salt). The cobalt chloride is a deep blue color when it is dry and turn from blue to purple to pink as its becomes saturated with moisture. Typically, the color changes as the desiccant goes past 8% moisture levels (by weight) and indicates it is time to replace the desiccant. The most typical use for an indicating silica gel is for a moisture sensitive product that will be inspected regularly as it gives a quick visual indication of how well it is doing. Because of the addition of cobalt chloride, indicating silica gel should not be used in contact with products of consumption such as food or pharmaceuticals.
6. What is Molecular Sieve?
Molecular sieve is a synthetic desiccant that has a very strong affinity of moisture molecules. As part of manufacturing process, the pore size on the molecular sieve particles can be controlled.
The most commonly used pore size is 4 angstrom (4A) although 3 Angstrom (3A), 5 Angstrom (5A) and 10 Angstrom (13X) are available. Because the pore sizes controllable, molecular sieve can be used for picking up specific gases as well as moisture. Molecular sieve can hols moisture to temperature well past 450℉ (203℃). Because of its high affinity for moisture, molecular sieve is able to bring the relative humidity in packages down as low as 10% Rh.
7. What is Oxygen Absorber?
Oxygen absorber is to protect packaged foods, pharmaceuticals and other products against spoilage, oxidation, mold growth, color change, rancidity, loss of nutritive values, insect damage and loss of quality. Produced in packet from using food grade ingredient, OUKPAK® have 2 types of major absorber are Oil proof and Normal Type.
8. What is saturation and equilibrium capacity?
Although technically they are different situations, for most practical purposes these two terms cover the point at which a desiccant no longer adsorb moisture. Saturation is when the desiccant is full and even if there were moisture molecules to pick up, the desiccant could not do it, Equilibrium capacity is when the desiccant has pulled has much moisture out of the air that retains the strong hold on the moisture molecules that the desiccant can exert. At equilibrium capacity, adding more desiccant will not bring the relative humidity any lower.
9. Why do you say adsorption? Don’t you mean absorption?
Adsorption and absorption is two different things. Absorption is the chemical integration of one chemical into another. When you drink a glass of water, you are absorbing it, as the water becomes part of you. Adsorption occurs when one substance holds another via physical bonds. Of you spill a glass of water on your shirt; it is adsorbed as the fibres will hold the water until heat dries out the shirt.