- What is a desiccant?
A desiccant is a material that Adsorps moisture from the atmosphere.
- What types of desiccant are available and why are they different?
There are two main types of desiccants.
The first and most common is silica gel. It is glass-like in appearance but it contains many small inter-connected channels opening as pores at the surface. The structure is similar to a sponge where the interior has a very high surface area. Silica gel can Adsorp water molecules onto the surfaces of the channels and pores and hold them there.
The second is molecular sieve. Molecular sieve materials also have very high internal surface areas but the pores in the surface are all the same diameter. The pores connect to a series of regular-shaped cavities where water molecules are attracted to the surface and remain.
Silica gel has a higher capacity to Adsorp moisture than molecular sieve and Adsorps water more slowly.
Silica gel is capable of reducing moisture to a certain level, whereas molecular sieve can remove almost all moisture.
In cost terms, silica gel is much less expensive.
- How is a desiccant used?
Desiccants are used to reduce the moisture inside packaging. This can be done in a number of ways. For instance a desiccant stopper can be used as a closure for tubes of effervescent tablets.
Other ways of using desiccants are as desiccant capsules that can be inserted into bottles or medical devices. Various closure formats can also be used such as screw closures for bottles.
Alternatively a desiccant chamber can be designed into packaging to provide in situ moisture protection.
- How do I decide which desiccant I need?
Your moisture protection requirements will help determine which desiccant to use. If your product or packaged items require a very low level of moisture, it is best to use a molecular sieve. If your goods are less moisture sensitive, a silica gel desiccant will do.
- How much desiccant do I need to protect my product?
There are various calculators that enable you to determine the approximate amount of desiccant needed to provide moisture protection. A desiccant calculator is available here. It is always advisable to speak to one of our team of desiccant experts who can help you best meet your needs.
- What will happen if I do not protect my product from moisture?
The effects of moisture are many and varied. If your product is moisture sensitive, it is not worth taking the risk of not having moisture protection.
Some of the more common effects of moisture are:
- Misleading results from blood and urine test strips that have been exposed to moisture
- Corrosion of metal surfaces, eg, in a medical device
- Reduced potency in many drugs if they are exposed to moisture
- Unpleasant aromas
- Fungal growth on tablets
- Discolouration of tablets
- Smeared surfaces of tablets and illegible print
It is best to be sure and consult one of experst if you think your product may have a problem with moisture
- Do desiccants get wet as they Adsorp moisture?
No, desiccants remain dry to the touch at all times. The moisture is held inside the desiccant not on the surface.
- What is Relative Humidity?
Relative Humidity, or RH, is a measure of the amount of moisture present in air at a particular temperature.
It is defined as the following ratio for a given volume of air at a particular temperature:
Amount of moisture present in the volume of air
--------------------------------------------------------------------- x 100%
Maximum amount of moisture that is possible
- Is there a “safe” level for Relative Humidity where my product will not be damaged by moisture?
It is not possible to give a “safe” level for Relative Humidity as each product will react to moisture at different levels.
However, as a very rough guide, if moisture is reduced below around 30% RH, many moisture related problems will be prevented.
- Can desiccants be used in applications which involve contact with food or drugs?
Yes, most desiccants are approved for use by regulatory authorities around the world.
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