Desiccant substances are often contained in desiccant packs which are used to decrease humidity for a variety of applications. A desiccant is able to attract water from its immediate environment, thereby maintaining a state of dryness within a contained space. There are two chemical drying processes describing desiccant action: absorption and adsorption.
Although chemicals that dehumidify by either absorption or adsorption produce similar results, the scientific reasons that desiccants work are decidedly different. Absorption occurs when one substance becomes part of another, while adsorption occurs when a physical bond is created between two substances, holding one within the other. Most desiccants, like silica gel, montmorillonite clay, activated charcoal and products which function as a molecular sieve, work to adsorb moisture to their porous surfaces.
How Are Desiccant Packs Used?
Desiccants are used mostly to stabilize environmental moisture conditions in packaged products. Many products need to be kept dry since the presence of moisture can create contamination, resulting in damage. Desiccant packs are commonly used for food, fabrics, electronics, leather articles, tools, pharmaceuticals, sporting goods, scientific instruments, historical artifacts, artwork, film and manuscripts.
Shipping is one of the most common applications in which desiccants, especially silica gel, are used. Indicating silica gel shows that moisture is present by changing colors when exposed to it. Activated charcoal is a particularly good desiccant for use in water or air filters. Montmorillonite clay is widely used to prevent animal feeds from clumping. A desiccant is classified as a molecular sieve when it has the ability to differentiate molecules to be filtered, on the basis of their size. A molecular sieve can adsorb molecules from both gases and liquids, making it ideal for separation of compounds and drying of reactive materials, such as required by flammables industries like oil and petroleum.
Selecting The Appropriate Desiccant Pack For Specific Uses
Selection of a desiccant should be based on the characteristics of both the packaging and product that it will be protecting, in addition to the characteristics of the desiccant itself. Environmental factors to which the product may be exposed, as well as desiccant size and the material from which desiccant packs are made, are some factors to consider.
Indicating silica gel is typically sold in granular form, since it needs to be seen in order to accomplish its purpose. However, indicating silica gel should never be used with consumable goods, due to the presence of the toxic salt, cobalt chloride. Other desiccants like silica gel, activated charcoal and montmorillonite clay are produced in a wide variety of sizes and their desiccants packs can be selected from various materials.