Desiccants – Types And Suitability For Packaging

When packaging goods for storage or transportation, there is always a risk of moisture seeping in and destroying them all. Depending on their nature, they could get corroded and rusty, develop mold, mildew, or fungus. They could even become swollen. Many different kinds of undesirable outcomes are thus possible. Activated Alumina manufacturers and producers of eco-friendly silica gel are the ones that help your products remain safe. Their products, known as desiccants or adsorbents, prevent the moisture from reaching the goods.

The moisture can seep into the packaging through four sources, namely the vapors inside the package, vapors adsorbed by the materials inside it, vapors on the walls of the box, and lastly, the permeation of vapors into the container. When choosing an adsorbent, all four sources need to be tackled at once. The adsorbent type must consider the size of the container, type of container, temperature, humidity, and the conditions of the goods being packed. Avoid using desiccants with high adsorption if over desiccation can spoil the goods.

What are the different products used to keep goods safe inside the packaging, and how do they work? How do they compare with each other?

1. Silica Gel 

It is the most commonly used desiccant and is manufactured using sodium silicate and sulphuric acid. It is amorphous and holds water through adsorption and capillary condensation. Its efficiency is very high at temperatures lower than 77 degrees Fahrenheit but cannot function well at higher temperatures. It is popular because it is non-toxic and non-corrosive. It can be regenerated at a temperature of 180 degrees centigrade.

1. Activated Alumina

Aluminum hydroxide, when dehydroxylated, produces Activated Alumina. It is a highly porous material and is used as a desiccant for adsorbing air from the water and the removal of certain chemicals in drinking water. The good thing about this product is its high adsorption power and its reusability. The desiccant can be regenerated by heating it at high temperatures close to 200 degrees centigrade.

1. Molecular Sieve

Also known as zeolite, it is a material with tiny holes. These holes are uniform and precise in their dimensions and allow smaller molecules to pass through while blocking the larger ones. Many of these can be used as desiccants. Regeneration of these desiccants requires a temperature of around 550 degrees centigrade. Their adsorption levels may not be very high, but it dries up the air to a shallow PPMv level. It is humanmade and hence more expensive but offers good value for money because of its range of adsorptive capabilities.

1. Montmorillonite Clay

This adsorbent is crafted for use by controlled drying of naturally occurring aluminum silicate (sub bentonite). It is highly cost-effective when used in average temperature and humidity conditions but unsuitable for use when packaging is exposed to rising temperatures. That is because it can regenerate at very low temperatures. That makes it unsuitable as it releases water into the container in the process.

Calcium Oxide and Calcium Sulphate are some other desiccants used in the industry.

Choosing the Right Adsorbent

So, how does one choose the most appropriate desiccant? The two crucial factors to be considered for this are temperature and humidity.

• Silica Gel

When the products are stored at steady and ”not so high” temperatures, silica gel can be used effectively as it is highly stable. It is also non-toxic, making it safe to use with products of all kinds, including pharmaceuticals and chemicals.

• Activated Alumina

This adsorbent’s uniform ball size is significantly vital for situations where pressure drop needs to be minimized. They exhibit high adsorption capacity without losing their shape. They can endure a combination of high pressure and high humidity levels.

• Molecular Sieve

It is as adsorbent as silica gel but is more aggressive and quicker at it. It regenerates at much higher temperatures. These features make it suitable for use when the goods require to be protected from moisture instantly. It will continue to absorb moisture even with rising temperatures.

Choosing the right variant of the desiccant is as crucial as selecting a suitable desiccant. Each variant is designed with a specific function, and the wrong choice will not be as effective, and you will not get the desired results. Some important parameters to be considered are loss On Drying (LOD), Moisture Adsorption Capacity (MAC) at low RH and high temperatures.

While the adsorption capacity, regeneration temperatures, and pressure resistance are fundamental, one must not forget to consider the product and its reactivity levels. Some products can get spoiled when over-desiccated. Factors like packaging headspace and the destination’s climate must also be given sufficient thought before deciding on the desiccant to be used.