In various industrial fields, including plastics dehumidification, the concept of dew point and its meaning are important. In fact, the dew point is a physical condition to be carefully considered for companies operating in sectors where humidity can influence the quality of processes, the material used and results.

In this article, we will go into the technical meaning of the term, presenting the impact of dew point in the industrial sector and highlighting its applications in plastic granules drying process.

Dew point: meaning and general applications

To better understand the meaning of dew point, let us start from its basic definition. Basically, the dew point is the temperature at which the air becomes saturated with water vapour, resulting in the condensation of moisture in the form of water droplets.

The quantity of water vapour that the air can retain before becoming saturated and initiating the condensation phenomenon increases with increasing temperature. Consequently, a cubic metre of air at a lower temperature requires less water to reach saturation. For example:

  • 1 kg of air at 20°C becomes saturated with 14.7 g of water;
  • 1 kg of air at 3°C becomes saturated with 36.6 g of water.

Thus, the temperature at which the air reaches the saturation point corresponds to a certain quantity of water present in it. Consequently, this temperature, known as “dew point”, in turn becomes an indication of how much water is contained in the air when water vapour condenses.

What are the practical implications? In industry, dew point has a direct impact on production processes, the quality of materials used and final products. In fact, humidity-sensitive materials such as plastics can undergo undesirable changes.

For this reason, an accurate control of the dew point is very important: the careful measurement and management of this parameter allows preventing condensation by activating drying processes when necessary. In this way, processed and transformed materials can comply with the required parameters regarding the tolerated quantity of humidity.

The dew point finds application in various industries. For example, monitoring it in the food and pharmaceutical sectors is crucial to preserve the quality and integrity of products. The same goes for electronics, where humidity can affect devices performance.

Looking specifically at the plastics processing sector, the issue is similar: keeping plastic granules within the expected humidity parameters prevents defects in the appearance and properties of the plastic product. We will see this in more detail in the next section.

Applications in plastic granule drying

Understanding the meaning of dew point and the correspondence between temperature and the amount of water in the air has significant practical implications. It is particularly important in the processes used to maintain polymers at the right humidity level by drying.

Plastics naturally retain humidity. However, depending on the type of material, the methods are different:

  • in non-hygroscopic plastic materials, humidity stops at the surface;
  • in hygroscopic plastic materials, on the other hand, humidity is present on the surface, but also penetrates inside the plastic granule.

If the humidity is not removed or kept within the allowed tolerance limits, the final product resulting from the granules processing could be opaque or streaked, smudged or bubbled. Then, from a functional point of view, the presence of residual humidity could worsen the mechanical properties of the object, deform it or lead to uneven wear over time.

To avoid problems of this type, the plastic granule is passed through a stream of hot air during the drying process. The initial explanation about the meaning of the terms “dew point” and how the phenomenon works makes us understand why.

In fact, the air can retain humidity until it becomes saturated. As we have seen, this capacity increases with increasing temperatures. Therefore, the humidity and temperature of the air used to dry the plastic granules in the drying process can be adjusted according to the result to be achieved.

When we design drying systems, we take all these parameters into consideration. In addition, our systems have a further advantage: they allow for very significant energy savings which reach up to 40 per cent and more.

This element makes the process more efficient and sustainable in terms of consumption and use of resources. In other words, Vismec dehumidifiers ensure excellent performance: top quality results and reduced energy costs.

Our drying systems include:

  • Drycube, which enables perfect drying and efficient transport of the technical plastic granule. Drycube can reach a drying temperature of 180°C and a constant dew point, adjustable down to -50°C.
  • Drywell, a compact high performance dehumidifier. Again, drying temperature and dew point are adjustable up to 185°C and -50°C respectively, depending on the type of material and its condition.
  • Dryplus, a floor standing dehumidifier used mainly in on-board installations.

In this article, we have presented just a few of Vismec’s solutions for the drying of plastic granules. 

Nevertheless, we can provide you with a much wider range of machinery and accessories, according to your company’s needs. 

Want to know more? Contact our team.