The presence of ambient humidity in a wide range of processes carried out in the plastics industry has a direct impact on the quality of end products, and is especially significant with regard to transformation operations involving the injection and moulding of raw materials.
Injection: the presence of humidity
Thermoplastic or resinous raw materials undergo heating processes aimed at increasing the plasticity of the materials so the desired forms can be created in moulds.
Humidity in this hygroscopic raw material (high water absorption capacity), and ambient humidity around the raw material, vaporizes when temperatures rise, which causes structural damage and aesthetic imperfections in end products, resulting in a high percentage of the production being rejected.
Most moulding processes refrigerate by using cold air to lower mould temperatures in order to reduce manufacturing times and increase production volumes. Basically, the colder the mould, the quicker the manufacturing cycle becomes. However, operating at low refrigeration temperatures can cause condensation problems in the mould, especially in summer, which can result in deformations in end products.
A relatively simple alternative employed to prevent the formation of condensation just involves increasing the temperature of the surface of moulds, but higher mould temperatures mean longer manufacturing cycles and lower production volumes.
The optimum solution used in the industry to tackle this situation is the implementation of a desiccant rotor dehumidification system, which makes it possible to control dew points on the surface of moulds and in turn operate using lower mould refrigeration temperatures without the risk of condensation formation. Production volumes can therefore be increased while maintaining the quality of end products.
Corrosion can affect moulds during production processes and during storage.
- During production, as a result of the formation of condensation.
- During storage, due to ambient humidity.
In both cases, humidity control enables their preservation regardless of the temperature, prevents moulds from having to be repaired or replaced, and avoids the costs this incurs.