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Plastics Processing: Drying

Moisture, if not removed from resins, can cause serious problems with finished product strength and appearance. Non-hygroscopic resins tend to accumulate moisture on the surface of the individual pellets. This can normally be removed through the circulation of warm air through the bulk resin prior to introduction of the resin pellets into the production machinery. Hygroscopic resins absorb moisture. A combination of dry air and heat is required to remove moisture.

Plastics processors may use individual units dedicated to a specific machine or a central system which service several pieces of production equipment at the same time.

Dryers normally consist of a hopper holding a several-hour supply of material (due to the fairly lengthy drying cycle), a heat source, a fan / circulation system, and - depending on the type of unit - some form of desiccant material which will absorb the moisture being removed from the resin.