Dehumidifying of plastics resin is utilized to minimize or eliminate problems that may be caused by too much or too little moisture in a plastic material during processing. Although most processors accept the need to predry resins, particularly highly hygroscopic ones, many do not understand the basics - or even the vocabulary of resin drying.
The extent to which moisture affects the quality of a molded or extruded part is determined by the specific plastic resin being processed and the intended purpose of the part. Regardless, it is highly probable that improper or incomplete drying of the raw material will create problems, whether during processing or when the product is in use, or worse - both.
The following topics to the left under "Drying Basics" help form a guide to understanding the basics of dehumidifying plastics material as well as the esthetic and performance issues that present from improper drying.
Above schematic shows how dual bed desiccant bed dryers work. This is an old technology that has been largely replaced by desiccant wheel dryers and membrane dryers. Click on “Dryer Types” – on the left to get an idea of how many different drying methods are used for plastics resins.