Feeding Polymer to the Extruder The proper method of feeding polymer to a twin screw extruder depends on: the twin screw extruder design, the material being fed, and the feed location. In parallel counter and corotating twin screw extruders, single or multiple resin feed streams and additives are starve fed to the extruder feed section.…
Drying Polymer Material: Some polymers require drying prior to extrusion to prevent polymer degradation. Resins, e.g., nylon, polyester (polyethylene terephthalate [PET] and polybutylene terephthalate [PBT]), and polycarbonate (PC), are hygroscopic, absorbing moisture rapidly from the air. At higher temperatures moisture degrades these materials to lower molecular weight (shorter chains), resulting in poorer property performance.…
Raw Material Blending and Mixing Depending on the product requirements, some pre-blending or ingredient mixing may be required prior to extrusion. (Blending and mixing are covered in more detail in Part 5, “Auxiliary Equipment.”) Unless a single polymeric material is being added to an extruder, the best way to combine different raw materials and keep…