Plastic compounding is a process of melt blending plastics with other additives. Many additives can be used during the extrusion process to enhance processing characteristics of the polymer or to alter product properties. Such additives include lubricants, thermal stabilizers, antioxidants, radiopacifying agents, and colorants. The final product is called a compound or composite. During the compounding process heat is important as well the mixing capabilities, for this reason co-extruders or Twin-Screw Extruders are the most suitable in plastic compounding. Compounding is also used in the recycling process using scrap feedstock material that can be added into the process of compounding for compounding and regranulation purposes of recovered plastic materials.
The basic steps in compounding extrusion process are:
- Recipe determination, ratio of additives and polymer to be mixed
- Mixing and Melt mixing
- Extrusion and Cooling