Flexible Pelletizing for Twin Screw Extrusion Compounding
The water-cooling strand pelletizing line is one of the most widely used pelletizing solutions for twin screw extruder compounding lines. It provides a mature and reliable system for materials that can cool effectively in water and then cut into uniform cylindrical pellets.
Many compounding plants use this pelletizing method because of its simple structure, stable operation, easy maintenance, and broad material compatibility. It suits many standard compounding applications, including engineering plastics, polymer blends, filler masterbatches, color masterbatches, flame-retardant compounds, functional masterbatches, and biodegradable or bio-based compounds.
Because operators can easily understand and control the process, the water-cooling strand system also suits factories that require stable daily production with low operator training requirements.
How the System Works
After the polymer melt is compounded and homogenized inside the extruder, it is extruded through a strand die to form continuous polymer strands. These strands enter the water-cooling bath, where they cool and solidify.
After leaving the water bath, the strands pass through an air knife or strand dewatering unit to remove surface water. Proper water removal helps ensure stable feeding into the strand pelletizer and supports consistent pellet cutting.
The cooled and dried strands then enter the strand pelletizer, where rotating knives cut them into uniform pellets. In most commercial installations, the pellets pass through a vibrating classifier for pellet screening and removal of fines, dust, and oversized or irregular pellets. For smaller lines, such as HTE20 and HTE35, the classifier may be optional and may not be included in the standard configuration.
Main Components
The water-cooling strand pelletizing line typically includes:
- Strand die
- Water-cooling bath
- Air knife or strand dewatering unit
- Strand pelletizer
- Vibrating classifier
- Pellet collection system
Suitable Materials and Applications
This system is commonly used for:
- Fiber reinforcement: PP / PA / PBT / ABS / AS / PC / POM / PPS / PET + glass fiber or carbon fiber
- Polymer blending: PC + ABS, PA + ABS, CPE + ABS, PP + EPDM, PA + EPDM, PP + SBS, etc.
- Filling modification and filler masterbatches: PP / PE / EVA + CaCO3, talc, TiO2, carbon black, etc.
- High-concentration color masterbatches: PP / PE / ABS / PS / EVA / PET + pigments and additives
- Flame-retardant masterbatches: PP / PA / ABS / EVA / PBT + flame retardant additives
- Special functional masterbatches: anti-UV, antibacterial, antistatic, anti-blocking, anti-slip, heat-resistant, insulation, and other functional additive systems
- Biodegradable and bio-based compounds: PLA, PBAT, PBS, PHA, starch-based blends, and related biodegradable additive systems
Key Advantages
- Simple and robust system design
- Easy operation and process control
- Low operator training requirements
- Convenient maintenance
- Stable pellet quality
- Flexible for a wide range of polymer compounds
- Suitable for laboratory, pilot, and industrial-scale production
- Vibrating classifier available for dust, fines, and irregular pellet removal in most commercial installations
- Economical solution for many general compounding applications
Reliable and Economical Pelletizing Solution
For many compounding plants, the water-cooling strand line remains the most practical and economical pelletizing choice. Manufacturers can scale its layout from laboratory and pilot production to industrial operation, with cooling bath length, strand pelletizer model, classifier configuration, and collection method selected according to material type, throughput, and daily production needs.
For highly water-sensitive, very soft, sticky, brittle, or difficult-to-strand materials, other pelletizing methods such as water-ring, underwater, or air-cooling hot-cut pelletizing may be more suitable.