Introduction
The growing demand for sustainable materials has driven the rapid adoption of bio-based plastics like PLA (polylactic acid). This article explores the key factors in selecting a twin-screw extrusion line tailored for PLA and other bio-based polymers.
Material Characteristics & Processing Challenges
PLA and similar bio-based plastics exhibit several properties that complicate processing:
- Low thermal stability – Degrades easily at high temperatures, requiring strict temperature control.
- Shear and residence time sensitivity – Excessive shear or prolonged exposure to heat leads to molecular breakdown.
- Moisture absorption – PLA must be thoroughly dried before processing to prevent hydrolysis.
Equipment Solution: Optimized Twin-Screw Extruder for PLA
1. Twin-Screw Extruder Design
- Screw Configuration (Most Critical!)
- Low-shear mixing elements to prevent overheating.
- Short compression zones for rapid yet gentle melting.
- Optimized screw flights to minimize residence time.
- L/D Ratio Recommendation
- 40:1 to 48:1 (Avoid excessively long barrels to reduce degradation risk).
- Key Components
- Precision multi-zone temperature control – Ensures uniform heating without localized overheating.
- Vacuum venting – Removes moisture and volatile byproducts.
Vent and vacuum
2. Pelletizing System
- Recommended: Water Cooling Strands Pelletizing or Air Cooling Pelletizing
- Gentle cooling prevents thermal stress.
- Consistent pellet size for downstream processing.
Critical Reminder:
Since PLA plastic has a softening temperature of approximately 60°C, sufficient cooling must be ensured before the material enters the pelletizer—whether using air-cooled strand pelletizing or water-cooled strand pelletizing. This prevents re-agglomeration during cutting, which could compromise pellet appearance.
At Granuwel, our specialized cooling process guarantees zero pellet sticking, even under high-throughput production demands.
Processing Tips for PLA
- Strict temperature limits
- Minimize residence time
- Pre-drying essential
- Effective devolatilization
- Crystallization drying and sealed packaging of finished pellets
Why Choose Nanjing Granuwel for PLA Processing?
Our low-shear, short-residence-time twin-screw extruders are engineered specifically for heat-sensitive biopolymers. Key advantages:
✔ High-precision temperature control – Prevents degradation.
✔ Efficient devolatilization & drying systems – Ensures moisture-free output.
✔ Reliable strand or underwater pelletizing options – Consistent, high-quality pellets.
✔ Deep expertise in bio-plastics – Tailored solutions for PLA, PHA, PBS, and more.
? Contact Nanjing Granuwel today for a customized PLA processing solution!