Processing Bio-Based PLA Plastic with Twin-Screw Extruder

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!

🔗www.granuwelextruder.com