A practical guide to key techniques, temperature profiles, and critical parameters for stable production.
Polylactic acid (PLA) can be processed on conventional equipment used for PET, PP, or PS with minor adjustments. This article focuses on the core processing methods—injection molding, extrusion/thermoforming, and fiber spinning—detailing temperature profiles, critical parameters, and practical tips for stable production.
Injection Molding: Controlling Crystallization
Fast-crystallizing injection grades (e.g., Ingeo™ 3251D, 3001D, 2500HP) contain nucleating agents and low D-lactide content. By optimizing the mold temperature, manufacturers can significantly alter the heat resistance of the final part.
- Melt Temperature: 190–220°C
- Mold Temperature: 80–110°C (hot mold essential for crystallinity)
- Cycle Time: 15–35 s for thin-wall parts (0.4–0.8 mm)
Key Practices: Use general-purpose screws (compression ratio 2.5–3:1); maintain back pressure 50–100 bar to minimize hydrolysis; dry resin to <250 ppm moisture. Cold molds (<40°C) yield amorphous parts with low heat resistance, while 90–110°C molds achieve HDT up to 120°C. Coffee capsules and cutlery are common products under these conditions.
Extrusion and Thermoforming
High melt-strength extrusion grades (Ingeo™ 4032D, 4044D, 2003D) permit stable processing on single-screw extruders (L/D ≥ 30). Achieving the correct crystallinity in the sheet is crucial for subsequent thermoforming steps.
170°C
200–205°C
195°C
195–200°C
Chill Roll Settings: 25–40°C for amorphous sheet, 80–100°C for semi-crystalline sheet. For biaxial orientation, preheat sheets to 80–90°C and stretch 3–4× in both directions. Emerging high-melt-strength grades (e.g., 4060D) now support foam extrusion and limited blow molding with modified dies.
Fiber Spinning: Temp & Draw Ratio
Fiber grades (Ingeo™ 6202D, 6260D, 6100D; Luminy® series) offer a wide processing window of 220–250°C. Humidity control (<30% RH) in the spinning hall is vital to prevent nozzle blockage.
- Meltblown: Spinneret 230–245°C, air temperature 240–260°C, throughput 0.3–0.8 ghm.
- Spunbond: 225–240°C, quenching air 15–20°C, draw ratio 3–4× for 10–150 g/m² nonwovens.
- Staple/Multifilament: Spin 230–245°C, godet temperatures 60/80/100°C, total draw 3.5–5×.
Note: Higher stereoregularity grades (Luminy®) allow lower spinning temperatures and higher tenacity.
Raw Material Foundation
All grades are polymerized from fermentation-derived L-lactic acid. Drying to <250 ppm (dew point –40°C, 4–6 h at 80–100°C) remains critical across all processes to prevent molecular weight loss. Certified under EN 13432 and ASTM D6400, these resins achieve >90% degradation in industrial composting within 90 days.
By matching grade selection to equipment capabilities and following the parameters above, manufacturers can achieve stable, high-output Polylactic acid (PLA) production comparable to conventional plastics.
For a detailed overview of currently available Ingeo™ grades (including MFI range, D-lactide content, and crystallinity level), please refer to the accompanying article: PLA Material: NatureWorks Injection, Extrusion & Fiber Grades
