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
