PLA Sheet Extrusion Machine: Why Crystallizing and Drying Are Essential

Polylactic Acid (PLA) is a widely used biodegradable material for food packaging, cups, trays, and disposable containers. However, PLA is highly hygroscopic and heat-sensitive. Without proper crystallizing and drying, PLA sheet extrusion can face serious quality issues such as bubbles, haze, and brittleness. This article explains why crystallizing and drying are critical in PLA sheet extrusion machines and how manufacturers ensure stable production.

Why Does PLA Need Crystallizing and Drying?

Unlike PP, PS, or PET, PLA easily absorbs moisture from the air. During extrusion, any residual moisture reacts with the melt and causes hydrolysis, leading to:

Reduced molecular weight → weaker and more brittle sheets
Surface defects → bubbles, crystal spots, or cloudy sheet appearance
Poor thermoforming performance → cups and trays may crack during forming

Therefore, crystallizing and drying are essential steps before PLA sheet extrusion.

PLA Crystallizing Process

Purpose: Prevent PLA pellets from sticking or clumping during drying by converting them into a crystalline state.
Typical temperature: 90–120°C
Time: 30–60 minutes
Equipment: PLA crystallizer with agitation or hot-air circulation

PLA Drying Process

Purpose: Remove absorbed moisture to stabilize extrusion.
Required moisture content: ≤200 ppm
Typical temperature: 80–120°C
Drying time: 4–6 hours
Equipment: PLA dehumidifying dryer (honeycomb type recommended)

Standard Process Flow

Raw Material Storage → Crystallizing → Dehumidifying & Drying → Vacuum Loading → Extrusion → Calendering → Sheet Winding

Recommended Machine Configuration

A professional PLA sheet extrusion line usually includes:

1. PLA crystallizer & dehumidifying dryer
2. Automatic vacuum feeding system
3. Single-screw or parallel twin-screw extruder
4. Three-roll calender and winding unit

FAQ: PLA Sheet Extrusion and Drying

Q1: Can PLA be extruded without drying?

A: No. Undried PLA degrades quickly, causing poor sheet quality and mechanical properties.

Q2: Why is crystallizing important before drying PLA?

A: Crystallizing keeps PLA pellets free-flowing and prevents sticking during the drying process.

Q3: What defects occur if PLA is not dried properly?

A: Common defects include bubbles, haze, crystal spots, and brittle sheets.

Conclusion

Crystallizing and drying are non-optional steps for PLA sheet extrusion. By using a reliable PLA sheet extrusion machine with crystallizer and dryer, manufacturers can ensure high-quality, transparent, and strong PLA sheets ready for thermoforming into cups, lids, and food containers.

If you are looking for a PLA sheet extrusion line manufacturer, choosing a supplier that provides complete crystallizing and drying solutions will guarantee more stable production and higher-quality products.

PLA Sheet Extrusion Machine: Why Crystallizing and Drying Are Essential