PE Ekstrüzyon

PE (Polyethylene) extrusion is the process of melting polymer granules under heat and pressure in a screw extruder and shaping them along a continuous production line. Once the material becomes molten, it is pushed through a die, cooled, and then wound, cut, or slit to the desired dimensions.
In short: “melt, shape, cool, and wind”—the pasta machine of the plastics world. 🍝

Materials Used

• LDPE (Low-Density PE):
  Soft, transparent, good sealability; used for flexible packaging films.

• LLDPE (Linear Low-Density PE):
  High tensile and puncture resistance; used for stretch film and load-holding applications.

• HDPE (High-Density PE):
  Rigid, chemically resistant; used for pipes, jerrycans, carrier films, and coatings.

• Optional additives:
  Masterbatch (color), UV stabilizers, slip/antiblock agents, antistatic additives, recycled material blends.

Main Steps of the Process

• Feeding & Melting:
  Granules are melted along the screw at around 160–230 °C (depending on grade and MFI).
  Screw L/D ratio is typically 24:1–34:1.

• Homogenization & Pressure Build-Up:
  The melt is homogenized by screw flights and mixing elements; melt pressure and temperature are monitored via sensors.

• Die (Kalıp) Design & Shaping:

  • Circular die (blown film): Film formed by bubble inflation.

  • Flat die (cast): Film/sheet cast onto a chill roll for high optical quality and flatness.

  • Pipe/Profile die: For HDPE pipes and special technical profiles.

  • Coating die: Extrusion coating/lamination of melt onto paper or aluminum.

• Cooling & Sizing:
  Using water baths, air rings, or chill rolls to stabilize dimensions and surface quality.

• Haul-Off, Edge Trimming & Winding:
  Line speed and draw-down ratio (BUR, draw ratio) control thickness and mechanical properties. Edge trimming and winding define final roll format.

Types of Extrusion

• Blown Film Extrusion:
  More balanced mechanical properties in MD/TD, lower investment cost; used for packaging films, bags, shrink films.

• Cast Film/Sheet Extrusion:
  Better optics and thickness tolerance; used for laminations and barrier structures.

• Pipe/Profile Extrusion:
  HDPE pipes for water/gas lines, cable conduits, technical profiles.

• Extrusion Coating & Laminating:
  PE coating on paper/foil; e.g. milk cartons, various food packages.

• Co-Extrusion:
  Multilayer structures (e.g. PE/tie/EVOH/tie/PE) to achieve barrier and adhesion properties.

Advantages

• High output and continuity:
  Long, uninterrupted production runs.

• Cost-effectiveness:
  Efficient in both energy and material usage; can incorporate recycled material.

• Wide application range:
  Packaging, pipes, wire & cable, agricultural films, construction membranes.

• Chemical and moisture resistance:
  Suitable for food contact and outdoor conditions (with proper formulation).

Typical Applications

• Packaging:
  Shopping bags, carrier films, shrink films, stretch films, vacuum pouches.

• Infrastructure:
  Potable water and gas HDPE pipes, drip irrigation laterals.

• Electrical:
  Cable jacketing and semiconductive layers (with suitable compounds).

• Industrial:
  Pallet covers, construction sheeting, membranes.

Quality Parameters (Example)

• Thickness tolerance: Typically ±5–8 %, depending on process and film width.

• Width tolerance: Typically ±2–5 mm.

• MFI (190 °C/2.16 kg):
  For films usually 0.3–4 g/10 min; for pipes lower MFI grades are preferred.

• Optical properties: Haze, gloss, gel/fish-eye count.

• Mechanical properties: Tensile strength, elongation, dart drop impact, tear resistance.

• Food contact: Compliance with relevant regulations (e.g. EU 10/2011) must be declared.

Process Tips

• Moisture and dust control:
  PE is non-hygroscopic, but dust and contamination impair surface quality; use drying/sieving if needed.

• Temperature profile:
  Lower MFI (higher viscosity) grades require higher temperature/pressure; avoid thermal degradation.

• Thickness control:
  Automatic thickness gauges and air rings (IBC) significantly improve thickness uniformity.

• Recycling:
  Regrind usage typically 10–50 %, adjusted according to end-use performance requirements.