What is Extrusion? Plastic Extrusion Process

What is Extrusion? Plastic Extrusion Process

Profile Extrusion Process

Typical Thermoplastic Extruder

The selection of the extruder barrel diameter depends on the dimensions of the profile being produced. As the throughput increases, the diameter must be increased. A length to diameter ratio (L/D) of 24:1 is recommended. If a higher capacity is needed, L/D ratios of 30:1 are preferred as they deliver a higher output capability, a more uniform output rate, and a better melt quality with the proper screw design.

Thermoplastic Extruder Barrel Diameter

The extrusion of Elastron TPE products requires medium to high shear to plasticize properly (high shear for Elastron V products) and to ensure proper processing at the recommended temperatures. General purpose three zone screw designs (feed, transition/compression, metering) having a compression ratio of 2.5 to 3.5 with an L/D of 18:1 to 24:1 are recommended. Barrier screws, especially for Elastron V products, are used successfully and are recommended.

In order to change the melt flow from rotational to uniform laminar flow, there is a relaxation zone after the extruder barrel. During extrusion, the melt inside the barrel is compressed and stressed, and it requires uniform flow before profiling.

Extruder Screen

The breaker plate must be used for screening. Special screens must be installed on the breaker plate to catch the foreign or burned particles coming from the screw or barrel inside. Depending on the extruder size and the capacity of the breaker plates, holes from 2mm to 4mm can be used, and 20 or 40 mesh screens are recommended.

The advantages of using screens:

  • Homogenize melting due to pressure
  • Catch burned particles coming from the screw,
  • Catch unmelted particles due to non-uniform screw design,
  • Increasing shear,
  • Increasing the surface quality,
  • Increased back pressure for better melt quality.

Extrusion Requirements

EXTRUSION REQUIREMENTS
REQUIREMENTS Elastron D Elastron G Elastron V Elastron TPO FR 6 Series
G201 Other V101 V201 V601 G601
Drying temperatures No need 90 ℃ 90 ℃
2 hours
recommended
90 ℃ 90 ℃ No need 90 ℃ 90 ℃
Drying time 2 hours 2 hours 2 hours 2 hours 2 hours
Screw Comp. ratio 1.5:1 – 2.0:1 1.5:1 – 3.0:1 1.5:1 – 2.0:1 1.5:1 – 2.0:1 2.0:1 – 4.0:1 2.0:1 – 4.0:1 1.5:1 – 3.0:1 1.5:1 – 3.0:1
Screw L/D 18 - 30 18 - 30 18 - 30 18 - 30 18 - 30 18 - 30 18 - 30 18 - 30
Feed Zone temp. 140 - 160 165 - 185 150 - 170 155 - 165 155 - 165 160 - 180 155 - 165 150 - 170
Rear Zone temp. 140 - 160 170 - 190 155 - 175 160 - 180 160 - 180 165 - 185 160 - 180 155 - 175
Center Zone temp. 145 - 165 180 - 200 165 - 185 165 - 185 165 - 185 170 - 190 165 - 185 165 - 185
Front Zone temp. 155 - 175 190 - 220 175 - 205 170 - 190 170 - 190 185 - 205 170 - 190 175 - 205
Head temp. 155 - 185 195 - 225 180 - 210 180 - 210 180 - 210 190 - 220 180 - 210 180 - 210
Die temp. 165 - 195 205 - 225 190 - 210 185 - 215 185 - 215 195 - 225 185 - 215 190 - 210