What is Extrusion? Plastic 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.

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