Extrusion of Thermoplastics Elastomer & Thermoplastic Vulcanizates
SCREW DESIGN & LENGTH
All general purpose plastic extrusion machines with compression ratio from 2.5/1 to 4/1 and length/diameter ratio above 24/1, can be used to process our elastomers and vulcanizates by extrusion.
MACHINE CAPACITY
The approximate output of different size extrusion lines are given below.
For more accurate values please consult your machine supplier.
|
Barrel Diameter (mm) |
Machine Capacity (kg/hour) |
| 30 | 15-20 |
| 45 | 60-85 |
| 60 | 100-150 |
| 90 | 225-300 |
PREDRYING
ENSOFT SEBS compounds should be predried at 90ºC for 1 hour, whereas ENFLEX Thermoplastic vulcanizates should be predried at 90ºC for 3 hours. Predrying increases the surface quality of the extruded profiles. The predrying oven, should preferably have dry air circulation.
BARREL TEMPERATURE SETTINGS (oC)
55A 65A 75A 85A 40D 45D
Feed Zone 170 170 175 185 190 190
Compression Zone 180 180 185 195 195 195
Metering Zone 190 195 200 205 205 205
Extruder Head 195 200 205 210 210 210
Die 200 205 210 21 220 220
BARREL TEMPERATURE SETTINGS (oF)
55A 65A 75A 85A 40D 45D
Feed Zone 340 340 347 365 375 375
Compression Zone 355 355 365 385 385 385
Metering Zone 375 385 392 400 400 400
Extruder Head 385 392 400 410 410 410
Die 392 400 410 410 430 430
PURGING & CLEANING THE MACHINE
Polypropylene or Polyethylene should be used to clean out or purge the machine.
CO-EXTRUSION
ENSOFT thermoplastic elastomers and ENFLEX vulcanizates can be
coextruded with polyolefins and elastomer or vulcanizate with a different hardness level. Specialty grades have been developed for coextrusion with amorphous and polar materials please consult with your sales representative for these grades.
COOLING BATH
The length of the cooling bath should be between 2.5-10 meters (8.2-32.8 feets) long according to the extrudate thickness, extrusion speed and profile design. At the entrance to the cooling bath, cold water should be sprayed onto the profile, which will improve shape retention and ensure more efficient overall cooling.
SHRINKAGE
The shrinkage level of the thermoplastic elastomers and vulcanizates depends on the material hardness, melt temperature, melt viscosity and extrusion speed. For hardness levels below 80 Shore A, the shrinkage percentage is 5% for thin wall profiles (less than 3mm. - 0.118 in), 5-10% for thick wall profiles (3-6 mm - 0,118-0,236 in),, 10-15% for very thick wall profiles (above 6 mm - 0,236 in.). For the hardness levels above 80 Shore A, the shrinkage percentage will be 5-10% for thin wall profiles and 10-20% for thick wall profiles. For complex shapes we strongly recommend to do preliminary tests in order to determine the mold shrinkage and die swell characteristics.
