D1-S2-P2-A-Rheologically-optimized
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02.06.2017<br />
What happens if s the extrudate is pulled out<br />
of the die?<br />
• Polymers are stretched / oriented during extrusion.<br />
• After leaving the die the polymers are “suddenly” free to move<br />
• They tend to return to their “chaotic” stage (= stage of max entropy) Melt<br />
elasticity<br />
• Extrudate swell may be hindered in case the extrudate is pulled out of the dieopening.<br />
‣ This means profile shrinkage as soon as the tension in the profile is released (at<br />
latest at the tyre building machine)<br />
© Harburg-Freudenberger Maschinenbau GmbH<br />
All rights reserved<br />
Dr. Gerard Nijman: Relaxed Extrusion<br />
June 16, 2017<br />
11<br />
The answer is relaxed extrusion:<br />
Picture removed)<br />
Different swell factors across the section<br />
may lead to waviness pulling necessary<br />
Relaxed (l) vs pulled (r) extrusion conditions<br />
The die opening should be designed<br />
such that the extrudate swell behavior<br />
of the compound is “completely”<br />
obeyed.<br />
Tension in the downstream should be<br />
avoided<br />
© Harburg-Freudenberger Maschinenbau GmbH<br />
All rights reserved<br />
Dr. Gerard Nijman: Relaxed Extrusion<br />
June 16, 2017<br />
12<br />
6
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