Extrusion & Post
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Random copolymer polypropylene pipe special material (Nordic standard） pipe longitudinal reversion rate exceeding standard（Variant: Strengthened Measures）
Problem Phenomenon
After the pipe is heated under the specified temperature and time conditions, the longitudinal reversion rate exceeds the standard limit.
Excessive reversion rate reflects large internal stress or imperfect crystallization of the pipe, affecting pipe use reliability.In particular, extra attention is needed on top of the original basis, this problem is more prominent and requires key attention.
Cause Analysis
（1）The random copolymer polypropylene pipe special material (Nordic standard） has large residual internal stress after extrusion\
（2）Cooling rate too fast, molecular chain orientation not relaxed\
（3）Haul-off speed too large, the pipe is over-stretched longitudinally\
（4）Barrel temperature too low, melt plasticization insufficient\
（5）Sizing cooling insufficient\
（6）On top of the original basis, extra attention is needed: process parameter fluctuations or equipment status changes aggravate this problem
Solution
（1）Appropriately increase the barrel temperature to a reasonable value within the 200-220°C range, improve plasticization\
（2）Appropriately reduce the cooling rate, allow the molecular chains time to relax\
（3）Adjust the haul-off speed, reduce the draw ratio\
（4）Increase the cooling water tank length, ensure full cooling\
（5）After demolding, perform water bath annealing on the pipe to eliminate internal stress\
（6）And strengthen process monitoring; on top of the original basis, extra attention is needed, paying special attention to parameter stability
Key Takeaway
Excessive reversion rate is caused by large internal stress or excessive orientation, and needs to be solved from temperature control, cooling rate and haul-off speed.Targeted preventive measures need to be taken in different production scenarios.
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