Extrusion & Post
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Insufficient long-term hydrostatic strength of heat-resistant polyethylene PPR pipes (Variant: strengthened measures)
Problembeschreibung
PPR/PP-R pipes break in long-term hydrostatic tests (1000h, 8760h) and cannot meet the ISO 15874 requirements.
Insufficient long-term strength affects the service life and design safety factor of the pipes.
In particular, extra attention is needed on the original basis, this problem is more prominent and needs key attention.
Ursachenanalyse
（1）The molecular weight of the raw material is low or the molecular weight distribution is unreasonable
（2）The extrusion temperature is improper, and the material is partially degraded
（3）The pipe wall thickness is insufficient or uneven
（4）The cooling rate is improper, and the crystallinity is inappropriate
（5）The welding joint is a weak point with insufficient strength
（6）On the original basis, extra attention is needed: process parameter fluctuations or equipment status changes have aggravated this problem
Lösung
（1）Select special grades that meet the PPR pipe standard (MFR 0.2-0.5g/10min)
（2）Strictly control the extrusion temperature at 200-220°C to avoid material degradation
（3）Ensure that the pipe wall thickness meets the SDR value requirements and is uniform
（4）Optimize the cooling conditions to ensure a reasonable crystallinity (50-60%)
（5）Strengthen the quality control and inspection of welding joints
（6）And strengthen process monitoring; on the original basis, extra attention is needed, with special attention to parameter stability
Wichtigste Erkenntnis
Insufficient long-term hydrostatic strength is caused by material selection and processing quality, and needs to be comprehensively controlled from raw materials, processes, and welding.
In different production scenarios, targeted preventive measures need to be taken.
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