Extrusion & Post
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Insufficient long-term hydrostatic strength of polyolefin plastomer PPR pipes
Problem Phenomenon
PPR/PP-R pipes rupture in long-term hydrostatic tests (1000h, 8760h) and cannot meet the ISO 15874 requirements.
Insufficient long-term strength affects the service life of the pipes and the design safety factor.
Cause Analysis
（1）The molecular weight of the raw material is too 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 welded joint, as a weak point, has insufficient strength
Solution
（1）Select special grades that meet PPR pipe standards (MFR 0.2-0.5g/10min)
（2）Strictly control the extrusion temperature at 200-220°C to avoid material degradation
（3）Ensure the pipe wall thickness meets the SDR value requirements and is uniform
（4）Optimize the cooling conditions to ensure reasonable crystallinity (50-60%)
（5）Strengthen the quality control and testing of welded joints
Key Takeaway
Insufficient long-term hydrostatic strength is caused by material selection and processing quality, and needs to be comprehensively controlled from raw materials, process, and welding.
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