Extrusion & Post
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Random copolymer polypropylene pipe special material (Nordic standard） PPR pipe insufficient long-term hydrostatic strength
Problem Phenomenon
PPR/PP-R pipes rupture in long-term hydrostatic tests (1000h, 8760h) and cannot meet ISO 15874 requirements.
Insufficient long-term strength affects pipe service life and design safety factor.
Cause Analysis
（1）The raw material molecular weight is too low or the molecular weight distribution is unreasonable\
（2）Extrusion temperature improper, material partially degraded\
（3）Pipe wall thickness insufficient or uneven\
（4）Improper cooling rate, unsuitable crystallinity\
（5）The welded joint is a weak point with insufficient strength
Solution
（1）Select special grades meeting 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 the pipe wall thickness meets the SDR value requirements and is uniform\
（4）Optimize cooling conditions, ensure reasonable crystallinity (50-60%)\
（5）Strengthen quality control and testing of welded joints
Key Takeaway
Insufficient long-term hydrostatic strength is caused by material selection and processing quality, requiring comprehensive control from raw material, process and welding.
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