Extrusion & Post
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Insufficient Long-Term Hydrostatic Strength of Polypropylene PPR Pipe
Problem Phenomenon
PPR/PP-R pipes rupture in long-term hydrostatic tests (1000h, 8760h) and cannot meet the requirements of ISO 15874.
Insufficient long-term strength affects the service life and design safety factor of the pipe.
Cause Analysis
(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 partially degrades
(3) The pipe wall thickness is insufficient or uneven
(4) The cooling rate is improper, and the crystallinity is unsuitable
(5) The welding joint, as a weak point, has insufficient strength
Solution
(1) Select a special grade that meets 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 requirement 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
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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