Extrusion & Post
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Insufficient long-term hydrostatic strength of low density polyethylene PPR pipes
Fenómeno del problema
PPR/PP-R pipes rupture in long-term hydrostatic tests (1000h, 8760h), failing to meet ISO 15874 requirements.
Insufficient long-term strength affects pipe service life and design safety factor.
Análisis de la causa
(1) Raw material molecular weight too low or unreasonable molecular weight distribution
(2) Improper extrusion temperature, partial material degradation
(3) Insufficient or uneven pipe wall thickness
(4) Improper cooling rate, inappropriate crystallinity
(5) Welding joints as weak points with insufficient strength
Solución
(1) Select dedicated grades meeting PPR pipe standards (MFR 0.2-0.5g/10min)
(2) Strictly control extrusion temperature at 200-220°C, avoid material degradation
(3) Ensure pipe wall thickness meets SDR value requirements and is uniform
(4) Optimize cooling conditions, ensure reasonable crystallinity (50-60%)
(5) Strengthen quality control and inspection of welding joints
Conclusión clave
Insufficient long-term hydrostatic strength is caused by material selection and processing quality; comprehensive control of raw material, process, and welding is needed.
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