Extrusion & Post
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PVDF Weld Line Weak Strength
Problembeschreibung
【Problem phenomenon】Multi-gate PVDF products crack at the weld line, and pressure tests leak from the weld line
Ursachenanalyse
When two melt fronts converge, insufficient molecular entanglement forms a weak interface, and the solidified film at the front of semi-crystalline materials further hinders fusion; in-die confluence in extrusion similarly produces in-die weld lines
Lösung
Increase melt temperature, mold temperature, and holding pressure to promote fusion; change multi-gate to single gate or adjust positions so the weld line avoids pressure-bearing areas; lengthen the mixing section after confluence in the extrusion die to increase molecular entanglement
Wichtigste Erkenntnis
PVDF weld lines rely on temperature to promote fusion plus structural avoidance; pressure-bearing parts must be checked at weld positions; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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