Injection Molding
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PVC Injection Products Brittle
Problem Phenomenon
PVC injection molded pipe fittings and valves break when bent, impact strength unqualified, brittle even at room temperature.
Cause Analysis
Both insufficient plasticization (unmelted material) and overheating degradation cause brittleness; exhausted stabilizer and too much regrind are also factors; the two mechanisms are opposite in direction but lead to the same result, need to be distinguished (insufficient plasticization has unmelted particles, degradation has yellowing and black specks).
Solution
①Verify plasticization degree (dichloromethane immersion method, etc.); ②Control melt temperature and residence time to prevent degradation; ③Control regrind proportion; ④Check the stabilizer system; ⑤Optimize lubrication balance to aid plasticization.
Key Takeaway
PVC brittleness 'check both ends': both insufficient plasticization and degradation cause brittleness, opposite directions must be distinguished; use immersion method and appearance features to distinguish, then treat accordingly — insufficient plasticization: raise temperature and add shear; degraded: lower temperature and shorten time.
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