Material Drying
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PP '2079851475616104452 Silver Streak
Fenómeno do problema
Occasional silver streaks on PP part surfaces, more obvious with high regrind ratio or after masterbatch change.
Análise das causas
PP itself has very low hygroscopicity; silver streaks mostly come from moisture in regrind/masterbatch, heat volatilization of additives (lubricants, antistatic agents, etc.), or local decomposition gas from shear overheating; they must be distinguished from true 'moisture splay' and cannot all be attributed to drying.
Solução
①Strengthen drying of regrind and masterbatch and control ratios; ②appropriately lower melt temperature and screw shear (speed/back pressure); ③raise back pressure to help gas escape; ④check thermal stability of additives in the formulation; ⑤improve mold venting.
Conclusão principal
When silver streaks appear on PP, don't rush to blame drying—first check regrind, masterbatch, and additive volatilization, then shear heat; PP silver streaks are more a 'volatiles and shear' problem than the raw material itself absorbing water.
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