Material Drying
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Silver streaks from insufficient PA66 drying
Fenómeno do problema
Fan-shaped silver streaks and material streaks on PA66 product surfaces, obvious at the gate area, appearance parts scrapped, often accompanied by tiny bubbles.
Análise das causas
PA66 is strongly hygroscopic; water-containing particles vaporize in the 270~290℃ melt; PA66 has a high melting point and high processing temperature and is more sensitive to residual moisture than PA6; trace moisture can produce silver streaks.
Solução
①Dehumidifying drying at 85℃ for 4~6 hours, moisture content <0.15% (GF grade <0.12%); ②monitor dryer dew point (below -20℃) and regularly regenerate molecular sieves; ③seal after drying; ④use the upper limit of drying time for doubtful batches to ensure moisture compliance; ⑤verify moisture content compliance by the Karl Fischer method.
Conclusão principal
PA66 drying standard is 'stricter than PA6': control moisture content toward the low end; high-temperature processed PA66 has zero tolerance for moisture, and drying verification must be a hard prerequisite for startup.
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