Material Drying
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Silver streaks from insufficient PA66 drying
Fenómeno del 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.
Análisis de la causa
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.
Solución
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.
Conclusión clave
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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