Material Drying
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PESU Insufficient Drying Surface Streaks
Fenómeno do problema
Streaks or silver streaks (splay) appear on the surface of PESU products, especially obvious on transparent parts; appearance is poor but mechanical properties may be normal.
Análise das causas
PESU is hygroscopic and needs drying; although hydrolytically stable, processing wet resin produces surface streaks or silver streaks; moisture does not degrade the polymer but causes appearance defects; internal bubbles cause strength reduction; extruded profiles blister severely.
Solução
①According to Veradel PESU: dry at 177℃×3h or 150℃×4h or 135℃×5h; ②moisture content <0.05% for '2079851475616104452, <0.01% for extrusion; ③dehumidifying drying at dew point -40℃; ④defective parts can be ground, dried, and re-molded without loss of performance.
Conclusão principal
PESU drying is the prerequisite for appearance quality; 500ppm/100ppm are different standards for '2079851475616104452/extrusion; the ability to recycle, dry, and reuse defective parts is a material advantage.
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