Material Drying
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TPU bubbles (moisture type)
Fenómeno del problema
Bubbles and cavities appear inside or on the surface layer of TPU products, the surface bulges, and they decrease significantly after drying treatment.
Análisis de la causa
TPU is highly sensitive to moisture; after the pellets absorb moisture, the moisture vaporizes at high temperature forming bubbles; insufficient drying temperature and time or secondary moisture absorption after drying both cause the moisture content to exceed the standard.
Solución
①dry at 80~100℃ for 4~6 hours to ensure moisture content ≤0.05%; ②use immediately after drying to avoid secondary moisture absorption; ③closed conveying to prevent re-absorption of moisture; ④check the dew point and air volume of the dryer.
Conclusión clave
Eighty percent of TPU bubbles originate from moisture management; meeting the drying standard is only the first step, and controlling the exposure time after drying is equally critical; repeated heating cannot replace drying.
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