Material Drying
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Product defects caused by excessive moisture content in random copolymer polypropylene raw material
Fenómeno del problema
Silver streaks and bubbles appear on the product surface, voids form inside, and mechanical properties decline.
Excessive moisture content in raw material is a common root cause of multiple defects, manifested in both product appearance and performance.
Análisis de la causa
(1) Raw material absorbs moisture due to improper storage; although random copolymer polypropylene has low water absorption, long-term exposure still absorbs water
(2) Drying equipment failure or improper drying process results in insufficient dehumidification
(3) The hopper is left open for too long, and dried raw material absorbs moisture again
(4) Ambient humidity is high, and raw material absorbs water during conveying
(5) Regrind is used directly without drying
Solución
(1) Use a dehumidifying dryer; random copolymer polypropylene drying temperature is 60-80°C, drying time 2-4h
(2) Use dried raw material promptly; install an insulated cover on the hopper, with residence in the hopper not exceeding 2h
(3) Control workshop ambient humidity below 60%
(4) Regrind must be dried before use, with drying parameters the same as new material
(5) Regularly test raw material moisture content, controlled below 0.02%
(6) Store raw material sealed, using moisture-proof packaging
Conclusión clave
Excessive raw material moisture content is solved by full drying; a complete drying and storage management system needs to be established.
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