Material Drying
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Decreased Transparency/Yellowing of Cast Polypropylene Film SAN/AS Products
Fenómeno del problema
The transparency of SAN/AS products is below standard or yellowing appears.
SAN is known for its transparency and heat resistance.
Análisis de la causa
(1) The processing temperature is too high, and the material thermally degrades and turns yellow
(2) The moisture content of the raw material is high, and micro-bubbles form in the product
(3) The regrind is used multiple times, and the material ages and turns yellow
(4) The additives are poorly dispersed, affecting transparency
(5) The mold temperature is improper, and the surface replication effect is poor
Solución
(1) Control the processing temperature within the range of 230-270°C
(2) Fully dry the raw material, with moisture content ≤0.02%
(3) Control the regrind ratio to not exceed 10%
(4) Use additives with good dispersibility
(5) Optimize the mold temperature to the higher value within the range of 15-40°C
Conclusión clave
The decrease in SAN transparency is caused by thermal degradation or micro-bubbles.
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