Material Drying
2 views
Decreased Transparency/Yellowing of Biaxially Oriented Polypropylene Film SAN/AS Products
Problem Phenomenon
The transparency of SAN/AS products is below standard or yellowing appears.
SAN is known for its transparency and heat resistance.
Cause Analysis
(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
Solution
(1) Control the processing temperature within the range of 140-170(stretching)/230-260(extrusion)°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 20-60°C
Key Takeaway
The decrease in SAN transparency is caused by thermal degradation or micro-bubbles.
Was this helpful?
0 people found this helpful
Thank you for your feedback!