Material Drying
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Decreased transparency/yellowing of high impact polystyrene SAN/AS products
Problem Phenomenon
SAN/AS product transparency is below standard or yellowing appears.
SAN is known for transparency and heat resistance.
Cause Analysis
(1) Processing temperature too high, material thermally degrades and yellows
(2) High raw material moisture content, microbubbles form in the product
(3) Regrind used multiple times, material ages and yellows
(4) Poor additive dispersion, affecting transparency
(5) Improper mold temperature, poor surface replication effect
Solution
(1) Control processing temperature within the 180-240°C range
(2) Fully dry raw material, moisture content ≤0.02%
(3) Control regrind ratio not exceeding 10%
(4) Use additives with good dispersibility
(5) Optimize mold temperature to the higher value within the 40-80°C range
Key Takeaway
SAN transparency decrease is caused by thermal degradation or microbubbles.
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