Material Drying
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Transparency decline/yellowing of styrene-acrylonitrile copolymer SAN/AS products
Problem Phenomenon
SAN/AS product transparency is below standard or yellowing appears.
SAN is known for its transparency and heat resistance.
Cause Analysis
(1) Processing temperature is too high, and material thermal degradation causes yellowing
(2) Raw material moisture content is high, and micro-bubbles form in the product
(3) Regrind is used multiple times, and the material ages and yellows
(4) Additives are poorly dispersed, affecting transparency
(5) Mold temperature is improper, and surface replication effect is poor
Solution
(1) Control processing temperature within the 200-260°C range
(2) Fully dry the raw material, moisture content ≤0.02%
(3) Control the regrind proportion to no more than 10%
(4) Use additives with good dispersibility
(5) Optimize mold temperature to the higher value within the 50-90°C range
Key Takeaway
SAN transparency decline is caused by thermal degradation or micro-bubbles.
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