Production & Quality
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ASA excessive back pressure shear degradation
Problem Phenomenon
After ASA increases back pressure, the melt turns yellow and performance decreases; although mixing improves, the product becomes brittle and color batch stability deteriorates.
Cause Analysis
Although ASA can withstand relatively high shear, excessive back pressure still generates excessive shear heat and rubber phase damage; the material supplier explicitly recommends keeping back pressure as low as possible; accumulated shear heat breaks through the temperature red line.
Solution
①Back pressure adjusted to the lowest level required by the process; ②mixing needs preferably solved with color masterbatch; ③monitor the measured melt temperature; ④verify product impact strength to confirm the rubber phase is intact.
Key Takeaway
The back pressure principle of ASA is: as low as sufficient; high shear tolerance does not mean unlimited; rubber phase integrity is most directly verified by impact strength.; After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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