Material Drying
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PA66 drying 0.2% red line
Problem Phenomenon
PA66 products show silver streaks, bubbles, burn marks, impact and tensile strength significantly reduced
Cause Analysis
PA66 amide groups are strongly polar and extremely hygroscopic, equilibrium water absorption at 50%RH is about 2.5%; residual moisture hydrolyzes amide bonds in the 270-300℃ melt, molecular weight drops irreversibly, damage to appearance is hard to detect
Solution
①Dehumidifying drying 80-90℃×4-6 hours, moisture content <0.2%, high-quality parts <0.1%; ②vacuum drying 105℃×12 hours when moisture content >0.2%; ③Karl Fischer method actual measurement for release
Key Takeaway
0.2% is the PA66 moisture content red line; hydrolysis damage is irreversible, drying, drying, and more drying is the golden rule of PA66 processing; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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