Material Drying
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PA6 Drying 0.2% Red Line
Fenómeno do problema
PA6 products show silver streaks and bubbles, impact strength decreases, and the fracture surface becomes brittle and spongy
Análise das causas
The amide groups of PA6 are highly polar and extremely hygroscopic, with an equilibrium water absorption rate of 2.8% in a 50%RH environment; residual moisture vaporizes in the 240-270°C melt and hydrolyzes the amide bonds, causing an irreversible decrease in molecular weight
Solução
①Dehumidifying drying at 80-100°C for 4-8 hours, reducing the moisture content below 0.2%; ②use immediately after drying, re-drying is required if exposed to air for more than 30 minutes; ③verify by actual measurement with the Karl Fischer method
Conclusão principal
0.2% moisture content is the lifeline of PA6 processing; hydrolysis damage is irreversible and difficult to detect by appearance, so drying must be quantified by actual measurement rather than estimated by experience; after confirming effectiveness, fix the parameters and practices into the work instructions to prevent recurrence
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