Material Drying
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PET injection-grade drying 0.02%
Problem Phenomenon
PET engineering injection molded parts discolor and become brittle, strength tests fail, and the products carry color
Cause Analysis
PET molecules contain ester groups and are hydrophilic; when the moisture content exceeds the limit, hydrolysis occurs during '2079851475616104452, molecular weight decreases, and products discolor and become brittle; the moisture red line for injection grade is 0.02%, looser than for sheet but still requiring strict management
Solution
①Dehumidify and dry to moisture <0.02%; ②150℃ × more than 4 hours or 170℃ × 3-4 hours; ③air-shot method inspection: if the shot material strand is smooth and free of bubbles, the drying is qualified
Key Takeaway
PET injection-grade drying can be quickly checked on site with the air-shot method; the 0.02% red line plus air-shot verification is a practical standard executable in the workshop; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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