Material Drying
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PBT insufficient drying silver streaks and bubbles
Problem Phenomenon
Surface silver streaks and internal bubbles on products, alleviated after drying.
Cause Analysis
PBT is a polyester material whose moisture content exceeds the standard after moisture absorption; moisture vaporizes during melting and induces hydrolysis; insufficient drying is the main cause.; when troubleshooting on site, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Dry at about 120℃ for 3~4 hours; ②reduce moisture content to below 0.02%; ③sealed conveying after drying; ④check the dryer dew point.; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PBT drying standards are as strict as PET; moisture both produces apparent defects and causes hydrolysis damage, and the dual harm must be strictly controlled.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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