Material Drying
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PVDF Silver Streaks Caused by Omitting Drying
Problem Phenomenon
【Problem phenomenon】Silver-white streaks and radial patterns appear on the surface of PVDF products, accompanied by a decrease in local mechanical strength
Cause Analysis
Although PVDF's water absorption is only about 0.04%, trace surface moisture vaporizes at processing temperatures above 200℃ and causes slight hydrolysis, forming silver streaks; ZetarMold lists silver streaks as the number one defect in PVDF '2079851475616104452, and they almost all originate from residual moisture
Solution
Dry with a dehumidifying dryer at 120-150℃ for 2-4 hours with a dew point below -30℃; seal the hopper after drying or use an insulated hopper to maintain dryness; in humid seasons shorten the exposure time after opening and check hopper sealing
Key Takeaway
Silver streaks are PVDF's number one defect, ninety percent originating from inadequate drying; check the dew point first before adjusting the machine; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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