Processing Machinery
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PVDF Residence Time and Degradation
Problem Phenomenon
【Problem phenomenon】When small products are made on a large machine, the PVDF melt resides too long, turns yellow and loses strength, and product performance declines batch by batch
Cause Analysis
At 230-250℃, the typical residence time of PVDF must be controlled within 2-5 minutes; a small shot size with a large barrel makes the residence time exceed the limit several times over, and heat history accumulates and degrades
Solution
Calculate the ratio of shot size to barrel capacity and the residence time; switch small parts to a smaller machine or reduce the screw diameter; when recovery is slow, lower the rear zone temperature to reduce heat exposure; After adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
A residence of 2-5 minutes is the PVDF thermal safety window; machine matching is more fundamental than temperature adjustment; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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