Processing Machinery
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PVDF Screw Compression Ratio and Plasticization
Problem Phenomenon
【Problem phenomenon】General-purpose screws processing PVDF show uneven plasticization, large melt temperature fluctuations, and powder material is more prone to incomplete melting
Cause Analysis
PVDF recommends a gradual compression ratio of 2.5:1-3.5:1 and a medium shear rate; a mismatched compression ratio or excessive shear causes frictional overheating and degradation; direct powder molding relies more on the screw's mixing and plasticizing ability
Solution
Select a gradual screw with a compression ratio of 2.5-3.5:1 and control medium-low shear; strengthen mixing elements for powder material; monitor melt temperature uniformity, and first check screw suitability when fluctuations are large
Key Takeaway
A screw compression ratio of 2.5-3.5:1 is the PVDF plasticization benchmark; powder material is more demanding on the screw; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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