Injection Molding
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EVOH injection weld line strength is low
Problem Phenomenon
EVOH injection multi-gate product strength at the weld line is only 30-40% of the whole
Cause Analysis
The temperature of the two melt fronts has dropped, causing small molecular chain diffusion depth and insufficient entanglement; dispersed phase orientation discontinuous at the weld line
Solution
1) Increase injection temperature by 10-15°C to increase diffusion depth; 2) Increase injection speed to keep the front temperature relatively high; 3) Increase holding pressure to ensure compaction at the weld; 4) Set an overflow well at the weld line and cut it off afterward
Key Takeaway
Low weld line strength is caused by insufficient molecular entanglement; high-temperature high-speed injection and overflow wells are effective countermeasures
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