Material Analysis
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LCP Weld Line Strength Extremely Low
Problem Phenomenon
LCP product strength at weld line is only 30~50% of the body, and fails at the weld line under stress or sealing tests.
Cause Analysis
LCP rigid rod-like molecular chains cannot re-entangle and fuse at the weld line like nylon and PC, so the interfacial bonding is inherently weak; rapid crystallization also leaves the flow front no time to fully intermelt.
Solution
①Design the gate so the weld line avoids stressed areas and sealing surfaces; ②use multi-gate sequential valves to control confluence position and pressure; ③increase melt and mold temperature; ④select grades with weld-line-strengthening formulas.
Key Takeaway
Weld line is the Achilles' heel of LCP; gate position is more critical for LCP than for any other engineering plastic, and design avoidance is far better than process remedy.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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