Molds & Tooling
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PPO Melt Fracture
Problem Phenomenon
During high-speed filling of PPO, melt fracture patterns appear on the product surface; reducing speed leads to insufficient filling, and the contradiction is prominent in thin-walled parts.
Cause Analysis
The high-viscosity PPO melt has a low critical shear rate, and high-speed filling easily triggers melt fracture; small gates concentrate shear; low temperature increases viscosity and aggravates the fracture tendency.
Solution
①Multi-stage injection with reduced speed in the gate area and increased speed in the filling area; ②enlarge the gate to reduce shear rate; ③increase melt temperature to reduce viscosity; ④switch to a high-flow grade if necessary.
Key Takeaway
The contradiction between PPO melt fracture and insufficient filling is resolved by multi-stage injection; gate size is a structural solution; high-flow grades are a material-level way out.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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