Molding Process
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PEEK Coefficient of Thermal Expansion Tg Jump
Problem Phenomenon
【Problem Phenomenon】PEEK precision parts undergo sudden dimensional changes when working conditions cross 143℃, and the fitting clearance goes out of control
Cause Analysis
The coefficient of thermal expansion of PEEK is about 55ppm/K below Tg (143℃) and jumps to 120-140ppm/K above it; dimensional changes across Tg working conditions are nonlinear, so the design must be calculated in segments
Solution
For cross-Tg applications, check the dimensional chain according to segmented CTE; precision fitting parts avoid working temperatures spanning 143℃; design conservatively at 140ppm/K for the high-temperature segment
Key Takeaway
CTE doubles on both sides of 143℃; precision parts should avoid working across the Tg range; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for similar problems in the future
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