Molds & Tooling
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Mold Temperature Below Tg Forming Amorphous Brittle PEEK Parts
Problem Phenomenon
[Problem Phenomenon] PEEK products with insufficient mold temperature are transparent and brittle, with chemical resistance and fatigue life far below expectations
Cause Analysis
PEEK's glass transition temperature is 143℃; when the mold temperature is below this value, the melt is quenched into an amorphous structure, and the product is transparent but brittle with poor chemical resistance; at 160℃ mold temperature the crystallinity is about 25-30%, and at 200℃ it can reach 35-40% with the best performance
Solution
Set the mold temperature in the 160-200℃ range, taking the 180-200℃ upper limit for performance parts; the mold temperature controller must be an oil-type high-temperature unit (a water temperature unit cannot reach it); for crystallinity-sensitive parts, verify with DSC or the density method
Key Takeaway
The 143℃ mold temperature is the crystalline-state boundary of PEEK, and performance parts should take the upper limit with an oil-type mold temperature controller; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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