Production & Quality
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Stress Cracking of PEEK
Problem Phenomenon
Cracks appear in PEEK after assembly or a period of use; cracks mostly originate from weld lines, sharp corners, or metal insert interfaces, and expand faster at locations in contact with environmental media.
Cause Analysis
Internal stress in the product originates from uneven crystallization shrinkage and over-packing; the shrinkage difference between inserts and plastic generates interface stress; specific chemical media erode stress concentration areas and induce cracking.
Solution
①Optimize the holding curve to reduce residual stress; ②Eliminate sharp corners and enlarge transition fillets; ③Preheat inserts to reduce shrinkage-difference stress; ④Anneal to release internal stress when necessary and verify media resistance.
Key Takeaway
Although PEEK has excellent chemical resistance, the superposition of stress and media can still cause cracking; annealing is a reliable post-treatment for eliminating internal stress; eliminating stress concentration through structural design is the fundamental measure.
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