Production & Quality
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High internal stress and easy cracking of PPO
Problem Phenomenon
Cracks appear in PPO products during storage or use, mostly at assembly stress locations and sharp corner positions, and the cracks expand faster after solvent contact.
Cause Analysis
PPO molecular chains have high rigidity and a high glass transition temperature; after forced orientation, they are difficult to relax, so the residual internal stress of the product is high; rapid cooling and excessive holding pressure further freeze the stress; solvent media induce stress cracking.
Solution
①Anneal after molding when necessary to release stress; ②increase the mold temperature to 100~150℃ to slow stress freezing; ③eliminate sharp corners and enlarge fillets in the structure; ④avoid contact with non-compliant solvents.
Key Takeaway
The high internal stress of PPO is the inherent result of rigid molecular chains; annealing post-treatment is industry practice; stress cracking verification must simulate the actual media environment.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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