Material Analysis
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COC Bottle Cap Seal Failure
Problem Phenomenon
The sealing test of the COC medicine bottle and bottle cap fit leaks, the torque retention decays over time, and the shelf-life seal integrity is unqualified.
Cause Analysis
Internal stress relaxation of COC products causes slight changes in the thread fit dimensions; creep characteristics cause the compression force to decay over time; unstable molding shrinkage control causes fit tolerance drift.
Solution
①Mold with low stress and fully set to reduce relaxation; ②consider creep compensation in the seal structure design; ③shelf-life verification of dimensions and sealability; ④fix the fit tolerance according to the measured shrinkage.
Key Takeaway
The long-term performance of COC seals is governed by creep and stress relaxation; shelf-life verification is a compulsory question for pharmaceutical packaging materials; structural compensation is more economical than material replacement.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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