What causes weak seals and packaging leaks?
Direct answer
Weak seals and leaks can be caused by material incompatibility, contamination, incorrect heat-pressure-time conditions, poor alignment, wrinkles, damaged tools or inadequate cooling. The investigation should identify where and how the seal failed before settings are changed.
Classify the failure using a consistent test. A channel through product contamination, a peel failure at the interface and a film tear beside the seal indicate different causes. Keep accepted and rejected samples for comparison.
Use the production material and product because sealant layer, thickness, coating, print, moisture, oil and particulates can change the process window.
Decision framework
Use the actual product, pack and site conditions when applying this comparison.
| Failure | Possible cause area | Check |
|---|---|---|
| Channel leak | Product or wrinkle crossing the seal. | Seal-area cleanliness and pack presentation. |
| Incomplete seal | Low or uneven heat, pressure or dwell. | Tool temperature profile and contact. |
| Burn-through or distortion | Excess heat, dwell, pressure or unsuitable material. | Material specification and process window. |
| Seal opens after cooling | Material compatibility, cooling or stored stress. | Delayed test under relevant conditions. |
Questions buyers ask
Answer-first guidance for specification, testing and practical decision-making.
Why should seal temperature be measured rather than assumed?
A controller set-point does not prove the temperature at every point of the sealing surface. Tool condition, sensor position, cycling and heat loss can create differences. Use an appropriate validated method and follow safe procedures.
How does product contamination affect a seal?
Powder, liquid, oil or product fibres can prevent the seal layers from contacting and bonding uniformly. Filling accuracy, dust control, settling time and pack presentation may need attention as well as the sealer.
What is a sealing process window?
A sealing process window is the combination of heat, pressure and time that produces an acceptable seal with the actual material and product. A robust process operates within a range rather than at one fragile setting.
When should leak testing be included in acceptance?
Include leak testing when package integrity is a defined requirement. Agree the test method, sample conditioning, failure criteria and responsibility before testing because different methods reveal different failure modes.
Information to provide for a technical review
- product and operating condition
- container, closure, label, film or pack formats
- current method and observed problem
- target result and acceptance method
- photographs, drawings and representative samples
- line layout, interfaces, utilities and production constraints
State which information is measured, which is supplied by a component vendor and which remains an assumption. Final machinery suitability depends on the complete application and may require a sample trial or site review.
Discuss your packaging application
Send the product, pack formats, samples, target output and site information so Lancing can review the most suitable next step.
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