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Review pouch formats with the intended opening, zipper, valve or spout and filling method defined.
Flexible-pack troubleshooting
Why do pouch seals fail, leak or form channels?
Pouch seals fail when the sealant surfaces do not form a continuous bond under the actual time, temperature and pressure conditions. Product contamination, wrinkles, web structure, fitments and cooling can all create leak paths. A visually closed seam is not enough; validate the exact pouch, product and sealer together.
Direct answer
Control sealant compatibility, contamination and the machine’s sealing window.
Separate seal formation from damage that occurs later. Inspect the seal area before sealing, record the machine window and cooling, then test the filled pouch after handling and distribution conditions. A channel caused by product contamination requires a different remedy from a web or fitment defect.
Seal integrity is specific to the pouch structure, product, sealing equipment and conditions. Use production-representative pouches and contents, define the acceptable seal result, and investigate both the material and the process before changing temperature alone.
Decision summary
Separate material, contamination, setup and fitment-related causes.
| Seal symptom | Variables to investigate |
|---|---|
| Channel or unsealed path | Check contamination, wrinkles, jaw alignment and pressure |
| Weak peel or opening seal | Check sealant, temperature, dwell and cooling |
| Burn-through or distortion | Reduce excess energy and verify web structure/settings |
| Leak around spout/zipper | Check transition thickness, fitment position and local pressure |
| Intermittent failures | Compare web batch, product cut-off, jaw condition and line speed |
Buyer question
How do product contamination and sealing-window control affect a seal?
Powder, liquid, oil, fibres or product stringing across the seal can prevent continuous contact. The sealing window is the workable combination of temperature, pressure, dwell and cooling that forms a reliable bond without damaging the web. Settings copied from another pouch structure may not apply.
Control fill height and product cut-off, keep the seal area flat and clean, and record the successful process range rather than one nominal setting.
Buyer question
Why do pouch structure and sealant layer matter?
The outer layers provide print, stiffness or barrier; the inner sealant layer must bond under the chosen process and resist the contents. Thickness, coatings and laminate construction influence heat transfer and the risk of distortion or delamination. A pouch described only as “PE” or “foil lined” does not provide enough detail for sealing approval.
Request the exact structure and confirm it against the mono-material versus laminated pouch guide.
Buyer question
What changes when a zipper, valve or spout is added?
A zipper adds multiple layers and transitions near the top seal. A valve or spout introduces a fitment interface with different thickness, stiffness and potential leak paths. Seal jaws, pressure distribution and cooling may need to accommodate those transitions.
Test around the fitment, not only across the flat web. Confirm cap fit, fitment retention and repeated use where the pack is reclosable.
Buyer question
How should seal integrity be checked before release?
Use a defined combination of visual inspection and an integrity method appropriate to the product and risk, then add storage and distribution checks. Record sample condition, orientation, time, temperature and acceptance criteria. A single squeeze test can miss slow channels or failures that develop after cooling.
Retain passing and failing examples during development and link the approved settings to the exact pouch reference and product.
Related guidance
Use the pouch, material and test pages to control the seal system.
Prepare a pouch material brief
Prepare a material brief covering web structure, barrier, sealant, fitment and any end-of-life evidence requirement.
Plan seal validation
Build an approval trial that records samples, machine conditions, seal checks and the changes that require requalification.
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