Foil liner compatibility guide
A strong induction seal depends on the complete pack: cap, liner, container mouth, cap torque and the product environment.
What must be compatible?
The aluminium foil heats during induction sealing, but the layer that bonds to the container mouth must be designed for the container material. A liner intended for one plastic may not seal correctly to another. Glass, PET, HDPE and PP applications can require different liner constructions.
Cap torque matters
The cap holds the liner against the container mouth during heating. Inconsistent torque can cause partial contact, edge leaks or uneven seal pressure.
Container mouth finish
The sealing land should be flat, clean and free from product contamination. Damaged or irregular rims reduce the chance of a continuous seal.
Need a compatibility check?
Send cap, liner and container details before final machine selection.
Foil-liner construction and material matching
A typical induction liner includes an aluminium layer that heats in the induction field and a heat-seal layer that bonds to the container mouth. The sealing layer must match the container material; a liner intended for one plastic may not bond correctly to another. The cap supplier or liner supplier should confirm the intended material match before trials.
| PET bottles and jars | Use a liner specified for PET. Check heat input carefully because some packs can distort if over-heated. |
|---|---|
| HDPE containers | Use a liner designed for HDPE and confirm cap torque so the liner has even pressure during heating. |
| PP containers | Use a PP-compatible seal layer and trial the highest and lowest intended line speeds. |
| Glass packs | Confirm the liner is suitable for glass and the finish is consistent enough for full mouth contact. |
| Unknown or mixed packs | Do not guess. Send samples and request confirmation of liner/container compatibility before machine selection. |
Compatibility evidence to keep
Keep the liner datasheet, cap details, container material, torque setting, accepted induction sealer settings and a retained sample set. This evidence is useful when a supplier changes liner material or when a production fault appears after a cap or bottle change.
Check the liner, cap and container as one sealing system.
Induction sealing fails most often when one part of the pack is assumed rather than confirmed. Use this table to identify what needs to be checked before a machine is specified.
| Component | What to confirm | Risk if missed |
|---|---|---|
| Foil liner | Heat-seal layer intended for the actual container material and closure construction. | Weak bond, partial bonding or a seal that peels away too easily after cooling. |
| Cap | Consistent thread fit and pressure on the liner during induction heating and cooling. | Uneven contact, edge leaks and different results between bottles in the same batch. |
| Container mouth | Flat sealing land, clean surface and no moulding damage or product residue. | Channels under the foil, incomplete contact or localised leaks. |
| Line speed | Dwell time under the induction head at the intended production rate. | Under-heating at high speed or overheating if speed and power are not balanced. |
Do not treat all foil-lined caps as the same component.
One-piece, two-piece, easy-open, weld, barrier and vented liner constructions can behave differently under induction. Ask the supplier to identify the heat-seal layer, intended container material, backing arrangement and any product or storage limitations.
When a liner changes supplier or product code, repeat the relevant setup and acceptance checks even if the cap diameter appears unchanged.
| One-piece or two-piece | Compare the constructions and reseal behaviour. |
|---|---|
| Container material | Check PET, HDPE, PP and glass requirements. |
| Production evidence | Record liner code, cap batch, container batch, accepted setup and the agreed peel or leak result. |