What is a pre-laminated hole (PLH) in carton packaging?
Learn how a pre-laminated hole differs from an open hole and why the cap, membrane and carton must be matched.
Is the package already open beneath the cap?
A pre-laminated hole is a prepared opening in the paperboard, not an uncovered hole through the complete laminate. During lamination, barrier and polymer layers cover the area. The resulting membrane remains part of the unopened package structure.
This distinction matters when discussing cap compatibility. The closure must work with the prepared opening and the membrane construction, rather than simply fit over a visible circular area.
How is PLH connected to cap design?
The technical references describe post-applied carton caps used with PLH material. In a cutter-based one-step opening design, opening the lid activates a mechanism that opens the membrane. Other systems use a different opening arrangement, such as a separate pull tab.
A cap’s external appearance therefore does not establish that it can open a particular carton correctly. The cap, membrane and package-opening geometry need to be reviewed as a combination.
| Question | Information to provide |
|---|---|
| Which carton is being used? | Exact format and capacity |
| What is beneath the closure? | PLH, pull-tab or another specified opening system |
| Which material is proposed? | Material reference and opening specification |
| How is the closure applied? | Applicator model and current configuration |
| Which closure is being replaced? | Current model or approved reference |
Can the same cap suit two cartons with the same capacity?
Capacity alone is not sufficient. Two cartons can have the same nominal volume and still differ in panel shape, opening location, prepared-hole geometry or the equipment used to apply the cap. A model name and volume should start the discussion, not end it.
How should a purchasing team approach a change?
Identify the current material and opening system first. Then review the proposed cap and application arrangement with the supplier. Keeping these references together makes sample discussions and subsequent qualification more specific.
For readers comparing opening mechanisms, see one-step versus two-step carton caps. To discuss an actual package, browse our cap portfolio.
Technical background: Basic Course TBA (2008), Packaging Material chapter; Aseptic Carton Caps Overview (June 2023), sections on post-applied closures and PLH. Model-specific suitability is not established by this general explanation.
Frequently Asked Questions
Is PLH an open hole through the whole carton wall?
No. The paperboard opening is covered by laminate layers in the conventional construction described here.
Does a PLH identify the correct cap by itself?
No. The opening geometry, membrane, closure mechanism and application equipment must be considered together.
Is carton volume enough to choose a closure?
No. Cartons of equal volume can have different opening and application requirements.