What does the longitudinal seal strip do in an aseptic carton?
A buyer-focused explanation of the LS strip, the paperboard edge and why strip selection belongs in a material review.
Where is the longitudinal seam?
A roll-fed carton begins as a continuous web of packaging material. During package formation, the web is formed into a tube and its edges are joined along a longitudinal seam. This seam is different from the transverse seals used to divide the tube into individual packages.
The inner raw edge of the laminate needs protection. The longitudinal seal strip, commonly called the LS strip, covers that edge on the product side of the package.
What functions does the strip provide?
The Packaging Material chapter of Basic Course TBA describes three connected roles: protecting the material edge against product penetration, contributing to oxygen protection, and supporting the sealing of the tube. The strip therefore belongs in the overall package specification, even though it is a small component.
| Item under review | Why it matters |
|---|---|
| Packaging laminate | The strip must be considered with the material being sealed |
| Strip construction | Different polymer constructions have different properties |
| Product application | The packaged product is part of the material-selection discussion |
| Filling equipment | Application and sealing arrangements depend on the equipment |
Is an LS strip the same as an opening strip?
No. The training document distinguishes longitudinal seal strips from tab strips, inner strips and outer protection strips. A strip used at the longitudinal seam should not be treated as interchangeable with a strip used for a consumer opening feature.
Names such as “strip” or “sealing tape” can be too broad for an enquiry. Identify the location and function of the component, and share the current reference if one is available.
What should be included in a strip enquiry?
Send the machine model, packaging-material reference, current strip designation and the intended product. If the enquiry concerns a change or a production observation, describe the relevant material and strip batches as well. This helps the supplier discuss the correct component rather than infer it from a general product name.
Actual machine settings and inspection procedures should come from the documentation for the equipment and material combination. This guide explains the component’s role, rather than prescribing line adjustments.
Explore strips and packaging accessories or contact a regional team.
Technical background: Basic Course TBA, Issue 7/0809 (2008), Basic Machine Introduction and Packaging Material chapters.
Frequently Asked Questions
Why cover the raw paperboard edge?
The LS strip helps keep the packaged product from reaching the raw edge of the material at the longitudinal seam.
Can any sealing strip replace an LS strip?
No. Different strips serve different functions; the construction and application must be identified before substitution.
What information helps identify the correct strip?
Provide the machine model, packaging-material reference, current strip designation and intended product.