Barrier layers 101: what buyers should verify

Flexible packaging performance usually comes from the right stack of layers, not from a single “magic” film. When you review a supplier proposal, map each layer to a function: structural support, barrier, sealant, or print carrier.

Questions that save rework

• What is the target water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) at your expected thickness?
• Which side contacts the product, and is the sealant compatible with your filling temperature and contents (oils, acids, alcohol)?
• Do you need metalized or true aluminum foil for your shelf-life claims?

Practical takeaway

Ask for test reports tied to the exact material code and thickness—not a generic datasheet from a different structure. If you change ink coverage or add a window, re-validate barrier assumptions.