Flexible barrier packaging is almost always a multi-layer laminate. No one polymer blocks oxygen, moisture, and light equally well while also sealing reliably and surviving handling.
A typical structure pairs an outer layer for print quality and puncture resistance, a barrier core for oxygen and moisture blocking, and an inner sealant layer chosen for heat-seal performance against the product. The flexible packaging fundamentals cover how those layers get assembled.
EVOH (ethylene vinyl alcohol) is one of the best oxygen barrier materials in flexible packaging, but it loses barrier performance when wet. That is why it is almost always sandwiched between moisture-blocking layers.
Metallized film, a thin vacuum-deposited aluminum layer on a polymer substrate, and true foil laminations offer strong oxygen and light barrier at lower cost than EVOH structures. The tradeoff is losing microwave compatibility and, with foil, the ability to see the product through the package.
Polyolefins, meaning PE and PP, are naturally good moisture barriers but poor oxygen barriers. That is the opposite profile from EVOH.
This is why moisture-sensitive and oxygen-sensitive products, including many edibles and some cosmetic formulas, need a structure combining both barrier types. The same barrier physics that governs rigid containers applies here, just distributed across layers.
PET is the usual outer layer, chosen for dimensional stability, print quality, and puncture resistance. The inner sealant is typically an LDPE grade selected for a low seal-initiation temperature, since the seal has to form fast enough to keep up with fill-line speed.
Over-specifying barrier film, using a high-barrier EVOH or foil structure on a product that does not need it, adds real cost without a corresponding benefit.
Under-specifying shows up as product degradation, staleness, color shift, or potency loss for cannabinoid products, well before the printed best-by date. The right call depends on the product's measured oxygen and moisture sensitivity from stability testing.
Laminate cosmetic tubes are built from the same layer thinking in a semi-rigid body. Understanding the film stack carries over directly to the tube.
Jadewell runs laminate structures across metallized, foil, and EVOH barrier cores with OTR and MVTR values stated on the film spec. Request a quote with the product, target shelf life, and required OTR.