Metallized PET Film Pinholes After Folding

Metallized PET Film can meet a demanding flat-film barrier target yet lose protection when a sharp crease concentrates stress in the metal layer. When failures appear after gusseting or repeated flexing, the investigation must reproduce the actual fold rather than repeat only an incoming-roll test.

A Metallized Film Supplier needs the laminate construction, folding geometry, metal-side orientation and post-fold OTR or WVTR conditions. The film grade is only one variable; adhesive cure, adjacent-layer stiffness and the way the pouch is packed also affect strain at the crease.

Locate the Barrier Loss

Cut specimens from flat panels, fold lines, corners and gusset roots. Test matched controls from the same roll and conversion batch. If deterioration is concentrated along a crease, the next trial should modify fold radius or laminate support. If results are poor everywhere, investigate coating continuity, lamination and specimen preparation.

Inspect seals and punctures at the same time. A pouch leak near a fold can look like broad barrier loss when the actual entry path is a small channel or damaged corner.

Structure Controls the Stress on the Metal Layer

In a printed outer film / metallized PET / sealant structure, the outer web carries graphics, the metallized PET supplies barrier and light protection, and the sealant forms the package closure. Layer gauge, modulus and adhesive condition determine how bending strain is shared.

A softer package is not automatically safer, and a stiffer package is not automatically worse. The goal is to prevent one thin barrier interface from taking most of the deformation. Compare candidate structures after the same cure time and fold protocol.

Build a Repeatable Fold Test

Define fold angle, radius, load, number of cycles and conditioning. Keep machine-direction and transverse-direction specimens separate. Measure barrier before and after folding, then inspect the same area microscopically if available. This connects a transmission change with a real damage pattern.

Send Cailong the current structure, required barrier, pouch drawing, fold location, filling process and failure samples. Grade selection should be made against the finished-package test, not a flat-film number alone.