Direct answer: choose the barrier layer and the sealant system as one package decision. Oxygen, moisture, aroma or light protection is useful only when the laminate survives converting, filling, distribution and sealing without channels, pinholes, contamination or incompatible machine settings.
Start with the product’s sensitivity and use conditions, then compare candidate barrier routes at stated test conditions. Do not select PET, PE, EVOH, metallized film or aluminum foil from a generic ranking, and do not treat one OTR, WVTR or seal-strength result as a guarantee of shelf life.
Separate barrier functions from sealant functions #
| Function | Possible route | Buyer confirmation |
|---|---|---|
| Oxygen or aroma control | EVOH, metallized film, foil or another coated/multilayer barrier | Actual grade, thickness, test conditions, humidity response, flex damage and completed-package pathways. |
| Moisture control | PE, PP, foil, metallized or coated-film combinations | Whether the product needs moisture gain or moisture loss control, plus temperature and humidity conditions. |
| Light protection | Opaque print, metallization, foil or another light-blocking construction | Required wavelength or practical exposure, inspection window, artwork and product sensitivity. |
| Heat sealing | PE, CPP or a purpose-selected sealant formulation | Seal initiation, operating window, hot tack, contamination, dwell, pressure, seal geometry and filling line. |
A barrier layer may sit inside a laminate and never contact the sealing bars. The inside sealant layer may have modest barrier performance yet determine whether the completed pouch closes consistently. The flexible-film laminate material-selection guide explains how these layer roles fit into the complete structure.
Interpret OTR and WVTR with their test conditions #
ASTM D3985 and ASTM F1249 describe methods for measuring oxygen and water-vapor transmission through film or sheeting. Results must be tied to the specimen and stated temperature, humidity and preparation conditions. Values from different conditions should not be compared as if they were equivalent.
Barrier data supports candidate screening. The finished pouch also includes seals, folds, gussets, zippers, valves, spouts, pinholes, flex damage, package area and headspace. Use the shelf-life validation guide when converting material data into a product-package study.
Choose the barrier route by failure mechanism #
EVOH may be used for gas barrier within a protected multilayer construction. Kuraray identifies EVOH as a gas-barrier material used in packaging, but grade, thickness, surrounding layers and humidity conditions still matter.
Metallized film can provide barrier, opacity and appearance with a thin deposited metal layer. Performance depends on the base film, deposition continuity, converting and flex damage. It is not the same construction as continuous aluminum foil.
Aluminum foil may be considered where strong light, gas or moisture protection is required. Gauge, pinholes, folds, flex cracking, lamination and package geometry remain part of the decision.
Transparent coated or coextruded routes may be considered where product visibility or metal-free construction is important. The coating, adhesion, flex resistance and performance after converting must be confirmed for the actual material.
Build a sealing window instead of copying one temperature #
A useful sealing study varies temperature, dwell and pressure across the intended production range while keeping specimen preparation and evaluation consistent. It should identify incomplete seals, distortion, burn-through, wrinkling, sealant squeeze-out and the effect of product contamination in the seal area.
ASTM F88/F88M measures seal strength for flexible barrier materials and identifies the specimen failure mode. Seal strength is valuable for process control, but it does not replace leak detection, visual inspection or a production-line trial. The flexible-pouch seal integrity and failure guide separates these checks.
Storage temperature changes more than the barrier value #
Chilled, frozen, ambient and heated distribution can change film stiffness, sealant response, adhesive behavior, product viscosity, condensation and package handling. Buyers should state the real temperature range rather than request a structure described only as “for food” or “high barrier.”
When the product or process is new, evaluate production-representative samples after the intended filling, storage and distribution exposures. The flexible-pouch sample validation FAQ outlines what a sample can and cannot confirm.
RFQ and approval checklist #
- product, product state, oil/aroma sensitivity and direct-contact side;
- oxygen, moisture, aroma and light requirements, including test conditions for numerical targets;
- filling temperature, storage range and distribution environment;
- pouch format, folds, gussets, zipper, valve, spout and seal geometry;
- filling-machine sealing method, time, pressure and usable temperature range;
- seal-area contamination risk and hot-tack requirement;
- complete layer declaration, grades, thicknesses, adhesive and treatment;
- barrier, seal-strength, leak and production-trial evidence required for approval.
In Chinese flexible-packaging procurement, some quotations may use shorthand structures and a single “typical” barrier value. This is not a universal China-wide specification. UGI Packging recommends requesting the complete material declaration and the conditions behind every reported value before comparing quotations. The material-structure specification FAQ can be attached to the RFQ.
Frequently asked questions #
Is the lowest OTR always the best flexible-pouch specification? #
No. The barrier must match the product and use conditions without creating unnecessary cost or incompatibility. Seals, flex damage, closures, filling and package area can also control the completed-package result.
Can a strong seal-strength result prove that a pouch is leak-free? #
No. Seal strength and leak integrity answer different questions. A programme may need consistent seal-strength measurement, visual inspection and an appropriate package-integrity method.
Can the same sealing temperature be used for every laminate? #
No. The usable window depends on sealant formulation, thickness, machine, dwell, pressure, line speed, seal geometry and contamination. Confirm a range on representative equipment rather than copying one setting.
Does aluminum foil automatically guarantee the required shelf life? #
No. Foil can provide strong barrier, but the completed package still depends on foil gauge, pinholes, flexing, lamination, seals, closures, filling, storage and product validation.
Official technical references #
- ASTM D3985-24: Oxygen Gas Transmission Rate Through Plastic Film and Sheeting
- ASTM F1249-25: Water Vapor Transmission Rate Through Plastic Film and Sheeting
- ASTM F88/F88M-23: Seal Strength of Flexible Barrier Materials
- Kuraray EVAL EVOH gas-barrier product information
