Direct answer: select a flexible film or laminate from the packaged product and its intended use, then assign a function to each layer. The outside may carry print and provide stiffness or handling resistance; a middle layer may add mechanical support or barrier; the inside layer must contact the product appropriately and seal on the intended equipment. A material name by itself does not establish shelf life, food-contact suitability or machine performance.
Before comparing PET, PE, PP, PA, EVOH, metallized film or aluminum foil, define what the package must survive: product sensitivity, filling process, oxygen, moisture and light exposure, seal-area contamination, storage temperature, distribution handling, package format and filling-machine conditions.
Start with the product and intended-use conditions #
A laminate should solve a defined product-and-process problem. Dry powders, roasted coffee, oily snacks, sauces, frozen products and non-food goods can place different demands on oxygen barrier, moisture control, aroma retention, light protection, puncture resistance and sealing. The same printed pouch shape may therefore require different structures.
The buyer should state the product state, contact side, filling temperature, whether sterilization or another thermal process is used, expected storage and distribution conditions, target market, package size, closures or fitments and the actual filling method. The flexible-packaging material structure FAQ provides a concise specification checklist for this first step.
Give every layer a defined job #
| Layer role | Materials that may be considered | What the buyer must confirm |
|---|---|---|
| Printing and outer layer | PET, BOPP or another print-support film | Print side, surface treatment, ink and adhesive compatibility, stiffness, heat exposure, scuffing and the required appearance. |
| Mechanical or support layer | PET, PA, oriented PP or another structure-support film | Puncture, flexing, tear behavior, dimensional stability, package geometry and handling loads. |
| Barrier layer | EVOH, metallized film, aluminum foil, coated film or another functional barrier | Required oxygen, moisture, aroma and light protection; test conditions; flex or pinhole risk; transparency; and compatibility with the rest of the structure. |
| Sealant or product-contact layer | PE, CPP or a purpose-selected sealant system | Food or product contact, seal initiation and operating window, hot tack, contamination in the seal area, filling temperature, closure geometry and machine settings. |
This is a functional model, not a rule that every package needs four separate films. One material may perform more than one role, and a coating or coextruded layer may replace a separate laminate layer. The final declaration should identify the actual grade, thickness or basis, treatment and sequence rather than only listing broad polymer abbreviations.
How common materials are used conditionally #
PET is often considered for an outer or support layer where print presentation, stiffness, dimensional control or resistance to converting heat is useful. It is not automatically the correct product-contact sealant, and a PET-containing structure does not by itself define the package barrier.
PP films, including oriented PP and cast PP routes, may be selected for print, moisture-management, stiffness or sealing functions depending on the grade and construction. BOPP and CPP are not interchangeable descriptions: orientation, treatment, sealing formulation and intended position in the laminate matter.
PE is commonly considered for sealant and product-contact functions because suppliers can formulate it for different sealing and mechanical requirements. Actual performance depends on resin selection, thickness, additives, contamination, sealing time, temperature and pressure, and the filling line.
PA may be introduced where toughness, puncture resistance or flex performance is important. Its contribution still depends on grade, orientation, conditioning, thickness and the complete laminate. It should not be treated as a universal oxygen- or moisture-barrier answer.
EVOH is used as a gas-barrier material, commonly protected within a multilayer construction. Kuraray identifies EVOH as an oxygen-barrier material used in food packaging, but buyers still need the actual grade, layer thickness, surrounding layers and performance data at relevant conditions. A resin-family name is not a finished-package guarantee.
Metallized film uses a thin deposited metal layer on a film substrate. It can add barrier and opacity or a metallic appearance, but performance depends on the base film, deposition quality, coating continuity, converting damage, flexing and the completed laminate.
Aluminum foil is a separate continuous-foil route, not another name for metallized film. It may be selected where strong light, gas or moisture protection is required, while gauge, pinholes, flex cracking, folds, sealing construction and converting conditions must still be evaluated. Neither foil nor metallization should be selected only from a generic “high barrier” label.
OTR and WVTR support screening, not an exact shelf-life promise #
ASTM D3985 and ASTM F1249 describe methods for measuring oxygen and water-vapor transmission through film or sheeting under stated conditions. The reported value belongs to the tested specimen and conditions. Temperature, relative humidity, specimen construction and test preparation affect how the result should be interpreted.
The completed package adds surface area, seals, folds, zippers, valves, spouts, pinholes, flex damage, headspace, filling conditions and product-specific failure mechanisms. Buyers should use OTR and WVTR to compare candidate materials, then validate the intended product-package system. The flexible-packaging shelf-life validation guide explains why a barrier value alone cannot establish an exact number of months.
Check sealing and filling-machine compatibility together #
A protective structure can still fail commercially if it does not form, track or seal consistently. Confirm the sealing method, jaw or bar configuration, dwell time, pressure, operating temperature range, line speed, seal width, product contamination risk and whether hot tack is important. For roll-fed material, web width, repeat, unwind direction, core, roll diameter, winding quality and registration marks are also part of the material decision.
Use the rollstock specification guide for filling equipment when the laminate will run on an automatic line. Do not copy settings or a structure from another machine without confirming the interface with the operator or co-packer.
Food-contact status belongs to the complete intended use #
A polymer name does not automatically make the completed printed laminate suitable for every food-contact use. The contact layer, inks, adhesives, coatings, additives, migration conditions, food type, contact time and temperature, and destination-market requirements must be considered together. The European Commission’s food-contact-material legislation page describes the EU framework, plastics rules, migration limits and declaration-of-compliance chain.
Overseas buyers should request a structure declaration and food-contact documentation that matches the intended use rather than a generic certificate for an unrelated material. The food-contact documentation guide for flexible-packaging buyers lists the records and use conditions that should be aligned.
What to include in the RFQ #
- product name, physical form, oil or aroma sensitivity and any aggressive ingredients;
- direct-contact side and destination market;
- filling, sealing, pasteurization, retort, freezing or other process conditions where applicable;
- required oxygen, moisture, aroma and light protection, with test conditions when numerical targets are used;
- package format, dimensions, gussets, zipper, valve, spout or other fitments;
- filling-machine or co-packer specification and production speed expectations;
- storage temperature, humidity, distribution route and handling risks;
- printing, appearance, surface finish and scuff-resistance requirements;
- requested structure declaration, supporting documents, sample stage and approval tests;
- order quantity and forecast, used to assess setup requirements and material-purchase conditions rather than to assume a universal MOQ.
The custom flexible-pouch RFQ checklist can be used to organize these commercial and technical inputs.
How Chinese laminate quotations may describe the structure #
In Chinese flexible-packaging procurement, some suppliers may initially quote a familiar shorthand such as PET/PE, PET/VMPET/PE or PA/PE. That shorthand is useful for early comparison but may omit grade, thickness, surface treatment, adhesive, sealant formulation, barrier test conditions and material-supplier starting purchase quantity. This is not a universal China-wide quotation rule.
UGI Packging recommends converting the selected shorthand into a controlled structure declaration before sample approval. If a specialty resin, coated film, foil gauge or sealant route has a supplier starting quantity, it should be identified as an order-specific sourcing condition rather than presented as a universal finished-package MOQ.
Sample approval and change control #
- Approve the intended layer sequence, grades or material identifiers, thicknesses and treatment requirements.
- Review available barrier, mechanical, seal and food-contact evidence against the stated use conditions.
- Evaluate a material or converted sample for appearance, construction and basic handling.
- Run a production-representative forming, filling and sealing trial when the material-machine combination is new.
- Validate the completed package with the actual product and defined storage or distribution conditions.
- Freeze the approved revision and require written review of changes to film supplier, grade, thickness, adhesive, ink, coating, sealant or process route.
Frequently asked questions #
Is PET/PE enough information to approve a flexible laminate? #
No. PET/PE identifies broad material families but not grade, thickness, treatment, adhesive, sealant formulation, barrier performance, food-contact scope or machine compatibility. Buyers should approve a complete structure declaration and intended-use conditions.
Does adding more laminate layers always improve performance? #
No. Each layer should have a defined function. An additional layer can change stiffness, sealing, flex behavior, cost, converting complexity and end-of-life options. It is useful only when the complete structure solves a verified requirement.
Can OTR and WVTR values determine the exact shelf life? #
No. They support material screening under stated test conditions. Exact shelf life also depends on the product, package area, seals, headspace, filling, storage, distribution and the chosen failure endpoint.
Should a buyer approve the laminate before a filling-line trial? #
A material sample may be approved for early screening, but a new material-machine combination should be confirmed with production-representative forming and sealing conditions before mass production. The trial should use the intended structure and record the approved settings and observations.
Official technical references #
- Kuraray EVAL EVOH product information and gas-barrier applications
- ASTM D3985-24: Oxygen Gas Transmission Rate Through Plastic Film and Sheeting
- ASTM F1249-25: Water Vapor Transmission Rate Through Plastic Film and Sheeting
- European Commission food-contact-material legislation and compliance documentation overview
