Complete Food Barrier Film Lines
for Vacuum, MAP and Cold Chain Packaging

Both structures can achieve OTR below 1 cc/m²/day. The key difference is what surrounds the EVOH core. A 5-layer PE/TIE/EVOH/TIE/PE structure uses PE on both sides of the EVOH. A 7-layer PE/TIE/PA/EVOH/PA/TIE/PE structure adds PA (nylon) layers between the TIE and EVOH. The PA layers add puncture resistance — critical for bone-in meat and shellfish — and act as a moisture shield that protects the EVOH barrier performance in humid cold-chain environments. If your application does not require puncture resistance and operates in low-humidity conditions, a 5-layer structure is often sufficient and more cost-efficient to produce.

The die head, not the extruder count, determines the number of film layers. In a 5-extruder 7-layer machine, the die head splits certain melt streams into two channels before they reach the die exit. For example, Extruder A feeds both the outer PE layer (L1) and inner PE layer (L7) simultaneously via two separate die channels — the two layers are identical in material because they come from the same extruder. Similarly, the TIE extruder feeds both L2 and L6. Only the EVOH extruder (L4) and the PA extruder (L3 and L5 via split) require dedicated single-channel feed. This die-head flow-splitting design reduces machine cost and footprint while still producing a true 7-layer film structure.

EVOH (Ethylene Vinyl Alcohol Copolymer) is a semi-crystalline polymer whose tightly packed molecular structure creates an extremely low-diffusion path for oxygen molecules. At 32% ethylene content, EVOH achieves an OTR of approximately 0.1–0.5 cc/m²/day at 23°C and 65% RH — roughly 100 times lower than PET and over 1,000 times lower than LDPE. It is transparent, food-safe and processable via co-extrusion. Its primary limitation is moisture sensitivity: barrier performance decreases as the EVOH layer absorbs water. This is why EVOH is always sandwiched between moisture-resistant layers (PE or PA) in co-extruded structures rather than used as a standalone film. [TIER 3 — SOURCE: CloudFlexFilm, 2025]

EVOH's oxygen barrier relies on its crystalline structure. When EVOH absorbs moisture, water molecules disrupt the hydrogen bonding between polymer chains, reducing crystallinity and allowing more oxygen to diffuse through. In a simple PE/EVOH/PE structure, moisture can migrate through the PE layers over time and reach the EVOH core — particularly in refrigerated or high-humidity storage. A 7-layer PA/EVOH/PA structure solves this: PA (nylon) is hygroscopic and absorbs ambient moisture before it reaches the EVOH layer, acting as a sacrificial moisture buffer. For cold chain, seafood and any application involving condensation or ice contact, a PA-containing structure is strongly recommended over a PE-only outer structure.

A 5-layer PE/TIE/EVOH/TIE/PE structure typically achieves an OTR below 1.0 cc/m²/day under standard test conditions (23°C, 65% RH). The EVOH layer itself — at 32% ethylene content — achieves 0.1–0.5 cc/m²/day. Two variables affect the final film OTR: ethylene content and EVOH layer thickness. Lower ethylene content (e.g. 29%) gives better barrier but requires more careful processing to avoid brittleness. Higher ethylene content (e.g. 44%) is easier to process and more flexible but has slightly higher OTR. EVOH layer thickness of 5–10% of total film thickness is the industry standard — a 10 μm EVOH layer in a 100 μm film provides approximately 90% of the barrier efficiency of a 20 μm layer, making thin-gauge EVOH the cost-efficient choice. [TIER 3 — SOURCE: CloudFlexFilm, 2025]

Yes, with important qualifications. Blown film is suitable for shallow-to-medium draw depth thermoforming applications — typically up to 40–60 mm draw depth depending on film thickness, PA content and the thermoforming machine's forming conditions. The biaxial orientation inherent in blown film actually improves puncture resistance compared to cast film. However, cast film (CPP) remains the standard for deep-draw thermoforming (over 60–80 mm) because of its superior thickness uniformity and forming consistency. If your thermoforming application involves shallow trays, skin packaging or medium-depth MAP trays, a 7-layer asymmetric blown film structure with PA outer layer is a viable and cost-competitive option. Confirm draw depth requirements with your thermoforming machine supplier before specifying the film structure.

A TIE layer (also called adhesive layer) is a maleic anhydride grafted polyolefin (MAH-g-PE or MAH-g-PP) that bonds chemically incompatible materials together within the film structure. PE and EVOH do not adhere to each other — without TIE, the layers will delaminate under mechanical stress, heat sealing or flexing. If TIE is omitted, the film structure physically fails. If TIE is incorrectly specified (wrong grade, wrong melt index or wrong thickness), peel strength between layers is reduced, leading to delamination during pouch forming or in-use. TIE layer selection must be matched to the specific EVOH and PA grades being used — resin suppliers typically provide compatibility data for their products.

In-house barrier film production is viable for food manufacturers with consistent, high-volume packaging requirements — typically where a single film specification is run continuously. The main advantages are supply chain independence, lower per-unit film cost at scale and faster response to specification changes. The main challenges are: (1) EVOH and PA processing requires more operator skill than standard PE film — temperature control and material handling discipline are critical; (2) raw material sourcing for EVOH and PA requires approved food-contact grade suppliers; (3) food contact compliance documentation (resin certificates, migration test reports) becomes the manufacturer's responsibility. LayerQuestar recommends a minimum daily output of 300–500 kg of barrier film to justify the investment in a 5-layer line. Contact us with your annual film consumption figure for a more specific assessment. [NEEDS CLIENT VERIFICATION — minimum output threshold]

Yes. LayerQuestar's bag making machines are compatible with EVOH barrier film processing. The key requirement for barrier film bag making is a lower and more precisely controlled heat-seal temperature compared to standard PE film — EVOH-containing structures have a narrower heat-seal window, and excessive temperature can damage the EVOH layer near the seal zone. LayerQuestar's servo-driven bag making machines include adjustable seal temperature and dwell time settings suitable for multi-layer barrier film. Confirm your specific film structure and thickness with LayerQuestar's technical team when specifying the bag making machine to ensure the seal bar configuration is matched to your film.

Food contact compliance applies to the finished film, not to the production machine. The machine manufacturer (LayerQuestar) is not responsible for film compliance — the film producer is. Compliance is achieved by using resin grades that are approved under the applicable regulation for the target market: EU 10/2011 (European Union), FDA 21 CFR (United States), GB 9685 (China) or JHOSPA (Japan). Each resin supplier — EVOH, PA, PE, TIE — must provide a Declaration of Compliance (DoC) confirming their material meets the relevant regulation. As the film producer, you are responsible for collecting these declarations, maintaining traceability records and, where required, commissioning migration testing on the finished film. LayerQuestar can provide guidance on resin supplier selection and documentation requirements upon request.