9-Layer EVOH Barrier
Blown Film Machine

The core barrier structure — TIE/PA/EVOH/PA/TIE — is the same in both. The difference is in the PE layers on each side. A 7-layer machine has one PE layer on each side, which must handle both surface performance (printability, gloss, anti-block) and structural strength simultaneously.

A 9-layer machine adds a second PE layer on each side, splitting these functions: the outer PE-1 layer is formulated purely for surface performance, while the PE-2 layer is formulated purely for structural strength and stiffness. The inner side mirrors this. The result is a film where each layer does one job well, rather than two jobs acceptably.

For most food vacuum packaging applications, a 7-layer structure is sufficient. The 9-layer structure is specified when retort processing, ultra-long ambient shelf life, or independent surface and structural layer optimisation are genuine requirements.

The 9-layer structure PE/PE/TIE/PA/EVOH/PA/TIE/PE/PE is fully symmetric. Every layer has an identical mirror layer on the other side of the EVOH core: L1 mirrors L9, L2 mirrors L8, L3 mirrors L7, L4 mirrors L6. Only L5 (EVOH) has no mirror.

Because each pair of mirrored layers is identical in material, one extruder can feed both layers simultaneously via die-head flow splitting. Extruder A feeds L1 and L9, Extruder B feeds L2 and L8, Extruder C feeds L3 and L7, Extruder D feeds L4 and L6. Extruder E feeds only L5 (EVOH) — dedicated, never split. Five extruders produce nine layers.

Yes — a fully independent 9-extruder configuration is available on request, where each of the 9 layers has its own dedicated extruder and can carry a completely different material formula. This enables full asymmetric design: for example, the outer PE-1 surface layer can carry a white masterbatch and UV stabiliser package, while the inner PE-1 seal layer carries a specific anti-fog and slip additive package — with no compromise between the two.

For most applications, the standard 5-extruder symmetric configuration is sufficient. The 9-extruder configuration is a custom order — contact LayerQuestar to discuss your specific requirements.

The 9-layer PE/PE/TIE/PA/EVOH/PA/TIE/PE/PE structure is better suited to retort applications than a 7-layer structure, primarily because the dual PE layers provide greater structural integrity under the thermal and pressure stress of retort processing, and the dual PA layers provide stronger protection for the EVOH core against moisture absorption during the retort cycle.

However, retort packaging involves specific material grade requirements — not all PE, PA or EVOH grades are retort-rated. Contact LayerQuestar with your retort temperature, processing time and shelf-life requirements for a specific structure and material grade recommendation.

As a theoretical reference, a PE/PE/TIE/PA/EVOH/PA/TIE/PE/PE structure with approximately 9% EVOH layer thickness can achieve an OTR in the range of 0.3–1.0 cc/m²·day at 23°C, 0% RH — marginally better than a 7-layer structure at equivalent EVOH thickness, primarily because the dual PA layers provide better moisture protection for the EVOH core, which preserves barrier performance under humid conditions.

Actual barrier performance depends on EVOH grade, layer thickness ratio, BUR, processing conditions and end-use humidity environment. Contact LayerQuestar with your specific application for guidance.

The capital cost of a 9-layer line is higher than a 7-layer line, primarily due to the more complex 9-channel die head and the larger machine footprint. The extruder count is the same (5 extruders), so the motor and drive cost difference is smaller than it might appear.

On running costs, the dominant variable is resin cost. A 9-layer structure uses more PA than a 7-layer structure (two PA layers vs. two PA layers at similar thickness — comparable), but the additional PE-2 structural layers add PE resin cost. In practice, the total resin cost per kilogram of film is similar to a 7-layer structure of equivalent total gauge. Contact LayerQuestar for a detailed cost-per-kilogram analysis based on your specific structure and output requirements.

The machine can be operated with selected extruders purged and channels substituted, effectively producing a reduced-layer structure on the 9-layer platform. This gives the line flexibility to serve multiple product families from a single machine.

However, a 9-layer line is optimised and priced for 9-layer barrier film production. If your primary application does not require the full 9-layer structure, a 7-layer or 5-layer line will deliver better value. Contact LayerQuestar to discuss the right configuration for your product mix. [NEEDS CLIENT VERIFICATION — confirm partial-layer operating mode support for 9-layer platform]

Commissioning a 9-layer line is the most complex installation in the LayerQuestar range, due to the 9-channel die-head alignment requirements, the number of resin drying systems to qualify, and the EVOH processing validation. Typical commissioning duration is [NEEDS CLIENT VERIFICATION — confirm standard commissioning timeline for 9-layer lines].

LayerQuestar provides on-site commissioning engineers as standard. The commissioning scope includes mechanical installation verification, electrical and control system check, initial film run with all 9 layers, layer distribution verification and operator training on EVOH and PA handling protocols.