Multi-layer co-extruded barrier film

01

Set the oxygen barrier from EVOH grade and thickness

Kuraray's technical data sheet for EVAL F101B, a 32 mol% ethylene–vinyl alcohol copolymer, gives an oxygen transmission rate of 0.3 cm³·20 µm/m²·day·atm on cast film at 20 °C and 65% RH (ISO 21309-2 Annex C), with density 1.19 g/cm³, melting point 183 °C and glass transition 60 °C. [1]

Kuraray's data sheet for EVAL E105B, a 44 mol% ethylene grade, gives an oxygen transmission rate of 1.9 cm³·20 µm/m²·day·atm on cast film at 20 °C and 65% RH by the same ISO 21309-2 Annex C method, with density 1.14 g/cm³, melting point 165 °C, glass transition 53 °C and MFR 5.5 g/10 min (ISO 1133, 190 °C, 2.16 kg). [3]

Editorial calculation: at equal thickness and test conditions, the 44 mol% grade's 1.9 against the 32 mol% grade's 0.3 cm³·20 µm/m²·day·atm is about 6.3 times the oxygen transmission, so a higher-ethylene layer needs to be about 6 times thicker for the same barrier; check the grade named in the film specification. [1] [3]

Mokwena, Tang and Laborie at Washington State University (Journal of Food Engineering, 2011) tested a laminated PET//EVOH//PP film (12//12//75 µm, biaxially oriented EVOH) and a PET//PP/tie/nylon 6/EVOH/nylon 6/tie/PP film (non-oriented EVOH co-extruded with nylon 6), noting that EVOH and nylon 6 bond without a tie layer, while PP needs a maleic-anhydride-modified tie resin. [2]

Editorial calculation: if OTR scales inversely with barrier thickness, 0.3 cm³·20 µm/m²·day·atm corresponds to about 1.2 cm³/m²·day·atm through a 5 µm EVOH layer and 0.6 through 10 µm, at 20 °C and 65% RH. Layer thicknesses are assumed examples; measure the finished film. [1]

Give the supplier the product and shelf life, required OTR and WVTR with test conditions (temperature, RH), retort or pasteurisation conditions, structure or barrier-layer thickness preferences, sealant and seal temperature, total thickness and width, mechanical and optical needs, printing or lamination, food-contact compliance, and reel specification.

02

Protect the barrier from humidity and retort

The WSU study found that oxygen transmission of both EVOH films increased with water absorption at 121 °C, in two roughly linear regions: up to about 4% water content the two films behaved similarly, but they differed sharply at higher water content. It notes EVOH can absorb more than 10% water at equilibrium in saturated humidity, and that moisture plasticises the EVOH matrix. [2]

Reviewing earlier work, the paper reports OTR rising over 10 times, from 0.16 to 1.75 cc/m²·day, for a PET/EVOH/PP film and 47 times for the PET/PP/nylon 6/EVOH/nylon 6/PP film after retorting at 125 °C for 28 min; a 456-fold rise in oxygen permeability for PP/EVOH/PP after 121 °C for 20 min; and a more than 60-fold rise from 0.3 to 18.8 cc/m²·day for PET/EVOH/PP. [2]

Editorial note: because barrier loss depends on how much water reaches the EVOH, ask suppliers for OTR measured after your actual retort or humidity exposure, and how the outer layers (PP, PET) shield the EVOH core.

03

Check the US food-contact clearance for the EVOH layer

The US Food and Drug Administration lists "Ethylene-vinyl acetate-vinyl alcohol copolymers" (CAS Reg. No. 26221-27-2) in 21 CFR 177.1360 as substances that may be safely used in articles in contact with food under set conditions. The section sorts the copolymers by composition by weight, and the group with 17 to 40 percent ethylene and 60 to 83 percent vinyl alcohol units may be used as described in its paragraph (d). [4]

Paragraph (d) allows contact with all foods except those containing more than 8 percent alcohol, under conditions of use B through H of table 2 in § 176.170(c), and names a Kuraray Co., Ltd. analytical method dated March 23, 1987 for the oligomer test. Paragraph (e) states the section does not apply to these copolymers in food-packaging adhesives under § 175.105. [4]

Kuraray states ethylene content in mole percent: 32 mol% for EVAL F101B and 44 mol% for EVAL E105B [1] [3]. The regulation uses percent by weight, so the two figures cannot be compared without conversion. In the co-extruded film the WSU study tested, PET//PP/tie/nylon 6/EVOH/nylon 6/tie/PP, the EVOH sits between nylon 6 layers away from both surfaces [2]; ask the supplier which layer touches the food, and for the regulation or clearance it relies on for that layer and for the full structure.

Editorial calculation: assuming a fully hydrolysed copolymer with no remaining vinyl acetate, and molar masses of 28.05 g/mol for ethylene and 44.05 g/mol for vinyl alcohol units, 32 mol% ethylene is about 23.1% by weight and 44 mol% is about 33.3% by weight, both inside the 17 to 40 percent range of paragraph (d). [4] [1] [3]

Text is from the eCFR version of 21 CFR 177.1360 dated 2026-09-01. Other markets, such as the EU, apply their own food-contact rules.

04

BOPP, BOPET, nylon, EVOH, foil and AlOx films from the listed converters

Listings include flexible films from BOPP, BOPET, BOPA, CPP and PE to EVOH, aluminium and AlOx barriers, with printing and pouch making; ask for OTR at your conditions and the structure of each film.

05

Outer, tie, nylon, EVOH core and sealant layers in a retort laminate

The layer order follows the PET//PP/tie/nylon 6/EVOH/nylon 6/tie/PP film in the WSU retort study, with the EVOH barrier kept away from both surfaces. [2]

06

Laminate thickness, OTR, WVTR and seal temperature for a barrier film order

Kuraray's OTR figures are for the EVOH resin on cast film, not for a finished laminate, so the OTR row still needs the film supplier's value at your temperature and humidity. [1] [3]

07

Send the product, barrier and process data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Product: [food; shelf life; fill]
Barrier: [OTR; WVTR; test conditions]
Process: [retort; pasteurisation; humidity]
Structure: [layers; EVOH mol%; thicknesses]
Seal: [sealant; temperature]
Properties: [tensile; haze; COF]
Compliance: [food contact]
Reel: [width; diameter; core]

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