EVOH EW-3201

In seven-layer blown-film coextrusion lines producing vacuum pouches and modified-atmosphere lidding for processed meat, cheese, and ready-meal trays, EVOH EW-3201 is placed as the internal oxygen barrier core between two maleic anhydride-grafted polyolefin tie layers. The grade designation EW-3201, if interpreted under the common ethylene-content nomenclature as a 32 mol% ethylene vinyl alcohol copolymer, positions the barrier layer in the intermediate ethylene-content window; grade-specific oxygen transmission data for EW-3201 under ASTM D3985 at 23°C and 0% RH should be confirmed against the supplier certificate of analysis, because published data for this specific configuration is limited. The barrier layer is typically applied at 3–10 µm core thickness within a total film thickness of 45–120 µm, corresponding to 4–8 vol% of the structure, with 2–4 µm tie layers on each side and LDPE or LLDPE skins. For oxygen-sensitive processed meat, the packaging specification commonly requires oxygen transmission rate below 0.5 cm³/(m²·day·atm) at 23°C and 50% RH after film conversion; at 0% RH the same EW-3201 core typically reduces transmission by one to two orders of magnitude relative to unbarriered polyolefin films. Processing on a 7-layer blown-film line uses a spiral mandrel die with die gap 1.6–2.2 mm, blow-up ratio 2.5:1–3.2:1, and frost-line height set to stabilise the EVOH core without crystallinity loss. EVOH EW-3201 must be pre-dried in a desiccant hopper dryer at 80°C for at least 4 h to 0.3% maximum residual moisture, with drying air dew point at or below -40°C; barrel profile from feed to metering is typically 180°C, 195°C, 205°C, 210°C, 215°C, and residence time above 200°C is kept below 15 min to prevent gel particles. Adhesion between EVOH and tie layers is measured per ASTM F904 with minimum peel strength 2.5 N/15 mm after 24 h conditioning, and film tensile properties are verified according to ASTM D882 to ensure the EVOH core does not embrittle under vacuum-pack compression. The regulatory basis for food contact includes FDA 21 CFR 177.1360, Regulation (EU) No 10/2011 Annex I, and GB 4806.7-2023, with migration testing under EU 10/2011 conducted as part of the converter’s compliance documentation. Terminal finished products include vacuum pouches, MAP lidding films, and thermoformed meat trays where the EVOH core remains between moisture-protective polyolefin layers to limit oxygen transmission loss above 80% RH.

What limits hydrocarbon permeation in multilayer fuel tanks under cyclic diurnal load?

In six-layer blow-molded high-density polyethylene fuel tanks, EVOH EW-3201 is buried as a discrete hydrocarbon barrier layer between two maleic anhydride-grafted HDPE tie layers, with the layer stack commonly configured as HDPE skin/regrind/tie/EVOH/tie/HDPE. The EVOH layer is specified at 1.5–3.0 vol% of total wall thickness; for a tank shell wall of 6–8 mm, the EVOH layer thickness is approximately 0.10–0.40 mm, and the tie layers are each 2–4 vol%. This low addition ratio preserves the impact strength, weldability, and recyclability of the HDPE shell while reducing hydrocarbon permeation under the EPA 40 CFR Part 86 evaporative emission certification procedures and the CARB LEV III requirements; equivalent China 6 limits are enforced under GB 18352.6-2016, and permeation measurement is performed according to SAE J1737 or the sealed housing evaporative determination procedure in 40 CFR 86.1844; EW-3201-specific permeation data for this configuration should be obtained from supplier technical bulletins because published data for this specific configuration is limited. The production process uses an accumulator-head multilayer blow molder with a 6-layer coextrusion head and parison programming to control wall distribution at pinch-off and corners; the EVOH extruder is a 24:1–30:1 L/D barrier screw with compression ratio 3.0:1–3.5:1, and EVOH melt temperature is held between 195°C and 215°C. HDPE melt temperature is maintained at 220–240°C, and the coextrusion head adapter is held at 205–225°C to prevent degradation at the EVOH layer interface. Pre-drying conditions require 80°C for 4–6 h to residual moisture below 0.3%, with a desiccant dryer dew point below -40°C. Once blow molded, the tank shell is cooled in the mold for 15–25 min, and the EVOH layer is inspected by ultrasonic thickness mapping to confirm absence of thinning below 0.08 mm at pinch-off zones. Operational boundaries include the requirement that the EVOH layer not be exposed directly to external moisture or fuel contact—both sides must remain encapsulated by tie layers and HDPE to prevent barrier collapse under humid or solvent swelling conditions. Terminal finished products include automotive fuel tanks and filler pipes where the EVOH layer provides the hydrocarbon barrier required for evaporative emission compliance.

Before a 1.2 mm five-layer PP/EVOH sheet enters a plug-assist thermoforming cavity, EVOH EW-3201 is coextruded as the central oxygen barrier layer between polypropylene skins and maleic anhydride-grafted PP tie layers. The EVOH addition ratio is held at 3–7 wt% of the sheet, corresponding to an absolute core thickness of 0.08–0.20 mm; thicker EVOH cores above 8 wt% are generally avoided because the sheet stiffness differential and the narrower forming window increase the incidence of plug-stretch thinning at container corners. The flat sheet process uses a 5-layer coextrusion line with a feedblock and flat die, chill-roll stack temperature maintained at 25–35°C, and EVOH melt temperature set between 200°C and 225°C. Pre-drying of EW-3201 is performed at 85°C for 4 h to residual moisture below 0.3%; barrel residence time above 200°C is limited to 15 min to avoid gel formation. The downstream thermoforming step heats the sheet surface to 145–160°C and forms it in a plug-assist machine with plug temperature controlled to avoid sticking; mold temperature is kept at 60–85°C, and draw ratios up to 3:1 are typical for shallow barrier containers. Oxygen transmission rate of the formed container is verified per ASTM D3985 or ASTM F1307, with the EVOH core providing the required barrier for oxygen-sensitive sauces and dairy products at 23°C and 50% RH. The regulatory basis for food contact includes FDA 21 CFR 177.1360, Regulation (EU) No 10/2011 Annex I, and GB 4806.7-2023; compliance testing includes overall migration and specific migration for any residual ethylene-vinyl alcohol oligomers. Terminal finished products are barrier cups, trays, and retort-stable containers for ambient sauces, dairy desserts, and ready-meal components.

When oxygen diffusion in underfloor heating pipes exceeds 0.1 g/(m³·d) at 40°C

In five-layer coextruded PE-RT barrier pipes for underfloor heating, EVOH EW-3201 is applied as an oxygen diffusion barrier between two tie layers and PE-RT inner and outer skins, with the pipe wall structure PE-RT/tie/EVOH/tie/PE-RT. The EVOH layer addition ratio is 4–6% of total wall thickness; for a pipe wall of 3.0–4.0 mm, the EVOH layer is 0.10–0.20 mm and is positioned closer to the outer surface to reduce inner-surface damage during fitting installation. The governing compliance condition is DIN 4726:2008, which requires oxygen permeability not exceeding 0.1 g/(m³·d) at 40°C for plastic piping in warm water heating systems, with oxygen diffusion measured under ISO 17455:2005. In the extrusion process, PE-RT skins are processed from a 33:1 L/D single-screw extruder at 220–250°C, while the EVOH layer is processed from a 24:1–30:1 L/D barrier screw at 195–215°C; the five-layer die is maintained at 210–230°C. EW-3201 must be pre-dried at 80°C for 4 h to residual moisture below 0.3% using desiccant air at -40°C dew point. Post-extrusion crosslinking of the PE-RT layers, if silane-crosslinked, occurs at 80–95°C in a water bath or steam chamber; the EVOH layer must not be subjected to external peroxide crosslinking because radical attack can degrade the vinyl alcohol segments and produce gel defects. Inline ultrasonic thickness scanning at 360° around the pipe circumference is used to verify EVOH layer continuity above 0.08 mm, because local thinning below this threshold creates oxygen ingress paths that invalidate the DIN 4726 requirement. The terminal products are oxygen barrier underfloor heating pipes and radiator connection pipes; published field data for EW-3201 in this specific five-layer PE-RT configuration is limited, so supplier monolayer data under ISO 14663-2 should be reviewed before extrusion trials.

A 500 mL extrusion blow-molded pharmaceutical bottle with a 5-layer HDPE/tie/EVOH/tie/HDPE wall structure uses EVOH EW-3201 at 2–5 wt% of total bottle mass, equivalent to an EVOH layer thickness of 0.05–0.15 mm in a wall of 0.6–1.0 mm. The EVOH barrier reduces oxygen ingress into oxygen-sensitive pediatric syrups, electrolyte solutions, and desiccant-free effervescent tablet packs, where the packaging oxygen transfer requirement is verified according to ASTM F1307 at 23°C and 40% RH, with acceptance often below 0.1 cm³/(package·day·atm) for the finished bottle. The pharmaceutical packaging regulatory package includes USP <661.1> for plastic components and USP <661.2> for the finished packaging system, supported by FDA 21 CFR 177.1360 and Regulation (EU) No 10/2011 Annex I; extractables profiling is performed under ICH Q3C solvent limits for packaging leachables where required. In production, the five-layer coextrusion blow-molding head is operated with HDPE melt temperature at 210–230°C, tie layer at 190–210°C, and EVOH EW-3201 at 195–215°C; parison programming is used to distribute the EVOH layer around the pinch-off and shoulder regions. Pre-drying is performed at 80°C for 4–6 h to residual moisture below 0.2% because pharmaceutical packaging lines often run lower moisture tolerance to avoid visible splay and gel streaks. Blow mold temperature is maintained at 8–15°C, and cycle time for a 500 mL bottle is typically 12–18 s, depending on wall thickness and line automation. A critical operational limitation is that steam autoclaving at 121°C temporarily saturates the EVOH layer and raises oxygen transmission until the bottle is dried at 23°C and 50% RH for at least 48 h; if immediate post-autoclave barrier is required, the structure should be replaced with aluminium foil laminate or glass. Terminal finished products include barrier bottles for oxygen-sensitive liquid pharmaceuticals and desiccant-free closures where EVOH EW-3201 allows omission of silica gel insert packages.

Retort pouch interlayer adhesion and post-sterilization oxygen recovery

In retort pouches and medical device sterile barrier packaging, EVOH EW-3201 is used as the oxygen barrier core in PET/EVOH/PP or BOPA/EVOH/CPP laminate structures, with the EVOH layer representing 5–12% of total film thickness and typically measuring 3–7 µm within a 50–80 µm laminate. The regulatory basis for food retort pouches includes FDA 21 CFR 177.1390 for laminated food contact structures and Regulation (EU) No 10/2011 Annex I; medical device sterile barrier packages follow ISO 11607-1:2019, with oxygen permeation tested per ASTM F1927 and seal strength per ASTM F88. The downstream production process uses either cast coextrusion with adhesive tie layers or dry-bond lamination with aliphatic polyurethane adhesives applied at 2–4 g/m² coat weight; the EVOH film or extruded layer is pre-dried at 80°C for 4 h to residual moisture below 0.3%. When the pouch is retorted at 121°C for 30 min under 0.18 MPa overpressure, the polypropylene inner layer must shield the EVOH core from full steam saturation; immediately after retort, oxygen transmission rises due to moisture uptake, then recovers toward dry values after 48 h at 23°C and 50% RH, measured per ASTM F1927. Interlayer adhesion is verified by ASTM F904 with peel strength above 2.5 N/15 mm after retort; failure at the EVOH-to-tie interface due to hydrolysis of unstabilized adhesive is a known production rejection mode. Terminal finished products include retortable MRE pouches, pet food pouches, and sterile barrier pouches for disposable medical devices, where the EVOH core provides oxygen exclusion without the thickness or cost of aluminium foil.

At the bale edge of an oxygen-barrier silage film, the EVOH EW-3201 core layer is most vulnerable to oxygen ingress through folds, puncture damage, and weathered tie-layer interfaces, so the film is designed as a 5-layer blown structure with polyolefin skins, tie layers, and an EVOH core representing 3–6% of total film thickness or 5–12 µm within a 150–250 µm film. The governing standard is EN 13207:2018, which specifies requirements for thermoplastic silage films; food contact considerations for silage films used around feedstocks are assessed under Regulation (EU) No 10/2011, although silage films are not generally treated as food contact materials. The EVOH layer is processed on a blown-film line with blow-up ratio 2.5:1–3.0:1, frost-line height 500–900 mm, and EVOH melt temperature 190–210°C; pre-drying at 80°C for 4 h to moisture below 0.3% is mandatory to prevent hydrolysis gel at the die lip. The finished film is surface-treated to 38–42 dyn/cm for printing or sealing, and the EVOH layer is checked by a 360° online thickness gauge to prevent thin bands that would allow aerobic spoilage at the oxygen ingress sites. Published field data for EW-3201 in silage applications is limited, so the converter usually verifies oxygen transmission per ASTM D3985 at 23°C and 50% RH on film samples taken from the bale edge and from the unweathered body, rather than relying on supplier monolayer data alone. Terminal finished products include oxygen-barrier bale wrap, silage clamp sheets, and aerobically stable feed preservation films where the EVOH layer slows yeast and mold growth at the feed surface.