Soarnol E3808

Soarnol E3808 is an ethylene vinyl alcohol copolymer containing 38 mol% ethylene and a melt flow rate typically reported at 8.0 g/10 min under ISO 1133-1:2022 at 190 °C and 2.16 kg. In rigid barrier food packaging, the grade is selected for thermoformed polypropylene containers where the oxygen barrier must survive hot-fill or retort-like conditions and where a 29 mol% ethylene EVOH would show insufficient draw uniformity. A five-layer sheet line producing PP/tie/EVOH/tie/PP sheet places E3808 as the central barrier layer at a thickness between 12 µm and 25 µm for ambient-stable food, while outer PP skins contribute mechanical strength and moisture protection. The resin hopper must be dried to a residual moisture content below 300 ppm using a desiccant dryer with a dew point of -40 °C and an air inlet temperature of 80–90 °C for 4–6 h; inadequate drying produces splay, microvoids, and barrier loss in the sheet. The extrusion barrel profile for a 65 mm single-screw extruder with an L/D of 30:1 is normally set from 180 °C at the feed throat to 220–230 °C at the metering zone and die; maintaining melt temperature below 240 °C prevents gel formation from thermal degradation. When thermoformed into trays, sheet temperature is typically held at 150–170 °C based on PP crystallization, and the forming tool is kept at 30–60 °C to reduce sidewall thinning that would compromise the EVOH layer. Oxygen transmission rate for a 20 µm E3808 layer at 23 °C and 0% RH is normally in the range of 0.3–0.6 cm³/(m²·day·atm) when measured by ASTM D3985, but the value increases by a factor of 5–10 at 85% RH; therefore the outer PP skin must remain free of cracking and the package must be tested at the intended storage humidity. For direct food contact, E3808 is used under the conditions of FDA 21 CFR 177.1360 for ethylene-vinyl alcohol copolymers and the finished multilayer article is assessed under EU Regulation (EU) No 10/2011, including overall migration below 10 mg/dm² in the appropriate food simulant. Avoid using the bare EVOH layer as the product contact surface in acidic or high-moisture products because the barrier layer can plasticize and may delaminate if tie-layer adhesion is inadequate.

Barrier uniformity in formed containers cannot be inferred from sheet thickness alone. Sidewalls of thermoformed trays are frequently 30–50% thinner than the base, and the EVOH layer may drop below 8 µm in the corner radius. Quality control requires microtome sectioning of the formed part at the flange, sidewall, and corner at 200× magnification, followed by oxygen transmission testing on samples cut from each region. A forming study with draw ratios from 1.0:1 to 2.5:1 shows that E3808 retains a continuous barrier layer better than lower-ethylene EVOH grades under equal preheating because the higher ethylene content reduces crystallinity and enlarges the forming window. However, the same property lowers the absolute dry oxygen barrier relative to 27 mol% or 29 mol% EVOH, so the barrier layer thickness must be increased by 15–25% when replacing a 29 mol% grade in an existing structure. The tie layer must be a maleated PP with a maleic anhydride content sufficient to produce a peel strength above 3 N/15 mm when tested by ASTM F88/F88M after retorting at 121 °C for 30 min. In retort conditions, the EVOH barrier temporarily loses oxygen resistance as the package absorbs moisture; published data for E3808 in retorted PP/EVOH/PP structures is limited, so barrier recovery must be confirmed by measuring oxygen transmission at 24 h and 72 h after retort.

What Limits Regrind Addition in Six-Layer Fuel Tank Coextrusion?

Six-layer blow moulding for automotive fuel tanks uses an HDPE outer skin, an adhesive tie layer, an E3808 barrier layer, a second tie layer, an HDPE regrind layer, and an HDPE inner layer. The EVOH layer thickness in a passenger car fuel tank is typically 30–80 µm depending on tank surface area and the evaporative emission limit applicable to the market. E3808 offers a balance between hydrocarbon permeation resistance and blow moulding process stability when the parison die head pressure must remain uniform across a 1,000 mm accumulator head. Incoming resin is dried to 300 ppm or lower moisture before the barrier extruder; a separate extruder with a barrier screw having a compression ratio of 2.5:1 to 3.0:1 is preferred to limit shear heating. The melt temperature at the die is held at 210–230 °C for E3808, while HDPE runs at 230–250 °C; the difference in melt viscosities is controlled by selecting an EVOH grade with a melt flow rate close to 8.0 g/10 min, which reduces interfacial instability at the tie layers.

Regrind addition is limited by particle size, moisture, and dispersed EVOH domain deformation. Multilayer scrap generated at the pinch-off and flash zones contains E3808 fragments that do not fully melt into the HDPE matrix; at regrind loading above 40 wt%, elongated EVOH domains can form visible streaks and reduce layer uniformity. A continuous melt filter with a screen pack of 80–100 µm is used on the regrind extruder to remove agglomerated gel particles. Regrind must be dried to 150–300 ppm moisture before feeding; wet scrap introduces steam at the tie layer and causes micro-delamination at the barrier interface. On a shuttle blow moulder with a 15 kg shot weight, the barrier layer thickness is monitored by ultrasonic wall-thickness gauging and maintained within ±5 µm of the target. The layer distribution is adjusted through parison programming; a programmed die gap of 6–12 mm is common, with radial programming steps of 1 mm to compensate for die swell variations. Fuel permeation is measured on the complete tank by a sulphur hexafluoride or hydrocarbon test method, with acceptance criteria determined by EPA 40 CFR Part 86 or CARB LEV III evaporative emission requirements. The EVOH layer is not compatible with direct contact with fuel blends containing aggressive polar oxygenates; published data for E3808 in long-term exposure to high-ethanol fuels is limited, and tank makers should run a 12-week soak trial with the target fuel blend at 40 °C.

For a fuel tank line, start-up and shutdown procedures are critical because EVOH degrades when held at processing temperature without throughput. When the line is idled for more than 15 min, the barrier extruder should be purged with a low-melt-index LDPE until the EVOH is displaced. The shut-down sequence is to run the barrier extruder at 180–200 °C for 5–10 min before stopping, to avoid a temperature spike in the barrel. During start-up, the first 5–10 kg of barrier material from the die is discarded because it may contain crosslinked gel from stagnant flow paths. These operational boundaries reduce the formation of black specks in the EVOH layer, which are a known cause of local permeation failure in fuel tanks.

For emulsifiable concentrates and oil-based agricultural formulations, coextruded HDPE bottles incorporate a thin E3808 layer to block oxygen and reduce solvent vapour loss through the wall. The bottle wall typically consists of an HDPE outer skin at 70–75% of total thickness, two tie layers at 2–3% each, and an E3808 core at 2–4%, giving a barrier layer thickness of 15–30 µm in a 1 L container. The material is processed on a multilayer blow moulder at a melt temperature of 210–225 °C; the die gap is adjusted to avoid parison sag that would expose the barrier layer at the pinch-off seam. Chemical compatibility must be validated under ASTM D543 or a 54 °C storage trial for 14 days; ketones, strong organic acids, and some chlorinated solvents can plasticize EVOH, causing a temporary increase in oxygen transmission and possible delamination at the tie layer. Xylene, trimethylbenzene, and aliphatic hydrocarbons show lower permeation through E3808 than through monolayer HDPE, but published permeation coefficients for specific solvent systems are limited and should be obtained from the resin supplier. For fluorinated HDPE agricultural bottles, E3808 can be used as an inner barrier where fluorination alone is insufficient for oxygen-sensitive actives.

The pinch-off region must be inspected by microtoming at 400× magnification because the EVOH layer can migrate to the outer wall and form a visible line; a proper parison programming control is required to keep the barrier at the centre of the wall. Bottles for UN-certified agricultural chemicals may be tested under the applicable performance requirement for hazardous goods packaging, and the EVOH layer is not a substitute for closure-level permeation control if the cap gasket allows vapour escape. After filling, the bottle should be stored upright for 48 h before a drop test to allow the EVOH layer to stabilise its moisture state. The coextrusion process for E3808 in agricultural bottles requires drying of all hygroscopic components; the HDPE skins are not normally dried, but the tie layer and barrier material must be protected from ambient moisture if the line is located in a high-humidity plant area above 60% RH.

Cosmetic Airless Pump Bottle Barrier Requirements and Oxygen Ingress After Actuation

Cosmetic airless pump packages created from PP/EVOH/PP multilayer preforms protect retinol, ascorbic acid, and unsaturated oils from oxygen ingress through the sidewall. E3808 is incorporated at 20–40 µm in the preform wall, placed closer to the outer PP layer to limit direct contact with a water-rich emulsion. Injection blow moulding requires preform injection temperatures for EVOH of 210–230 °C; the PP skins are processed at 220–240 °C. The tie layer must survive the stretch and thermal history of the blow process without delamination. Oxygen permeation of the empty package is measured by ASTM F1307 at 23 °C and 50% RH; however, total oxygen ingress into the product also depends on the piston seal, closure, and actuator. For an airless system with a silicone valve, the closure may dominate the total oxygen ingress rate. A package wall oxygen transmission of less than 0.001 cm³/(package·day·atm) is of limited value if the piston seal allows many times that ingress.

The inner PP layer must be at least 100 µm thick to prevent rapid moisture transfer from a water-rich cream to the EVOH layer. If the formulation contains more than 30% water, the oxygen barrier of E3808 will decline after filling because water plasticises the EVOH core. In such designs, a 45 °C storage trial for 12 weeks is used to quantify barrier loss. Formulations with ethanol above 20 wt% or pH below 4 can also reduce interlayer adhesion through tie-layer attack; a laminate peel test after 4 weeks at 45 °C should show peel strength above 2.5 N/15 mm. The preform injection gate is a critical location because the EVOH layer can become discontinuous at the gate; injection speed is set to fill the preform in 0.4–0.8 s to limit shear heating at the gate.

In pharmaceutical lidding film for oxygen-sensitive tablets, a polyester outer layer, a printed layer, an E3808 barrier core, and a peelable polyolefin sealant are combined by adhesive lamination. The E3808 layer is commonly 12–20 µm in the laminate. The film surface must be dry before lamination; a residual moisture level below 300 ppm is necessary to avoid bond strength loss at the adhesive interface. The oxygen barrier is measured on the finished lidding by ASTM D3985 at 23 °C and 0% RH. During a moisture vapour transmission test following ASTM F1249, E3808 contributes only limited moisture barrier; a separate aluminium foil or desiccant is required when the drug product has a USP <671> moisture vapour transmission rate limit below 0.5 mg/day per container. Sealing occurs at 160–180 °C for 0.5–1.0 s depending on the sealant; the EVOH layer must not be heat-damaged during sealing. The laminate must pass seal integrity testing per ASTM F88/F88M and dye penetration testing after forming. For blister cavities, E3808 is less common as a direct cavity material because high forming temperatures and deep draws may exceed its thermal stability; transparent barrier blisters usually use PCTFE or cyclic olefin. Published data for E3808 in cold-formed pharma structures is limited, so pilot-scale validation is required.

If the Outer Polyolefin Skin Is Replaced with Post-Consumer Recyclate

When post-consumer recyclate replaces virgin HDPE in the outer skin of industrial solvent drums, volatile contaminants and odour compounds can migrate toward the product unless a continuous barrier layer is present. E3808 is positioned between the recycled outer skin and a virgin HDPE inner layer; the layer thickness is increased to 20–50 µm when PCR content exceeds 30 wt%. In a three-layer blow moulded container, the E3808 core is separated from the PCR by a tie layer and from the product by virgin HDPE to maintain chemical compatibility. During extrusion, the recycled skin melt is filtered through a 80–100 µm mesh pack to remove particulates that could disrupt the thin EVOH layer. Barrier performance for specific solvents is tested at 23 °C with a filled storage trial of 28–90 days rather than by oxygen permeation alone; the EVOH layer may show lower permeation for aliphatic hydrocarbons but may plasticise if the recycled outer layer contains residual oxygenates or unsaturated monomers.

Using PCR does not change the FDA status of E3808 for non-food packaging. However, the finished container must still meet UN packaging requirements for dangerous goods under 49 CFR 178.509 if the container is used for UN-certified liquids. Since E3808 absorbs moisture during warehouse storage, the resin should be dried before processing and the PCR outer layer must be dried separately to 150–300 ppm residual moisture to prevent edge delamination at the pinch-off. The PCR layer can introduce random melt-flow variation; a melt pump is recommended between the extruder and die to hold throughput variation below 1–2%, because a fluctuating outer layer flow disturbs the thin EVOH core and produces wavy barrier distribution.

Underfloor heating circuits with ferrous components require an oxygen diffusion barrier to prevent corrosion, and multilayer PE-RT/EVOH/PE-RT pipe uses E3808 for this barrier function. The EVOH layer is exposed to 40–70 °C in service and must be protected from liquid water on both sides by tie layers and PE-RT skins. A five-layer pipe extrusion line feeds E3808 through a separate extruder at 210–225 °C, while the PE-RT outer layers are processed at 210–240 °C; vacuum calibration at -0.2 bar to -0.6 bar locks the molten composite into the desired outside diameter. The barrier layer thickness is typically 15–30 µm in a 16 mm outside diameter pipe with wall thickness 2.0 mm; the layer must be centred within the pipe wall, and wall thickness variation is controlled to ±0.1 mm.

Oxygen permeation is tested according to DIN 4726:2000, which requires oxygen diffusion below 0.1 g/(m³·day) at 40 °C; the E3808 layer provides this after extrusion, but kinking during installation can crack the EVOH layer if the minimum bend radius is not respected. In service, the inner PE-RT layer prevents water contact with the EVOH; if the inner layer is scored during installation, local swelling of EVOH can occur and reduce oxygen barrier at the damaged spot. The pipe must not be exposed to external steam cleaning above 95 °C for prolonged periods, because the thermal stability of the EVOH layer is lower than that of the PE-RT matrix.