EVOH EVAL E171B

For coextruded PP/EVOH/PP sheet intended for high-speed thermoformed ready-meal trays, EVAL E171B is introduced as the central oxygen barrier layer at 30–50 µm gauge, with two maleic anhydride-grafted PP adhesive layers at 20–30 µm and homopolymer PP skins at 350–500 µm per side. The barrier resin is pre-dried in a desiccant dryer at 90°C for 4–6 h until the moisture content is below 0.05 wt%; higher residual moisture produces bubble-like voids in the core and a measurable loss of oxygen barrier due to microvoids rather than polymer plasticization alone. A 32:1 L/D single-screw extruder with a 3:1 compression ratio and a 60/120/60 mesh screen pack delivers the core melt to a multi-manifold feedblock; the EVOH melt temperature is kept between 205°C and 225°C, while the PP melts are processed at 230–250°C and the adhesive at 220°C. Residence time above 220°C is limited to 20 min; longer intervals generate visible gel particles and a pressure differential increase across the screen pack. Sheet regrind is added to the PP and adhesive layers up to 20 wt%, but never to the EVOH core, because cross-contamination raises haze and reduces interlayer peel force. Thermoforming is conducted at sheet surface temperatures of 150–165°C; the higher 44 mol% ethylene content of E171B lowers corner-cracking tendency relative to 32 mol% EVOH grades at draw ratios above 2.0. Oxygen transmission through formed trays is measured by ASTM D3985 at 23°C and 50% RH; the measured permeance must be interpreted in relation to the actual sidewall gauge distribution after plug-assisted forming, which can thin the barrier core by 30–40% in tray corners.

Why Does 44 mol% Ethylene in EVAL E171B Shift Layer Distribution in Seven-Layer MAP Film Dies?

On seven-layer blown-film lines producing transparent lidding and vacuum skin packaging for modified-atmosphere poultry and red meat, EVAL E171B is placed as a 4–6 µm core between two maleated polyolefin tie layers of 3–5 µm, with LLDPE or mLLDPE skins making up the remaining thickness. The grade’s melt flow rate of 1.7 g/10 min at 190°C under 2.16 kg load, determined by ISO 1133-1:2022, is intentionally selected against low-viscosity LLDPE skin resins to stabilise the core layer in a low-gauge annular die; a significant mismatch in elongational viscosity across the die gap would otherwise drive layer encapsulation defects at the weld line of the spiral mandrel. Die temperatures are set at 215–220°C for the EVOH core, while the polyolefin layers run at 200–230°C; the air ring must keep the film frost line within 300–500 mm of the die exit to limit moisture uptake by the EVOH surface before full encapsulation. A documented processing bottleneck is the formation of gel streaks at the die lip after 12–18 h of continuous operation, which is managed by purging the barrier extruder with LDPE for 15 min at the end of each run and by using screen packs no finer than 80 mesh on the EVOH stream. Oxygen permeation is evaluated by ASTM F1927 under 23°C and 0% RH, but the packaging specification must also include a 75% RH measurement because EVOH barrier capacity declines sharply as absorbed moisture disrupts hydrogen bonding in the amorphous region. The film produced from E171B has a measured oxygen transmission below the specification required for 5–10 day red meat MAP at retail display, provided the core remains continuous at all points; any neck-in or die-lip encrustation that reduces core coverage below 80% of the film width causes the pack to fail shelf-life testing.

In extrusion blow moulding of 500–1000 mL multilayer barrier bottles for sauces, liquid fruit pulps, and cosmetic refill packs, EVAL E171B is processed as the centre layer in a five-layer HDPE/tie/EVOH/tie/HDPE wall structure, with the barrier accounting for 4–6% of the total wall thickness. The EVOH layer is pre-dried to below 0.05 wt% moisture and delivered at a melt temperature of 195–215°C, while HDPE skins are run at 200–230°C and the maleated tie layer at 210°C. Continuous rotary wheel machines with multi-parison die heads are preferred over shuttle-type equipment when output above 6,000 bottles/h is required, because the lower melt flow of E171B resists parison sagging during the brief transfer interval to the mould. The wall-distribution limit is controlled by adjusting the die gap and parison programming; the EVOH core is thinned at pinch-off and neck flash areas, and insufficient adhesive layer flow at those regions produces localised delamination that is detectable as a clear blister in the wall. Oxygen transmission of the finished container is tested by ASTM F1307 at 23°C and 50% RH; product-specific limit values for oxygen-sensitive sauces commonly fall between 0.005 and 0.02 cm³/package·day, depending on fill volume and headspace oxygen tolerance. The internal HDPE layer isolates E171B from aqueous product contact, so the common incompatibility with high-pH or aqueous amine-containing fillings is avoided. Regulatory compliance for food-contact use is established under EU 10/2011 with overall migration testing in the prescribed food simulants; the processor must verify that residual EVOH trim is not re-introduced into the food-contact skin layer because it raises the migration of low-molecular-weight species above the 10 mg/dm² limit.

When Retort Pouch Laminates Remove Aluminium Foil, Post-Steam Barrier Recovery Determines Release

Transparent retort pouches for ready-to-eat rice, soups, and wet pet food replace aluminium foil with an EVAL E171B core when microwaveability or metal-detector compatibility is required. A typical lamination sequence is 12 µm polyamide or polyester outer film, 12–15 µm EVAL E171B core, and 70–100 µm cast polypropylene inner sealant, bonded through adhesive lamination or coextrusion with maleated polyolefin tie resins. The retort cycle at 121°C for 30 min forces condensate through the outer laminate and plasticises the EVOH layer; oxygen transmission measured immediately post-retort by ASTM F1927 can be 5–10 times the dry-condition value, but a measurable fraction of the original barrier is recovered after the pouch is held in a dry atmosphere at 25°C for 7–14 days as water desorbs from the EVOH matrix. The 44 mol% ethylene content of E171B provides better retort crack resistance than 32 mol% grades in the creased side-gusset area, but the intrinsic dry-state oxygen barrier is correspondingly lower, so converted structures use a thicker EVOH layer than a foil replacement based on 32 mol% resin would require. Adhesion between the EVOH core and the adjacent ply is evaluated by ASTM F904 after the steam cycle; a peel strength below the pre-retort value by more than 30% indicates moisture attack at the tie interface, not necessarily EVOH layer failure. Delamination is initiated when the tie resin contains insufficient maleic anhydride functionality to bond through the water layer that accumulates at the interface during retort. Published data for this specific retort pouch configuration is limited, so each converter must establish its own post-retort oxygen transmission limit derived from product shelf-life and sensory acceptance.

Coextruded barrier bottles for agricultural chemical concentrates such as emulsifiable concentrates and oil dispersions use EVAL E171B as a 3–5% core layer in a six-layer wall of HDPE/tie/EVOH/tie/regrind/HDPE. The primary role of E171B in this structure is not hydrocarbon resistance but oxygen transmission control during 18–24 month warehouse storage, because the surrounding HDPE layers already limit solvent permeation for nonpolar carriers. Solvent permeation through the container wall is tested according to ASTM F739 at 49°C and 50% RH for the filled product package; the EVOH core must remain continuous at top, bottom, and chime regions where parison pinch-off can reduce core coverage to 0 µm if the die head is not balanced. The grade’s higher ethylene content lowers the brittle failure tendency at low ambient storage temperatures, but it also means that oxygen barrier in the EVOH layer will be degraded by moisture absorbed from the product or the environment; the internal HDPE layer is, therefore, not treated as optional. The processing window for E171B is set at 195–215°C; excursions above 225°C during accumulator blow moulding idle cycles produce gel contamination in the next parison. At shutdown, the barrier extruder is purged with LDPE until the melt pressure falls below 50 bar, after which the head is depressurised and the die face cleaned to remove oxidised EVOH residue.

Multilayer Tube Laminates for Cosmetic Creams: A 250 µm Cast Coextrusion Sequence and Heat-Seal Compatibility

Plastic barrier tubes for cosmetic creams, hair colourants, and fluoride-containing toothpaste paste are extruded as a flat cast sheet of PE/tie/EVOH/tie/PE in total thickness around 250–300 µm, with the E171B core set at 10–15 µm. The barrier layer is added to prevent oxygen permeation into the tube shoulder and sleeve; the measured oxygen transmission of the laminate by ASTM D3985 at 23°C and 0% RH is specified before tube forming because the subsequent longitudinal weld and shoulder sealing can introduce pinholes at the PE/EVOH interface if the EVOH layer is too viscous or too brittle. The cast coextrusion process runs E171B at 210–220°C with the PE skins at 220–240°C; the die gap is set to 0.6–0.8 mm, and the vacuum box cools the sheet at 15–20°C to ensure that the EVOH core crystallises rapidly enough to resist blocking on the take-off rolls. Heat sealing of the tube sleeve is performed at 170–190°C sealing bar temperature with 1.5–2.0 s dwell; the EVOH core must be fully encapsulated by the PE/tie border to prevent seal contamination. The finished tube is tested for oxygen transmission after side-seam welding by ASTM F1927, and for adhesion at the EVOH/tie interface according to ASTM D1876; seal integrity is validated by vacuum leak testing using ASTM D3078. E171B is preferred over lower-ethylene EVOH grades in larger-diameter tubes because the 44 mol% ethylene comonomer reduces flex-cracking in the sleeve when squeezed repeatedly during consumer use.