The INEOS Eltex mLLDPE Metallocene series is a single-site catalyzed linear low-density polyethylene family specified over a melt mass-flow rate range of 1.2 g/10 min to 20 g/10 min when measured at 190 °C under a 2.16 kg load according to ISO 1133-1:2022 or ASTM D1238-23. The series falls within the linear low-density density envelope, with commercial grades typically supplied at nominal densities from 0.912 g/cm³ to 0.940 g/cm³; the exact density, comonomer identity, additive package, and shear-viscosity behavior are grade-specific and listed in the current INEOS technical datasheet. Applications include high-toughness blown film, thin-gauge cast film, extrusion coating, coextruded sealant layers, and selected injection molded closures and technical components.

The primary functional difference against conventional Ziegler-Natta LLDPE is not the melt flow rate range but the uniformity of molecular and comonomer structure. Single-site catalysis narrows the molecular weight distribution and creates a more even short-chain branch distribution along the polymer backbone. The result is a different processing and property profile in film: lower seal-initiation temperature under ASTM F2029, higher dart impact under ASTM D1709 at equivalent gauge, improved optical clarity under ASTM D1003, and lower hexane-extractable content. The trade-off is less shear thinning at high shear, because a narrow-MWD polymer develops lower melt-flow acceleration under pressure than a broad-MWD Ziegler-Natta LLDPE.

Compared with high-pressure low-density polyethylene, the series has essentially linear main chains without the long-chain branching that gives LDPE its high melt strength and strong shear thinning. A converter moving from LDPE to Eltex mLLDPE should therefore expect higher die pressure or torque at equivalent melt flow rate, wider neck-in, and a more sensitive bubble in single-layer blown film unless melt temperature and die gap are retuned.

What Material Architecture Distinguishes the Eltex mLLDPE Series from Ziegler-Natta LLDPE?

High-temperature gel permeation chromatography according to ISO 16014-4 shows that metallocene LLDPE grades in this class typically have a molecular weight distribution ratio between 2.0 and 3.0. Ziegler-Natta LLDPE of comparable melt flow rate commonly falls between 3.5 and 5.0. The narrow distribution reduces the fraction of very low molecular weight chains that contribute to extractables and organoleptic transfer, and the fraction of very high molecular weight chains that can form gels or raise haze. The even comonomer distribution also gives a narrower melting range as measured by differential scanning calorimetry under ISO 11357-3, so the heat-seal curve is sharper and the film can be sealed at lower temperatures without losing hot-tack strength.

The rheological boundary is critical in extrusion. At shear rates above 1000 s⁻¹ measured by capillary rheometry under ISO 11443, an equal-MFR metallocene grade may retain higher viscosity than a Ziegler-Natta LLDPE, which increases screw torque and melt temperature. In blown film this can be managed with wider die gaps of 1.8 mm to 2.5 mm, lower compression ratios, and, when surface melt fracture appears, a fluoropolymer processing aid at 300 ppm to 800 ppm.

On a production-scale blown-film line using a 65 mm grooved-barrier screw with 34:1 L/D, a 160 mm spiral-mandrel die, and a dual-lip air ring, a 1.2 g/10 min grade in the series is typically processed at 195 °C to 210 °C to keep the bubble stable under internal bubble cooling at output rates above 150 kg/h. Lower melt temperatures reduce oxidation and maintain the low seal-initiation plateau, but they also increase frost-line height and make the bubble more prone to oscillation at the collapsing frame. A rise of 5 °C to 10 °C can restore stability at the cost of reduced transverse-direction tear and increased blocking tendency. Melt temperature, die pressure, and frost-line position must be recorded as lot-to-lot variables because the MFR band alone does not capture the viscosity differences that affect bubble geometry.

Blown Film Collapse, Frost Line Height, and Property Balance

A high-stalk bubble with frost-line height set at 6 to 10 die diameters is commonly used for low-MFR metallocene LLDPE to improve machine-direction orientation and reduce film blocking. On a 200 mm die running a 1.2 g/10 min grade, a lower frost line improves bubble stability but reduces machine-direction tear strength because the film enters the nip before the oriented skin layer is fully frozen. The collapse frame angle and gusset geometry control crease formation in heavy-gauge sacks and agricultural films; tubular film should be cooled below 35 °C before the nip to prevent blocking. Dart impact, Elmendorf tear, and tensile balance must be measured on the final film under ISO 7765-1, ISO 6383-2, and ISO 527-3 at a fixed gauge and blow-up ratio because property rankings change with test direction and processing history.

In multilayer structures, an MFR 1.2 g/10 min to 2.0 g/10 min grade may serve as the abuse-resistance core, while an MFR 4 g/10 min grade may be used in the skin for low-temperature heat sealing. The change in MFR between layers must be managed by separate extruder sizes and screw speeds; mismatched layer viscosity can cause interfacial instability and irregular layer distribution. Skin layers above 10 µm of the low-MFR grade can also increase blocking and reduce gas-flush efficiency in packaging lines.

Heat-seal behavior is assessed by sealing samples at controlled temperature and pressure, then measuring peel force under ASTM F2029 or ASTM F88. Seal-initiation temperature is not fixed by MFR alone; it depends on density, comonomer type, and additive package. Lower density grades seal at lower temperatures, but they have lower stiffness and higher blocking tendency. A converter must not select a grade solely on the basis of a low seal-initiation target without confirming hot-tack values on the packaging machine, because hot-tack failure at the filling station is a line fault that cannot be detected by hermetic seal tests alone.

When an Eltex mLLDPE Grade with MFR Above 4 Is Run on a Coextrusion Line

In a coextruded sealant web, grades with MFR between 4 g/10 min and 8 g/10 min are used to reduce melt temperature and improve layer bonding with EVA, ionomer, or tie-resin layers. The extruder profile is normally set from 170 °C in the feed zone to 220 °C at the die. Melt temperature should not remain above 240 °C for extended residence because thermo-oxidative chain scission produces gels, reduces seal strength, and shifts sensory performance. Die gaps for the metallocene layer are typically 1.8 mm to 2.5 mm; narrower gaps increase die-lip shear stress and may initiate sharkskin or gross melt fracture.

For cast-coextrusion coating with MFR above 8 g/10 min, the lower molecular weight reduces melt viscosity and may lower the heat-seal initiation temperature, but it also reduces melt strength and load-bearing capacity. The sealant layer is therefore coextruded with a supporting layer rather than used as a monolayer coating at high gauge. Neck-in is wider than that of LDPE because the metallocene polymer lacks long-chain branching; air-gap length and die-to-substrate draw must be set by trial on the specific coating line. Typical melt temperatures are 260 °C to 300 °C, with air gaps of 100 mm to 200 mm for polyolefin coating, but line-speed limits for a specific grade must be established on the converter’s own die geometry.

Published run-to-run data for every grade across all coextrusion die profiles is limited; neck-in, draw-down, and substrate adhesion should be confirmed by measurement on the production line rather than inferred from MFR alone.

When cast-film converters run grades with MFR 8 g/10 min to 20 g/10 min, the line typically uses a 90 mm barrier-screw single-screw extruder with a flat die set at 240 °C to 260 °C. Higher melt flow reduces extrusion pressure and permits higher line speed, but it lowers molecular weight and may reduce puncture resistance and gauge uniformity. Chill-roll temperature between 15 °C and 35 °C controls crystallinity, haze, and blocking; a low roll temperature quenches the web rapidly but can cause surface condensation when the surrounding air dew point is above 10 °C. In stretch-film constructions, the mLLDPE is usually blended or coextruded with a more branched polyethylene to maintain load retention while minimizing transverse-direction tear propagation.

In injection molding of mid-range MFR 4 g/10 min to 20 g/10 min grades, attention must be given to flow path, gate size, and mold temperature. At the same MFR, the narrow molecular weight distribution of a metallocene LLDPE can increase pressure loss by 10% to 20% compared with a broad-MWD Ziegler-Natta LLDPE in a long flow path, even though the ISO 1133-1:2022 value appears equivalent. Mold temperatures of 15 °C to 40 °C are used for thin-wall packaging, but the gate must be sized to avoid flow-induced stress cracking at the injection point. Published data on spiral-flow behavior for this specific series across all tooling geometries is limited; pressure-drop curves should be established through tool trials before production.

Standards and Compliance Codes Must Be Verified Grade by Grade

Food-contact status for a particular Eltex mLLDPE grade must be confirmed against the relevant national or regional regulation, including EU 10/2011 and FDA 21 CFR 177.1520 for olefin polymers. General series-level statements are not sufficient because additive package, comonomer, and catalyst residues differ between grades. REACH registration in the EU and RoHS 2011/65/EU restrictions in electrical and electronic equipment also require grade-level confirmation. The table below lists the standard test methods used to characterise the series; it does not replace the current grade datasheet or certificate of analysis.

Operational boundaries follow the general limits of linear low-density polyethylene. Melt temperature should not remain above 240 °C for long residence times unless inert gas blanketing is used; oxygen exposure at high temperature increases oxidized gel formation, off-odor, and reduced seal-strength retention. Grades above 8 g/10 min have lower molecular weight and are more sensitive to thermal degradation and thermo-oxidative chain scission. The polymer does not require drying under normal indoor conditions below 60% RH, but surface condensation on pellets stored in cold rooms must be removed by dry-air conveying to avoid feed-bridge and moisture-related film defects. High-shear, high-pressure dies that force operation beyond the critical shear stress of the selected grade are incompatible unless die-lip geometry is changed or a processing aid is used. Peroxide-based modifications or oxidative additives should not be introduced without evaluating free-radical melt reaction and the resulting shift in rheology.