Dow ELITE AT mLLDPE AT 6202 is a metallocene-catalysed ethylene-1-octene copolymer supplied as pellets. The nominal density is 0.920 g/cm³ according to ASTM D792 or ISO 1183-1, and the nominal melt flow rate is 1.0 g/10 min at 190 °C under a 2.16 kg load, as determined by ASTM D1238 or ISO 1133-1. The melt flow rate places the grade in the medium-viscosity film resin class, while the density positions the product in the linear-low-density range. These values are nominal rather than specification limits; lot-to-lot variability is documented on the certificate of analysis.

Because the polymer is produced in a solution process with a single-site catalyst, the short-chain branch distribution is more uniform than that of a conventional Ziegler-Natta LLDPE. The primary comonomer is 1-octene, which produces C6 branches after incorporation. This branch length increases the probability of interlamellar tie-molecule formation at equivalent density, altering the balance between stiffness and impact resistance. The reduced concentration of very high-melting crystallites contributes to a narrower seal initiation temperature profile and a lower soluble fraction than C4-based Ziegler-Natta resins of similar density.

The primary application space includes high-strength industrial liners, heavy-duty shipping sacks, collation shrink film, agricultural stretch film, and lamination film. The grade is also used in coextruded structures where the skin layer requires low seal initiation temperature and the core layer provides stiffness or barrier. The resin can be blended with LDPE to improve bubble stability and with slip or antiblock masterbatches to control film-to-film friction. Typical masterbatch addition levels are 3–5 wt% for a silica antiblock concentrate and 1–2 wt% for a slip concentrate, but exact loadings depend on film thickness and surface treatment.

In monolayer blown film extrusion, the grade is typically processed on grooved-feed or smooth-bore single-screw extruders with L/D 24:1 to 30:1. The melt temperature at the die is maintained between 195 °C and 230 °C. Die gaps of 1.5 mm to 2.5 mm are used; gaps below 1.5 mm can raise die pressure and promote melt fracture. Because the molecular weight distribution of mLLDPE is narrower than that of Ziegler-Natta resins, the shear viscosity in the die region can be higher at the same melt flow rate, and extruder drive load may increase by 10–20% relative to a fractional-MI C4-LLDPE of equivalent density. A dual-lip air ring with chilled air between 10 °C and 15 °C is used to stabilize the bubble when downgauging below 25 µm.

The melt temperature profile over the extruder zones is commonly set from 180 °C at the feed section to 220 °C at the die. A reverse temperature profile is sometimes used in grooved-feed extruders to increase output and reduce shear heating. The output rate is limited by the cooling capacity of the air ring and the bubble stability of the narrow-MWD resin rather than by the extruder screw. On a 90 mm die with a 2.0 mm die gap, a 2.5:1 blow-up ratio, and a 45 mm extruder, output rates above 100 kg/h are attainable only with an optimized dual-lip air ring and chilled air. At higher throughput, bubble instability appears as a low-frequency oscillation in film thickness, measurable by an online capacitance gauge with a repeatability of ±0.5 µm.

Bubble stability in high-stalk configurations is lower than that of long-chain-branched LDPE because the resin lacks long-chain branching. Coextruding with 5–10 wt% LDPE or adding a fluoropolymer processing aid improves bubble stability when line speed exceeds 30 m/min. The frost-line height is typically set at 1.5 to 2.0 die diameters for a 2.5:1 blow-up ratio. A 60/80/100 mesh screen pack has been used on 65 mm extruders to provide homogenization without excessive residence time, but screen packs must be monitored because gels and degraded polymer can raise backpressure.

When Seal Integrity Governs Packaging Line Uptime

Heat-seal performance is one of the primary reasons for selecting AT 6202 over conventional C4-LLDPE in flexible packaging. On a laboratory heat sealer with 0.5 MPa jaw pressure and 0.5 s dwell time, seal strength develops at temperatures near 90 °C, while hot-tack approaches a practical plateau above 110 °C. The exact seal initiation temperature varies with film thickness, dwell time, and jaw design. The lower initiation temperature relative to C4 Ziegler-Natta LLDPE results from the narrow composition distribution and the absence of very high-melting crystallite populations. In high-speed vertical form-fill-seal lines operating above 40 packs/min, the hot-tack window must be wider than 15 °C to prevent seal pop-open during product drop loading. Seal strength measured according to ASTM F88 on a 50 µm blown film can exceed 15 N/25 mm at 130 °C; published data for this specific configuration is limited and should be verified on the target line.

The hot-tack strength measured by ASTM F1921 is more relevant to vertical form-fill-seal operations than final seal strength. Hot-tack failure occurs when the sealing interface is still partially molten under load; the narrow melting distribution of AT 6202 produces a steeper solidification profile, which can narrow the effective operating window if the seal jaw temperature is not controlled within ±5 °C. On machines with proportional-integral-derivative temperature control, the control band is typically maintained at ±2 °C to avoid drifting out of the hot-tack plateau.

In extrusion lamination and extrusion coating, the narrow molecular weight distribution reduces neck-in and improves drawdown relative to high-pressure LDPE. The melt temperature can be set between 280 °C and 310 °C. Residence time at the upper end of this range should be minimized because the antioxidant package is consumed more rapidly above 310 °C, and oxidative gel formation may increase. Adhesion to aluminium foil and oriented polyester requires corona treatment at 42–46 dyn/cm and, where necessary, a tie layer. This grade is not recommended for acid-contact lamination at sustained temperatures above 40 °C without a barrier layer; published data for prolonged acid contact is limited.

What Distinguishes AT 6202 from Conventional Ziegler-Natta LLDPE?

The most significant difference is the catalyst system and the resulting comonomer distribution. Ziegler-Natta C4-LLDPE resins have broad short-chain branching distributions: ethylene sequences with low comonomer incorporation crystallize into thick lamellae, while highly comonomer-rich chains remain as lower-melting fractions. In AT 6202, the single-site catalyst incorporates 1-octene more uniformly; the composition distribution is narrower and the extractable fraction is lower. The consequence is a relatively flat melting endotherm with a peak near 122 °C by ASTM D3418, but fewer very high-melting crystallites. This architecture lowers seal initiation temperature while preserving stiffness and improving puncture and dart impact at the same density. In a 25 µm blown film, the dart impact of AT 6202 is generally higher than that of a C4 Ziegler-Natta LLDPE at the same melt index and density by a factor of 1.5 to 2.0; this is a literature tendency rather than a guaranteed value for all conversion lines.

Compared with conventional mLLDPE grades such as a standard 1.0 MI / 0.918 g/cm³ octene mLLDPE, AT 6202 is positioned at a slightly higher density to increase modulus while retaining film toughness. The “AT” designation refers to the advanced process architecture used to manage molecular weight distribution and comonomer placement; it should not be read as an additive package. The resin is not equivalent to a plastomer. The density of 0.920 g/cm³ places it in the linear-low-density range, while polyolefin plastomers are below 0.910 g/cm³ and are used where elastic recovery and low-temperature sealability dominate.

In cast film, the draw resonance onset is shifted to higher draw ratios relative to conventional LLDPE, but the overall tensile force at break remains lower than that of a high-molecular-weight LDPE. The film optical properties are also different: at 25 µm thickness, the haze of AT 6202 is generally lower than that of a C4 Ziegler-Natta LLDPE at the same thickness because of reduced surface roughness from high-crystallinity fractions; published data for this specific configuration is limited.

Melt Rheology and Extrusion Backpressure Considerations

Capillary rheometry data for this class of resin indicates shear-thinning behaviour with a power-law index of approximately 0.4 to 0.5 in the 100–1000 s⁻¹ shear-rate region. The extrusion head pressure is therefore sensitive to die-gap changes; reducing the die gap from 2.0 mm to 1.5 mm can increase die pressure by more than 20%. On a 65 mm extruder operating at 120 kg/h, a melt pump may be used to isolate die-pressure fluctuations from the screw. Screw designs with barrier flights and Maddock mixers are preferred; simple three-zone screws may deliver melt-temperature non-uniformity exceeding 5 °C, which causes gauge bands. The resin is not hygroscopic; pre-drying is not required at ambient relative humidity below 60%. If condensation has formed on pellet surfaces, a 4 h drying step at 70 °C using a desiccant dryer is applied before processing.

Extensional viscosity data for mLLDPE resins show no strain-hardening plateau, which is why LDPE is added for high-stalk bubble stability and heavy-duty sack structures. The strain-hardening behaviour of LDPE at Hencky strains above 1.0 compensates for the lack of long-chain branching in AT 6202. When LDPE is compounded at 10 wt%, the melt strength measured by a Göttfert Rheotens apparatus increases by approximately 25–40%, while the dart impact may decrease slightly. This compromise is documented in technical literature for mLLDPE/LDPE blends; the exact magnitude depends on the LDPE grade and its melt index.

When moulding or compounding is performed, the melt should not be held above 240 °C for more than 10 min unless oxygen is excluded, because oxidative degradation generates crosslinked gel particles. The resin should not be purge-mixed with polyamide or polycarbonate without a full purge transition; residual incompatible resin can form plate-out on the die lip. In blown film, the die lip deposit rate is influenced by additive masterbatches, particularly those containing high levels of migratory slip agents. The use of a slip masterbatch based on erucamide at 1–2 wt% addition is typical for coefficient of friction control.

The narrow molecular weight distribution also affects injection moulding and compounding operations. The resin has a relatively high viscosity at low shear rates, which may cause short shots in thin-wall injection moulding unless high injection speeds are used. In rotational moulding or compounding, the powder form may be preferred; pellet handling is the standard form for film extrusion. Because the resin is an ethylene-1-octene copolymer, it has a lower brittle temperature than C4-based LLDPE of the same density, but low-temperature impact data should be generated per ASTM D746 or ISO 974 for the specific part geometry.

Regulatory status is application-dependent. Olefinic resins of this class may be evaluated under US FDA 21 CFR 177.1520 for food-contact articles when the finished article meets the specified density and extractives limits. European food-contact compliance is evaluated under EU No 10/2011, with overall migration testing per EN 1186-1. Electrical and electronic applications require screening against EU 2011/65/EU for lead, cadmium, mercury, hexavalent chromium, PBB, and PBDE. REACH SVHC status should be confirmed through the supplier declaration.

On production-scale lines for heavy-duty shipping sacks, the resin has been used in 80–120 µm monolayer and coextruded structures. At 100 µm thickness, the dart impact measured by ASTM D1709A may exceed 1000 g depending on blow-up ratio and frost-line height; field reports from sack filling lines indicate fewer drop failures than with C4 Ziegler-Natta LLDPE of equivalent density. Tear propagation in the transverse direction is a limiting factor when the film is notched by pallet edges; it is controlled by orienting the film and avoiding excessive blow-up ratios above 3.0:1. In a three-layer heavy-duty sack structure, outer skins of AT 6202 at 20 µm each can be combined with an 80 µm HDPE core at a total thickness of 120 µm; the polyethylene layers are miscible in the melt state, but the die body temperature should be held near 210 °C to avoid viscosity mismatch across layers.

The resin has also been used in collation shrink and agricultural silage wrap, where puncture and low-temperature flexibility are required. In silage wrap, UV stabilisation must be added via masterbatch; unpigmented film is not suitable for more than 12 months of outdoor exposure.