Dow ATTANE mLLDPE NG4701 is a single-site catalysed ethylene-1-octene copolymer produced in a solution polymerisation train. The nominal density is 0.904 g/cm³ when measured to ASTM D792-20, and the nominal melt index is 0.8 g/10 min when measured to ISO 1133-1:2022 using a 190°C/2.16 kg load. It is an ultra-low-density metallocene linear-low-density polyethylene, not a high-pressure LDPE; the 1-octene comonomer creates short-chain branches that are distributed more uniformly by the single-site catalyst than by conventional Ziegler-Natta systems. This microstructure reduces crystalline layer thickness and lowers the melting endotherm relative to a 0.918 g/cm³ ZN-LLDPE when analysed by differential scanning calorimetry according to ASTM D3418-15. The resin is intended for blown-film structures, sealant webs, and toughened monolayer packaging, but its processability is not interchangeable with high-pressure LDPE because melt strength is lower and shear viscosity is higher at equivalent melt index. The melt-flow ratio I10/I2, determined according to ISO 1133-1:2022 with 10 kg and 2.16 kg loads at 190°C, is lower than that of a typical ZN-LLDPE, indicating a narrower molecular-weight distribution.

In pellet form, NG4701 is supplied as nominal 3–4 mm cylindrical or lenticular granules depending on pelletising equipment. Bulk density measured by ASTM D1895-17 is typically 0.48–0.56 g/cm³, which affects silo design and conveying. The moisture content of polyethylene is generally low; however, condensation on cold surfaces at relative humidity above 60% can introduce surface moisture and should be managed with a dry-air hopper sweep rather than a hot-air dryer. Because the resin is non-polar, it is not compatible with high-moisture polar materials; this matters in reclaim streams where EVOH or polyamide dust must be kept below specified levels to avoid interfacial gels in coextrusion.

The Solution Polymerisation Route Narrows Short-Chain Branching Variability

Solution polymerisation permits a higher comonomer conversion uniformity than gas-phase or slurry polymerisations used for conventional Ziegler-Natta LLDPE. In NG4701, the metallocene catalyst and 1-octene comonomer create short-chain branches that are more uniformly distributed across the molecular-weight distribution. The effect is measurable in the solid state: density test values with ASTM D792-20 are lower than a 0.918 g/cm³ LLDPE at equivalent comonomer content, while differential scanning calorimetry according to ASTM D3418-15 produces a broader, lower-temperature melting endotherm with a reduced high-melting shoulder. The structural uniformity lowers the weight fraction of highly crystalline molecular species that scatter light; therefore 25 µm blown film made from NG4701 can show lower haze per ASTM D1003-13 and higher gloss per ASTM D2457-13 than a Ziegler-Natta LLDPE at equivalent gauge. The same architecture also reduces the extractable fraction; film extraction tests conducted under FDA 21 CFR 177.1520 or EU Regulation (EU) No 10/2011 conditions generally show a lower mass loss than conventional LLDPE of comparable density, although absolute values depend on conversion conditions, film thickness, and additive masterbatch. The solution route also yields lower inorganic catalyst residues than some supported Ziegler-Natta gas-phase routes, which reduces the risk of seal-bar corrosion and improves organoleptic performance in food packaging.

What Distinguishes NG4701 from Conventional Butene- and Hexene-Based LLDPE Resins?

The differences are most evident in film property balance. A conventional butene ZN-LLDPE at 0.918 g/cm³ typically provides adequate stiffness but lower dart impact resistance because its heterogeneous short-chain branching creates local high-crystallinity regions that initiate failure. NG4701 at 0.904 g/cm³ shifts failure from brittle puncture to ductile deformation in 25 µm film; dart impact resistance measured by ASTM D1709-16a is therefore higher at equal gauge, although the exact F50 value depends on die gap, frost-line height, and film cooling rate. Elmendorf tear propagation measured by ASTM D1922-09 is more balanced between machine and transverse directions; this is a practical difference in heavy-duty sacks, where machine-direction tear resistance of conventional LLDPE is frequently the failure mode. Seal initiation temperature is lower in the mLLDPE when seal strength is tested by ASTM F88-15; the lower density allows a 4.4 N/25 mm threshold to be reached at lower platen temperature, but the offset is not fixed because jaw geometry, dwell time, and sealing pressure control the measured value. Processing-side differences include narrower bubble-stability limits on film lines, higher extruder backpressure, and greater sensitivity to melt fracture on shallow dies.

On a 50 mm 28:1 L/D single-screw blown-film line with a 100 mm die and 2.0 mm die gap, the stable operating envelope for 40 µm NG4701 film is commonly a blow-up ratio of 2.0–2.5 and a frost-line height of 3–5 die diameters. When blow-up ratio is raised above 2.8 without internal bubble cooling, the low melt strength of the resin produces bubble flutter and gauge variation; frost-line displacement of ±3 cm has been observed to create 10–15% thickness bands across the layflat. A dual-lip air ring with fine lip adjustment is recommended. Barrel zone settings of 180°C, 190°C, 200°C, 210°C with adapter and die at 215°C are representative starting values; melt temperature measured at the die with an immersion thermocouple should be held between 193°C and 221°C to balance melt fracture and oxidative gel formation. At melt temperatures below 185°C, the viscosity curve steepens and die-line melt fracture appears as regularly spaced surface roughness; at temperatures above 240°C, hold-up zones in unheated adapters or transfer pipes can generate oxidised gel defects.

Haze values below 5% and gloss above 70% at 25 µm are representative for NG4701 when extruded at 200°C with a 2.0 mm die gap and a 2.2:1 blow-up ratio, but these values are not guaranteed; they shift with cooling air temperature and frost-line height. The same processing conditions affect dart impact; a low frost-line height increases orientation and can reduce tear in the machine direction. Consequently, film properties are not determined by resin selection alone but by the interaction between cooling rate, haul-off speed, and die gap. For moisture barrier, the lower density raises water vapour transmission rate relative to 0.918 g/cm³ polyethylene when measured by ASTM F1249-13; therefore the resin is more often placed in the sealant layer than in the bulk barrier layer.

When High-Speed Form-Fill-Seal Lines Require Low Seal Initiation and Elevated Hot-Tack Strength

Sealant webs of NG4701 are used in multilayer coextrusions with oriented polyester, biaxially oriented polypropylene, or aluminium foil as the structural layer. The lower density reduces the heat required to fuse the seal interface; ASTM F88-15 seal-strength curves on a 25 µm sealant layer show a leftward shift of the sealing curve relative to a 0.918 g/cm³ ZN-LLDPE, although the exact temperature offset must be determined on the target machine because seal-bar profile, jaw pressure, and dwell time dominate the result. Hot-tack strength measured by ASTM F1921-18 is controlled by the balance between rapid crystallisation and seal-interface separation; because crystallinity is reduced, the molten layer remains tacky over a wider platen-temperature window, but the resin’s lower melt strength limits maximum jaw-open speed before web sag becomes visible. Vertical form-fill-seal machines with jaw cycles above 60 packages per minute generally benefit from a blend of 10–15 wt% high-pressure LDPE to restore melt strength, at the cost of a slight increase in seal initiation temperature and a measurable reduction in dart impact resistance per ASTM D1709-16a.

Compared with ethylene-vinyl acetate sealants, NG4701 may have a higher seal-initiation temperature than high-VA grades but lower extractables and a more neutral sensory profile; organoleptic evaluation under ASTM E1879-09 is commonly used to compare odour and taste contributions. The coefficient of friction is adjusted by additive masterbatch; ISO 8295-2004 measurements on film without slip can exceed 0.6, whereas a target range of 0.15–0.25 is common for vertical form-fill-seal machine surfaces.

Blending with high-pressure LDPE also reduces extruder backpressure. On a 65 mm 30:1 L/D barrier-screw extruder, replacing 15 wt% of NG4701 with a 0.923 g/cm³ LDPE lowers melt pressure at constant screw speed by a routinely observed 8–12%, and it widens the bubble-stability window enough to permit blow-up ratios of 2.5–3.0. The same blend reduces dart impact and low-temperature tensile toughness; the trade-off should be evaluated according to ASTM D1709-16a and ASTM D882-18 on the final film gauge. If the line is torque-limited, the extruder backpressure can also be reduced by raising the die temperature within the 210–230°C range, but die-lip cleanliness and melt fracture must be monitored. A fluoropolymer polymer processing aid added at 400–800 ppm can delay melt fracture during high-rate extrusion, but the screw should be purged thoroughly before switching to non-PPA grades because moisture or certain pigment masterbatches can reduce PPA efficacy.

Heavy-Duty Sack and Industrial Liner Performance at Sub-Ambient Temperatures

Industrial sacks and freezer liners require low-temperature puncture resistance rather than stiffness. NG4701 is used in 50–100 µm monolayer and coextruded structures where the end-use temperature approaches -20°C. At these thicknesses, the lower crystalline fraction of the 0.904 g/cm³ resin delays brittle failure; film impact resistance measured by ASTM D1709-16a at 25 µm is retained at sub-ambient conditions more effectively than a 0.918 g/cm³ ZN-LLDPE, although exact differences depend on comonomer type and orientation. Low-temperature tensile elongation measured by ASTM D882-18 is also higher because the ductile-to-brittle transition temperature is suppressed. The processing drawback at high gauge is heat removal: the tackiness of the resin increases blocking tendency, so the film must be cooled below 35°C at the winder and a slip/antiblock masterbatch may be required. In 80 µm sacks, a blow-up ratio of 2.0–2.5 and a die gap of 2.5 mm maintain gauge uniformity; frost-line height is held lower than for LDPE to prevent bubble instability.

The trade-off relative to 0.912 and 0.918 g/cm³ metallocene grades is a lower secant modulus measured by ASTM D882-18 and a lower tensile yield. Applications requiring pallet-load stability or creep resistance may need a higher-density core layer or a HDPE outer layer.

Regulatory status is dependent on the final formulation and layer structure. The base resin is typically evaluated for food-contact use under FDA 21 CFR 177.1520(c) 3.2a and European Commission Regulation (EU) No 10/2011; the plastics regulation requires migration testing on the finished package because base-polymer compliance does not automatically demonstrate compliance of the final multilayer film. REACH registration and RoHS Directive 2011/65/EU apply to the compounded product or article rather than the polymer as placed on the market; a supplier certificate of compliance should be obtained for each production lot. The resin should be stored below 50°C and protected from ultraviolet exposure to prevent oxidative degradation that raises gel count during extrusion.