Dow INNATE mLLDPE ST100 is a pelletized ethylene-α-olefin copolymer supplied for blown film and coextrusion structures. The resin carries a nominal density of 0.912 g/cm³ measured by ASTM D792 and a nominal melt index of 1.0 g/10 min measured by ASTM D1238 at 190 °C with 2.16 kg. These values are vendor nominal points and do not replace a lot-specific certificate of analysis. ST100 is manufactured with a constrained geometry catalyst system that introduces controlled sparse long-chain branching; the result is a molecular architecture that differs from conventional linear Ziegler-Natta LLDPE of the same density. The product is intended for monolayer and multilayer blown film in food packaging, e-commerce mailers, heavy-duty shipping sacks, and frozen food laminates. It is not intended for injection molding, blow molding, or rotational molding. The base pellet does not contain slip or antiblock additives; when coefficient-of-friction reductions below 0.20 are required by ASTM D1894, additives must be incorporated by masterbatch at the converter’s validated letdown ratio.

How does ST100 differ from Ziegler-Natta LLDPE in molecular architecture and film failure?

Conventional Ziegler-Natta C4-LLDPE exhibits a broad molecular weight distribution and a heterogeneous intermolecular comonomer distribution. Short chains in that distribution are highly branched and low in density, while longer chains are relatively linear and crystallizable. The resulting amorphous phase has a lower and more variable tie-chain concentration, so high-speed impact failures measured by ASTM D1709 often appear as brittle shatter. ST100 narrows the molecular weight distribution and places long-chain branching on the high-molecular-weight fraction without generating a detectable gel network. Under ASTM D1709, the film tends to fail by ductile puncture rather than brittle shatter; under ASTM D1922, machine-direction and transverse-direction Elmendorf tear values remain balanced because the orientation state is supported by the melt strength of the branched chains. Tensile properties evaluated by ASTM D882 show higher secant modulus at a given density than C4-LLDPE because the controlled composition distribution increases the fraction of load-bearing crystallites in the oriented film. Rheological measurements according to ISO 1133-1:2022 and rotational rheometry indicate a narrower molecular weight distribution and lower shear thinning than conventional LLDPE. The practical consequence is a higher die pressure and higher melt viscosity at low shear, which improves bubble stability but requires an extruder drive capable of higher torque. Unlike C8-LLDPE produced in solution processes, the public datasheet for ST100 does not identify the α-olefin comonomer; published technical statements emphasize catalyst and reactor architecture rather than comonomer length alone as the source of the performance differentiation.

Differential scanning calorimetry performed according to ISO 11357-3 on ST100 generally yields a narrower melting endotherm than Ziegler-Natta LLDPE of equal density. The narrower endotherm means that the seal initiation response is sharper because sealing begins when the crystalline fraction melts; this is not solely a consequence of the 0.912 g/cm³ density but also of uniform crystallite thickness distribution. A converter comparing ST100 with C6- or C8-LLDPE should therefore measure seal strength as a function of seal-bar temperature by ASTM F88 and hot-tack by ASTM F1921, rather than inferring seal performance from density alone.

In monolayer blown film extrusion, a starting melt temperature between 190 °C and 225 °C is used for ST100. A grooved-feed single-screw extruder with an 24:1 to 30:1 L/D ratio and a barrier screw with a Maddock mixing section provides sufficient dispersive mixing for the 1.0 g/10 min melt index. The die gap is normally set between 1.5 mm and 2.5 mm. A blow-up ratio of 2.0:1 to 2.8:1 is a conventional starting point for lay-flat widths below 1.2 m. Frost line height is maintained at 6 to 10 die diameters; a high frost line reduces bubble chatter but may lower machine-direction tear resistance. Because the narrow molecular weight distribution and sparse long-chain branching reduce shear thinning, ST100 develops a higher die pressure than an equal-melt-index Ziegler-Natta LLDPE on the same die. A melt-pressure transducer upstream of the screen pack should be used to establish the extruder-specific baseline. If the drive reaches torque limit before target output, melt temperature may be raised within the 225 °C boundary, but sustained operation above 240 °C increases the risk of oxidative gel formation. No predrying is required for resin stored below 60% relative humidity. When ambient storage exceeds 80% relative humidity, surface condensation should be removed with a hopper dryer at 60–70 °C for 2–4 h to prevent bubble defects. Bubble instability is managed by reducing external cooling air velocity and raising the lower nip height rather than by increasing melt temperature alone.

In coextruded structures, ST100 is placed in the sealant skin layers of polyamide or ethylene vinyl alcohol barrier films. The sparse long-chain branching contributes melt strength that stabilizes the interfacial layer between the skin and tie resin and reduces layer waviness. Layer viscosity ratios should be checked by melt rheology before layer ratio selection, particularly when the adjacent substrate has a melt index below 0.5 g/10 min. Processing on small extruders may require screw-speed reductions compared with C4-LLDPE because the higher low-shear viscosity can increase amperage at equivalent output; the exact reduction is equipment-specific and should be determined during startup.

Seal initiation, hot-tack, and coefficient of friction

The sealant performance of ST100 is evaluated by ASTM F88 seal strength and by ASTM F1921 hot-tack strength. A low seal initiation temperature permits form-fill-seal lines to run with seal-bar dwell times below 0.3 s, but the acceptable seal window must be established on the target packaging machine because seal-bar pressure, film backing, jaw geometry, and contamination shift the onset of sealing. The base resin does not contain slip or antiblock; when a coefficient of friction below 0.20 is required by ASTM D1894, a slip and antiblock masterbatch should be incorporated at the supplier’s recommended letdown ratio. Over-addition of antiblock can raise haze and reduce hot-tack strength. In high-speed vertical form-fill-seal operations, sealant skins of ST100 generally show fewer leakers at equal seal-bar temperature than C4-LLDPE skins of the same density, but this comparison is process-specific and must be confirmed with seal-strength data rather than assumed from resin type. Films with a coefficient of friction above 0.40 may require the addition of slip for automated bag insertion; the amount depends on film gauge, sealant layer thickness, and the metal or plastic surface of the filling line.

Optical performance is characterized by ASTM D1003 haze and ASTM D2457 gloss. The controlled composition distribution reduces spherulitic size and surface roughness, but haze and gloss are strongly affected by cooling rate, frost line height, and the type and amount of antiblock. A monolayer film without antiblock may achieve haze readings below 5%, but the addition of conventional silica antiblock at supplier-recommended levels can raise haze above 8%; converters should evaluate the trade-off between blocking resistance and optical clarity with their own masterbatch supplier.

For frozen food laminates, ST100 is used as the sealant skin in coextruded film structures because the low seal initiation temperature reduces heat exposure to barrier layers and the density of 0.912 g/cm³ preserves flexibility at freezer temperatures. Slow puncture resistance is characterized by ASTM D5748 or by ASTM D3420; these methods are preferred over ASTM D1709 for converting operations because they simulate the puncture of a sharp object through a stretched film. The controlled long-chain branching increases melt strength during coextrusion with polyamide or ethylene vinyl alcohol, reducing layer nonuniformity and improving sealant layer thickness consistency. Downgauging trials from a 60 µm Ziegler-Natta C8-LLDPE sealant to a 45 µm ST100 sealant should use ASTM F88, ASTM D5748, and oxygen transmission rate as gate criteria. Published data for this specific configuration is limited; thickness reduction must be validated on the specific coextrusion line because layer distribution interacts with frost line height, die gap, and interfacial viscosity.

When ST100 is incorporated into heavy-duty shipping sacks

In heavy-duty shipping sacks, the primary film requirements are high-speed drop impact resistance, tear propagation resistance, and stiffness sufficient to prevent sack elongation on automated filling lines. ST100 is processed in monolayer and three-layer films at thicknesses between 80 µm and 150 µm. Dart impact resistance is tested by ASTM D1709 Method A or Method B depending on film thickness; the controlled architecture shifts failure from brittle puncture to ductile deformation at low temperatures, which reduces product loss in cold warehouses. Machine-direction and transverse-direction Elmendorf tear values are determined by ASTM D1922; the balanced orientation produced by the recommended blow-up ratio maintains transverse tear resistance more effectively than C4-LLDPE at the same gauge. The film stiffness is measured by ASTM D882 secant modulus at 1% strain. Because the density of 0.912 g/cm³ is lower than that of a typical C8-LLDPE of 0.918 g/cm³, a direct modulus match may require a slightly thicker film; however, the improved dart and tear reserves permit downgauging relative to C4-LLDPE in many abuse-dominated sacks. Comparative evaluations should include the incumbent film at equal gauge and the candidate film at the proposed lower gauge, with tests performed after conditioning at 23 °C and 50% relative humidity according to ASTM D618. Sack filling lines that use vacuum-assisted insertion may require a minimum film-to-metal coefficient of friction; this must be adjusted with a slip masterbatch because the base resin is not formulated for that purpose.

For direct food contact, the finished package must comply with 21 CFR 177.1520(c) 3.2a for polyolefin polymers, and the relevant European framework is (EU) No 10/2011 with an overall migration limit of 10 mg/dm². The base resin supplier provides regulatory statements for the pellet; these statements do not automatically apply to the converted film because printing, lamination, and adhesive layers introduce additional migrants. REACH reporting under 1907/2006 requires confirmation that the substance of very high concern content is below the 0.1 wt% threshold; this is a manufacturer declaration item and should be requested from the resin supplier. ST100 is not recommended for use in direct flame-retardant applications or in contact with strong oxidizing agents; it is a combustible thermoplastic and should be processed below 240 °C to minimize thermal degradation. These limitations are operational boundaries for the base resin and do not replace packaging validation under the end-use food simulant conditions specified in (EU) No 10/2011 annexes III and V.

During extended storage, pellets should be kept below 40 °C and away from direct sunlight. If the resin is exposed to high ambient humidity and then processed without drying, moisture condensation on pellet surfaces can produce surface defects in the film; the defect is not a resin degradation mechanism but can be mistaken for gel formation. A 100% visual inspection of the film for gel counts and optical defects should be conducted during startup, but no single ASTM method defines all gel types. Converters should maintain their own internal gel-count limits and compare them against the product’s lot-to-lot variability determined from supplier certificates of analysis.