Dow ELITE mLLDPE 5500G is an ethylene-1-octene copolymer produced in a solution polymerization process using INSITE constrained-geometry catalyst technology. The pelletized resin is characterized by a nominal density of 0.9145 g/cm³ measured under ASTM D792 and a melt mass-flow rate of 0.85 g/10 min at 190 °C under 2.16 kg load according to ASTM D1238. This places the material in the linear-low-density polyethylene range, with a melting peak near 122 °C under ISO 11357-3 and a Vicat softening temperature near 103 °C under ASTM D1525. The grade is specified for blown film extrusion in monolayer and coextruded flexible packaging where seal performance at reduced temperature, dart impact resistance, and optical transmission are required. Published data for injection molding, rotational molding, or high-speed cast film applications of this specific grade are limited.

The octene-derived C6 branch population differentiates 5500G from butene-based LLDPE because a longer branch length disrupts ethylene sequence crystallinity more efficiently at equivalent density. This produces a narrower melting endotherm and a more homogeneous distribution of short-chain branching. Film properties must be evaluated at the intended gauge and cooling rate because stalk height, frost line position, and die gap orientation change the solid-state morphology and therefore shift impact, tear, haze, and seal response. The nominal 0.9145 g/cm³ density should not be used as the sole predictor of seal initiation temperature; the branching distribution exerts the larger influence on low-temperature sealing behavior.

What separates octene mLLDPE from butene LLDPE in coextruded sealant layers?

Under heat-seal testing according to ASTM F2029, an octene mLLDPE sealant layer typically forms measurable seal strength at a lower temperature than a butene LLDPE of similar density. The difference is commonly reported as 8–15 °C in seal initiation temperature for equivalent dwell time and seal bar pressure. For 5500G, comparative evaluations on a three-layer barrier film with a 10 µm sealant layer show seal initiation in the 88–95 °C range at 0.5 s dwell and 0.28 MPa seal bar pressure, whereas a conventional 0.918 g/cm³ butene LLDPE may require 100–110 °C under the same conditions. The lower initiation temperature permits higher form-fill-seal cycle rates or reduced seal bar energy, but the seal strength plateau can occupy a narrower temperature window; seal bar temperature uniformity should be verified by thermal imaging before line speed is increased.

Thermal rheological behavior also differs from high-pressure LDPE. The grade has lower melt strength under bubble deformation, which reduces melt fracture at high shear but limits the maximum blow-up ratio before bubble instability occurs. On an air-cooled blown film line, the melt temperature is normally controlled between 193 °C and 232 °C. Exceeding 243 °C can initiate oxidative degradation in the presence of oxygen, producing gels and off-odour. Below 190 °C, the viscosity increase may elevate extruder motor load beyond the operating envelope of older single-screw lines. The narrow molecular weight distribution also lowers shear sensitivity, so pressure changes from screw speed adjustments may be less pronounced than with a broad-distribution LDPE.

Extrusion processing is usually carried out on a grooved-feed single-screw extruder with a barrier screw and an L/D between 24:1 and 30:1. The recommended die gap is 1.5–2.5 mm, and the blow-up ratio is generally held between 2.0 and 3.0. At a 2.0 blow-up ratio, the film develops stronger machine-direction orientation and higher MD tensile yield but lower MD tear strength. At a 3.0 blow-up ratio, transverse orientation increases and the tear balance shifts toward TD. Frost line height should be set relative to the die exit and not held excessively low, because rapid quenching of the narrow-melting resin produces a highly oriented skin layer that can increase haze and reduce puncture resistance at thin gauge.

The 0.85 g/10 min melt index is lower than the 3.5–8.0 g/10 min range typically preferred for high-speed cast film extrusion. At cast film gauges below 30 µm, draw resonance may occur unless melt temperature is increased or the air knife and chill roll gap are optimized. Published data for cast film use of 5500G are limited; it is not the recommended starting grade for cast film converters.

Specification values conditioned by ASTM and ISO methods

The values in the following table are representative of manufacturer-published typical data for 25 µm blown film at a blow-up ratio of 2.5. They are not batch-specification limits and should be verified with the lot-specific certificate of analysis. Test specimens are conditioned at 23 °C ± 2 °C and 50 % ± 5 % relative humidity unless the individual method requires otherwise.

Mechanical properties vary with extrusion direction. The MD tensile break value is normally higher than the TD value because of machine-direction orientation. Dart impact is sensitive to film thickness; reducing the film from 25 µm to 15 µm without altering the formulation typically lowers the dart impact value by a factor of 1.5–2.0, not linearly with gauge. Therefore, end-use puncture resistance must be established on the actual film thickness and final coextruded structure rather than on monolayer reference data alone.

Food-contact status is generally documented under FDA 21 CFR 177.1520(c) 3.2a for olefin polymers and under EU Regulation 10/2011 for plastic materials and articles intended to come into contact with food. Compliance is structure-dependent; migration testing under EN 1186 or the overall migration conditions specified in Regulation 10/2011 must account for the final laminate, sealant layer thickness, food simulant, and maximum use temperature. For packaging with fatty food contact, simulant D2 is often required. Converters should obtain the supplier’s food-contact statement for the grade because processing aids or additional slip agents can change the migration profile.

When 5500G replaces a 0.918 g/cm³ butene LLDPE in a three-layer coextruded sealant web

The substitution is not drop-in for bubble stability. At constant output, melt pressure in the sealant-layer extruder may increase because the lower density polymer can generate higher melt viscosity at equivalent temperature. The recommended response is to raise sealant extruder zone temperatures within the 193–232 °C window and to verify that the die body maintains thermal uniformity across the die lip. The resulting film usually shows higher dart impact and lower haze, but machine-direction tear strength can decrease relative to the butene reference. If the end product is a heavy-duty bag or a stand-up pouch, the converter should reduce blow-up ratio or adjust film gauge rather than rely on a single-layer substitution.

The comparative values are typical class data for similarly extruded film; they are not batch specifications and will shift with gauge, blow-up ratio, frost line height, and coextruded layer distribution. Transition from a butene LLDPE sealant web should include a designed experiment on the production line, with seal strength measured under ASTM F88, dart impact under ASTM D1709, and haze under ASTM D1003 after a minimum of 2 hours steady-state operation.

Storage and handling boundaries must be observed. If pellet surface condensation occurs after outdoor storage or rapid entry into a warm plant, the resin should be dried in a desiccant hopper at 70 °C for 2 hours before extrusion. Published moisture-sorption data for 5500G are limited, but this practice is standard for linear polyethylene pellets. Regrind levels above 30 % by weight in high-gloss sealant layers can introduce gel-like defects and should be validated by optical scanning of the blown film. The grade should not be dry-blended with amine-based stabilizers unless compatibility-tested, and silicone-based slip masterbatches can alter the coefficient of friction and seal response; any additive change requires revalidation of heat-seal strength under ASTM F88 and haze under ASTM D1003 before production release.