ExxonMobil mLLDPE C4LL 50026RQ is a metallocene-catalyzed linear low density polyethylene produced with butene as the short-chain branching comonomer. The grade carries a nominal melt index of 0.50 g/10 min at 190 °C under a 2.16 kg piston load, measured by ASTM D1238-20 or ISO 1133-1:2022, and a nominal density of 0.926 g/cm³, measured by ASTM D792-20 or ISO 1183-1:2019. The 50 series identifies the melt-index class and the 026 series identifies the density class. The material is supplied as antioxidant-stabilized pellets for blown film extrusion and is typically converted in a gauge range of 25 µm to 150 µm. Primary application fields include heavy-duty shipping sacks, industrial liners, frozen-food packaging, collation shrink film, agricultural overwrap, and protective packaging. The metallocene polymerization route yields a narrower molecular weight distribution and more uniform comonomer incorporation than conventional Ziegler-Natta butene LLDPE of the same melt index and density, which influences both film optics and melt processing behavior. Additive package, regulatory status, and lot-specific values require confirmation against the supplier certificate of analysis and safety data sheet. For food-contact applications, the base olefin polymer may be evaluated under FDA 21 CFR 177.1520, but article compliance depends on additives, conversion aids, and final contact conditions.

What melt processing boundaries apply on 80–90 mm blown-film extruders?

The stable processing envelope is limited at low temperatures by melt fracture and excessive die-entry pressure, and at high temperatures by oxidation-driven gel formation. On a grooved-feed extruder with 90 mm screw diameter and 30:1 L/D, barrel setpoints typically range from 160 °C near the feed section to 200 °C at the metering section, with adapter and die zones held between 200 °C and 220 °C. A barrier screw with a Maddock mixing section and a spiral mandrel die of 250 mm to 350 mm diameter is normally specified; the die gap should be maintained between 1.8 mm and 2.4 mm. The blow-up ratio is held between 2.0:1 and 2.5:1, with frost line height from 650 mm to 900 mm above the die face for film in the 50–100 µm range. Because mLLDPE exhibits less shear thinning than high-pressure LDPE of comparable melt index, melt pressure and screw torque can be higher at a given output; raising barrel temperatures by 5–10 °C or selecting a screw with deeper feed depth may be required to stay within motor amperage limits. Pellet moisture below 0.05 wt% permits direct processing without pre-drying. If storage occurs above 60 % relative humidity, a 4 h dry-air purge at 70 °C is a common precaution. Purging with low-melt-index LDPE or a commercial purging compound after heavily pigmented or filled runs reduces gel carryover. The melt-temperature upper boundary of 240 °C should not be exceeded for prolonged residence times; startup and shutdown procedures should be executed under nitrogen purge if the line will be idle for more than 30 min at high temperature.

Tensile, tear, and drop-impact data under ASTM D882, D1709, and D1922

Film property characterization for this resin is executed according to ASTM D882-18 for tensile stress and elongation, ASTM D1709-16a for dart drop impact, ASTM D1922-15 for Elmendorf tear, ASTM D1003-21 for haze, and ASTM D2457-21 for 45° gloss. These values are not intrinsic resin constants; they depend on die gap, blow-up ratio, frost line height, haul-off speed, and cooling air temperature. A film specimen produced at 25 µm gauge with blow-up ratio 2.2:1 and frost line height 700 mm will not reproduce the values obtained on a cast-film line or on a blown-film line with a 1.2 mm die gap because orientation and quench rate differ. Published film-property data for this specific grade outside the supplier technical data sheet is limited; converter qualification should therefore include line-specific sampling after steady-state thermal equilibrium is reached at the target gauge and output. The certificate of analysis normally reports pellet-level properties such as melt index and density, not film tensile or dart impact.

For incoming resin verification, the melt-index measurement requires a dead-weight extrusion plastometer with a 2.095 mm die orifice and a 2.16 kg load, and the density measurement is run on a gradient column at 23 °C according to ASTM D792-20. The melting peak, if used for thermal history or additive dispersion checks, is measured by differential scanning calorimetry under ASTM D3418-21 or ISO 11357-3:2018, with a nominal peak near 124 °C for this density class. A dart impact test under ASTM D1709-16a uses a 38.1 mm diameter dart and a 127 mm specimen clamp; the result is expressed as the mass failing 50 % of specimens. Elmendorf tear under ASTM D1922-15 reports force in N or grams-force and is highly sensitive to film orientation.

Compared with a conventional Ziegler-Natta butene LLDPE of the same 0.926 g/cm³ density and 0.50 g/10 min melt index, the metallocene single-site catalyst produces a narrower molecular weight distribution and a more regular sequence distribution. The reduction in the high-molecular-weight fraction lowers visible gel counts and melt memory effects in the die land, which can translate into lower haze as measured by ASTM D1003-21 and more consistent gauge as measured by in-line thickness scanning. At the same density, the improvement in dart impact under ASTM D1709-16a arises from a more uniform distribution of short-chain branches, which distributes tie-molecule density more evenly among lamellae. The rheological consequence is that mLLDPE has a lower melt flow ratio and less shear thinning than an equivalent Ziegler-Natta grade; therefore, an existing screw designed for conventional LLDPE may show higher back pressure and lower output at constant screw speed and 200 °C melt temperature until temperature or screw geometry is modified. Blending with 10–30 wt% high-pressure LDPE is a common route to increase melt strength and improve bubble stability, but the blend also shifts tear resistance and optical properties.

The butene comonomer in C4LL 50026RQ introduces ethyl short-chain branches, whereas hexene-based mLLDPE introduces butyl branches. For films of equivalent density and melt index, hexene-based metallocene grades generally provide higher Elmendorf tear and greater slow crack growth resistance because the longer butyl branch is more effective in promoting tie-chain connectivity between crystalline lamellae. C4LL 50026RQ is therefore positioned for applications where butene-based metallocene economics and processability are acceptable and where the specification does not require hexene-level tear propagation energy. This distinction should be verified by tear tests under ASTM D1922-15 on the actual blown film line rather than inferred from resin density alone.

When the resin is converted on a 250 mm spiral mandrel die for heavy-duty sacks

In heavy-duty sack production, the target gauge is typically 80–120 µm, and the converter requires high dart impact, controlled heat-seal strength, and sufficient surface energy for flexographic printing. The die gap is set at 2.2 mm, blow-up ratio at 2.2:1, and frost line height at 700–800 mm. Output is often cooling-limited rather than screw-limited; exceeding approximately 0.55 kg/h per mm of die circumference may produce blocking or gauge bands unless air-ring volume, die rotation, and collapsing frame tension are adjusted. The film is corona-treated to a minimum wetting tension of 38 mN/m for ink adhesion, with surface-energy retention checked at 24 h intervals. Heat seal evaluation is conducted under ASTM F2029-16 or ASTM F88/F88M-21, with the seal initiation curve established for the specific dwell time and jaw pressure used on the sack line. Published data for this grade’s specific seal initiation and hot-tack curve is limited; converter validation is required across the full sealing-jaw temperature range. Regrind use above 50 % should be avoided unless melt index shift, gel count, and film dart impact are reassessed because multiple heat histories can reduce antioxidant capacity and broaden the molecular weight distribution.

For printed sacks, the coefficient of friction is not an inherent property of the base resin; slip and antiblock masterbatches are required. Erucamide or oleamide slip and silica antiblock are typically added at combined levels from 1,000 ppm to 5,000 ppm, depending on gauge and blocking tendency. Overdosing slip can raise the seal initiation temperature and reduce hot-tack force, so the seal window should be remeasured after any masterbatch change.

Agricultural overwrap and silage film lines run the resin at 25–50 µm gauge, frequently in blends with 10–20 wt% LDPE to stabilize the bubble when the frost line is lowered for layflat tolerance control. The LDPE fraction contributes extensibility and reduces the risk of bubble flutter in side-gusseted structures, while the mLLDPE fraction maintains puncture propagation resistance during bale wrapping and outdoor exposure. Film blocking and surface slip are not derived from the base resin; they must be adjusted with masterbatch additives because the metallocene surface can show a higher coefficient of friction than an oxidized LDPE surface at the same slip loading. When the film is exposed to high-nitrogen agricultural liquids or silage acids, available published data for this specific grade in those environments is limited, and article-level testing is required before specification. Corona treatment for agricultural film printing or lamination should not exceed 42 mN/m unless in-line re-treatment is available, because excessive treatment can oxidize the surface and reduce sealability.