Metallocene linear low density polyethylene grade SABIC SUPEER mLLDPE 7118NJ is a pelletized blown-film extrusion resin supplied for monolayer and coextruded packaging structures. The grade belongs to the SABIC SUPEER mLLDPE family and is specified where puncture resistance, tear resistance, optical clarity, and low-temperature seal initiation are processing-critical. The molecular architecture is produced by metallocene catalysis, giving a narrow molecular weight distribution and a more uniform comonomer distribution than a conventional Ziegler-Natta linear low density polyethylene. This architectural difference controls haze, dart impact, tear balance, heat-seal response, and extrusion shear thinning, and it is the reason the grade is specified by melt flow rate, density, and film property tests rather than by polymer class alone.

What Separates a Metallocene Film Resin from a Conventional LLDPE on the Same Blown-Film Line?

On a production-scale blown-film line, the practical difference appears first in viscosity and bubble stability. At a nominal melt flow rate of 1.0 g/10 min measured at 190 °C under ISO 1133-1:2022, SABIC SUPEER mLLDPE 7118NJ exhibits less shear thinning than a broad-molecular-weight-distribution Ziegler-Natta LLDPE. The narrow chain-length distribution translates into a higher apparent viscosity at die shear rates; the extruder motor load and die pressure increase when the grade is dropped into a line previously set up for a conventional C4 LLDPE. Operators commonly report a need to raise barrel temperature settings by 5–10 °C or to add a fluoropolymer polymer processing aid at 200–800 ppm to suppress melt fracture and reduce die-lip deposit formation.

Because linear metallocene chains lack long-chain branching, strain hardening in the melt is lower than that of high-pressure LDPE. In practice the bubble becomes more sensitive to frost-line height and cooling air velocity. Stable operation on lines without internal bubble cooling is generally achieved at a die gap of 1.6–2.2 mm, a blow-up ratio of 2.0–3.0, and a frost-line height below 3 times the die diameter. When the frost line is raised above that threshold, the bubble can oscillate and produce gauge variation detectable by on-line capacitance or beta gauges. Reducing melt temperature from 210 °C to 195 °C or increasing the cooling air flow often restabilizes the process. Internal bubble cooling systems permit higher frost-line positions without the same degree of instability because the quench is decoupled from ambient air velocity.

Extrusion engineers can compensate for the higher die pressure by using a barrier screw with a Maddock mixing section and an L/D ratio of 24:1 to 30:1. Excessive shear heating from high-shear barrier elements can damage the stabilizer package and should be avoided. Melt temperature should not exceed 240 °C in any barrel zone; at temperatures above 260 °C, simultaneous chain scission and crosslinking can produce gel formation, odour, and reduced dart impact in subsequent film.

Nominal Melt Flow and Density Acceptance Window

Table 1 summarizes the principal resin and film property data used by converters to verify material identity and film performance before commercial use. The melt flow rate is determined at 190 °C and 2.16 kg; the density is measured at 23 °C on annealed compression-moulded specimens. Film data are based on 30 µm blown film produced under standard conditions.

The combination of 918 kg/m³ density and 1.0 g/10 min melt flow rate places SABIC SUPEER mLLDPE 7118NJ in the fractional-melt-index film class. Lower density reduces crystalline volume fraction and lowers haze, while the strong axial orientation generated in the blown film contributes to machine-direction tensile properties. Because the density is near the low end of the LLDPE film range, the resin has a broader melting interval and lower dimensional stiffness than a 0.926 or 0.932 kg/m³ grade; converters should evaluate the trade-off between impact and stiffness for heavy-duty sack lines.

Pre-drying is not normally required if the pellet surface is free of condensation. When sacks have been stored in unheated warehouses below the dew point, moisture can condense on the pellet surface and generate steam streaks in the extrudate. Under such conditions the resin should be dried at 70–80 °C for 4–6 h using a desiccant dryer. Avoid long hot-air drying above 80 °C because pellet surface softening can lead to bridging in the hopper.

When Conventional LDPE Is Partially Replaced in Heavy-Duty Sack or Collation Shrink Structures

In a heavy-duty sack blown-film structure, replacing 20–30 wt% of a high-pressure LDPE with SABIC SUPEER mLLDPE 7118NJ increases puncture and dart impact values without requiring a change in the total film gauge. The improvement is measured by ASTM D1709-A or ISO 7765-1 and is more pronounced at lower temperature. However, the addition of a linear metallocene resin to an LDPE-rich formulation reduces melt strength; the bubble must be supported with a lower blow-up ratio or a higher internal bubble cooling setting. The converter may also observe a decrease in specific energy consumption per kilogram because the lower-viscosity LDPE phase acts as a lubricant in the screw and die.

In collation shrink film, the resin contributes optical and seal properties. Shrink films require a balance of machine-direction orientation, transverse-direction tear, and seal-through-contamination performance. The low haze of the mLLDPE phase is retained after orientation if the die gap is not reduced below 1.4 mm; below that gap, shear-induced surface roughness can raise haze. Seal initiation is commonly evaluated by ASTM F1921 at 0.27 MPa sealing pressure and 0.5 s dwell; mLLDPE grades generally begin sealing at a lower temperature than an equivalent-density LDPE, which allows faster packaging line speeds. Published data for this specific grade in a given coextrusion ratio are often limited to the supplier’s application laboratory studies, so verification on the actual blown-film line is required.

For lamination or print adhesion, the film surface should be treated to a wetting tension of 38–42 mN/m measured by ASTM D2578 or ISO 8296. The metallocene surface oxidizes during corona or plasma treatment, but the treatment decays with time; converters should measure dyne level immediately before the coating station. A minimum of 40 mN/m is typical for polyurethane laminating adhesives and UV flexographic inks on high-speed lines.

Which SABIC SUPEER Slot Should Be Selected When Haze or Seal Performance Is the Constraint?

Within the SUPEER mLLDPE family, the 7118NJ designation identifies the film grade by its nominal melt flow rate and density class. Converters comparing it with higher-melt-flow mLLDPE grades should not assume identical film properties: a 2.0 g/10 min grade will generally permit higher throughput and lower melt pressure but gives lower dart impact and tear. A lower-density grade reduces haze and seal initiation temperature but lowers modulus. The choice among these trade-offs is made on the basis of blown-film property balance, not solely on price per kilogram.

The main difference between SABIC SUPEER mLLDPE 7118NJ and a conventional C4 Ziegler-Natta LLDPE of the same density is in organoleptics, optics, and impact. The metallocene grade is the preferred candidate when the film must pass low-temperature drop tests under ASTM D1709 or when the converter must reduce film gauge while retaining a specified dart impact. The conventional resin may be preferred when the line has limited motor torque or no processing-aid dosing capability, because its broader molecular weight distribution gives more shear thinning and lower die pressure.

Food Contact and Regulatory Status

The grade is typically covered by a supplier statement for polyolefin food-contact use in the United States under FDA 21 CFR 177.1520 and in the European Union under EU Regulation 10/2011 for plastic materials intended to come into contact with food. Compliance is formulation-dependent and requires migration testing on the final film, because overall migration limits depend on film thickness, contact mode, and food type. Converters must request the current SABIC regulatory statement and perform end-use compliance under the applicable clauses. The resin is not marketed as a medical-grade material unless a separate change notification has been issued.

For industrial applications, the grade is normally subject to a REACH SVHC declaration under Regulation (EC) No 1907/2006; no SVHC above 0.1 wt% is intentionally present. RoHS is not directly applicable to PE packaging, but converters needing a heavy-metal statement should request the supplier’s lot-level certificate.