SABIC LLDPE 218NJA is a linear low-density polyethylene resin designed for injection-moulded rigid packaging and consumer articles. The product is specified with a melt flow rate of 20 g/10 min at 190°C/2.16 kg under ISO 1133-1:2022 and a density of 0.928 g/cm³ under ISO 1183-1:2019. This density places the material between conventional low-density polyethylene and high-density polyethylene in stiffness and top-load resistance, while the melt flow index permits short fill times in multi-cavity injection tools. The grade is supplied as natural pellets with a molecular weight distribution controlled for injection-moulding rheology. Because the polymer backbone is linear with short-chain branches, the resin exhibits shear-thinning behaviour under injection shear rates but retains lower melt strength than high-pressure LDPE in extrusion processes.

Specification profile and standards

Published product data for SABIC LLDPE 218NJA are summarised in the following table. The values are representative lot averages and should not be used as contractual specification limits without confirmation from the supplier.

The specified melt flow rate of 20 g/10 min places the grade in the high-flow category for injection moulding. Standard injection-moulding LDPE grades typically operate in the 2 g/10 min to 8 g/10 min range, while blown-film LLDPE grades usually remain below 2 g/10 min to maintain bubble stability. The density of 0.928 g/cm³ is higher than that of film-grade LLDPE and contributes to flexural modulus and top-load resistance. The melt flow rate and density combination defines a material that can be injected into thin-wall sections without excessive cavity pressure, but it is not suited to blown-film extrusion or large-part blow moulding because its low melt strength cannot support a stable bubble or parison.

During injection moulding on hydraulic or electric units with screw L/D ratios of 20:1 to 24:1, melt temperatures of 200°C to 240°C and mould temperatures of 10°C to 40°C are commonly used. The high flow index reduces injection pressure demand in thin-wall sections, but screw back pressure should be kept below 0.5 MPa to avoid excessive shear heating. When the material is processed after storage in ambient conditions above 60% relative humidity, pre-drying at 70°C to 80°C for 1 h to 2 h is recommended to prevent splay from surface moisture. Hot-runner systems with internal nozzle diameters below 1.0 mm may require a 5°C to 10°C increase in melt temperature because pressure loss across the nozzle increases nonlinearly with reduced diameter.

Thin-wall parts may exhibit gate blush or jetting if gate velocity exceeds 200 mm/s and gate diameter is less than 0.8 mm. Increasing gate diameter or reducing injection velocity to below 150 mm/s typically eliminates jetting without raising fill pressure beyond machine capacity. Sink marks are controlled by pack pressure and cooling time; pack pressures of 50 MPa to 80 MPa are common for wall thicknesses between 0.6 mm and 1.5 mm. These values are starting points for production-scale tools and must be refined using gate-seal and part-weight stability data from the actual moulding machine.

What distinguishes SABIC LLDPE 218NJA from fractional-melt film grades?

The molecular architecture is linear with short-chain branching, but the molecular weight distribution and comonomer placement are weighted toward injection-moulding rheology. A fractional-melt blown-film LLDPE typically has a melt flow rate of 0.8 g/10 min to 2.0 g/10 min and a density of 0.916 g/cm³ to 0.920 g/cm³; these values favour bubble stability and dart impact but increase fill pressure in thin-wall moulds. SABIC LLDPE 218NJA shifts the melt flow rate to 20 g/10 min and density to 0.928 g/cm³. The result is lower apparent viscosity at injection shear rates, shorter screw recovery time, and higher flexural modulus for demoulding and top-load resistance. The corresponding limitation is reduced melt strength, so the grade is not designed for blown-film extrusion or large-part blow moulding.

Compared with injection-moulded HDPE of density 0.952 g/cm³ to 0.965 g/cm³, SABIC LLDPE 218NJA exhibits lower stiffness and lower heat resistance but greater environmental stress crack resistance and better hinge flex life. This positions the grade for lids and closures that undergo repeated flexing or cap installation, where an HDPE grade may crack at the hinge or closure detail. Conversely, the LLDPE grade is not a substitute for HDPE in applications requiring continuous service above 70°C or high top-load at elevated warehouse temperatures.

Mechanical performance in service is influenced by density and comonomer distribution. The tensile yield stress of 10 MPa and elongation at break above 500% permit snap-fit assembly and hinge flexing in closures. The flexural modulus of 260 MPa is lower than high-density polyethylene but higher than typical LDPE; this positions the grade for lids and containers that require a balance between hermetic sealing and top-load resistance. Environmental stress crack resistance measured under ASTM D1693-15 in 10% Igepal solution is reported above 50 h, which supports resistance to surfactants and household cleaning agents but does not replace chemical compatibility testing with the specific packaged liquid.

The grade is used in thin-wall containers for dairy products, lids, closures, pails, and housewares. In dairy packaging, the low-temperature impact resistance of LLDPE is retained at refrigeration temperatures of 2°C to 8°C; the density of 0.928 g/cm³ provides sufficient top-load resistance for stacking in distribution. In closure applications, hinge flex life is supported by the linear backbone and high elongation at break, but ultimate performance depends on gate location, mould flow direction, and colourant loading. No direct substitution from an LDPE grade should be made without verifying the closure dimension after annealing, because the higher density changes shrinkage behaviour relative to LDPE.

The shear-viscosity curve of SABIC LLDPE 218NJA can be fitted to the Carreau-Yasuda model for injection-moulding simulation. The model coefficients should be obtained from the manufacturer's flow-simulation database rather than from a generic LLDPE description; simulation accuracy depends on the transition from Newtonian to shear-thinning behaviour and on temperature sensitivity as measured by Arrhenius shift factors. Melt viscosity data for injection simulation are measured by capillary rheometry under ISO 11443:2021. In high-shear regions such as hot-runner tips and sub-gates, the apparent viscosity is lower than that of fractional-melt LLDPE, but the exact pressure reduction is tool-specific and requires validation by short-shot studies on the production mould.

When cycle-time reduction in thin-wall tools is the primary process objective

The thermal and rheological profile of SABIC LLDPE 218NJA interacts with tool design through two mechanisms. The first is fill pressure: high flow reduces the hydraulic pressure required to reach the end of cavity under a given injection velocity. The second is solidification: a density of 0.928 g/cm³ increases thermal conductivity relative to lower-density LDPE and shortens cooling time in wall sections below 0.8 mm. These effects are realised only when the tool has adequate venting, uniform cooling, and gate geometry that does not restrict flow. In practice, cycle-time savings are tool-specific and depend on part mass, wall thickness, gate diameter, and cooling-channel placement; published data for this specific configuration is limited, so process development on the actual production tool is required.

SABIC LLDPE 218NJA falls within the olefin polymer class defined by FDA 21 CFR 177.1520 and is suitable for food-contact applications when the finished article meets the migration limits set out in EU Regulation 10/2011. Under EU Regulation 10/2011, the overall migration limit is 10 mg/dm² of food-contact surface; specific migration limits for monomers and additives apply. Converters must verify after colouring, printing, or post-treatment operations that the final article remains compliant, because additives that are not part of the base resin can alter overall migration. The product may be used in food-contact packaging in many jurisdictions, but converters must confirm the specific food type, time-temperature exposure, and surface-to-volume ratio before commercial use.

On high-speed electric moulding machines with injection velocities above 300 mm/s, shear heating can elevate melt temperature by 10°C to 20°C, increasing the risk of splay and degradation if the barrel temperature was set near the upper limit. Barrel residence time should not exceed 5 min at melt temperatures above 240°C. If a hot-runner system drops below 0.5 mm nozzle diameter, pressure losses become nonlinear and may require raising melt temperature to maintain fill; however, this also narrows the thermal degradation margin.

Operational boundaries include the avoidance of melt temperatures above 260°C to limit oxidative chain scission and the exclusion of the grade from blown-film lines, pipe extrusion, and large-part blow moulding. The resin has limited compatibility with high-shear hot-runner nozzles below 0.5 mm unless the melt temperature is increased to compensate for shear heating. Colour concentrates based on high-melt-flow polyethylene carriers are preferred; concentrates based on low-melt-flow or high-viscosity carriers can create visible dispersion defects in thin-wall mouldings. The grade should not be blended with high levels of regrind from low-density LDPE film scrap if the scrap contains surface-active additives such as migratory slip or antifog agents, because the resulting melt-flow shift and surface migration behaviour are not characterised in the standard product data.