LyondellBasell Icorene 3546 GRN 6619 is a pigmented linear low-density polyethylene rotational moulding powder. The base resin is identified as Icorene 3546; the suffix GRN 6619 denotes a green colour package. The nominal density is 0.934 g/cm³ when determined in accordance with ISO 1183-1, and the melt flow rate is 4.0 g/10 min at 190°C under a 2.16 kg load when determined in accordance with ISO 1133-1. These two values are the primary classification parameters used to distinguish this rotational-moulding LLDPE from injection-moulding grades, which often exhibit melt flow rates above 15 g/10 min, and from film-extrusion grades, which commonly operate below 1.5 g/10 min. The material is supplied as a powder rather than as pellets, a critical requirement for rotational moulding because the powder must distribute uniformly over the internal surface of a biaxially rotating mould before melting begins.

In the rotational moulding process, the powder is charged into a hollow metal tool, heated while biaxially rotated, and cooled while rotation continues. The density of 0.934 g/cm³ provides a lower crystalline content than high-density polyethylene, which supports low-temperature impact strength but reduces room-temperature flexural modulus. The melt flow rate of 4.0 g/10 min is high enough to permit sintered powder particles to coalesce and release entrapped air at typical peak internal air temperatures, yet low enough to resist excessive melt sag or pinhole formation during the cooling phase. Published data for the specific GRN 6619 green variant are more limited than for the unpigmented base resin, so any critical application should use the supplier's certificate of analysis and application-specific ageing data as the governing reference.

What Distinguishes a Rotational Moulding LLDPE from Film-Grade and Injection-Moulding LLDPE?

The primary differences are physical form, melt flow rate, comonomer distribution, and stabiliser package. Film-grade LLDPE is typically pelletised and has a melt flow rate below 1.5 g/10 min to maintain bubble stability in blown film. Injection-moulding LLDPE is pelletised and may have a melt flow rate above 15 g/10 min to fill thin-wall moulds. Icorene 3546 GRN 6619 is ground to a rotational-moulding powder with a melt flow rate of 4.0 g/10 min, positioned to allow powder coalescence at oven temperatures between 260°C and 300°C. The linear low-density polyethylene backbone contains short-chain branches introduced by an α-olefin comonomer; this branching controls density and reduces spherulitic growth compared with high-density polyethylene. The molecular architecture is therefore optimised for slow, contact-free melting in a biaxially rotating mould rather than for high-shear extrusion.

Within the rotational-moulding polyethylene family, the main performance trade-off is between flow and toughness. A rotational-moulding LLDPE with melt flow rate 4.0 g/10 min fills complex mould features more readily than a high-density polyethylene with melt flow rate near 2.0 g/10 min, but it has lower room-temperature stiffness. In a chemical tank, the LLDPE grade may require a wall thickness increase of 10–20% compared with HDPE to achieve equivalent top-load or hydrostatic hoop stress. Conversely, the LLDPE grade commonly provides longer environmental stress crack resistance and better low-temperature impact at -20°C under ASTM D3763, which is why it is used for outdoor products in cold climates. Comparative testing under ASTM D1693 is required to confirm the specific ESCR advantage for a pigmented formulation.

Representative property values for the unpigmented Icorene 3546 base resin are summarised below. The pigmented GRN 6619 variant may show small shifts in density, tensile yield stress and low-temperature impact due to colourant addition; the values should therefore be treated as design guidance, not as guaranteed limits for the green compound.

The property profile places Icorene 3546 between low-density polyethylene rotational moulding grades with density below 0.920 g/cm³ and high-density polyethylene rotational moulding grades with density above 0.940 g/cm³. At 0.934 g/cm³, the material retains sufficient modulus for moderately loaded parts while providing improved low-temperature ductility compared with HDPE. The tensile strain at break exceeds 800% in published data for the base resin, indicating ductile behaviour at room temperature. Low-temperature impact testing of rotationally moulded parts is commonly performed using an instrumented falling-weight test based on ISO 6603-2 or ASTM D3763. Values depend on wall thickness, cooling rate and pigment dispersion, so no single numerical impact strength can be applied to all articles.

Particle-size distribution is also part of the product specification. Rotational-moulding powders are normally characterised by sieve analysis or laser diffraction and reported as cumulative weight retained on 500 µm, 355 µm and 125 µm screens. A high fines fraction can reduce dry-flow and cause uneven coating of the mould wall; a high coarse fraction can produce surface pits because large particles require longer sintering times. Rotational moulders should request the supplier’s particle-size distribution and dry-flow test data before introducing a new lot of GRN 6619 into an established production process. Significant changes in bulk density after storage indicate compaction and may require screening before use.

When Oven Residence Time Is Extended Beyond the Sintering Plateau

On a carousel-type rotational moulding line with a biaxial rotation ratio of 4:1 to 8:1 and an oven air temperature of 280°C, the powder bed transitions through particle surface tack, sintering, densification and coalescence. The peak internal air temperature inside the mould is the controlling variable for part quality; for this grade, peak internal air temperature is typically held between 190°C and 220°C. If the mould is removed from the oven before the internal air temperature reaches 180°C, residual powder or incompletely coalesced bubbles remain at the inner surface, reducing impact strength and producing pinholes in thin-wall sections. Prolonged holding above 220°C accelerates thermo-oxidative degradation of the LLDPE, especially where residual oxygen is present in the mould cavity. The green pigment can mask early yellowing, making melt flow stability checks after simulated oven ageing a more reliable degradation indicator than visual colour change alone.

Production-scale failure modes recorded on biaxially rotating machines include uneven wall thickness at the parting line due to non-uniform powder flow, internal void formation at sharp mould radii below 10 mm, and gloss variation on the outer surface when cooling is too rapid. Demoulding should be attempted only after the part surface has cooled below 70°C to avoid deformation of unsupported walls. Because rotational moulding is a low-shear process, the powder must contain no large agglomerates; particle-size control above 500 µm is necessary to avoid delayed sintering at the inner surface. If the green pigment is melt-compounded before grinding, compounding is typically carried out on a co-rotating twin-screw extruder with L/D ratio 40:1 to 52:1 and strand pelletising before cryogenic grinding. The additional heat history of this route can reduce powder bulk density and shift particle morphology; rotational moulders should use the supplier’s reported particle-size distribution rather than relying solely on the unpigmented base resin.

Environmental stress crack resistance is a critical differentiator for rotationally moulded tanks. The base resin is evaluated under ASTM D1693, condition B in 100 vol% Igepal CO-630; LLDPE grades in this density and melt-flow class can show F50 failure times above 1000 h, whereas lower molecular-weight injection-moulding LLDPE can fail in fewer than 100 h under identical conditions. The green colourant package may influence the measured value, so direct testing of the compounded GRN 6619 variant is recommended for chemical storage applications. In-house test programmes on rotationally moulded containers should also include a constant-strain chemical exposure test at 50°C for 30 days with the intended fluid, because ESCR is accelerated by temperature and stress concentration.

Pigmentation, Dispersion and Colour Stability in Green Rotational Mouldings

The suffix GRN 6619 identifies a green pigmented product. Rotational-moulding powders can be coloured by dry blending pigment concentrates with the base powder or by melt compounding and regrinding. Melt-compounded pigmented grades generally provide more uniform colour and better batch-to-batch consistency than dry blends, but the additional heat history can reduce low-temperature impact strength if regrind is not controlled. The pigment used in a green LLDPE must remain chemically inert toward the phenolic antioxidant and acid-scavenger package at peak internal air temperatures up to 220°C. Certain transition-metal pigments can catalyse hydroperoxide decomposition and shorten oven life. A quality-control programme for GRN 6619 should therefore include a melt flow rate retention test after multiple simulated oven cycles and colour measurement by ASTM D6290 or spectrophotometric evaluation using CIE L*a*b* coordinates.

Because the pigmented outer surface can absorb infrared energy differently from natural powder, the heating and cooling rates of a green moulding may differ slightly from those of an unpigmented control part. Rotational moulders should verify the internal air temperature profile when switching from natural to green powder, particularly on shuttle machines with fixed cycle timers. For a part with nominal wall thickness of 6 mm, differential cooling may produce measurable warpage; dimensional validation against the mould geometry should be performed after 24 h of conditioning at 23°C and 50% relative humidity, as specified in ISO 291 for thermoplastics conditioning.

Applications for Icorene 3546 GRN 6619 include rotationally moulded agricultural tanks, outdoor furniture, playground components, containers and general industrial covers. These applications use the balance of low-temperature toughness and processability of the grade. When direct substitution for a high-density polyethylene rotational moulding resin with density 0.942 g/cm³ is considered, the lower modulus of the LLDPE must be offset by increasing wall thickness or adding ribs. The modulus measured under ISO 178 for the base resin is approximately 550 MPa; high-density rotational moulding grades in the same application class can exceed 800 MPa. Published load-deflection data for the specific green configuration are limited; finite-element design validation using the supplier’s creep and tensile data should be performed for large structural parts.

For food-contact applications, the base polyethylene may be evaluated under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011, but the green colourant system must be assessed separately for specific migration limits. For electrical and electronic equipment enclosures, the finished article is subject to Directive 2011/65/EU RoHS restrictions, with cadmium limited to 0.01 wt% and lead, mercury, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers each limited to 0.1 wt% in homogeneous materials. A completed article made from this grade should be verified against these limits because pigment and additive packages, not the base polyolefin alone, determine the final regulatory status.