LyondellBasell Icorene 3560 GRN 6198 is a linear low-density polyethylene rotational moulding powder. The designation Icorene 3560 refers to the base resin, while GRN 6198 identifies the precoloured green compound. Unlike conventional extrusion or injection moulding grades, this material is supplied as a dry-flowable powder and is intended for powder-fed rotating moulds. The producer-specified nominal density is 0.935 g/cm³ when tested to ISO 1183-1:2019, and the melt flow rate is 6.0 g/10 min under a 190 °C/2.16 kg load according to ISO 1133-1:2022.

What compositional profile and melt-state rheology does Icorene 3560 GRN 6198 exhibit?

The base polymer is an ethylene/alpha-olefin linear low-density polyethylene; the alpha-olefin short-chain branching reduces density below that of conventional HDPE while retaining a linear backbone structure absent from free-radical LDPE. The 6.0 g/10 min melt flow rate assists bubble release and particle coalescence during the melt-in phase of rotational moulding. Because the process is primarily time-at-temperature driven rather than shear driven, rheological behaviour must be interpreted through oven residence and peak internal air temperature rather than screw back-pressure. At 190 °C, the melt develops sufficient surface tension to wet the mould steel and consolidate the powder layer. Below approximately 175 °C, sintered powder particles may remain only partially coalesced, producing pinholes, reduced elongation at break, and a rough inner surface.

Powder handling before charging controls wall-thickness consistency. Apparent density is commonly found in the 0.40–0.48 g/cm³ range under ISO 60:2023, and this value must be re-established on incoming lots because bulk storage compaction or moisture uptake can shift charge weight and dry-flow time. A dry-flow time below 35 s/100 g under ASTM D1895-17 is typical for this powder class. Fines content passing 75 µm should be controlled to avoid dust generation, electrostatic accumulation, and irregular wall formation. Precompounded green pigment rather than dry blending reduces pigment segregation that can occur during tumbling; however, the pigment loading may alter flow behaviour slightly relative to natural Icorene 3560, making incoming dry-flow verification more important for the GRN 6198 lot.

Dry-flow, particle size, and colourant dispersion in a powder-fed mould

GRN 6198 identifies a melt-compounded green pigment system, not a dry-blend masterbatch added at the moulding machine. The colourant is dispersed in the polymer before grinding, then the coloured compound is ground and screened to rotational moulding particle size. The powder should not show visible pigment agglomerates above 0.5 mm when examined at 20× magnification; larger pigment specks can act as stress concentrators in the finished wall. Rotational moulders commonly monitor the ratio of material retained on a 35-mesh screen to fines passing a 100-mesh screen because a narrow particle-size distribution improves corner fill and bulk density. A wide distribution can cause particle segregation inside the rotating mould, especially in deep ribs or complex tooling.

On a 2.0 m biaxial shuttle machine producing 3.2 mm nominal walls, operators have observed wall-thickness variation greater than ±10% when powder does not consolidate during the first oven pass. The defect typically appears as a discontinuous inner skin at the base of ribs with a depth-to-width ratio above 1.5:1. Splitting the charge or preheating the mould surface to approximately 90 °C reduces bridging and improves initial powder tack. A heated mould also minimises condensation that can generate surface pinholes when humid powder is charged directly from cold storage.

Assigning the thermal window to avoid undercure, bubble retention, and oxidative tack

The practical processing window is narrower than the broad oven setpoint commonly used for rotational moulding. Forced-air ovens with average air velocities of 3–6 m/s may be set at 260–300 °C, but cycle quality is determined by the measured peak internal air temperature inside the mould. For 3.0–3.5 mm wall sections, a peak internal air temperature of 190–210 °C is generally required. Below 185 °C, the inner surface may retain a sandy texture and low elongation at break because powder particles have not fully coalesced. Above 230 °C, the green pigment system may undergo chroma shift and the polymer may develop an oxidative carbonyl signature detectable by FTIR near 1715 cm⁻¹. The upper PIAT limit should therefore be treated as a critical control, not merely an advisory range.

After demoulding, representative tensile properties for the unpigmented 3560 base are a tensile yield stress of 13–15 MPa and elongation at break above 700% when tested to ISO 527-2:2012 at 23 °C. Flexural modulus is typically 500–600 MPa under ISO 178:2019. The GRN 6198 precoloured lot may show a flexural modulus increase of 2–5% from pigment nucleation and a slight reduction in high-speed impact; published data for this specific precoloured configuration is limited, so validation should be performed on plaques cut from the production tool. The following table summarises representative values for the Icorene 3560 grade.

How does Icorene 3560 GRN 6198 compare with LDPE, HDPE, and higher-density LLDPE alternatives?

Compared with free-radical LDPE rotational moulding powders, Icorene 3560 has a higher density and a linear short-chain branching structure, which produces higher tensile yield and flexural modulus. Compared with HDPE rotomoulding grades, the 0.935 g/cm³ density sacrifices stiffness and heat deflection but provides higher environmental stress-cracking resistance and improved low-temperature impact ductility. Compared with higher-density LLDPE grades above 0.940 g/cm³, the material is selected where cold-temperature toughness and ESCR are more important than panel rigidity. The 6.0 g/10 min melt flow rate is relatively high for an LLDPE rotational moulding powder, favouring thin-wall flow and bubble release but requiring slower rotation on thick sections to prevent sag.

The linear microstructure also produces a sharper melting endotherm than free-radical LDPE, narrowing the demoulding window. HDPE grades with density above 0.940 g/cm³ may tolerate higher peak internal air temperatures but are less ductile at subzero temperatures. Natural Icorene 3560 differs from the GRN 6198 precoloured version mainly in colour, weathering opacity, and slight shifts in impact and flexural response; these shifts are not generally captured by natural-resin datasheets and must be assessed on moulded articles.

When the green precolour is specified in fuel-tank service

Green rotational-moulded articles are used in agricultural chemical storage, diesel tanks, and colour-coded fluid-handling components. The LLDPE backbone provides resistance to dilute aqueous acids, alkalis, aliphatic hydrocarbons, and saline solutions. It is not suitable for continuous immersion in strong oxidising acids, aromatic solvents, or high-concentration peroxides, because these media can soften the surface or promote environmental stress cracking. For diesel or agricultural pesticide service, hydrocarbon swell is lower than LDPE but higher than HDPE or barrier-modified rotomoulding grades; selection of Icorene 3560 over HDPE is normally driven by low-temperature impact resistance and ESCR rather than by permeation performance. After chemical exposure, tensile properties should be measured according to ISO 175:2010 or ASTM D543-21; a reduction in elongation at break above 50% may indicate an unsuitable service environment. The green pigment in GRN 6198 must also be checked for bleeding or extraction using EN 1186-1:2002 when the article contacts food or potable water.

For food-contact applications, the base LLDPE may meet 21 CFR 177.1520 for olefin polymers under permitted conditions of use, but the precoloured compound requires separate evaluation of the green pigment and processing aids. A full regulatory statement from LyondellBasell for GRN 6198 should be obtained before food packaging or toy articles are approved. In the European Union, finished rotomoulded articles must satisfy overall migration limits in Regulation (EU) 10/2011, and specific migration testing may be required for pigment decomposition products. RoHS compliance for electrical enclosures requires cadmium and lead content below 100 mg/kg and 1000 mg/kg, respectively. The powder should be stored below 60% relative humidity; if bags have been exposed to condensation, desiccant-air drying at 40–50 °C for approximately 4 h is recommended before charging. Extended outdoor exposure of the moulded article may require an additional UV-stabilizer package because the green pigment alone is not a complete weathering system.