LyondellBasell Icorene 3545 GRN 6670 is a linear low density polyethylene rotational moulding powder supplied with a green pigment package already incorporated. The base resin, Icorene 3545, belongs to the ethylene copolymer class used in low-shear rotational moulding; the suffix GRN 6670 denotes a specific green colour formulation rather than a separate masterbatch blend. Production-scale handling of this grade should proceed on the assumption that the material is a pulverised powder with a controlled particle-size distribution, because segregation of pigmented fines during pneumatic transfer can shift both colour consistency and wall-thickness distribution in deep-draw tools. Published data for the GRN 6670 variant is limited; the product should not be treated as interchangeable with natural Icorene 3545 without review of the lot-specific certificate of analysis and colour-match record.

At incoming inspection, the base polymer is typically characterised by melt flow rate under ISO 1133-1 at 190 °C and 2.16 kg, density by ISO 1183-1 or ASTM D1505, and oxidative-induction time by ISO 11357-6. The green pigment package can shift melt flow rate by ±0.5 g/10 min relative to the natural base resin depending on pigment loading and carrier type, and density may be 0.003–0.010 g/cm³ higher. These shifts are measurable and justify qualification of incoming pigmented lots before moulding parameters are fixed. When ambient relative humidity exceeds 60%, surface moisture on the powder can produce porosity in thick sections; pre-drying in a desiccant hopper or heated air stream may be required for sensitive parts.

What Rotational Moulding Variables Govern the Processing Window for Icorene 3545 GRN 6670?

On carousel, shuttle, and rock-and-roll machines, the conversion of Icorene 3545 GRN 6670 follows the conventional LLDPE powder densification sequence: powder coating, bubble dissolution, coalescence, and densification. The critical control variable is peak internal air temperature, not oven setpoint alone. For rotationally moulded LLDPE powders of this density class, production-scale carousels with arm speeds between 4 rpm and 12 rpm and a rotational ratio near 4:1 are typically started with a peak internal air temperature of 190–210 °C. A lower peak internal air temperature can leave unmelted particles at the inner surface, producing pinholes and reduced impact strength; a peak internal air temperature above 220 °C accelerates thermo-oxidative chain scission and shifts the green colour toward a yellower hue. The allowable window is therefore narrow enough that oven residence time should be adjusted in 2–4 min increments while recording peak internal air temperature with a calibrated infrared probe.

Differential scanning calorimetry by ISO 11357-3 provides the actual melt peak and crystallinity of the coloured powder; oxidative-induction time by ISO 11357-6 indicates the residual stabiliser reserve for a given oven profile. In deep-draw parts with wall sections from 3 mm to 8 mm, the inner surface is the last to densify and the first to exhibit oxidation haze if oven dwell is excessive. Metallic and organic green pigments can affect nucleation and thermal conductivity; therefore, transfer of processing parameters from natural Icorene 3545 without empirical verification is not recommended. Cooling rate also affects dimensional stability: forced-air cooling to a demoulding temperature of 60–80 °C reduces warpage but may increase internal stress in thick sections. The moulder should establish a fixed cooling curve after measuring part shrinkage against tool dimensions.

Mechanical assessment of Icorene 3545 GRN 6670 should be performed on specimens cut from rotationally moulded plaques, not compression-moulded plaques, because the low-shear process produces anisotropic morphology and residual stress that standard compression moulding does not reproduce. The following test matrix is the minimum set for incoming material qualification and moulded-part validation.

Published representative values for the natural Icorene 3545 grade are commonly cited at a nominal density of 0.934 g/cm³ and a nominal melt flow rate of 5.0 g/10 min under 190 °C/2.16 kg. Tensile yield and flexural modulus in this density class are typically in the range of 16–20 MPa and 500–650 MPa, respectively, when tested on slow-cooled compression-moulded specimens. The GRN 6670 variant may exhibit slightly higher density and modulus and slightly lower stress-crack resistance than the natural resin because rigid pigment particles and carrier resins modify the amorphous tie-chain population. Published data for the specific green variant is limited; therefore, end-use validation should rely on actual moulded plaques tested under ISO 527-2, ISO 178, and ASTM D1693, with the environmental exposure condition stated on the test report.

Thermal Oxidation and Colour Retention in Outdoor Service

Outdoor exposure of green rotationally moulded parts requires separation between pigment screening and stabiliser performance. A green pigment package such as GRN 6670 may reduce ultraviolet penetration at the surface but can also increase surface temperature under solar load because darker green absorbs near-infrared radiation. Accelerated weathering is therefore specified by ISO 4892-2 or ASTM D2565 with the irradiance and black-panel temperature matched to the end-use climate. Colour change is measured by ISO 7724 or ASTM D2244; a ΔE value greater than 3 after accelerated exposure is generally visible under inspection lighting, although the acceptance limit is application-specific. Retention of mechanical properties after weathering should be confirmed by tensile and impact testing, not by colour alone.

The oxidative-induction time of the moulded inner surface is a practical screening parameter after processing. When OIT at 190 °C or 210 °C falls below the control value established on the raw powder, the part has consumed a portion of the stabiliser package during the moulding cycle. For long-term outdoor tanks, hoppers, or agricultural equipment, qualification by ISO 4892-2 at a defined irradiance and cycle is required; no universal service life can be claimed from resin datasheet values. The green colour in GRN 6670 should be evaluated in combination with the intended stabiliser package, and any change of pigment source from the original formulation requires re-qualification because impurity profiles in pigments can reduce oxidative-induction time without altering colour significantly.

At ambient relative humidity below 60%, pre-drying is not normally required for this class of LLDPE rotational moulding powder. Above that threshold, moisture adsorbed on the powder surface can volatilise during the moulding cycle and create internal bubbles that weaken the part. A frequent production-floor observation with pre-coloured powders is colour streaking in deep ribs when the powder is conveyed through long drop lines that allow fines segregation. The moulding service should therefore sample the powder after transfer for particle-size distribution by ISO 4610 or ASTM D1921 to confirm that the d50 value remains within the supplier’s control range. If the green pigment is present as a separate free-flowing component rather than fully compounded, segregation can also produce local variation in melt flow rate and surface gloss.

Regrind of Icorene 3545 GRN 6670 can be re-introduced into the moulding charge, but the colour balance shifts unless the regrind fraction is controlled and recorded. Particle-size distribution of reclaimed powder differs from virgin powder because of attrition and partial melting at the tool surface. A maximum regrind addition of 20–30% is commonly used in production for non-critical parts; critical parts with tight colour tolerance require validation of the exact regrind ratio before release. The pigment package does not provide electrical conductivity, flame retardancy, or chemical compatibility; those properties must be addressed by separate additive systems or design controls and verified by the relevant IEC, UL, or DIN standards.

When Crosslinked Polyethylene or HDPE Would Be Selected Instead of Icorene 3545 GRN 6670

For applications requiring stiffness and creep resistance, an HDPE rotational moulding powder with a density above 0.945 g/cm³ may be substituted, but the trade-off is reduced low-temperature impact strength and higher melt viscosity. Icorene 3545 GRN 6670 occupies a lower-density LLDPE position that provides higher elongation and lower warpage in complex parts than many HDPE rotomoulding grades. For chemical tanks requiring maximum ESCR performance, a single-sided crosslinked polyethylene or a high-density ESCR grade may outperform this LLDPE in hot chlorinated-water service, particularly where failures occur at sharp corners or weld-line regions. Crosslinked polyethylene requires different processing equipment and cannot be reground and re-moulded, whereas Icorene 3545 GRN 6670 remains thermoplastic and can be reground within the limits of the moulding plant’s colour-control plan.

Compared with conventional LDPE rotational moulding powders, the linear low density structure of Icorene 3545 provides higher tensile yield and flexural modulus at equivalent density because short-chain branches create a more regular crystalline network. Compared with metallocene-catalysed LLDPE rotational moulding grades, the 3545 designation may exhibit different peak melting temperature and organoleptic behaviour; selection for food-contact or potable-water service requires confirmation against 21 CFR 177.1520 and REACH obligations for the finished part. The pre-coloured green package does not automatically confer UV stabilisation, chemical resistance, or impact modification; those performance properties must be validated under the intended service conditions using the standards applicable to the final fabricated part.

On production-scale carousel machines, a recurring processing boundary is the interaction between the green pigment package and the narrow peak internal air temperature window. When cycle time is shortened to increase throughput, the inner surface may remain under-densified even though the exterior colour appears acceptable. This failure mode is detected by cutting a representative part and inspecting the inner surface for pinholes, unmelted powder, or glossy oxidation bands. If the part passes visual inspection, mechanical validation should still include tensile elongation and impact tests on specimens taken from the thickest and thinnest sections, because wall-thickness-dependent cooling history determines local crystallinity and residual stress. The absence of published lot-specific data for the GRN 6670 variant makes such part-level validation the controlling method for release to production.