The LyondellBasell Icorene 3545 GRN 6665 Polyethylene, Linear Low Density product is supplied as a green-pigmented rotational moulding powder. The base resin is a linear low-density polyethylene produced by low-pressure copolymerization of ethylene with a short-chain α-olefin. Industrial trade literature identifies the base resin by a nominal density of 0.935 g/cm³ and a melt mass-flow rate of 4.5 g/10 min measured under ISO 1133-1:2022 at 190 °C with a 2.16 kg piston load. The suffix GRN 6665 is a LyondellBasell color code denoting a green pigment package dispersed in the powder; it does not identify a separate polymer base. The material is delivered as a pulverized powder with controlled particle size distribution, dry-flow character, and bulk density intended for biaxial rotation in carousel, shuttle, or rock-and-roll rotational moulding machines. It is not intended for injection moulding, blow moulding, or film extrusion because the powder morphology and particle size distribution are optimized for slow melt coalescence on large hollow parts rather than for high-shear plastication.

The values are indicative lot-averaged data for the natural base resin and should not be read as guaranteed specification limits. The GRN 6665 pigmented variant may shift tensile yield, flexural modulus, and heat absorption because the colorant package alters crystalline nucleation and surface infrared absorption. Published data for this specific pigmented configuration is limited, and lotwise certificates of analysis remain the controlling reference.

For rotational moulding powder, the particle size distribution is a specification parameter separate from polymer properties. A typical LLDPE rotational moulding powder is controlled to pass a 35 mesh (500 µm) sieve, with limited fines below 75 µm to reduce dust and static adherence. Bulk density in the range 0.33–0.36 g/cm³ is normal for LLDPE powders of this density; a lower bulk density can reduce part fill efficiency, while a higher bulk density can enhance oven heat transfer. These values are general powder-handling characteristics and should be confirmed on the lot certificate.

What Limits Oven Peak Internal Air Temperature in Thin-Walled Green Parts?

In rotational moulding, the peak internal air temperature is a more direct control parameter than oven zone temperature. For a linear low-density polyethylene with an MFR of 4.5 g/10 min, the standard PIAT window is 190 °C to 210 °C, while oven air temperatures are typically set between 280 °C and 320 °C for wall sections from 3 mm to 15 mm. Below the lower PIAT boundary, the powder particles do not fully coalesce, leaving internal voids, pinholes at the mold surface, and weak knit lines at internal corners. Above the upper boundary, thermal-oxidative chain scission can cause discoloration and skin embrittlement. Dark green pigmentation increases radiative absorption relative to natural powder; the processing window can therefore be narrower than that of an unpigmented powder. Published data for the GRN 6665 configuration is limited, but factory-level trials on independent-arm carousel equipment indicate that dark pigmentation can require a reduction in oven air temperature of 10–15 °C relative to natural powder to maintain equivalent skin condition.

The critical process variables are mold swing diameter, oven residence time, cooling rate, and mold release. On a machine with a biaxial rotation ratio between 3:1 and 5:1, a mold wall thickness variation greater than 2:1 can produce non-uniform heating: the thinner section reaches PIAT first and may begin to degrade while the thicker section remains below coalescence. This constraint is amplified by green pigmentation because the darker surface absorbs more infrared energy. A PIAT window of ±5 °C is commonly required for thin-walled parts because the transition from incomplete sintering to surface degradation is abrupt. Production-scale failures associated with this boundary include pinholes at sharp internal corners, weld-line porosity, and green-surface yellowing from mold release residue burnt onto the cavity.

The melt mass-flow rate of 4.5 g/10 min is an inverse indicator of flow resistance. At rotational moulding temperatures, the resin behaves as a low-shear viscous liquid; MFR alone does not fully capture coalescence rate, which also depends on surface tension, particle size, and oxidative induction time. A higher MFR can improve flow into complex mold geometry, but when MFR is too high, the final part may show reduced impact toughness and greater mold shrinkage. The reported value positions this grade for medium-complexity parts with wall sections between 3 mm and 15 mm.

Moisture control is an operational boundary. LLDPE is not hygroscopic, but powder stored at >60% relative humidity or transferred from a cold warehouse into a warm shop can carry surface condensation. Pre-drying at 70–80 °C for 2–4 h is recommended only when visible condensation or cold-powder handling has occurred. Continuous desiccant drying is not required for dry powder and can create static-charge difficulties during dry-flow feeding. Apparent density and dry-flow can be checked according to ISO 60 or ASTM D1895 when lot-to-lot feeding behavior changes.

After demolding, linear mold shrinkage for a 0.935 g/cm³ LLDPE rotational moulding powder typically falls between 0.020 and 0.030 mm/mm, with large flat panels at the upper end of the range. Warpage in green-pigmented parts is driven by differential cooling between the mold-contact surface and the free interior surface; water mist cooling applied too early can freeze the outer skin before the middle wall has fully crystallized, producing residual stress and dimensional instability. Mold release agents alter demolding forces and part gloss. Water-based semi-permanent release systems are preferred over silicone spray because silicone transfer can interfere with subsequent bonding or painting of the green surface.

Applications for the pigmented grade are concentrated in rotationally moulded outdoor housings, agricultural tanks, bins, and recreational components where the green color is part of the design. The environmental stress-cracking resistance measured by ASTM D1693 condition B at >1000 h supports service in contact with mild detergents and aqueous solutions. The material is not a crosslinked polyethylene and should not be specified for sustained contact with aromatic solvents, strong oxidizing acids, or continuous pressurized service above 60 °C without creep-rupture evaluation under ISO 9080.

Mechanical Property Benchmarks and Design Ceilings

The density of 0.935 g/cm³ places the base resin at the boundary between high-density and medium-density polyethylene. The flexural modulus of 600 MPa is approximately three times that of a high-pressure LDPE homopolymer, but lower than many rotational moulding HDPE grades with density near 0.945 g/cm³, which can exceed 900 MPa. Tensile elongation at break greater than 700% indicates ductile failure under tensile loading. Designers should apply a safety factor of 2.0 to 3.0 on the tensile yield value for long-term static loads, with higher factors where the part is exposed to ultraviolet radiation, chemicals, or elevated temperature.

Compared with butene-based LLDPE rotational moulding powders of similar density, this grade may show a different balance of processability and low-temperature ductility; the specific comonomer type is not consistently disclosed in public literature, and published data for this specific configuration is limited. Direct comparisons must use the same test method and moulded plaque thickness because rotational moulding impact values are sensitive to cooling rate and part wall thickness. Compared with general-purpose HDPE, the grade has lower stiffness but higher environmental stress-cracking resistance and better low-temperature ductility. Compared with high-pressure LDPE, it has higher tensile yield and greater environmental stress-cracking resistance. Compared with crosslinked polyethylene, it is reprocessable and can be ground and recycled, but it has a lower maximum continuous service temperature and lower resistance to oxidative environments.

The environmental stress-cracking resistance of >1000 h under ASTM D1693 condition B is not merely a single-point property; it reflects tie-molecule concentration and comonomer distribution in the amorphous phase. In rotational moulded parts, slow cooling increases crystallite size and can leave a lower tie-molecule density at the inner free surface, so the quoted ESCR value should be applied to parts that have been molded near the center of the process window rather than to severely over-baked or rapidly quenched parts.

Outdoor UV resistance should not be inferred solely from the presence of a green pigment. If discoloration, chalking, or loss of physical properties is a design limit, accelerated weathering should be performed according to ISO 4892-2:2013 or ASTM D2565. Pigment agglomerates larger than 10 µm can act as stress concentrators in tensile-loaded areas; dispersion quality can be assessed on microtomed sections by optical or scanning electron microscopy under ISO 18553.

When a Green-Pigmented LLDPE Grade Replaces Natural Powder in Existing Tooling

Tooling trials are required when converting from natural powder to Icorene 3545 GRN 6665. The pigment package can change melt coalescence behavior and may alter mold shrinkage by 0.002–0.005 mm/mm; this range is observed in industrial pigmented-polyethylene comparisons and should be verified on the target tool because published data for this specific configuration is limited. The colorant may also shift the coefficient of friction and release behavior, requiring adjustment of semi-permanent mold release protocols. Wall thickness distribution can change if the pigmented powder has a different bulk density or dry-flow angle; bulk density should be checked per ISO 60 or ASTM D1895, and the particle size distribution should be verified against the supplier’s lot report.

Finished part color should be measured against an agreed reference standard using ASTM D2244 or CIE L*a*b* coordinates. Lot-to-lot color variation is a practical limitation for visible parts; tolerances are commercial rather than universal. The green colorant may also reduce weld-line strength if it is not adequately dispersed, so weld lines at tool parting locations should be sectioned and tested before production release.

Compliance documentation is not a substitute for lotwise verification.

The resin supplier’s regulatory certifications apply to the natural base polymer unless explicitly extended to the pigmented compound. For food-contact use, the base olefin polymer may fall under FDA 21 CFR 177.1520; the green colorant must carry its own clearance or be listed for the intended use temperature and food type. In the European Union, the product is governed by REACH (EC) No 1907/2006; Annex XVII restrictions on cadmium, lead, and polycyclic aromatic hydrocarbons must be verified for the green concentrate. Under RoHS Directive 2011/65/EU, unpigmented polyethylene generally passes heavy metal limits, but colored grades require screening by IEC 62321 because pigment carriers and heavy-metal toners can introduce restricted substances.

In outdoor service, the green surface temperature under solar load can exceed 60 °C in high-sunlight climates; designs should account for thermal expansion and potential creep. The heat-aging resistance of the base resin should be measured by ISO 188 or ASTM D3045 if hot-air aging is a specification requirement. Published data for the GRN 6665 configuration is limited, so outdoor validation should include part-level testing rather than reliance on unpigmented resin data.

Rotational moulding with Icorene 3545 GRN 6665 is normally conducted with peak internal air temperature of 190–210 °C and cooling initiated after full coalescence. The material works best in wall thicknesses from 3 mm to 25 mm; thinner walls risk surface degradation before full fusion, while thicker walls may develop internal voids unless cooling is extended. The powder should be kept in sealed packaging and not mixed with moisture-retaining fillers above 5 wt% unless the filler is fully dry and has a particle size below 75 µm. These boundaries are general rotational moulding practice for medium-density LLDPE powders; lot-specific confirmation should be obtained from the LyondellBasell certificate of analysis.