The designation LyondellBasell Icorene 3560 GRN 6208 identifies a linear low density polyethylene rotational molding feedstock in which the suffix GRN 6208 is a green pigment code. The base resin is a mid-viscosity LLDPE with a nominal melt flow rate of 3.5 g/10 min when measured under ISO 1133-1:2022 at 190 °C and 2.16 kg. The grade is intended for rotationally molded enclosures, portable tanks, agricultural hoppers, and recreational parts requiring low-temperature ductility and environmental stress crack resistance. Published lot-specific certificates from LyondellBasell control the green-compounded lot values; natural-grade data should be treated as a baseline only.

The green pigment affects infrared absorption during the oven cycle. In biaxial rotational molding machines, darker molds filled with green powder typically approach peak internal air temperature faster than natural or white grades when oven set point and air-flow rate are held constant. That difference requires thermocouple-based cycle adjustment rather than a fixed time-based recipe. On a four-arm carousel with 4:1 arm ratio and forced-air oven set at 280–300 °C, the operator should track peak internal air temperature and adjust oven dwell until the part reaches the target range; published data for this specific pigment code is limited, and lot-specific processing trials are recommended.

The nominal density of the natural resin is 0.936 g/cm³ under ISO 1183-1:2019. A green lot can shift density by a small amount, typically within the reproducibility limits of the method, but that shift is not negligible for mass-to-volume conversions in part design. The lower density compared with HDPE reduces specific part weight for a fixed wall thickness; however, it also lowers flexural modulus, meaning that load-bearing panels may require thicker nominal sections or ribbing.

The Oven Set Point Is Not the Process Limit; Peak Internal Air Temperature Is

Thermocouple placement is the controlling measurement. For this grade, the practical target for peak internal air temperature is normally between 190 °C and 205 °C; values below 185 °C produce incomplete densification and microscopic voids at the wall core. Values above 220 °C accelerate chain scission and carbonyl formation, which degrades impact strength and can change the green surface to a matte or oxidized appearance. The oven set point often exceeds 290 °C, but the internal air temperature is the process limit, not the oven dial setting.

Because polyethylene has a thermal conductivity near 0.4 W/m·K, the heat-up rate is dominated by wall thickness and mold material. Steel molds with 6 mm nominal wall require appreciably longer densification time than aluminum molds of the same wall; on an aluminum mold, the lower heat capacity allows faster approach to peak internal air temperature but increases sensitivity to overcure. Rotational molding machines with uniaxial drive may produce less uniform wall thickness on complex parts than biaxial machines with 4:1 or 5:1 arm ratios; the choice of equipment is part of the process boundary for this powder.

Cooling after densification modifies crystallinity and warpage. Forced air cooling at 10–20 m/s across the mold surface reduces cycle time but can set up differential shrinkage on flat panels. Slow cooling from 120 °C to 70 °C in still air minimizes warpage but increases total crystallinity and post-molding shrinkage; the effect is measurable as dimensional change after 24 h at 23 °C under ISO 291 conditioning. The green powder should not be mist-cooled unless the specific color formulation is known to withstand rapid shell release without stress whitening.

What Limits the Use of a 3.5 g/10 min LLDPE in Thin-Wall Rotomolded Liners?

Flow at rotomolding shear rates is best assessed by sintering rate and dry powder flow, not by capillary melt flow alone. The 3.5 g/10 min melt flow rate indicates mid-viscosity, which supports wall thickness retention in deep vertical draws but may delay particle coalescence in very thin sections below 2.5 mm. In those sections, the cycle must be extended or the oven set point increased, which narrows the margin against overcure. For nominal wall thickness from 4 mm to 10 mm, the grade tends to produce a more homogeneous wall than higher-melt-flow LLDPE, provided the powder is dry and mold rotation is continuous.

Powder particle size and dry flow control the thin-wall limit. Rotomolding powders for this class are conventionally through 35 mesh (500 µm) at high retention, with limited fines to avoid dust accumulation. A dry-flow funnel time is usually specified on the certificate of analysis; if the powder has been stored in an unheated warehouse and moved to a humid molding hall, condensation raises interparticle friction and produces charge patterns that reduce the powder’s ability to coat deep corners. Pre-conditioning at 20–25 °C for 24 h is a conservative handling requirement when ambient relative humidity exceeds 60%.

The green colorant can be advantageous in thin walls because it absorbs radiant energy more efficiently than natural powder. But that same absorption accelerates the surface temperature at the mold wall, increasing the risk of oxidative degradation at the outer surface while the core remains below densification temperature. The resulting gradient can be measured by differential scanning calorimetry as a bimodal melting endotherm; FTIR carbonyl index increases at the outer surface before the core shows any sign of undercure.

Property Benchmarks, Test Standards, and Lot-Specific Certificates

Table 1 lists representative values for the natural Icorene 3560 grade. The GRN 6208 color lot may differ slightly in density, elongation, and weathering behavior; the lot-specific certificate of analysis is the controlling document.

The elongation at break value is a tensile test response on compression-molded plaques; it does not guarantee elongation in rotationally molded walls containing weld lines, pigment dispersion boundaries, or uneven cooling. For part validation, a low-temperature drop-weight impact test on actual molded panels is more relevant than tensile elongation.

Potential regulatory assessments used for this pigment-containing polyolefin are listed in Table 2. The table is not a declaration of compliance; it identifies the verification path for a specific end-use.

Application usage extends to outdoor equipment housings, portable tanks, recreational parts, and agricultural hoppers where the part is emptied and cleaned seasonally. The grade is not intended for continuous immersion in aggressive solvents at elevated temperature; compatibility testing should follow ASTM D543 using the actual chemical formulation. For potable water contact, the finished article must be validated against local regulatory extraction and migration protocols, not assumed compliant from the base resin alone.

When HDPE Rotomolding Grades Are Replaced by This LLDPE in Structural Shells

Substitution of a conventional HDPE rotomolding grade by this LLDPE changes the load-deflection response of the part. A typical HDPE rotomolding class at 0.945–0.960 g/cm³ density produces flexural modulus values in the range of 900–1200 MPa; the lower density of this LLDPE places flexural modulus near 700 MPa. For a pressure vessel or structural cover, the lower modulus may require an increase in nominal wall thickness or the addition of ribs to maintain the same deflection limit under the same load.

The offsetting benefits are environmental stress crack resistance and low-temperature ductility. HDPE rotomolding grades often show ASTM D1693-B F50 values below 200 h; the natural Icorene 3560 grade is reported above 1000 h. In impact at subzero temperatures, the LLDPE retains ductile tearing where a conventional HDPE might exhibit brittle fracture. This shift is particularly relevant for outdoor tanks exposed to agricultural chemicals, where stress concentrations at inserts and sharp drainage bosses dominate failure.

Compared with a high-flow LLDPE rotomolding grade with melt flow rate above 5 g/10 min, this product sacrifices some ease of thin-wall filling but provides greater resistance to melt slump and more uniform wall distribution on vertical walls. The lower melt index also supports higher molecular weight, which improves environmental stress crack resistance but reduces flow into intricate stiffening ribs. Tooling design should avoid sharp corners with radii below 3 mm on structural ribs to prevent powder bridging and local thinning.

Compared with cross-linked high-density polyethylene used for chemical tanks, this LLDPE does not rely on covalent cross-linking to achieve environmental stress crack resistance. The absence of a cure step simplifies recycling and reduces the risk of overcure gel defects, but it places a stricter ceiling on continuous service temperature. Rotational molding grades in the 0.936 g/cm³ density class typically retain lower modulus than cross-linked HDPE, so stress-cracking resistance is gained through tie-molecule and comonomer architecture rather than network formation.

Moisture control during storage and handling is a boundary condition. Although the LLDPE polymer itself is hydrophobic, a green powder brought from 5 °C storage into a 30 °C, 70% RH molding hall can condense surface water. If pinholing or surface roughness appears only after seasonal humidity changes, the root cause is often powder condensation rather than a shift in melt flow. Pre-conditioning the sealed powder to 23 °C before transfer and reducing open hopper dwell under humid conditions prevents most condensation-related defects.

Colored lot control is another limitation. The GRN 6208 color code should be quoted in full for replenishment orders; substituting a natural grade plus external colorant can create a different particle-size distribution and thermal absorption profile. If the part is used in outdoor service, the external colorant route may also reduce UV stabilization effectiveness unless the additive package is re-qualified. End-users should require a certificate of analysis for each lot and retain a molded plaque reference for color change and retained properties.

Because the green pigment modifies heat absorption, the safest processing route for lot changes is to compare three consecutive parts made from the previous lot and the new lot with identical oven residence time and mold rotation. If the peak internal air temperature differs by more than 5 °C, adjust the oven dwell before releasing production. This is an operational boundary, not an indication of resin failure.