LyondellBasell Icorene 3560 BWN 8808 is a linear low density polyethylene (LLDPE) supplied as a free-flowing rotational moulding powder. The grade designation separates it from general-purpose LDPE and HDPE by combining an alpha-olefin comonomer with a stabilizer system intended for low-shear sintering. In comparison with high-pressure low density polyethylene, the linear structure provides higher tensile strength, puncture resistance and environmental stress crack resistance when evaluated by ISO 527-2, ISO 6603-2 and ASTM D1693. Because the powder is optimized for oven sintering and air release, it is not a direct substitute for injection moulding grades with high melt flow rate.

Specification documents for this product should list density at 23 °C by ISO 1183-1, melt flow rate at 190 °C/2.16 kg by ISO 1133-1:2022, tensile yield and elongation by ISO 527-2, flexural modulus by ISO 178, and low-temperature impact resistance by ISO 179-1/1eA or ASTM D746. Exact nominal values for this specific grade should be confirmed against the latest LyondellBasell Technical Data Sheet and batch certificate of analysis, because production campaigns may shift selected attributes within the release window. Rotational moulding powders in this family are also characterized by dry flow, bulk density by ISO 60, and sieve retention; a typical LLDPE powder bulk density of 0.40–0.50 g/cm³ and a controlled fraction above 35 mesh help to reduce pinholing and porosity in the sintered wall.

Why Is the Melt-Flow/Density Balance Critical for Rotational Moulding Grade Selection?

Rotational moulding does not impose high shear on the melt; the melt flow rate at 190 °C/2.16 kg is therefore an indirect measure of low-shear sintering and bubble release rather than pumpability. Within a fixed density class, a higher melt flow rate shortens oven residence time and improves air removal, but it generally lowers low-temperature toughness and ESCR. For a linear low density polyethylene in the Icorene 3560 family, the practical processing range is normally bounded by a melt flow rate of 3.0–7.0 g/10 min and a density of 0.930–0.940 g/cm³; the exact lot-target values are listed on the certificate of analysis. A density below 0.925 g/cm³ reduces stiffness and increases creep, while a density above 0.945 g/cm³ raises warpage and lowers notched impact. The cliff edge is typically quantified by measuring notched Charpy impact at -40 °C on specimens prepared according to ISO 293 and tested by ISO 179-1/1eA.

On commercial carousel machines with an arm ratio of 4:1 and direct gas-fired ovens, the powder charge passes through heating, sintering, densification, bubble removal and cooling. Oven air temperature is commonly set between 280 °C and 320 °C; peak internal air temperature for LLDPE is typically held between 190 °C and 210 °C depending on wall thickness and mould-metal mass. Peak internal air temperatures below 180 °C produce incomplete coalescence, pinholes and weak weld lines, while values above 220 °C accelerate thermo-oxidative chain scission, discoloration and embrittlement. Cooling rate is equally critical: a water-mist or forced-air quench shortens cycle time but freezes lower crystallinity and increases differential shrinkage, while slow air cooling raises crystallinity and stiffness but can increase warpage across ribbed sections. Shot weight is derived from part wall thickness and solid polymer density; a 3 mm wall over a 1 m² surface corresponds to approximately 2.8–3.0 kg of LLDPE at a part density of 0.94–0.95 g/cm³, with additional allowance for flash and fill-port losses. Published data for this specific machine configuration is limited, so initial trials should establish the oven cycle, rotational speed ratio and cooling profile using instrumented moulds.

Mechanical Strength and Environmental Stress Crack Resistance

Tensile yield and elongation at break are usually measured on ISO 527-2 Type 5A specimens at 50 mm/min. Flexural modulus is determined according to ISO 178 at 2 mm/min. ESCR under ASTM D1693 condition B, 100% Igepal CO-630 at 50 °C, is the most useful separator between LLDPE and high-pressure LDPE. A representative LLDPE rotational moulding compound can remain crack-free beyond 500 h, whereas a high-pressure LDPE may fail at 1–100 h under the same bending strain. The test is sensitive to moulded-in stress: non-uniform cooling or contamination with high-melt-index regrind can reduce the measured value substantially. At -40 °C, the ductile-to-brittle transition depends on comonomer type, comonomer content and cooling history. A butene-based LLDPE usually has lower puncture resistance and ESCR than a hexene-based material of equivalent density, which is why chemical storage vessels and fuel-tank components often specify a hexene LLDPE within the 0.930–0.940 g/cm³ density range.

These ranges are typical for unfilled rotational moulding grades; the exact value for Icorene 3560 BWN 8808 may differ by comonomer type, additive package, and moulding conditions.

Field experience on single-arm shuttle machines indicates that powder conditioned at 20–30 °C and 40–60% relative humidity maintains reproducible dry flow and prevents electrostatic build-up in fill ports. When regrind above 15 wt% is introduced, the melt flow rate of the combined charge can drift upward and low-temperature puncture energy can decrease by more than 20% because oxidized regrind particles act as nucleation promoters. A dry-air dryer set at 60–70 °C is often used for powder stored in unsealed sacks, but drying should be limited because excessive thermal exposure may consume antioxidant reserves before moulding.

When Low-Temperature Ductility and Impact Requirements Govern

For parts that must withstand impact below -20 °C, the grade should be validated on rotomoulded plaques rather than compression-moulded sheets. Low-temperature Charpy impact by ISO 179-1/1eA or instrumented puncture by ISO 6603-2 reflects the influence of powder-sintering defects, microvoids and weld lines. At wall thicknesses below 2 mm, weld-line quality dominates impact results; above 8 mm, internal shrinkage can create cavitation. A typical HDPE rotomoulding grade may exhibit a flexural modulus of 800–1,200 MPa but a notched Charpy impact at -40 °C below 6 kJ/m², whereas an LLDPE formulation can retain a value above 10 kJ/m². The trade-off is lower stiffness; ribs, gussets or thicker walls are required when deflection limits govern the design.

Dry-blended pigments for rotational moulding require attention to carrier resin and powder particle size. A pigment masterbatch based on a high-pressure LDPE with a melt flow rate above 20 g/10 min may melt before the LLDPE powder sinters, creating localized color streaks and impact loss at the blend interface. When colorant loadings exceed 0.5 wt%, visual inspection is insufficient; instrumented puncture tests by ISO 6603-2 on conditioned plaques are recommended. Titanium dioxide and carbon black loadings should also be screened for ESCR retention under ASTM D1693, because these pigments can increase notch sensitivity.

Outdoor applications such as kayak shells, agricultural hoppers and water-storage tanks require a UV-stabilized formulation. The BWN 8808 suffix identifies a specified additive package, but the final UV performance must be confirmed with accelerated weathering according to ISO 4892-2 or ASTM G154. A QUV cycle with UVA-340 lamps and a 1,000 h exposure is used for screening chalking and discoloration, but it does not replace outdoor exposure for gloss retention. Titanium dioxide at 2–4 wt% is common for white parts; in walls below 4 mm, tensile elongation at break may decline by more than 50% within 3,000–5,000 h of accelerated weathering unless sufficient hindered amine stabilizer is present.

Regulatory status should be confirmed for the specific lot. In the European Union, the polymer itself is generally exempt from registration under REACH (EC) No 1907/2006, but monomers and additives may require dossier coverage. For food-contact uses, compliance with FDA 21 CFR 177.1520 for olefin polymers is the starting point, and the finished article must also satisfy migration limits in 21 CFR 176.170 or equivalent national legislation. A grade-specific compliance letter is required before use in potable water, toy or medical applications; a generic resin statement is not sufficient. The absence or presence of slip, antiblock, UV stabilizer and processing antioxidant depends on the BWN 8808 packaging designation and should be documented on the batch release.

Selection of Icorene 3560 BWN 8808 over a metallocene-catalysed LLDPE may be justified where a broader sintering window is more important than maximum dart impact. Metallocene grades often show higher impact strength at equivalent density and better organoleptic properties, but they may require a higher peak internal air temperature or a longer sintering hold to eliminate surface defects. Where a processor observes pinholes or bubbles on parts moulded from metallocene LLDPE at 190 °C internal air temperature, a conventional comonomer-distribution grade may allow a lower peak temperature. Conversely, for fuel tanks or solvent containers, LLDPE alone does not provide sufficient barrier performance; a multi-layer structure with HDPE or polyamide is required. Oxygen permeation testing should follow ASTM D3985, and liquid hydrocarbon permeation may be assessed by ASTM D2684 or an equivalent weight-loss method.

The material should not be processed in direct contact with copper-based mould release agents at elevated temperatures because copper can catalyse thermo-oxidative degradation. When external mould release is necessary, a polytetrafluoroethylene-based or silicone-based release agent is preferred, and the mould surface temperature should be maintained above 70 °C to prevent excessive release-agent transfer. Pre-drying is required at relative humidity above 60% only when the powder has been exposed to moisture; drying at 60–70 °C for 30–60 min is sufficient to restore dry flow without consuming stabilizer reserves.