LyondellBasell Icorene 3560 BWN 8410 is a linear low-density polyethylene supplied as a rotomoulding powder with a nominal density of 0.936–0.938 g/cm³ determined by ASTM D1505 and a melt flow rate in the range of 5.5–6.5 g/10 min at 190°C under 2.16 kg load measured according to ASTM D1238. The grade designation combines the 3560 base resin with the BWN 8410 formulation code; the suffix identifies a black, weather-resistant additive and colour package intended for outdoor exposure. The material is used principally on three-axis rotational moulding equipment for storage tanks, agricultural vessels, industrial containers, and structural parts with wall sections from 3 mm to 15 mm. The powder is not formulated as a general-purpose injection-moulding or blown-film grade; its particle size distribution, stabiliser package, and melt flow are tailored to carousel, shuttle, and rock-and-roll rotational moulding cycles. Lot-specific values should be verified against the manufacturer’s certificate of analysis before tooling decisions are finalised.

What Distinguishes Icorene 3560 BWN 8410 from Conventional Ziegler-Natta LLDPE Rotational Moulding Resins?

The distinguishing structural feature is the short-chain branch distribution of the ethylene/α-olefin copolymer and the resulting balance between crystallinity and impact resistance. Short-chain branches interrupt crystallisation more selectively than the long-chain branches found in low-density polyethylene. A density of 0.936–0.938 g/cm³ places this resin above conventional butene-based linear low-density rotomoulding grades in the 0.918–0.926 g/cm³ range and below high-density rotomoulding grades up to 0.965 g/cm³. The increase in density raises flexural modulus and Vicat softening temperature while retaining the environmental stress-crack resistance attributed to a higher concentration of tie molecules relative to high-density polyethylene. Under ASTM D1693 condition A with 100% Igepal CO-630, the F50 value for this resin class typically exceeds 1,000 h; a high-density rotomoulding resin of equivalent melt flow may fall below 200 h because of its higher spherulitic crystallinity and reduced interlamellar tie-chain density.

Compared with low-density polyethylene, the linear low-density architecture produces higher tensile yield and elongation but lower melt strength. The tensile strength at yield measured by ASTM D638 or ISO 527-2 is normally 16–18 MPa, whereas low-density rotomoulding grades of similar melt index commonly test below 12 MPa. The lower melt strength of linear low-density polyethylene is less critical in rotational moulding than in blow moulding because coalescence and densification occur against the tool wall rather than under free-surface extension. Compared with metallocene-catalysed linear low-density polyethylene grades, the Ziegler-Natta molecular weight distribution of this resin can provide a broader processing window by reducing melt elasticity and bubble stability during the later stages of densification, although dart impact and low-temperature toughness may be lower than those of a metallocene resin of comparable density. The following representative values are indicative; the manufacturer’s certificate of analysis controls for each commercial lot.

The physical form of the powder is equally important in rotational moulding. Bulk density measured by ASTM D1895 Method A is normally 0.32–0.38 g/cm³, and pourability by ASTM D1895 Method B is typically below 25 s for a standard cup. A nominal top size of 35 mesh with 5–12% passing 200 mesh is common for rotomoulding powders. Oversized particles slow densification and can create pinholes at the inner surface; excessive fines reduce bulk density and segregate during charging, leading to non-uniform wall thickness in ribbed areas. On production carousel machines with 100–300 kg charge per arm and fabricated carbon-steel or cast-aluminium tools, powder bulk density below 0.30 g/cm³ can cause bridging in feed hoppers and uneven distribution in narrow cores. The particle shape is nodular rather than spherical, which assists mechanical interlocking during the cold-packing phase but can increase static accumulation in dry conveying systems. If open bags are stored at relative humidity above 60%, drying in a dehumidified hopper at 60–70°C for 2–4 h is typical; the polymer is not hygroscopic, but surface moisture can interfere with electrostatic properties and powder flow.

When Oven Peak Internal Air Temperature Exceeds 280°C During Rotational Moulding

In rotational moulding, the powder is charged into a closed tool, and heating occurs by conduction through the metal wall and convection within the cavity. The process sequence is cold-packing, coalescence, densification, bubble removal, and cooling. Peak internal air temperature, referred to as PIAT, is monitored with a thermocouple inserted through a vent tube. For a 6 mm wall section processed in a forced-air oven at 280–300°C, PIAT normally reaches 180–220°C. If PIAT exceeds 280°C, the outer polymer layer can undergo thermal-oxidative degradation before the inner surface reaches complete densification. Oxidation induction time measured under ASTM D3895 at 200°C is used to monitor remaining stabiliser activity. The UV-stabiliser package is sacrificial at the exposed surface; prolonged oven residence consumes hindered amine stabiliser and can increase the carbonyl index measured by FTIR. The result is a decline in elongation at break and environmental stress-crack resistance, particularly at corners where local wall thickness is reduced by tool geometry.

Temperature distribution across the tool is not uniform. Thermocouple mapping on a 400 L cube tank tool with 6 mm walls can show a spread of ±8°C between the centre panel and corner ribs. This variation is sufficient to create differences in density, colour, and shrinkage if the oven profile is not adjusted. Tool surface temperature should be controlled within ±5°C to avoid under-fusion on the inner wall or oxidative degradation on the outer wall. Cooling rate is also a determinant of final shrinkage. Forced-air cooling at 10–15°C/min followed by water mist cooling is common; the part should remain in the tool until the demoulding temperature falls below 80°C. Cooling too rapidly through the recrystallisation range of 50–60°C can freeze in orientation and produce local shrinkage variation. Linear mould shrinkage of this density range is normally 2.0–2.5%, compared with 1.5–2.0% for low-density polyethylene and 2.5–3.5% for high-density rotomoulding grades.

Melt Rheology and Shrinkage Compensation in Tooling Design

A melt flow rate of 5.5–6.5 g/10 min places the resin in the medium-flow rotomoulding segment. This viscosity permits faster bubble removal and shorter heating cycles in thin-wall parts than grades in the 3–4 g/10 min range, but it can reduce impact resistance in thick sections because of lower molecular weight and reduced chain entanglement. Oscillatory rheology at 190°C indicates a broader molecular weight distribution than typical metallocene grades. The higher zero-shear viscosity and more pronounced shear-thinning response help the melt remain attached to the tool wall during heating, while sufficient elasticity assists bubble migration during the densification stage. For tooling design, linear shrinkage compensation should be based on free-shrinkage plaques tested under ASTM D955. A 1,000 mm internal tank dimension will generally require a tool dimension of 1,020–1,025 mm at room temperature when wall thickness is 6 mm. Draft angles of 1–2° and corner radii of at least 12 mm are used to prevent stress concentration and demoulding cracks.

Applications for Icorene 3560 BWN 8410 concentrate in outdoor storage tanks, agricultural chemical vessels, water-handling boxes, and industrial packaging. The black UV-stabilised formulation is intended for multi-year exterior exposure, but surface chalking and gloss loss alone should not be interpreted as mechanical failure until tensile property and stress-crack resistance retention have been assessed under ASTM D2565 or ISO 4892-2. For food-contact applications, compliance is established under FDA 21 CFR 177.1520 for olefin polymers. For potable water contact, component-specific testing under NSF/ANSI 61 or an equivalent national standard may be required; published data for this specific configuration in potable-water extraction is limited. The resin is not recommended for continuous immersion in aromatic solvents or strong oxidising acids above 40°C without compatibility testing. Under European legislation, compliance with REACH and, where applicable, RoHS must be confirmed for the final article. The difference from general-purpose linear low-density polyethylene is the combination of intermediate density, medium melt flow, black UV-stabilised formulation, and controlled powder morphology for rotational moulding. It should not be substituted into high-shear extrusion or injection-moulding operations without confirming that the particle form and additive package do not interfere with screw feeding, melt filtration, homogenisation, or die build-up. Qualification trials on production equipment remain necessary for final part certification.