LyondellBasell Icorene 3560 G BWN 8402 is supplied as a black, weathering-stabilized linear low-density polyethylene powder intended for rotational moulding. The commercial designation separates the base resin identifier 3560 G from the colour and additive suffix BWN 8402. The base resin is a butene-copolymer LLDPE with a nominal density of 0.935 g/cm³ when tested to ISO 1183-1:2019 and a melt flow rate of 3.5 g/10 min at 190 °C/2.16 kg when tested to ISO 1133-1:2022. The suffix denotes a black formulation with weathering stabilizers, although the exact carbon-black loading and stabilizer chemistry are not disclosed in the condensed public datasheet. The product is used for outdoor and industrial rotationally moulded hollow parts, including single-wall tanks, agricultural sprayer tanks, light-shielding enclosures, and playground components, where low-temperature ductility, environmental stress-cracking resistance, and ultraviolet resistance are required. Published data for this specific configuration is limited for long-term weathering and creep; converted-article testing and certificates of analysis are required for critical applications.

What Distinguishes a Rotational Moulding Powder from Film-Grade Butene LLDPE Resins?

At equivalent density and comonomer chemistry, the rotational moulding variant differs primarily in melt flow rate, additive formulation, and particle morphology. Film-grade butene LLDPE is typically pelletized and may carry a melt index below 1.0 g/10 min to maintain blown-film bubble stability, whereas 3560 G is ground into a free-flowing powder and is specified at 3.5 g/10 min to promote particle coalescence under low-shear sintering. A film resin is pumped through an annular die under high shear; a rotomoulding powder is not extruded through a die and relies on biaxial rotation, thermal conduction through the mould wall, and surface-tension-driven densification. The shift to powder increases oxidative surface area during heating. The BWN 8402 additive package therefore incorporates carbon black and weathering stabilizers to retard ultraviolet degradation in outdoor service. The exact stabilization chemistry remains proprietary, and published data for this specific configuration is limited for stabilizer migration behaviour in thick-walled parts.

Particle-size control is a critical incoming-lot parameter in stationary-mould charging. The powder is charged at ambient temperature before the mould enters the oven, and its particle-size distribution controls bulk density, corner fill, air release, and pinhole formation in undercut regions. Rotational moulding powders are generally screened to a nominal 35-mesh (500 µm) or finer top size, but the public datasheet for Icorene 3560 G BWN 8402 does not always publish a complete distribution. Bulk density affects shot weight and wall thickness; a variation of ±0.02 g/cm³ in apparent bulk density can shift wall thickness by several percent for a fixed-weight charge. Dry-flow time is measured under ASTM D1895 or equivalent funnel-flow methods, although many suppliers do not report a value for black rotomoulding powders. Accumulation of fines below 100 µm improves corner detail but increases dusting and reduces flow consistency, while coarse particles above 500 µm can leave pinholes if the peak internal air temperature is not maintained. Batch-to-batch particle-size drift in black UV-stabilized grades remains a recognized production bottleneck on carousel machines; incoming-lot verification should include mesh retention, bulk density, and dry-flow time before the tool is charged.

Rheological boundaries in low-shear rotational moulding

The melt flow rate of 3.5 g/10 min places 3560 G in the moderate-flow region for rotomoulding powders. The resin must sinter rapidly when the powder bed reaches its melting range, then densify without producing trapped bubbles. In low-shear rotational moulding, zero-shear viscosity is more relevant than capillary rheometry because the material is not mechanically mixed; heat transfer from the mould wall and internal air determines sintering. The moderate melt flow promotes coalescence in narrow ribs and inserts, but it also increases the risk of melt drainage on vertical walls if the peak internal air temperature is excessive. For a 0.935 g/cm³ butene-copolymer LLDPE, the sintering window is generally controlled by peak internal air temperature rather than oven set-point alone. Processors monitor the part internal air temperature with a thermocouple and adjust the oven cycle to hold the target band.

When 3560 G BWN 8402 Is Compared with Medium-Density HDPE Rotomoulding Powder

The comparison changes low-temperature impact, stiffness, chemical resistance, and cycle time. A 0.935 g/cm³ butene LLDPE has lower crystallinity than a 0.950 g/cm³ medium-density HDPE, so it normally exhibits lower flexural modulus and greater ductility. The lower melting peak shortens the required heat input, but it also lowers continuous-temperature resistance under load. Environmental stress-cracking resistance is generally higher for the LLDPE class, making the grade suitable for tanks and containers exposed to detergents, alcohols, or aqueous stress-cracking agents. The balance of properties is shown in the following comparative table for material classes; exact lot values for Icorene 3560 G BWN 8402 must be confirmed against the certificate of analysis.

The table is a material-class screening tool, not a substitute for part-specific validation. Because the exact comonomer content and molecular-weight distribution of 3560 G BWN 8402 are not disclosed, comparative conclusions should be based on actual tensile, flexural, and impact data measured on moulded specimens.

Thermal processing window and oven-cycle variance in biaxial rotational moulding

In production-scale carousel or shuttle machines, the powder layer is heated by conduction from the mould wall. For a 0.935 g/cm³ butene LLDPE, the target peak internal air temperature is commonly 190–210 °C, even though oven set-point temperatures may be 260–300 °C. If the peak internal air temperature remains below 180 °C, particle coalescence is incomplete and the inner surface can retain powder or pinholes. If the peak internal air temperature exceeds 220 °C for prolonged periods, oxidative degradation appears as yellowing, viscosity reduction, and bubble formation. The black BWN 8402 formulation contains carbon black, but carbon black does not eliminate oxidative attack on the polyethylene backbone; it screens ultraviolet light. Cooling rate is a second critical variable. Forced-air cooling produces a coarser crystalline structure and can increase warpage, while water-spray cooling quenches the part and reduces warpage but may freeze in residual stresses. Mould shrinkage for a 0.935 g/cm³ LLDPE is commonly 2.0–2.5%, depending on wall thickness, cooling rate, and cavity geometry.

In tank moulding, venting prevents pressure differentials during heating and cooling. A vent diameter of 10–15 mm per 0.1 m³ of cavity volume is a common starting point for LLDPE powders, but the porosity of the powder bed and the heat-up rate require adjustment. Blocked vents on a black grade are difficult to detect visually because carbon black obscures early thermal oxidation; ultrasonic thickness gauges and infrared imaging are used on production lines to identify delayed wall thinning. When a new lot of 3560 G BWN 8402 is introduced, the control practice is to maintain the same shot weight and oven recipe for the first article, then measure wall thickness at the parting line, sidewall, and corner radii. Adjustment of oven time by ±5% or peak internal air temperature by ±5 °C is often sufficient to return wall distribution to specification, but a shift greater than 10% in 35-mesh retention may require re-qualification of the tool. Incoming-lot verification remains essential because complete particle-size and stabilizer data are not always published in the condensed commercial datasheet.

Storage conditions affect dry-flow and surface quality. The powder should be stored in sealed containers at temperatures below 40 °C and protected from direct sunlight. Moisture uptake in LLDPE powder is usually low, but condensation on cold powder can introduce surface defects and porosity during heating. Pre-drying is recommended when the powder has been stored in an unheated warehouse with relative humidity above 60%; a desiccant dryer set to 60–70 °C for 2–3 h is typical, but the manufacturer's drying recommendation should take precedence. Black grades absorb radiant heat faster during handling in sunlight; closed containers reduce surface temperature variation and shot-weight drift.

For potable-water or food-contact uses, the grade's compliance status must be confirmed at the converted-article level. Polyethylene grades may be assessed under FDA 21 CFR 177.1520 for olefin polymers in the United States or under Commission Regulation (EU) No 10/2011 in the European Union, but black UV-stabilized formulations require additional attention to carbon-black purity and stabilizer migration limits. REACH registration and safety data sheet information are maintained by the supplier; the grade's status under the relevant packaging or waste directives depends on the final article and member-state implementation. Published data for this specific configuration is limited for potable-water approvals and specific migration testing; moulders should request the manufacturer's regulatory statement and perform article-specific extraction testing on the worst-case wall thickness.

Compared with hexene-copolymer LLDPE rotomoulding powders, butene-copolymer grades generally have lower dart impact and tear resistance at equivalent density and melt flow rate because hexene branches create longer tie molecules and improve toughness. The selection of a butene copolymer at 0.935 g/cm³ often balances cost against impact and environmental stress-cracking resistance. Published data for this specific configuration is limited for direct comparison with hexene-copolymer rotomoulding grades; direct laboratory comparison of ARM impact under ASTM D5420 or ISO 6603-2 and low-temperature ductility is required. Typical applications for black rotomoulding LLDPE include agricultural sprayer tanks, water storage vessels, outdoor seating, and industrial containers. The black UV package supports outdoor service, but the structural design must account for low modulus. For an unsupported flat panel, the lower flexural modulus relative to HDPE may require thicker walls or stiffening ribs. In chemical tanks, the stress-cracking resistance of butene-copolymer LLDPE is advantageous, but specific chemical compatibility must be tested with the actual filled fluid at the maximum service temperature. Published data for this specific configuration is limited for long-term chemical exposure at elevated temperature; no single polyethylene grade is universally resistant to all solvents, strong oxidizing acids, or aromatic hydrocarbons.