LyondellBasell Icorene 3560 BWN 8810 Polyethylene, Linear Low Density is a compounded linear low density polyethylene grade positioned for low-shear rotational moulding of hollow parts requiring a balance of impact strength, environmental stress-crack resistance, and processability. The Icorene 3560 base designation identifies a 3xxx-series rotomoulding powder; the suffix BWN 8810 denotes a formulation package rather than a neat reactor flake. Distributor literature for closely related Icorene 3xxx grades commonly places the melt flow rate between 4 g/10 min and 7 g/10 min at 190°C under 2.16 kg load, and the density between 0.930 g/cm³ and 0.940 g/cm³. These values are class-typical and should not be treated as a certificate of analysis; the BWN 8810 suffix may include colour and stabiliser additives that shift final density, ash content, and melt flow. Specific lot values must be obtained from the LyondellBasell technical datasheet or certificate of analysis.

What separates this LLDPE grade from high-pressure LDPE during densification?

The polymer architecture is produced by low-pressure coordination catalysis rather than radical autoclave or tubular polymerisation. As a result, the backbone contains short-chain branches from α-olefin comonomer incorporation but lacks the long-chain branching characteristic of high-pressure LDPE. At equivalent melt flow rate, the LLDPE exhibits less shear thinning and a broader sintering plateau; in rotational moulding, this means the powder particles coalesce into a continuous melt film with less rapid sag on vertical walls. High-pressure LDPE, by contrast, melts out more quickly and produces smoother internal surfaces but has lower environmental stress-crack resistance and lower long-term creep performance. The absence of long-chain branching also reduces strain hardening during bubble removal, so venting and cycle time become critical in thick sections.

The following table presents the property envelope commonly used for first-pass design with 0.930–0.940 g/cm³ rotomoulding LLDPE compounds. It should not replace lot-specific data for the Icorene 3560 BWN 8810 grade.

On a carousel rotational moulding line with swing diameter between 2.0 m and 4.5 m, the powder is charged into closed aluminium or steel moulds and heated by forced air at oven temperatures of 270°C to 310°C. The primary control variable is peak internal air temperature, which for a 3.5 mm nominal wall typically falls between 200°C and 230°C. Below about 190°C, residual unmelted particles or gas bubbles create pinholes; above 235°C, oxidative degradation reduces impact strength and can shift colour in unpigmented or lightly pigmented grades. Peak internal air temperature is measured with a thermocouple passing through the vent; the thermocouple must be located at the mould cavity centre and shielded from direct flame impingement. Production lines that rely only on oven set point produce larger wall-thickness scatter because heat flux varies with mould mass, colour, and airflow velocity.

Heat transfer in the mould is controlled by forced-air velocity and mould wall thickness, not by the polymer melt alone. For a 6 mm aluminium mould wall, an air velocity of 3–5 m/s across the mould face is commonly used; below this range, the outer surface may degrade before the inner surface reaches sintering temperature. Mould release agents should be selected for low surface energy without silicone migration; silicone levels above 0.1 mg/m² on the mould surface can cause surface defects in subsequent painting or welding operations. For welding, hot-plate or extrusion welding of rotationally moulded joints should follow the supplier's recommended surface preparation because carbon black and stabiliser additives affect weld strength.

Cooling is the dominant variable for warpage. Forced-air cooling followed by water mist shortens cycle time but increases through-thickness residual stress. Slow cooling through the 90°C to 70°C band at 5–10°C/min permits crystallisation shrinkage to distribute more uniformly and reduces corner lift in flat-sided tanks. On square moulds, an arm ratio below 4:1 creates localised thickening at the centre and thinning at corners; increasing secondary-axis speed relative to primary-axis speed can restore distribution but may introduce powder turbulence. Baffles, vent tubes, and fibre gaskets must be inspected after every shift because black compounded powders can generate more static charge and dust accumulation. The powder particle size distribution should be controlled such that material below 35 mesh does not exceed approximately 15% by weight; excessive fines increase dust explosion hazard and reduce bulk density flow into complex mould passages.

When the BWN 8810 suffix is a black UV-stabilised compound, venting and stabiliser depletion become the controlling variables.

For outdoor service, the BWN 8810 packaging may include carbon black, hindered amine light stabilisers, and phenolic antioxidants. Carbon black at loadings above about 2.5 phr can provide UV screening and extends service life under ASTM D2565-16 or ISO 4892-3:2016, but it also increases radiative heat absorption during oven residence. A black powder can reach peak internal air temperature faster than a natural powder of the same base resin; if the cycle is not reduced, the inner wall may exceed 235°C while the outer wall is still compacting. Field measurements on black rotomoulding grades show that cycle time reductions of 5–15% relative to natural grades are common to avoid thermal oxidative failure. Conversely, carbon black loadings below 1.0 phr may not provide adequate UV opacity for long outdoor exposure; published data for the exact BWN 8810 formulation is limited, so end-use weathering validation should be performed using the intended part geometry and wall thickness.

Venting must be maintained with PTFE or stainless steel tubes. Decomposition products from stabiliser systems and residual moisture can raise internal pressure, displace the powder bed, and create pinholes or blowholes at mould parting lines. The vent opening for mould volumes between 0.1 m³ and 0.5 m³ is typically 0.75 mm to 1.0 mm; smaller holes plug with carbon black deposits, while larger holes allow melt to creep into the vent during cooling. Vent tube replacement should be scheduled at least every 50 cycles when processing black compounds. Dry-blending with zinc stearate above 0.5 phr is not recommended because excessive acid scavenger can plate out on the mould surface and interfere with carbon black dispersion. Similarly, copper-based anti-fouling additives should not be introduced without comparative thermal-oxidative stability testing.

Applications for the grade include rotationally moulded agricultural tanks, industrial containment structures, marine floats, and outdoor furniture bases. In these parts, nominal wall thickness commonly ranges from 3 mm to 8 mm, with local corner thinning held to less than 20% of nominal wall. Moulded-in metal inserts should be preheated to the mould wall temperature before charging; a boss-to-plate thickness ratio below 1.5 prevents quench-induced cracking around the insert. Batch-to-batch shifts in powder bulk density from 0.35 g/cm³ to 0.42 g/cm³ change the effective charge volume, so the shot weight should be corrected by bulk density measured under ASTM D1895-17 Method A rather than by volumetric dosing alone. For potable water or food-contact use, certification under NSF/ANSI 61 or EU Regulation (EU) No 10/2011 is not automatic for every suffix and must be confirmed with the supplier for the exact BWN 8810 formulation. Chemical resistance is generally acceptable for dilute acids and alkalis at ambient temperature, but the material is not suitable for strong oxidisers, aromatic hydrocarbons, or chlorinated solvents above 50°C.

Mechanical property differences emerge only after controlled cooling through the 90–70°C band.

Compared with high-pressure LDPE of the same melt-flow rate, the LLDPE compound provides higher tensile yield stress and greater puncture resistance because linear chains generate a higher density of tie molecules, but it processes with a narrower bubble-removal window. Compared with HDPE rotomoulding grades at densities above 0.945 g/cm³, the LLDPE compound sacrifices flexural modulus and surface hardness while gaining environmental stress-crack resistance and low-temperature ductility. Under ASTM D1693-21 with 100% Igepal CO-630, condition B, class-typical 0.935 g/cm³ LLDPE rotomoulding compounds exceed 1000 h, whereas many HDPE rotomoulding grades fail below 100 h in the same test. The ductile-to-brittle transition is also displaced to lower temperatures; ASTM D746-20 brittleness temperature for unpigmented versions in this density class is typically below -70°C, while HDPE grades may become brittle between -20°C and -40°C. These differences are not thermodynamic constants; they depend on cooling rate, pigmentation, part wall thickness, and mould geometry.

Against metallocene LLDPE, the separation is smaller in density and melt-flow range but visible in thermal behaviour. Metallocene grades may show narrower melting ranges and lower seal initiation temperatures; older rotomoulding LLDPE grades often display a broader sintering plateau that is more forgiving on machines with uneven oven airflow. The choice between these materials should be made on the basis of process capability and the end-use standard, not on single-point melt index alone.

Handling and storage boundaries apply. Moisture uptake above 0.10% by weight can generate steam porosity; sealed packaging and storage below 60% relative humidity are required. When sealed bags are opened in humid conditions, pre-drying at 60°C for 2 h may be required. This powder is not designed for high-shear injection moulding or conventional screw plasticating; powder bridging in standard pellet feed throats and melt temperature overshoot can occur. Mixing with abrasive fillers or glass fibre is not recommended without a mould surface wear study, because the soft LLDPE matrix does not prevent erosion of aluminium tools at sharp corners. Avoid dry-blending with calcium carbonate above 5 phr if tensile strain at break must remain above 500%. The LyondellBasell technical datasheet and lot-specific certificate of analysis for Icorene 3560 BWN 8810 remain the controlling documents for procurement and part qualification.