LyondellBasell Icorene 3560 G BWN 8440 is classified under ISO 1043-1 as polyethylene, linear low density (PE-LLD). The material is supplied as a powder for low-shear thermoplastics conversion, predominantly rotational moulding. The designation string 3560 G BWN 8440 combines the manufacturer’s base-resin identifier, stabiliser or additive package, and packaging code; the alphanumeric suffix does not directly encode tensile, impact, or rheological properties. Lot-specific certificates of analysis should therefore control all incoming material decisions. Supplier-published nominal data for this grade place the density in the 0.935–0.940 g/cm³ band and the melt flow rate at 190 °C and 2.16 kg in the 3.0–6.0 g/10 min window, measured by ISO 1183-1 and ISO 1133-1:2022 respectively. Published data for the exact comonomer type and additive loading of this specific configuration is limited; the density and flow band indicate a medium-stiffness LLDPE intended for thick-section moulded articles rather than film or high-shear injection moulding.

The structural position of the grade is between high-pressure LDPE and unimodal HDPE. Short-chain branching from comonomer insertion reduces lamellar thickness, lowers density, and improves slow-crack growth resistance compared with HDPE, while the absence of long-chain branching reduces melt strength relative to high-pressure LDPE. This architecture influences both processing behaviour and end-use mechanical response, and it is the principal source of differentiation from other polyolefins.

What separates this linear low-density powder from high-pressure LDPE, unimodal HDPE, and higher-VA copolymers?

The differentiation originates in molecular architecture rather than melt flow rate alone. High-pressure LDPE carries long-chain branches that increase shear thinning and melt strength, but its density range of 0.912–0.930 g/cm³ and crystallinity of 40–50% provide lower stiffness than the present grade. Unimodal HDPE exhibits density of 0.940–0.965 g/cm³, crystallinity of 60–80%, and higher tensile yield stress, but rotomoulded HDPE can show lower cold-temperature impact and slower densification at equivalent internal air temperature. Higher-VA copolymers such as EVA with 18 wt% vinyl acetate have a lower crystalline melting range and greater low-temperature flexibility but lower tensile strength and higher gas permeability. The Icorene grade, by virtue of its linear backbone and short-chain branch distribution, exhibits an intermediate tensile modulus and better environmental stress crack resistance than a comparable melt index high-pressure LDPE.

Compared with a high-pressure LDPE rotomoulding powder of identical melt flow rate, the linear grade exhibits superior tensile yield, higher environmental stress crack resistance, and lower melt strength. It can be removed from the oven at a lower peak internal air temperature without excessive sag, but it may require a longer sintering hold because the linear chains have less long-chain branching to promote particle coalescence. Compared with a high-density polyethylene of identical density, the unimodal HDPE has higher crystallinity and stiffness but lower impact at −20 °C; the LLDPE architecture is therefore preferred where thin walls and impact toughness are combined. Ethylene-vinyl acetate copolymers with high VA content are selected for low-temperature flexibility and soft-touch surfaces, but their tensile modulus is generally too low for self-supporting tanks unless heavily crosslinked.

When the powder is rotated through a biaxial mould cavity

Rotational moulding converts the powder without imposing high shear. A carousel, shuttle, or rock-and-roll machine rotates the mould in two axes at low speed; primary arm speeds of 2–10 rpm and secondary plate speeds of 0.2–0.8 times the primary speed distribute the powder. Oven set points fall between 260 °C and 330 °C, and the peak internal air temperature is held between 190 °C and 220 °C for full densification. The critical upper limit is approximately 230 °C; excursions above that value initiate oxidative degradation of the polymer and consume the hindered phenol/phosphite stabiliser package, which results in yellowing, surface pitting, and measurable loss of instrumented dart impact. The lower limit of 185 °C produces incomplete sintering of powder particles, leaving pinholes and internal porosity at corners. The practical processing window of ±5 °C around the optimum peak internal air temperature is therefore an important production control parameter.

In shear-free rotomoulding, zero-shear viscosity controls coating and densification more than the melt flow rate in extrusion. An MFR of 3.0–6.0 g/10 min corresponds to a zero-shear viscosity of approximately 3×10³–7×10³ Pa·s at 200 °C. This viscosity permits the melt to wet aluminium or steel tool surfaces and release air bubbles before solidification, but it does not provide the high melt strength needed for blow-moulding parison stability. Powder particle size distribution is checked by dry sieve analysis following ASTM D1921-18 or an equivalent supplier internal method; a minimum of 90 wt% passing 35 mesh (500 µm) is normally required. Oversize particles reduce wall-thickness uniformity and increase surface porosity at sharp radii.

Production-scale experience on aluminium moulds shows that the most frequent failure mode is corner porosity from premature cooling. If the mould is removed from the oven before the thickest section reaches 190 °C, residual powder at the parting line or corners remains unsintered; this defect is observed as an orange-peel inner surface and local voids under a razor-cut cross-section. In contrast, overcure marks appear as discoloured, brittle patches on the thinnest section because the same thermal cycle drives the thin wall past 230 °C. The use of internal air temperature sensing in the thickest section, not oven temperature alone, is therefore mandatory for parts with wall thickness variation above 6 mm. On shuttle machines with sequential heating, an increase in oven residence time of 10–15 s per additional 1 mm wall thickness is a practical starting point, but infrared thermography of the mould surface should be used to verify uniformity.

Pigmenting is normally performed by high-shear dry blending. Mixer impeller tip speeds below 5 m/s fail to separate agglomerated carbon black masterbatch; speeds above 15 m/s can generate frictional heat, soften the powder, and form pigment-rich agglomerates. The maximum loading of external metal stearates should not exceed 0.3 wt% unless a formulated masterbatch has been qualified, because excess stearate migration during slow cooling can reduce adhesion of printed, foamed, or bonded surfaces. If the BWN 8440 additive package does not contain an ultraviolet stabiliser, outdoor parts require an additional UV masterbatch; carbon black at 2.0–2.5 wt% improves weatherability but can reduce retained impact if dispersion is poor.

Storage before processing also defines the operating limits. The powder is not hygroscopic, but condensation from cold outdoor storage should be evaporated before charging because trapped water forms steam porosities at peak internal air temperature. Storage below 10 °C and rapid transfer to a warm moulding hall can produce surface condensation; if relative humidity exceeds 60%, pre-drying at 60–70 °C for 1–2 h is used. Stack pressure on pallets should remain below the point of cold compaction because compacted powder clumps can survive the dry-blending step and produce localised gel-like defects.

Mechanical qualification uses moulded specimens rather than raw powder. Tensile yield stress and elongation at break are determined by ISO 527-2:2012 at 50 mm/min on type 1B specimens cut from rotomoulded plaques. For the 0.935–0.940 g/cm³ density band, tensile yield stress is typically 15–20 MPa and elongation at break exceeds 800%. Flexural modulus by ISO 178:2019 is typically 550–750 MPa. Instrumented puncture by ISO 6603-2:2000 at −20 °C often gives ductile failure with no crack propagation, although the numerical energy depends on specimen thickness and cooling rate. Vicat softening temperature by ISO 306/A120 is in the 110–120 °C range. These values should not be used for design without lot-specific data because rotational moulding cooling rates alter crystallinity and impact response.

Environmental stress crack resistance is the principal advantage of this grade over high-pressure LDPE and many HDPE rotomoulding grades. ESCR testing per ASTM D1693-21 in Igepal CO-630 at 50 °C commonly exceeds 1000 h at F50 for qualified LLDPE rotomoulding powders of this density band; the exact value is batch-dependent and can fall below 500 h if the internal air temperature is too low or the part is inadequately cooled. Slow-crack growth resistance can also be screened by full-notch creep test ISO 16770:2004 or notched pipe test ISO 13479, although published data for this specific configuration is limited.

Chemical compatibility is typical of medium-density LLDPE. Aqueous acids, alkalis, and salt solutions are generally tolerated at ambient temperature; aromatic hydrocarbons, chlorinated solvents, and strong oxidising acids cause swelling, softening, or stress cracking. For aggressive service, immersion testing by ISO 175:2010 or ASTM D543-21 is required before part release. The grade is not a high-barrier resin; oxygen permeation is higher than HDPE and lower than high-pressure LDPE at equivalent thickness, and design for fuel or solvent contact is outside the expected capability window.

Regulatory classification and certification limits

In Europe, food-contact polyethylene articles are governed by Regulation (EU) 10/2011, with an overall migration limit of 10 mg/dm² for plastic materials and specific migration limits for monomers and additives. In the United States, olefin polymers may be evaluated under 21 CFR 177.1520, which covers polyethylene and olefin copolymers for food contact and imposes density, solubility, and extractable fraction conditions. The supplier must provide a regulatory statement for Icorene 3560 G BWN 8440 for each lot; the absence of such a statement should be treated as non-qualified for food contact. RoHS 2011/65/EU compliance requires that cadmium is below 100 ppm and lead below 1000 ppm in homogeneous materials, but the resin supplier’s heavy-metal declaration should be obtained.

For demanding applications, the grade is best specified by a complete qualification matrix. Acceptance limits are agreed between converter and end user, not derived solely from the resin data sheet.

In practice, the grade is selected for low-shear moulded articles such as storage tanks, agricultural reservoirs, leisure parts, and industrial containers. It is not intended for high-shear injection moulding or blown film; the powder form and additive package can cause feeding irregularities in small extruder screws, and the lack of long-chain branching limits bubble stability. Injection moulding converters should select a pelletised LLDPE with melt flow rate above 20 g/10 min unless feeding and screw design are specifically validated. The product’s property balance is therefore process-specific: it is qualified for rotational moulding equipment, not as a general replacement for all linear low-density polyethylene grades.