LyondellBasell Icorene 3560 BWN 8435 Polyethylene, Linear Low Density is a low-pressure copolymer resin produced from ethylene and an α-olefin comonomer. The product designation belongs to the Icorene portfolio and is specified as a linear low-density polyethylene; the alphanumeric suffix BWN 8435 identifies a defined formulation in terms of colour, antioxidant package, processing stabiliser content, and ultraviolet stabilisation. Because the suffix can encode exact additive loadings that affect processing behaviour and end-use compliance, the density, melt mass-flow rate, additive composition, and lot-specific values should be verified against the manufacturer’s certificate of analysis and safety data sheet. Published data for this specific configuration is limited, and substitution against a datasheet without the full suffix is not advised when compliance with food-contact, drinking-water, or outdoor weathering standards is required.

What separates the BWN 8435 formulation from conventional high-pressure LDPE and metallocene-catalysed LLDPE grades?

Linear low-density polyethylene differs from high-pressure low-density polyethylene primarily in molecular architecture. High-pressure LDPE contains significant long-chain branching, which increases melt elasticity and improves bubble stability in blown film but reduces tensile strength and environmental stress crack resistance when compared with a linear copolymer of equivalent density. Icorene 3560 BWN 8435, as an LLDPE grade, comprises predominantly linear chains with controlled short-chain branches derived from the α-olefin comonomer. The short-chain branch length and distribution influence crystallisation rate, tie-chain concentration, and slow crack growth resistance. When compared with metallocene-catalysed LLDPE, a conventional Ziegler-Natta or modified-catalyst LLDPE may exhibit broader molecular weight distribution, higher melt strength, and different shear sensitivity. The BWN 8435 suffix should therefore not be treated as interchangeable with a standard metallocene LLDPE without confirming the molecular weight distribution, comonomer type, and additive package.

The density of LLDPE grades commonly falls between 0.918 g/cm³ and 0.940 g/cm³ when measured according to ISO 1183-1:2019 or ASTM D1505. Melt mass-flow rate values are typically determined at 190 °C under 2.16 kg load using ISO 1133-1:2022 Method A or ASTM D1238-20 Procedure A. For the present Icorene grade, exact values require the manufacturer’s specification, but the selection of a linear low-density polyethylene implies a designed compromise between low-temperature impact resistance, puncture resistance, and tensile modulus. In comparison with HDPE, the lower crystallinity of LLDPE results in reduced stiffness and hardness but improved dart impact and tear behaviour in film structures. In comparison with LDPE of the same melt index, LLDPE often exhibits higher tensile yield strength and greater resistance to environmental stress cracking when tested under ASTM D1693-22, although it may require higher extrusion backpressure and greater motor load on smooth-bore single-screw extruders.

For film extrusion, the absence of long-chain branching in linear polyethylene reduces melt strength. This can limit maximum blow-up ratio and require adjustments to die gap, frost line height, and air ring configuration compared with LDPE. On blown film lines equipped with internal bubble cooling and dual-lip air rings, LLDPE grades in this class are sometimes blended with up to 20 wt% LDPE to improve bubble stability without substantially reducing dart impact resistance. The suitability of such blending for Icorene 3560 BWN 8435 must be confirmed by melt performance trials because the BWN 8435 additive package may influence surface quality, slip behaviour, and plate-out on metal surfaces.

On a 75 mm single-screw extruder with 30:1 L/D and a barrier screw, dry-blended LLDPE of comparable density has been reported to reach melt temperatures of 210–240 °C and die pressures of 18–28 MPa at screw speeds of 60–90 min⁻¹. The exact pressure profile for this Icorene grade depends on melt index, screw geometry, and feed-section temperature control. Feed throat temperatures above 45 °C can produce bridging in pelletised LLDPE and should be avoided unless the hopper is equipped with a water-cooled throat. In cast film and sheet processes, melt temperature may be lower, typically 220–250 °C, with chill roll temperatures set between 15 °C and 35 °C to minimise surface haze and control crystallinity.

Thermal-oxidative stabilisation and ultraviolet resistance in outdoor service environments

LLDPE requires adequate stabilisation to survive repeated thermal processing and long-term service. The BWN 8435 suffix indicates a packaged stabiliser system that is specific to the grade; however, published data for this exact stabilisation package is limited. Standard LLDPE formulations for outdoor articles generally contain hindered phenolic antioxidants at 0.05–0.20 wt% and phosphite process stabilisers at 0.05–0.15 wt%, with additional hindered amine light stabilisers for ultraviolet exposure. When long-term outdoor service is required, oxidative induction time can be measured by ISO 11357-6:2018 or ASTM D3895-19 using differential scanning calorimetry at 200 °C. A short oxidative induction time does not necessarily indicate poor long-term heat ageing, but it can signal depletion of the primary antioxidant during processing.

For parts intended for outdoor exposure, ultraviolet stabilisation is confirmed by accelerated weathering methods such as ISO 4892-2:2013, ASTM D2565-16, or ASTM G154-23. These methods expose specimens to controlled ultraviolet irradiance and condensation cycles. The resulting changes in tensile elongation and colour are evaluated according to ISO 527-2:2012 or ASTM D638-14. Without manufacturer data for BWN 8435, additional ultraviolet masterbatch should not be added without testing because excessive additive loading can increase plate-out, reduce weld-line strength, and alter colour stability. The grade should be stored away from direct sunlight and sources of heat, and extended storage beyond 12 months under warm conditions should be avoided unless the certificate of analysis confirms retention of oxidative stability.

Thermal processing limits depend on melt temperature and residence time. Prolonged residence above 260 °C can initiate thermo-oxidative chain scission and crosslinking in LLDPE, producing gels in film, black specks in moulded parts, and volatile emissions. When processing interruptions exceed 15 min, the extruder should be purged with a lower-viscosity polyethylene or a commercial purge compound. Restart after a shutdown requires verification of melt pressure and visual inspection for discolouration before re-entering the product stream.

Chemical compatibility of the stabilised LLDPE should be assessed with appropriate immersion testing under ASTM D543-20 or ISO 175:2010. Linear low-density polyethylene generally resists dilute acids, alkalis, and aqueous salt solutions at ambient temperature, but concentrated oxidising acids, chlorinated hydrocarbons, and certain surfactant solutions can reduce tensile strength and accelerate environmental stress cracking. In applications where the material contacts fatty food, alcohol, or organic solvents, migration and extraction limits relevant to regional food-contact regulations should be confirmed. The presence of the BWN 8435 colour and stabiliser package may impose additional restrictions if compliance with FDA 21 CFR 177.1520, EU Regulation No 10/2011, or other jurisdictional requirements is claimed.

Table 1 provides representative ranges for general LLDPE grades and is not a substitute for the Icorene 3560 BWN 8435 specification sheet. When using these methods for lot acceptance testing, the specimen conditioning protocol, thickness, and test speed must be aligned with the manufacturer’s quality-control instructions. Failure to standardise thickness in impact and stiffness tests can shift results by more than 20 %, particularly when comparing rotational-moulded parts with compression-moulded test plaques.

When rotational-moulded wall thickness exceeds 6 mm and long-cycle heating is required

Rotational moulding of LLDPE powders requires particle size control, thermal profiling, and sufficient internal air temperature to achieve full densification. For Icorene 3560 BWN 8435 in pulverised powder form, a particle size distribution passing 35 mesh (500 µm) with a proportion retained above 80 mesh (177 µm) is common for uniform melt-out. If large particles exceed 500 µm, corner thinning and pinhole formation can increase because coarse particles sinter more slowly than fine particles. If the powder is excessively fine, dry flow and bulk density may decrease, causing bridging in hoppers and inconsistent shot weight.

Production-scale rotational moulding data for LLDPE in the 0.930–0.940 g/cm³ density interval indicate that peak internal air temperature should reach at least 200 °C and often 210–230 °C before cooling begins. At wall thicknesses above 6 mm, the oven residence time must be extended to allow thermal conduction through the polymer skin and prevent under-cured inner surfaces. Cycle time is governed by the ratio of oven temperature to part wall thickness, tooling thermal mass, and the peak internal air temperature required. Premature removal below 190 °C may produce weld lines with low tensile elongation, especially at ribs and inserts. Overheating above 250 °C may cause oxidative yellowing, odour, and surface imperfections if the BWN 8435 antioxidant package is depleted.

Injection moulding of thin-wall articles from LLDPE typically requires higher injection pressures than LDPE of the same melt flow rate. On a 1,200 kN clamp force machine, linear low-density polyethylene grades in the lower melt index range may require injection pressures of 70–100 MPa and holding pressures of 40–70 MPa. Back pressure should be kept below 5 MPa to reduce shear heating. Mould temperatures from 10 °C to 40 °C are customary, with lower temperatures reducing cycle time but increasing orientation and post-mould shrinkage. Shrinkage of LLDPE is anisotropic; after 24 h at 23 °C, linear mould shrinkage can range from 1.5 % to 3.0 % depending on part thickness, gate location, and mould temperature. Articles with tight dimensional tolerances require post-mould measurement at controlled temperature and humidity, with compensation for continued crystallisation during the first 48 h.

For film applications requiring low-temperature impact strength, the selection of Icorene 3560 BWN 8435 should be validated using the intended film thickness and test method. Dart impact of LLDPE films is commonly measured by ISO 7765-1:1988 or ASTM D1709-22 Method A or B, depending on expected failure weight. Tear resistance is evaluated by ASTM D1922-23 or ISO 6383-2:1983. Compared with a high-pressure LDPE of equivalent melt index, LLDPE typically shows greater machine-direction tear resistance and puncture resistance but lower clarity unless the film is quenched rapidly. In cast film, higher chill roll temperatures improve clarity but can increase blocking, especially if the BWN 8435 formulation does not include an antiblocking agent. In such cases, processing trials should establish the maximum roll temperature at which film unwinds without surface transfer.

The use of Icorene 3560 BWN 8435 in contact with potable water or in pipe applications requires verification against applicable standards and local approvals. Polyethylene used in water service is often assessed for long-term hydrostatic strength under ISO 9080:2012 or ASTM D2837-22, but these methods are normally associated with pipe-grade HDPE rather than generic LLDPE moulding grades. Without approval data for this specific BWN 8435 formulation, the material should not be substituted into pressurised piping systems or water-contact articles without a written confirmation from the manufacturer. Experience with LLDPE in unpigmented or stabilised formulations indicates that wetting agents and surface-active contaminants can reduce stress crack resistance and should be controlled in service and testing.

Industrial handling and drying requirements are similarly formulation-specific. LLDPE is hydrophobic and generally does not require predrying at ambient storage conditions. However, condensation on cold pellets can introduce surface moisture, and drying at 60–80 °C for 1–2 h with dehumidified air is recommended if the material has been moved from cold storage to a warm, humid production area. For rotational moulding powders, moisture levels above 0.05 wt% can generate steam blisters in thick sections. Avoid using desiccant dryers at temperatures above 100 °C because pellet agglomeration can occur before processing.

The BWN 8435 designation may also indicate a black or compounded colour formulation. Black polyethylene grades often contain carbon black at loadings between 2.0 wt% and 2.5 wt% for ultraviolet protection and opacity. Carbon black dispersion is critical to mechanical integrity and weathering performance. Poor dispersion produces agglomerates that can act as stress concentrators and reduce elongation at break under ISO 527-2:2012 or ASTM D638-14. If the grade is supplied in black form, incoming quality control should include dispersion testing by microscopy or pressure-rise filtration testing appropriate to the processing method. Published data for this exact BWN 8435 carbon black loading and dispersion is limited, so the manufacturer’s specification should be consulted before qualifying the material for outdoor structural parts.

Differences from other products in the LyondellBasell portfolio should be evaluated through the grade-specific datasheet rather than by assuming that all Icorene 35xx grades behave identically. Small shifts in comonomer type, molecular weight distribution, and additive package can change melt pressure, weld-line strength, organoleptic performance, and colour stability. When this grade is substituted for another LLDPE or LDPE in an existing tool, the processor should verify melt temperature, cycle time, part weight, after-shrinkage, and the relevant mechanical property according to the applicable ISO or ASTM method. If tooling was originally sized for a high-melt-strength LDPE, a linear low-density resin may require lower screw speed, higher melt temperature, or die gap adjustment to avoid melt fracture and excessive orientation.