LyondellBasell Icorene 3546 YEW 2125 is designated as a linear low-density polyethylene (LLDPE) product. The base-resin identifier is the 3546 designation; the YEW 2125 suffix is interpreted within the supplier’s colour/additive nomenclature as a yellow pigmented and stabilised variant. Exact colorant composition, masterbatch let-down ratio, and antioxidant/UV stabiliser loading must be confirmed against the commercial product specification and lot certificate rather than inferred from the grade name. Published data for this specific pigmented configuration is limited. A processor should not treat values for an unpigmented Icorene 3546 base resin as interchangeable with the YEW 2125 variant because masterbatch addition can shift melt mass-flow rate, density, tensile elongation, and oxidative induction time. The test framework below is therefore used for lot approval and process control in the absence of grade-specific published values.

As an LLDPE, the product class is defined by ASTM D883 as a polyethylene with density in the general range 0.915–0.940 g/cm³. This is a class range, not a certified lot-value limit. Grade-specific density and melt-flow values remain essential design inputs for tooling, cycle time, and mechanical performance calculations.

Rotational moulding is a principal process route for this LLDPE class because hollow, thick-section articles can be produced with uniform wall distribution. Typical applications include vertical storage tanks, agricultural hoppers, chemical transfer vessels, marine buoys, outdoor playground components, and material handling trays. The yellow pigmentation is not cosmetic; at the required loading it changes infrared absorption and heat transfer during oven heating. A converter moving from a natural powder to the YEW 2125 material on the same tool should re-establish the oven cycle using internal air thermocouple data, not visual melt appearance. Failure to do so can produce partially sintered walls or oxidation near the outer skin in thick sections.

What flow and density measurements define this product class?

Melt mass-flow rate is measured at 190 °C under a 2.16 kg load using ISO 1133-1:2022 or ASTM D1238-23. Density is measured after conditioning with ISO 1183-1:2019 density-gradient column or ASTM D1505-18. The two values define the melt-viscosity class and the solid-state crystalline fraction that controls stiffness, warpage, and chemical resistance. Melt flow ratio, measured as the high-load 21.6 kg flow divided by the 2.16 kg flow under ISO 1133-1:2022, indicates molecular-weight distribution breadth and shear-thinning behaviour. A compound lot with density shifted by more than 0.002 g/cm³ from the certified natural base may require adjustment of cooling rate or tool dimensions because shrinkage and sidewall modulus respond to crystallinity. In a quality-control laboratory, the DSC melting range under ISO 11357-3:2018 should be recorded as a supplement to density because a change in peak melt temperature is often the first sign that a different comonomer or compounding history is present.

Since the product may be supplied as pellet or powder, the powder state must be specified for rotational moulding. Dry-flow by ASTM D1895-17 Method A, bulk density, and sieve retention on a 35-mesh screen are relevant. Rotational moulding powders in this category typically show bulk density in the range 0.36–0.40 g/cm³ and dry-flow from 20–35 g/min, but these are process-class ranges and not lot specifications. Low dry-flow, excessive fines, or static charge will deposit unevenly in deep moulds and produce thin sections at corners. If the grade is supplied as pellets and ground on site, grinding heat can consume the antioxidant package; incoming and ground powder should be checked for oxidative induction time under ASTM D3895-19.

Specification, test designation, and process-control matrix

Mechanical design for tanks should not rely solely on short-term tensile data. Under continuous load at 40 °C, LLDPE can lose a considerable fraction of its short-term flexural modulus over 10,000 h; creep modulus is measured according to ISO 899-1:2017. The static liquid head at the base of a vessel imposes hoop stress that must remain below the allowable design stress derived from creep-rupture or hydrostatic design basis data. Where no long-term data specific to this pigmented grade exist, applying a factor of safety of at least 2.0 on short-term yield stress is conservative practice. The YEW 2125 colour package cannot be assumed to alter creep resistance linearly; therefore, qualification tests on a moulded or welded prototype are warranted when the part is used for chemical storage.

Tool design also affects moulded-part performance. Large flat panels can warp if cooling is non-uniform. Aluminium tooling in the thickness range 5–8 mm provides adequate heat transfer, but cast aluminium may contain porosity that creates surface defects. Zinc alloy or steel tooling can better tolerate high production volumes. With pigmented LLDPE, broad particle size distribution or excessive fines can make flow lines or pigment separation more visible at sharp corners. Generous corner radii, at least 12 mm, reduce thin-out and stress concentration at inside corners of rotomoulded parts.

When colour retention and oxidative degradation determine outdoor acceptance

Outdoor exposure degrades both the pigment system and the polyethylene matrix. Colour stability is quantified in CIELAB coordinates; a ΔE threshold of 3.0 under D65/10° is frequently used for visible yellow panels. Accelerated weathering follows ISO 4892-2:2013 cycle A1 with daylight filters, irradiance 0.55 W/m²/nm at 340 nm, black-standard temperature 65 °C, and a dry phase. Tensile elongation retention after xenon exposure is a more direct indicator of oxidative chain scission than colour fade alone. Processing history affects weather resistance: if the material is overheated during moulding, the antioxidant package is depleted and subsequent outdoor life may be shorter than the datasheet suggests. On a carousel rotational moulding line with independent-arm controls, the oven cycle should target the producer’s recommended peak internal air temperature; prolonged residence above 260 °C may consume stabilisers and shift the part toward yellowing or brown discoloration that is not a colour-match issue.

Incoming lots should be screened by oxidative induction time under ASTM D3895-19. An OIT below the certified control limit indicates antioxidant loss during compounding, transport, or storage. Material with depleted OIT should be restricted to noncritical indoor uses or rejected if the article carries UV resistance requirements.

The comparison with high-pressure LDPE, HDPE, and metallocene LLDPE is material-specific

Linear low-density polyethylene differs from high-pressure low-density polyethylene (LDPE) in chain architecture. LDPE produced in autoclave or tubular reactors contains long-chain branches that increase shear thinning and melt strength; LLDPE has a predominantly linear backbone with short-chain branches introduced by comonomer. At the same density, LLDPE generally offers higher tensile strength, higher puncture resistance, and longer environmental stress-crack resistance, but lower melt strength and less shear thinning. In extrusion, LLDPE generates higher die pressure and can require a narrower die gap; in rotational moulding, the powder may show a wider sintering window if internal air temperature is controlled. Compared with high-density polyethylene (HDPE), this LLDPE class has lower flexural modulus and lower softening temperature, but typically better low-temperature impact and stress-crack resistance at equivalent melt flow. The selection between HDPE and LLDPE for a tank therefore depends on whether stiffness or crack resistance controls the service failure mode.

Within the LLDPE family, comonomer type matters. Butene, hexene, and octene comonomers produce different short-chain branch lengths and toughness. Hexene and octene copolymers generally provide higher environmental stress-crack resistance and dart impact at equivalent density than butene copolymers, but the exact Icorene 3546 datasheet should be checked because the base resin may be formulated with a particular comonomer. Metallocene-catalysed LLDPE grades have narrower molecular-weight distribution and more uniform comonomer distribution than conventional Ziegler-Natta grades. As a result, metallocene LLDPE typically offers higher dart impact, better optical clarity in film, and lower seal-initiation temperature, but higher extrusion torque and a greater tendency to melt fracture if processing is not adjusted. The Icorene 3546 base grade should not be assumed to match metallocene LLDPE performance unless the producer explicitly states the catalyst and comonomer type.

Food-contact status cannot be assumed from the base LLDPE. A natural polyolefin may comply with 21 CFR 177.1520(c) or EU 10/2011, but the YEW 2125 colour package must be assessed separately under 21 CFR 178.3297 for colorants used in polymers. For RoHS, the heavy metals lead, cadmium, mercury, and hexavalent chromium are limited at the homogeneous material level under Directive 2011/65/EU Annex II. The concentrate or masterbatch used to create YEW 2125 may be the source of any restricted metal; therefore, a lot certificate stating compliance is required for electrical, electronic, or toy-related applications. REACH duties generally attach to monomers and additives rather than the finished polymer, but the safety data sheet should confirm registered uses and the presence or absence of substances of very high concern in the colour masterbatch.

Processing limits apply to the pigmented material as supplied. Polyethylene does not require drying for absorbed moisture, but surface condensation on cold pellets or powder stored at RH > 60% can create voids or streaks; hot-air drying at 60–80 °C for 1–2 h is used when condensation is present. On a twin-screw compounding line used to incorporate the colour system, a side-feed for the masterbatch after the polymer melt seal, located at 40–60% of the barrel length, reduces pigment thermal history. Barrel temperatures above 250 °C or residence time beyond the producer’s limit can reduce oxidative induction time and change the final yellow shade. Similar limits apply to injection moulding: a melt temperature above 250 °C may degrade the colorant or antioxidant package, and gates should be sized to avoid excessive shear heating.