LyondellBasell Icorene 3546 UV+ GRN 6413 Polyethylene, Linear Low Density is supplied as a free-flowing rotomoulding powder based on linear low density polyethylene. The UV+ suffix identifies a compounded light-stabilizer package, while the GRN 6413 suffix identifies a green colour concentrate incorporated before final grinding. The material is intended for low-pressure biaxial rotational moulding of hollow parts with service wall thicknesses typically between 3 mm and 25 mm. Because the grade is delivered as a powder, the processor avoids conversion grinding and the additional melt history associated with re-extrusion of pelletized feedstock.

The Icorene 3546 rotomoulding series is generally positioned in the 0.934–0.939 g/cm³ density band when measured according to ISO 1183-1, with a melt mass-flow rate between 4.0 and 6.0 g/10 min under 190 °C/2.16 kg using ISO 1133-1:2022. These values are class-typical for polyethylene intended for rotational moulding; the lot-specific certificate of analysis is the controlling document for exact compounded properties. Because the GRN 6413 pigment package is part of the final formulation, mechanical and weathering data should not be borrowed directly from the unpigmented UV+ grade. In pigmented LLDPE systems, pigment particle dispersion can shift elongation at break by 5–15% and reduce tensile yield stress by 1–3 MPa relative to an unpigmented control, which is why colour-grade-specific validation specimens are required.

What separates a UV-stabilized linear low density grade from a general-purpose butene LLDPE in rotomoulding?

The distinction is partly molecular and partly additive. Linear low density polyethylene differs from high-pressure low density polyethylene in that the backbone is essentially linear and the density reduction is achieved through short-chain branching introduced by an α-olefin comonomer. This architecture produces higher tensile yield strength, higher elongation at break, and improved environmental stress crack resistance when compared with a branched LDPE of similar melt flow rate. The UV+ stabilization system is the main differentiator from general-purpose butene LLDPE rotomoulding grades: it raises the threshold for carbonyl formation, surface chalking, and impact loss during outdoor exposure. For comparative outdoor performance, retention of tensile impact after accelerated weathering should be measured by ISO 8256 or ASTM D256 on rotomoulded plaques of the target wall thickness, not on thin compression-moulded films. Published data for the exact ΔE and gloss retention of this specific green formulation under ASTM D4329 or ISO 4892-2 is limited in publicly accessible form, so procurement specifications should request lot-specific accelerated weathering data from the manufacturer.

Compared with high density polyethylene rotomoulding grades, the LLDPE matrix accepts deeper draw and more complex multi-planar mould detail because the lower crystallinity reduces brittle fracture in sharp corners and undercut areas. The trade-off is reduced stiffness. Flexural modulus for the LLDPE class is typically in the 450–600 MPa range by ISO 178, whereas many HDPE rotomoulding grades fall between 800 and 1,100 MPa. Compared with LDPE, the LLDPE grade provides greater stress crack resistance under ASTM D1693 condition B, making it more appropriate for tanks and enclosures where hoop stress, thermal cycling, and outdoor exposure coincide. The limitation is a narrower sintering window in the mould; particle coalescence and densification require closer control of peak internal air temperature than is needed for a branched LDPE grade.

Compounding of the UV+ stabilization and green masterbatch into the resin is typically performed on a corotating twin-screw extruder with an L/D ratio of 40:1–48:1 before pelletizing and cryogenic grinding. In production-scale practice, incomplete pigment dispersion caused by worn screw elements or insufficient specific energy input appears as green streaks in the moulded part, particularly at rib intersections and weld lines. That failure mode is not visible in the raw powder and is detected only after a first article has been moulded and cross-sectioned.

On shuttle-type and carousel-type rotational moulding machines, a standard starting point for a 6 mm nominal wall section is an oven air temperature of 260–300 °C and a peak internal air temperature between 190 and 220 °C. The primary-to-secondary axis rotation ratio is usually set between 4:1 and 5:1. Powder particle size distribution is controlled by ASTM D1921; a rotomoulding powder is commonly specified with 95% passing a 35-mesh screen of 500 µm opening. Bulk density measured by ASTM D1895 is typically 0.33–0.40 g/cm³. If the material is stored at relative humidity above 60%, surface moisture can produce pinholes and internal porosity in thick sections; pre-drying at 60 °C for 4 h is recommended after condensation exposure.

Crystallization kinetics during the cooling phase control final part shrinkage and impact response. Slow ambient cooling increases crystalline fraction and can raise the measured density of the moulded article by 0.002–0.005 g/cm³ relative to the powder feedstock. Quench cooling produces smaller spherulites and lower modulus, but also reduces the available time for warpage-inducing thermal gradients to relax. For restrained geometries with metal inserts or large flat panels, shrinkage should be determined on a dedicated rotomoulding test tool at the intended wall thickness rather than inferred from injection moulding shrinkage data.

Residence-time limits and heat-stabilizer exhaustion in thick-section rotomoulding

Because rotomoulding is a low-shear process, melt densification depends on conduction rather than shear heating. The maximum permissible oven dwell is therefore governed by the oxidation induction time of the heat-stabilizer package. If oven air temperature is held above 295 °C, the outer skin of a 20 mm wall can remain above 220 °C for several minutes, which accelerates consumption of the phenolic antioxidant. Oxidation induction time measured by ISO 11357-6:2018 on the incoming powder is a more useful incoming control than melt flow rate alone. When OIT at 210 °C falls below 20 min, the stabilizer package may have been degraded by repeated extrusion, prolonged storage, or contact with oxidized powder; the lot should be segregated for non-critical parts or submitted for re-certification. Thermal deterioration in rotomoulding is frequently observed first as yellowing at the inner air-melt interface, not as melt index drift. That colour shift is particularly visible against the green 6413 background because the visual threshold for green-to-olive discolouration is lower than in black or natural grades.

In a carousel line running a 12–14 min total cycle for 6 mm walls, an oven setpoint above 295 °C may reduce cycle time by 60–120 s, but can also produce inconsistent colour at ribs, kiss-off points, and bosses because of uneven heat transfer. The processing trade-off is a known bottleneck on production lines where demand for output rate places a premium on shortened dwell. The preferred control strategy is to maintain PIAT within the 190–220 °C band and to adjust oven temperature only within the limits recommended by the supplier for this specific UV-stabilized color grade.

When the green 6413 colour package is specified for chemical-contact and outdoor exposure

Green rotomoulded parts are commonly used for agricultural sprayer tanks, outdoor enclosures, marine buoys, and playground components. In these applications, chemical resistance and weathering resistance must be evaluated separately. The polyethylene matrix generally resists dilute acids, alkalis, and aqueous salt solutions at ambient temperature, but published immersion data for this specific green-pigmented configuration under ISO 175:2010 is limited. Continuous immersion in aromatic hydrocarbons, chlorinated solvents, strong oxidizing acids above 40 °C, or diesel may produce swelling and environmental stress cracking. Suitability must be assessed with the target chemical at the expected service temperature, including intermittent exposure and thermal cycling.

The combined hindered-amine light stabilizer and green pigment package reduces the rate of ultraviolet transmission through the wall and delays the onset of surface chalking and gloss loss. Degradation rate depends on total UV irradiance, wall thickness, and thermal cycling. A 3 mm wall in a high-altitude, high-UV environment will exhibit earlier surface degradation than a 10 mm wall in temperate coastal service. The green 6413 pigment package should not be assumed to have identical electrical or microwave transparency to unpigmented LLDPE; if radome, buried-sensor housing, or other radio-frequency transparency is required, separate electrical testing at the intended frequency is necessary.

For outdoor durability verification, comparative testing should use rotomoulded panels with the intended wall thickness and edge finish, not thin-film test specimens. Stabilizer migration kinetics, pigment dispersion, and quench history in thick rotomoulded walls differ substantially from those in thin films, and the use of film data can overestimate service life by a wide margin. The primary test references are ASTM D4329 for fluorescent UV condensation exposure and ISO 4892-2 for xenon-arc exposure. Impact retention after weathering should be measured by ISO 8256 tensile impact or ASTM D256 Izod impact on specimens cut from rotomoulded parts because the outer degraded skin is the controlling layer in field failure.

For compliance verification, the following standards are typically applied to incoming resin, moulded plaques, or finished parts. The applicability of any specific clause depends on the intended end use and the regulatory jurisdiction.

The processor should additionally verify food-contact, potable-water, toy-safety, REACH, and RoHS status through the supplier’s lot-specific declaration because pigment and stabilizer packages can move a polymer formulation outside a generic resin compliance statement. For food-contact uses in the European Union, migration testing under Regulation 10/2011 may be required; in the United States, the relevant polyethylene monograph is 21 CFR 177.1520. These regulatory references apply only when the finished article meets the relevant extraction cell, temperature, and food-simulant conditions.