LyondellBasell Icorene 3546 BUE 5513 is a linear low density polyethylene powder intended for rotational molding. The polymer is an ethylene α-olefin copolymer with a nominal density of 0.935 g/cm³ when measured under ISO 1183-1. The melt mass-flow rate is 4.6 g/10 min at 190 °C under a 2.16 kg load according to ISO 1133-1. The BUE 5513 suffix identifies a stabilized formulation configured for extended outdoor exposure and thermal oxidative conditions during oven processing. In rotational molding, the grade sits between lower-density polyethylene and high-density polyethylene because it retains a self-supporting crystalline structure while providing reduced low-temperature brittleness compared with many ethylene homopolymer grades.

In commercial conversion practice, the material is processed on carousel, shuttle, or rock-and-roll machines with forced-air ovens. The powder is charged into fabricated steel or cast aluminum molds that rotate on two axes at a speed ratio near 4:1. Oven setpoints commonly fall between 260 °C and 290 °C, while the peak internal air temperature measured by infrared pyrometer is normally held between 220 °C and 235 °C. At this temperature, the powder particles melt, sinter, and densify against the mold wall. The melt flow rate of 4.6 g/10 min is low for pressure-driven processes such as injection molding, but it is suitable for rotational molding because the process depends on zero-shear coalescence rather than screw-generated pressure. The grade also resists excessive sag on deep vertical wall sections better than a high-flow polyethylene would, which is relevant for tanks with side walls above 1.5 m.

Rotational molding of linear low density polyethylene differs from injection molding because the material is not compacted by screw pressure. The powder relies on mold rotation, surface tension, and gravity to distribute and densify. The particle size distribution therefore affects dry flow, dust generation, and uniformity of the initial powder laydown. A typical rotomolding powder is controlled so that the coarse fraction above 500 µm is limited, while the fine fraction below 100 µm is controlled to prevent bridging in deep cavities. The supplier grinds the product to a specification suitable for commercial rotomolding equipment, but the exact sieve profile for a specific lot should be requested because grinding line and ambient conditions influence the distribution.

The sintering stage is governed by melt viscosity and the collapse of air pockets trapped between powder particles. With a melt flow rate of 4.6 g/10 min, the zero-shear viscosity is higher than that of a 10 g/10 min injection-molding grade, so bubble removal in thick sections requires attention to peak internal air temperature rather than oven time alone. If the wall thickness exceeds 8 mm, the diffusion path for residual gas becomes longer, and processors may raise the internal air temperature toward the upper end of the 220–235 °C window while extending the heating plateau. This approach must be balanced against oxidation at the inner surface when the mold is vented to ambient air.

Capillary rheometry data for a 0.935 g/cm³ linear low density polyethylene of this melt flow class generally show shear-thinning behavior. At low shear rates typical of rotational molding, viscosity may be in the range of 10³–10⁴ Pa·s at 220 °C, although the exact value depends on comonomer type, stabilizer, and temperature. The additive package has limited effect on shear viscosity but can alter oxidation induction time as measured by ISO 11357-6. This is why oven setpoint control and air infiltration are critical process variables during heating.

What limits the oven cycle when Icorene 3546 BUE 5513 is rotationally molded?

The main process limitation is the temperature band between bubble collapse and oxidative embrittlement. Rotational molding grades in the 0.935 g/cm³ density class are generally heated until the internal air reaches 220–235 °C. Below 210 °C, residual bubbles may remain because the melt has not achieved sufficient densification and bubble diffusion. Above 245 °C, the outer polymer layer is exposed to hot air for an extended period, and thermal oxidative degradation can reduce impact properties measured by ISO 6603-2. The stabilizer package in BUE 5513 is intended to widen this processing window, but it does not eliminate the upper limit.

Cooling is equally bounded. Rapid water quenching shortens the cycle but increases differential shrinkage between the mold side and the air side. Dimensional control on open-mouth vessels requires a staged cooling profile: air cooling to below the crystallization onset at approximately 100–105 °C, followed by water mist for sections above 5 mm. The crystallization temperature measured by differential scanning calorimetry is an important process input, and the value is generally lower than that of a high-density polyethylene rotomolding grade at equivalent wall thickness.

Process engineers commonly encounter porosity in deep recesses when mold surface temperature drops below the melting range before powder deposition is complete. Rotomolding lines therefore use infrared pyrometers to measure internal air temperature rather than relying on oven setpoint alone. At a melt flow rate of 4.6 g/10 min, the grade remains within the acceptable sintering window without requiring the high oven overshoot that a lower-flow grade would demand. Excessive overshoot above 245 °C internal air temperature can accelerate oxidative embrittlement and reduce the ductile failure energy.

Humidity is a secondary but real process variable. Polyethylene is not hygroscopic to the same degree as polyamide or polyester, but condensation on cold powder introduced into a warm mold can produce steam-induced porosity. When powder is stored in unheated silos at high relative humidity, pre-drying at 70–80 °C for 30–60 min is used before charging. A maximum moisture content near 0.05 % by mass is often targeted for rotomolding powders, although closed-mold venting and internal air temperature control remain more effective safeguards than drying alone.

Compared with a high-density polyethylene rotomolding grade of density 0.945 g/cm³, the 0.935 g/cm³ density of Icorene 3546 BUE 5513 produces a lower flexural modulus but better resistance to environmental stress cracking when tested under ASTM D1693 Method B in 10 % Igepal solution. The lower density is associated with lower crystallinity and a higher capacity for strain without brittle fracture. In chemical storage tanks and agricultural containers, this trade-off is often preferred because service failure is more frequently caused by stress cracking or impact than by short-term tensile deformation. A high-density rotomolding grade may be selected where thin-wall stiffness is the controlling requirement, such as structural covers or pipe sections.

Differences from low-density polyethylene are also significant. An LDPE of density 0.920 g/cm³ has lower tensile yield stress and lower heat resistance when measured by ISO 306/A50. Icorene 3546 BUE 5513 provides a higher melt softening range and can maintain dimensional stability at moderately elevated service temperatures. An LDPE may offer easier processing at lower oven temperatures because of lower melt viscosity, but it generally requires thicker walls to meet the same top-load or internal-pressure requirement. The rotational molder selects among these materials by comparing hoop stress resistance, environmental stress-cracking resistance, and impact performance measured on rotomolded specimens.

The product is not crosslinked. This distinction is operationally significant because a crosslinkable high-density polyethylene powder forms a thermoset network during the mold cycle and cannot be re-melted or recycled as a thermoplastic. Icorene 3546 BUE 5513 remains fusible, allowing damaged parts to be ground and reintroduced as regrind at controlled mass fractions. In contrast to crosslinked parts, the uncrosslinked linear low density polyethylene does not undergo a post-molding exotherm associated with peroxide decomposition and may exhibit lower solvent resistance but simpler reprocessing. In applications involving hot diesel fuel or aggressive aromatic solvents, crosslinked polyethylene may remain preferred; this LLDPE grade is not a direct substitute in all chemical environments.

Production scrap from Icorene 3546 BUE 5513 can be ground and returned to the process, but the regrind fraction changes powder morphology and can reduce dry flow. On production lines, regrind addition is commonly limited to 15–25 % by mass for nonstructural parts and lower for parts with visual, impact, or permeation requirements. Regrind must be freed of mold-release residues and stored dry because residual moisture at weld lines can produce pinholes. Melt flow rate and density are minimally affected by low regrind levels, but high levels of thermally oxidized regrind can lower elongation at break and environmental stress-cracking resistance.

Material specification anchors for Icorene 3546 BUE 5513

The values in the following matrix are representative supplier-published or technical literature values for a linear low density polyethylene rotomolding powder of this density and melt flow class. They are not batch-release specifications. Mechanical values are strongly influenced by mold surface temperature, part wall thickness, cooling rate, and specimen orientation. Qualification specimens should therefore be cut from rotomolded walls of the same thickness as production parts.

Documented application classes include storage tanks, agricultural hoppers, outdoor enclosures, portable water containers, playground structural shells, and industrial linings. In these geometries, part design often introduces a flange or stiffening rib that changes local wall thickness, and the molding cycle must be tuned for the thickest cross-section. The resin density and melt flow rate support wall thicknesses from roughly 3 mm to 12 mm in conventional rotational molding, depending on mold geometry and machine size. Parts outside this range require individual process validation because powder laydown and cooling rates become nonuniform.

At heavy wall thicknesses above 6 mm, the cooling rate through the crystallization plateau becomes the dominant source of shrinkage and warpage. If cooling is too rapid, the outer wall solidifies first and restrains the inner surface, producing internal voids and flange distortion. If cooling is too slow, cycle time increases without improving properties. The BUE 5513 stabilizer system does not fundamentally change crystallization kinetics, so the same cooling logic applies as for other linear low density polyethylene rotomolding grades. A controlled air-cooling step through the range of 105–90 °C is used to equalize part surface temperatures before water spray begins.

Laboratory tests on compression-molded plaques may overstate mechanical properties because the cooling history is faster and more uniform than that of a rotomolded part. For design allowables, tensile specimens are cut from flat sections of rotomolded tanks or from a standardized mold. Tensile properties are tested under ISO 527-2, and multiaxial impact may be evaluated under ISO 6603-2. Low-temperature impact tests detect brittle transitions; the ductile-to-brittle transition measured by ASTM D746 is often below -70 °C for this density class, although exact values vary with wall thickness and cooling rate.

When the BUE 5513 formulation enters outdoor service environments

The BUE 5513 additive configuration is selected where the molded part is exposed to ultraviolet radiation and cyclic temperature. Weathering performance is assessed by accelerated methods such as ISO 4892-2 cycle A with xenon-arc irradiation. Accelerated weathering does not fully reproduce the combined effects of ultraviolet radiation, thermal stress, and internal pressure. Outdoor service life prediction therefore requires correlation with field data from specimens of the same formulation and surface finish. The supplier may provide data on tensile elongation retention after xenon exposure and on carbonyl index development, but the end user is responsible for verifying part-specific performance under actual ultraviolet dose, humidity, and pressure conditions.

For food-contact applications, polyethylene grades may be evaluated against FDA 21 CFR 177.1520 and European Commission Regulation (EU) No 10/2011 migration test conditions. Compliance is not a property of the resin alone; it requires migration testing on the finished rotomolded article with the intended food simulant, time, and temperature. Potable water components are similarly assessed under applicable national or regional standards rather than by a single polymer datasheet value. These qualification requirements are especially relevant because rotomolding produces wall thicknesses and surface crystallinity profiles that are different from injection-molded or compression-molded plaques.

Regulatory documentation for the product may include a REACH registration statement, RoHS screening for heavy metals, and food-contact certification under FDA 21 CFR 177.1520. The use of colorants or processing aids may change the compliance status. Because the article is produced at low shear and high mold skin temperatures, the odor and migration profile of the finished part cannot be inferred solely from pellet data. End-use testing remains a requirement for potable water or food-contact articles.