LyondellBasell Icorene 3560 BLK 9001 Polyethylene, Linear Low Density

LyondellBasell Icorene 3560 BLK 9001 is a carbon-black-filled, UV-stabilized linear low density polyethylene powder intended for rotational moulding of hollow parts exposed to sunlight and aqueous chemicals. The grade is distinguished from pelletized LLDPE film extrusion resins by dry-powder morphology and from natural rotomoulding grades by the pigmentation package. Nominal density is 0.936 g/cm³ according to ISO 1183-1:2019. Nominal melt flow rate is 5.5 g/10 min at 190 °C and 2.16 kg as per ISO 1133-1:2022. Manufacturer-published typical properties include tensile yield stress near 17 MPa, elongation at break greater than 800 %, flexural modulus near 550 MPa, and an F50 environmental stress crack resistance exceeding 1,000 h when tested with 100 % Igepal CO-630 under ASTM D1693-15 condition B. These values place the product among medium-flow rotational moulding resins designed for tanks, containers, and outdoor enclosures.

The solid-state properties reflect a linear low density structure with short-chain branching along a predominantly linear backbone. Differential scanning calorimetry under ISO 11357-3:2018 shows a melting peak at approximately 126 °C and a crystallization temperature near 108 °C. The Vicat softening temperature of 116 °C under ISO 306:2022 method A50 indicates a practical upper limit for short-term shape retention under low load. These thermal data are used to set demolding temperature near 80 °C and to avoid stack distortion in thick parts. Because the grade contains carbon black, the surface of a moulding can reach higher temperatures than an unpigmented part under solar load, and thermal expansion must be considered when mounting large tanks. The coefficient of linear thermal expansion is typically in the range of 1.2 × 10⁻⁴ to 1.8 × 10⁻⁴ K⁻¹ for linear low density polyethylene, though published data for this specific grade are limited.

The powder is supplied with a bulk density of approximately 0.45 g/cm³ and a typical particle size top cut near 500 µm. Dry-flow measurement using a funnel method appropriate for rotomoulding powders may yield flow times below 30 s for a 100 g sample, but published data for this specific grade are limited. Particle size distribution control is critical because excessive fines above 15 % by weight below 150 µm can cause dusting, uneven wall thickness in deep cavities, and poor venting. Coarse particles above 500 µm can produce surface porosity because they sinter more slowly at the mold surface.

On shuttle and carousel rotational moulding lines with biaxial speed ratios between 3.5:1 and 4.5:1, the powder fills narrow ribs and deep cavities with less bridging than pelletized feedstocks. Processors typically set oven temperatures between 260 °C and 310 °C and maintain peak internal air temperature between 190 °C and 205 °C; mold surface temperatures of 150 °C to 190 °C are observed before forced-air or water-mist cooling. The cooling step is controlled at 5–15 K/min through the crystallization plateau to avoid warpage. For a mold wall thickness of 6 mm, total oven residence time is commonly 18–24 min depending on part mass, oven duty, and temperature recovery. Undercure in thin sections appears as subsurface microvoids along the mold parting line; overcure produces yellowing of the black surface and a measurable loss in low-temperature impact strength. Production-scale clamshell machines with infrared pyrometers and continuous internal air temperature logging are recommended because single-point IR readings of the mold outer surface do not reliably indicate the inner wall temperature.

Rotational moulding is a low-shear process. Melt viscosity is inferred primarily from the melt flow rate rather than from capillary rheometry. At 190 °C the nominal melt flow rate of 5.5 g/10 min corresponds to a low shear rate viscosity that allows powder particles to coalesce at the mold surface after peak internal air temperature is reached. Sintering kinetics change with the heating rate; slower heating above 260 °C oven set point lengthens the processing window but may increase oxidation in the outer layer, while faster heating can create a skin that traps air at sharp corners. Differential scanning calorimetry can be used to verify that the molded article reaches full melting at the inner surface; residual crystallinity at the inner surface indicates undercure. The low equilibrium moisture regain of polyethylene means pre-drying is unnecessary at relative humidity below 60 %. Above 60 % RH, condensation on powder stored in cold areas can carry surface moisture into the mold and generate pinholes in wall sections thinner than 4 mm, so hopper and feed lines should be kept above dew point.

How Does the Black UV-Stabilized Powder Differ from Pelletized Film Extrusion LLDPE?

The most immediate difference is melt flow rate. Pelletized LLDPE film grades are typically supplied with melt flow rates of 0.5–1.0 g/10 min to preserve bubble stability, while Icorene 3560 BLK 9001 is adjusted to a nominal 5.5 g/10 min. The higher MFR reduces time-dependent melt viscosity and permits sintering of powder particles at the low shear conditions characteristic of rotational moulding, where shear rates may be below 1 s⁻¹. Pelletized film resin cannot be substituted directly because pellet geometry produces voids and irregular wall thickness in the powder lay-up step. The black formulation also contains carbon black and stabilizers that absorb UV radiation and slow photo-oxidative chain scission; film-grade LLDPE typically relies on separate masterbatch addition. In accelerated weathering under ISO 4892-2:2013 cycle 1, black rotomoulding grades retain a higher percentage of original elongation at break than unpigmented or non-UV-stabilized LLDPE at equivalent exposure, although published data for this specific grade’s colour change after 5,000 h are limited. Compared with metallocene LLDPE rotomoulding powders, the molecular architecture of this grade is designed for balance between high-speed sintering and long-term creep resistance, but it does not exhibit the same high-impact performance at -40 °C as ultra-low-density metallocene products.

In comparison with the natural-pigment version of the same base resin, carbon black acts as a nucleating agent during solidification and increases thermal conductivity of the powder bed. This effect often manifests on production lines as a 5–10 % reduction in oven residence time for identical peak internal air temperature, although the exact magnitude depends on carbon black dispersion and part thickness. The black grade is normally selected when long-term outdoor weathering is required; the natural grade is preferred for indoor applications where colour matching or food-contact evaluation is simpler. The presence of carbon black raises the surface temperature of parts exposed to direct sunlight, which increases the risk of distortion under mechanical load. Designers reduce this effect by specifying a maximum design strain of 3–5 % and by using creep modulus values determined under ISO 899-2:2003 at the expected maximum service temperature.

When 3560 BLK 9001 Replaces Medium-Density Polyethylene in Outdoor Chemical Storage Tanks

Medium-density polyethylene rotomoulding grades often exhibit higher density and higher flexural modulus than this LLDPE grade, but they can be more susceptible to environmental stress cracking in constant-strain applications involving detergents, agricultural chemicals, or humid acid vapour. The F50 value exceeding 1,000 h under ASTM D1693-15 condition B supports use in rotationally moulded tanks where stress cracks at weld lines, inserts, or constrained bosses are the dominant failure mode. Trade-off data show that flexural modulus of this grade is lower than a typical medium-density rotomoulding resin, so unsupported vertical walls may require thicker sections or additional ribs to meet the same deflection criterion. For cylindrical vertical tanks, hoop stress at the base is calculated from the hydrostatic head; a typical allowable design strain of 3 % for continuous loading restricts wall thickness more than short-term burst strength. Creep modulus at 1,000 h and 60 °C is a better design input than flexural modulus measured at 23 °C. The black UV-stabilized formulation is suitable for outdoor storage enclosures and agricultural chemical tanks subject to ultraviolet radiation, provided the chemical compatibility of the outer skin and inner surface is validated by immersion testing at the maximum service temperature. The carbon black loading for UV protection is typically in the range of 2–3 % by weight, though the manufacturer does not publicly specify the exact concentration. Continuous service above 60 °C in aqueous environments reduces creep rupture strength, and aggressive oxidizers may attack the stabilizer package before visible surface cracking occurs. For structural calculations, short-term flexural modulus from ISO 178:2019 should not be used as a long-term design modulus without applying a creep reduction factor derived from ISO 899-2:2003 data.

Compared with high-density polyethylene rotomoulding grades of density 0.945–0.950 g/cm³, Icorene 3560 BLK 9001 offers lower stiffness but higher stress crack resistance. When a storage tank requires resistance to slow crack growth under internal pressure, the LLDPE grade is often selected instead of an HDPE grade with similar melt flow rate because the HDPE may fail earlier in notched constant-strain tests. However, the HDPE part may have better resistance to hydrocarbon solvents due to higher crystallinity. Selection between the two requires chemical compatibility data from the specific service fluid, preferably generated according to ISO 22088-2:2006 or ASTM D543-21.

Compliance with food-contact and potable-water standards is not an inherent property of the base polyolefin; it must be established for the final moulded article because carbon black, UV stabilizers, and processing aids may migrate under specific simulant conditions. The base linear low density polyethylene can be assessed against FDA 21 CFR 177.1520 olefin polymer requirements, and European migration testing may be performed under EU Regulation 10/2011 with fatty and aqueous simulants. Potable water contact often requires certification to NSF/ANSI/CAN 61 or EN 12873-1. The black colour itself does not confer chemical resistance; it influences surface heating and weathering stability.

Processors should avoid contamination with polypropylene, PVC, acetal, or silicone mold release residues because these materials form low-molecular-weight or incompatible phases that act as stress concentrators and can reduce environmental stress crack resistance. Silicone mold release applied in excess leaves a surface film that can interfere with post-moulding adhesion or ultrasonic welding. When welding or repairing rotomoulded parts made from this grade, unpigmented or non-UV-stabilized polyethylene welding rod should be avoided because the weld zone will lack equivalent weathering stability. Pre-drying is not required at relative humidity below 60 %; above 60 % RH, the powder should be stored in sealed hoppers above dew point to prevent pinholes in wall sections thinner than 4 mm. The upper continuous service temperature for load-bearing aqueous applications is typically below 60 °C. Contact with strong oxidizing chemicals at elevated temperatures requires validation by immersion testing because oxidation can consume stabilizers before mechanical property loss is visually detectable. Published data for this specific grade under high-energy irradiation or autoclave sterilization are limited. Storage of unused powder should remain below 50 °C and away from direct sunlight to preserve stabilizer activity prior to moulding.