LyondellBasell Icorene 3560 BUE 5767 is a linear low-density polyethylene powder supplied for rotational molding. The grade is specified by a nominal density of 0.935 g/cm³ and a melt mass-flow rate of 5.5 g/10 min at 190°C and 2.16 kg in accordance with ISO 1133-1:2022; density is determined according to ISO 1183-1:2019. The material belongs to the butene-comonomer branch of LLDPE, with the BUE and 5767 suffix indicating the stabilizer and delivery package rather than a generic molecular architecture. The powder is typically supplied with a controlled particle-size distribution for carousel, shuttle, and rock-and-roll rotomoulding lines. Lot-level density, melt flow, and stabilizer content should be confirmed on the supplier’s certificate of analysis because published commercial datasheets are not release specifications.

Under ASTM D4976, the material falls within the linear low-density polyethylene cell classification when the full property set is supplied by the manufacturer. The grade is not interchangeable with pelletized injection-molding LLDPE or with pipe-extrusion LLDPE because the particle size distribution and stabilizer package are designed for long oven residence times and low-shear coalescence. Typical rotomoulding powder top-size is near 35 mesh (500 µm); finer fractions improve inside-surface smoothness, while coarse fractions can help bridging resistance in deep corners. The exact particle size distribution should be requested as a lot-specific value when qualifying a new source.

Which mechanical and thermal benchmarks appear in a specification review?

Representative values from published commercial data are shown in the following table; they do not replace the supplier’s release limits. Tensile, flexural, and hardness values are conditioned at 23°C and 50% relative humidity unless otherwise stated. The selection of these values for design requires the full stress-strain curve, not only yield and modulus.

The density of 0.935 g/cm³ lowers crystallinity relative to a 0.940–0.945 g/cm³ MDPE; this reduces flexural modulus but increases elongation and low-temperature ductility. In rotomolded parts, the material therefore suits service where wall deflection is less critical than impact and stress-cracking resistance. The melt mass-flow rate of 5.5 g/10 min is sufficiently high for rapid sintering but low enough to prevent excessive flow-induced thin-out in deep draw areas. The Vicat softening temperature of approximately 120–124°C is a single-point heat deflection indicator, not a continuous exposure limit; oxidative stabilizers and creep resistance control the upper use temperature. Because rotomolding is essentially shear-free, melt mass-flow rate is not a direct predictor of sintering rate; zero-shear viscosity and molecular weight distribution are more relevant when comparing alternative powders of identical MFR.

Rotomolded walls develop through-thickness crystallinity gradients because the outside surface cools faster than the inside surface. A part molded at 6 mm wall thickness from this powder can show lower yield stress near the inside surface than a compression-molded 2 mm plaque due to slower cooling and larger spherulite growth. For this reason, design allowable stress values should be derived from prototype rotomolded panels rather than from standard test specimens alone. The specified flexural modulus of 750 MPa is a short-term value; long-term creep modulus at 23°C and 1% strain may be significantly lower, and creep data should be obtained from suppliers for load-bearing applications.

On a two-arm shuttle rotomoulding line with forced-air convection heating, the powder is loaded into cast aluminum molds and subjected to biaxial rotation. Because rotational molding is a low-shear process, particle coalescence is driven by conductive heating, surface-tension-driven neck growth, and densification; the powder particle size distribution therefore has an outsized effect on inside-surface quality and pin hole formation. Oven air temperature is typically maintained between 280°C and 320°C, and peak internal air temperature is held between approximately 190°C and 230°C depending on wall thickness, mold geometry, and part mass. Exceeding 240°C internal air can accelerate additive depletion, particularly the UV stabilizer, while peak internal air temperatures below 185°C can produce incomplete sintering and corner porosity. Mold rotation ratios near 4:1 are conventional for symmetrical parts; asymmetrical parts can require non-integer ratios to prevent powder accumulation. Release from cast aluminium tooling depends on surface seasoning, mold release agent, and cooling mode. Rapid water-spray cooling increases thermal residual stress and can aggravate warpage in thin-walled LLDPE because shrinkage is anisotropic when crystallinity develops under a steep temperature gradient.

Published data for the exact internal-air/oven-air response of this specific suffix is limited; therefore process transfer should include instrumented trials in the actual mold and measurement of through-thickness bubble formation, inside-surface roughness, and post-mold shrinkage. Moisture above 0.1 wt% can produce steam pinholes and surface roughness; storage in sealed containers or dry silos is therefore required. Pre-drying is not normally necessary for rotomoulding powders, but if condensation has occurred, dehumidified-air drying at moderate temperature should be used.

Mold surface temperature at release is another process boundary. If the mold is opened while the inside surface is above 65°C, the soft LLDPE wall can deform under demolding stresses. Too rapid cooling to below 40°C can increase release force and promote gloss variation. A temperature-controlled cooling cycle with mold sensors is preferable to timer-based cooling. Thermal degradation can be screened by measuring MFR before and after molding; a shift greater than 10% indicates chain scission or crosslinking, and yellowness index above 4 on unpigmented plaques may indicate stabilizer depletion or contaminated regrind.

When this grade is substituted for a 0.940–0.945 g/cm³ MDPE in outdoor tank rotomoulding

The substitution changes the density-dependent mechanical balance. Reducing density from 0.940–0.945 g/cm³ to 0.935 g/cm³ typically lowers flexural modulus by 30–60 MPa while increasing low-temperature impact and slow-crack growth resistance. The design consequence is not uniformly favourable: if the tank wall is deflection-limited, the reduced modulus must be compensated by ribbing or increased wall section. If impact at −20°C is the governing failure mode, the lower crystallinity of the 0.935 grade is advantageous. The UV stabilization suffix reduces surface chalking and embrittlement compared with unstabilized general-purpose LLDPE, but weathering is still influenced by wall thickness, geographic solar irradiance, pigmentation, and chemical exposure. Accelerated xenon-arc data generated according to ISO 4892-2 should be used only with a clear linkage to outdoor results; published data for this specific configuration is limited.

Compared with an HDPE grade near 0.950 g/cm³, this LLDPE requires lower oven-air temperatures and offers better low-temperature ductility, but it sacrifices buckling stiffness and aggressive solvent resistance. Compared with an LDPE homopolymer, the butene-based LLDPE architecture increases yield stress and short-chain branching uniformity, improving mold release and reducing warp; however, the exact balance depends on molecular weight distribution and should not be inferred solely from density. Slow crack growth resistance under detergent stress and notch conditions is commonly evaluated by ASTM D1693, condition B; users should require lot-specific testing for stress-crack-sensitive tank designs.

Rotational molding of intermediate bulk container liners, agricultural chemical tanks, and outdoor water-storage vessels often uses this grade when the integrated UV stabilizer and butene-derived impact toughness are specified. The powder is dry-blended with 2–5 wt% pulverized pigment masterbatch. The carrier resin in the masterbatch can alter melt flow, nucleate crystallization, and increase lineal shrinkage by 0.2–0.4% relative to unpigmented powder; consequently, drop-impact results and wall-thickness distribution should be revalidated after any pigment or regrind change. Regrind addition above 20 wt% may reduce oxidation induction time and surface gloss. The rotomoulder should monitor OIT by ISO 11357-6 at 200°C for service with oxidizing chemicals. Ground regrind from sprues and test plaques can have a wider particle size distribution than virgin powder. If regrind is used above 20 wt%, sieve analysis should be performed per ASTM D1921 or an equivalent mesh stack; a high fine fraction may increase bulk density but reduce air voids and change heat transfer, while a high coarse fraction may leave pinholes at corners.

Outdoor exposure, especially in agricultural chemical service, produces a combined oxidation and extraction environment. The stabilizer package in the 5767 suffix is intended to reduce carbonyl formation and surface cracking, but it does not prevent swelling from highly penetrant solvents. For parts that must withstand direct sunlight and occasional contact with pesticides, the conventional practice is to specify a UV-stabilized rotomoulding grade and then confirm performance by exposing molded plaques to the intended chemical mixture at 23°C and 50°C for weight change, tensile retention, and visual cracking. The accelerated weathering device should follow ISO 4892-2 cycle 1 or ASTM G155 cycle 1; direct comparison with outdoor benchmarks is required because xenon-arc acceleration factors for LLDPE vary with stabilizer type.

Quality control at receipt should record melt mass-flow rate, density, powder bulk density, and moisture. The material’s stabilization system is designed for multiple heat histories, yet repeated regrind cycles beyond 3–5 may consume antioxidant and UV stabilizer reserves; OIT and yellowness index should be trended. For regulatory compliance, the supplier’s safety data sheet under EU Regulation 1907/2006 and any food-contact statement under FDA 21 CFR 177.1520 must be checked for the purchased suffix; not all rotomolding additives carry identical food-contact status. Under EU Directive 2011/65/EU RoHS, the base polymer is not expected to contain restricted phthalates or heavy metals, but color concentrates must be selected from compliant suppliers.

Unlike pelletized injection-molding LLDPE grades of similar density and melt flow, this Icorene grade is supplied as a rotomoulding powder. Pelletized grades contain processing aids and may not separate into the fine fraction required for corner filling; rotomoulding powder particle size distribution is optimized for free flow and densification without screw mixing. The additive package is also tailored to withstand long oven residence times, whereas injection-molding stabilization is targeted to short barrel residence and high shear. This distinction is material to material replacement decisions, because substituting pelletized LLDPE ground in-house can change powder shape, bulk density, and the amount of fine particles, all of which influence pinholes and surface quality.