LyondellBasell Icorene 3560 BUE 5812 Polyethylene, Linear Low Density is an ethylene-butene copolymer supplied in powder form for rotational molding. The Icorene 3560 designation identifies the base resin, while the BUE 5812 suffix denotes a proprietary additive and pigmentation package that controls oxidative stability, ultraviolet screening, and colour consistency. Published supplier summaries place nominal density at 0.934 g/cm³ when measured by ISO 1183-1 and melt flow rate at 5.0 g/10 min under 190 °C/2.16 kg conditions according to ISO 1133-1. The powder is intended for hollow parts that need moderate stiffness, low-temperature impact resistance, and environmental stress-crack resistance in aqueous surfactant or mild chemical service. Common downstream parts include storage tanks, agricultural containers, playground structures, and industrial housings. Lot-specific certificate-of-analysis values govern release and should replace any representative published data.

How does a butene-copolymer LLDPE differ from LDPE, HDPE, and metallocene octene grades?

The primary structural difference is the short-chain branch distribution introduced by butene comonomer on an essentially linear backbone. Compared with high-pressure low-density polyethylene, the linear low-density architecture has fewer long-chain branches. This increases tensile yield stress and elongation at break, but reduces melt elasticity at low shear. In rotational molding, the lower low-shear elasticity means that the molten powder sheet does not sag and stretch as readily as LDPE under gravity; bubble release and inner-surface replication therefore require a controlled peak internal air temperature and sufficient plateau time. Relative to HDPE rotomolding grades with density above 0.940 g/cm³, the nominal 0.934 g/cm³ density lowers flexural modulus and continuous-use temperature but improves low-temperature impact and environmental stress-crack resistance. Against metallocene-catalyzed octene LLDPE, the butene branch distribution typically gives lower dart impact values under ISO 7765-1 or ASTM D1709 and lower Elmendorf tear resistance, but it usually offers easier grinding to powder and lower high-shear viscosity during extrusion or compounding. These distinctions matter when the same tool is used for multiple polyethylene families, because oven cycle time, internal air temperature, and wall thickness must be revalidated for each resin.

In practice, the powder is charged into a cast aluminium or fabricated steel tool rotated biaxially in a gas-fired shuttle, carousel, or rock-and-roll oven. Oven chamber temperatures are commonly maintained at 280–300 °C. The powder reaches optimum sintering and densification when the internal air temperature reaches 190–200 °C; this value is measured with a through-tool thermocouple and should be held to a tolerance of ±5 °C after the cavity becomes fully vented. At wall thicknesses of 6–12 mm, total oven residence times of 18–35 min are typical, but heating time must be adjusted for tool mass, charge weight, oven airflow, and ambient temperature. Under-fusion leaves partially sintered powder at the inner surface and creates microporosity; overheating consumes the stabilizer package and produces oxidative chain scission, yellowing, inner-surface bubbles, and loss of impact strength. Cooling is equally process-critical. Forced-air cooling at initial rates of 5–15 °C/min limits warpage, while water mist or spray quenching can increase low-temperature impact but may lock in differential shrinkage. Polyethylene does not require pre-drying for moisture, but cold powder stored above 60% relative humidity should be brought to room temperature before charging to prevent condensation on the powder surface.

Mechanical properties in rotomoulded parts are not isotropic. Tensile specimens cut from the tool wall in longitudinal and circumferential directions may show yield-stress differences of 2–5% because of biaxial flow orientation and uneven cooling. Flexural modulus measured on flat plaques according to ISO 178 may be 5–10% lower than values from compression-moulded sheets of the same resin due to microporosity and residual stress. For design, data generated on plaques cut from production tools should be used rather than injection-moulded or compression-moulded specimens.

Melt flow rate, density, and lot-to-lot acceptance criteria

Incoming quality control should verify melt flow rate and density on a conditioned sample. Density is measured by ISO 1183-1 or ASTM D792; melt flow rate is measured at 190 °C/2.16 kg according to ISO 1133-1:2022 or ASTM D1238. Because rotomolding powder is coarse and free-flowing, representative sampling from multiple silo locations is required. The table below summarizes the test matrix for a butene LLDPE rotomolding powder of this melt-flow class. Values are lot-dependent and do not replace the certificate of analysis or first-article qualification.

For outdoor parts, ultraviolet stabilization should be qualified by accelerated weathering under ISO 4892-2 cycle A or ASTM G154 practice; colour shift, chalking, and retained impact should be measured against an agreed specification. Food-contact status is not an intrinsic resin property because it depends on the complete additive package. Compliance must be confirmed with the supplier under 21 CFR § 177.1520 and EU Regulation (EU) No 10/2011. Heavy-metal and restricted substance compliance should be verified against REACH Annex XVII and RoHS Directive 2011/65/EU for the specific pigmented lot.

Powder dry-flow and bulk density affect mould filling. Rotomolding grades are typically screened through a 35 mesh (500 µm) sieve; particle-size distribution is measured by ASTM D1921 or dynamic image analysis. A narrow distribution improves wall-thickness uniformity in complex tools and reduces fine-particle accumulation at corners. Bulk density values commonly fall between 0.35–0.45 g/cm³. High fines content and static charge produce uneven powder distribution and thin spots during the initial heating phase.

Differential scanning calorimetry under ISO 11357-3 on a compression-moulded sample shows a broad melting endotherm, with the main peak typically between 122–126 °C and a heat of fusion of 140–160 J/g for this density class. The crystallization peak on cooling at 10 °C/min typically appears near 104–108 °C. These values are not fixed product constants; they shift with cooling rate, comonomer distribution, and additive package. The broad melting range is functionally significant: it allows the powder to sinter at lower oven temperatures than HDPE while still retaining enough melt strength to form a uniform wall.

For outdoor agricultural tanks and industrial containers, Icorene 3560 BUE 5812 parts are frequently qualified after conditioning at -20 °C using a falling-mass impact method according to ISO 6603-2 or a dart impact method according to ISO 7765-1. Detergent and wetting-agent stress cracking is assessed by ASTM D1693 condition B; for this density class, F50 values above 1000 h are typical, but moulded-in stress around inserts or sharp corners can reduce observed resistance. Notched constant ligament stress testing under ASTM F2136 is preferred when the part contains metal inserts, deep ribs, or local thickness transitions. The material is not recommended for continuous immersion in strong oxidizing agents, aromatic hydrocarbons, or chlorinated solvents; swelling and stress cracking may occur. In long-term outdoor service, dark colours may reach surface temperatures 20–30 °C above ambient under solar load, which increases antioxidant consumption and can lower the practical service envelope. Published data for the exact BUE 5812 formulation under all end-use chemical environments is limited, so application-specific compatibility testing is required before release.

When post-consumer HDPE or LLDPE scrap is incorporated into dry blends

Rotational molders sometimes blend clean regrind or post-consumer HDPE/LLDPE scrap with virgin Icorene 3560 BUE 5812 to reduce cost or meet recycled-content targets. The dry blend should be limited to 10–25 wt% clean, dust-free scrap of known density and melt flow rate; higher fractions increase variability in powder flow and can create two-phase melting behaviour if the scrap melt flow rate differs by more than 1.0 g/10 min. Because post-consumer HDPE usually has density above 0.940 g/cm³ and a melt flow rate below 3.0 g/10 min, a 10 wt% addition raises the blend density by roughly 0.0006–0.0012 g/cm³ and shifts the optimum peak internal air temperature upward by 1–3 °C. Immiscible contamination, particularly polypropylene or PVC, should be avoided; dispersed domains reduce weld-line strength and impact performance under ISO 6603-2. Repeated regrind cycles consume the active stabilizer reserve in the BUE 5812 package and can shift the melt flow rate upward; the blend should be re-qualified after each recycle loop rather than assuming equivalent performance.