LyondellBasell Icorene 3545 YEW 2517 Polyethylene, Linear Low Density is a rotational moulding powder based on linear low-density polyethylene. The grade is supplied as a formulated powder; the YEW 2517 suffix designates a colour and stabilisation package for which the supplier’s public datasheet provides limited component-specific detail. The base polymer is specified by nominal density of 0.934 g/cm³ per ASTM D1505 or ISO 1183-1:2019 and a melt flow rate of 5.0 g/10 min at 190 °C under 2.16 kg load per ASTM D1238 or ISO 1133-1:2022. These values place the material below the 0.940 g/cm³ threshold commonly used to separate low-density and medium-density rotomoulding grades. The grade is differentiated from high-density polyethylene rotomoulding powders by lower flexural modulus and higher environmental stress crack resistance; it is specified for service where ductility, low-temperature impact resistance, and chemical resistance dominate over creep modulus and heat distortion. Typical applications include rotationally moulded tanks, containers, agricultural hoppers, marine buoys, and ductile parts with wall thickness between 3 mm and 12 mm.

Extrusion compounding is not required in most rotational moulding shops, but powder temperature at oven entry should be controlled between 20 °C and 30 °C to maintain dry flow. Moisture uptake of polyolefin powder is low, but condensation at relative humidity above 60% can produce surface defects; pre-drying at 60 °C to 70 °C for 2 h to 4 h is recommended if visible moisture or cold-floor storage has occurred. The material is not intended for injection moulding or blow moulding without melt re-pelletising; powder handling and dry-flow properties form part of the rotomoulding specification.

The YEW 2517 suffix is commonly associated with an ultraviolet stabilisation package for outdoor service. If confirmed by supplier documentation, the compound may be used in continuously exposed applications such as marine buoys and agricultural tanks without painting; however, accelerated weathering per ASTM G154 or ISO 4892-3 should be performed on rotomoulded panels because powder pigmentation and surface oxidation interact with part thickness. Published data for this specific configuration is limited; outdoor service life estimates should not be extrapolated from laboratory data alone.

What Limits Slow Crack Growth Resistance in This LLDPE Versus Higher-Density Rotomoulding Grades?

The distinguishing structural feature is the short-chain branching introduced by alpha-olefin comonomer. In a linear low-density resin the branch content lowers lamellar thickness, reduces spherulite size, and increases the number of tie molecules linking adjacent crystalline lamellae. These tie molecules transmit stress across interlamellar regions; slow crack growth under ASTM D1693 condition B at 10% Igepal CO-630 and 50 °C is therefore improved relative to HDPE grades of equivalent melt flow rate. Published characteristic values for LLDPE rotomoulding powders in the 0.930 g/cm³ to 0.937 g/cm³ density interval commonly exceed 1,000 h F50, while a rotomoulding HDPE at 0.945 g/cm³ may fall below 300 h in the same test. For this specific grade, the supplier’s certificate should be consulted for lot-specific F50 values.

Tensile yield strength is typically near 14 MPa and flexural modulus near 400 MPa when measured according to ASTM D638 and ASTM D790; these are lower than typical rotomoulding HDPE values of 20 MPa and 700 MPa. The trade-off is greater creep compliance at elevated temperature; sustained pressure service above 50 °C is not recommended without creep testing. Elongation at break in this density class exceeds 800%, and low-temperature brittleness by ASTM D746 is commonly below -75 °C; these values are thickness-dependent and should be verified on rotomoulded parts rather than compression-moulded plaques.

Public documentation does not identify the catalyst type for YEW 2517. Many LLDPE rotomoulding grades in this density and melt flow interval exhibit a broad molecular weight distribution that improves low-shear particle coalescence and reduces melt sag during the rotating phase. The melting peak of linear low-density polyethylene of this density is typically 125 °C to 128 °C by differential scanning calorimetry per ASTM D3418, compared with 108 °C to 112 °C for high-pressure LDPE and 130 °C to 132 °C for HDPE. This intermediate melting range contributes to the grade’s ability to achieve full densification at lower peak internal air temperature than HDPE, but it also narrows the thermal window before oxidative degradation becomes visible at the inner mould surface.

Compared with metallocene-catalysed rotomoulding LLDPE grades of similar density, the conventional broad-distribution powder may show a wider sintering range and better dry flow in deep moulds, but may also retain higher soluble fraction and slightly lower clarity. Published data for this specific configuration is limited; these comparisons are based on general LLDPE product-family behaviour and must be confirmed on the production tool.

Rotational Moulding Temperature Control and Powder Coalescence Limits

Industrial rotomoulding machines—carousel, shuttle, and open-flame rock-and-roll units—can process this material if the heating phase is adjusted to account for the lower melt stiffness of LLDPE compared with HDPE. Oven air temperature is typically set at 280 °C to 300 °C. Peak internal air temperature should reach 190 °C to 210 °C for full densification; peak internal air temperatures below 185 °C are associated with incomplete sintering and internal porosity in wall sections exceeding 6 mm. A minor-to-major arm ratio of 4:1 is typical for cylindrical tanks; complex moulds may require 1:4 or programmed axis control to maintain uniform wall thickness.

On production lines, failure modes observed with LLDPE rotomoulding powders include inner-surface pinholes when mould release contamination is present, weld-line porosity at sharp inserts, and oxidative yellowing when oven temperature exceeds 300 °C or residence time is extended. On shuttle lines with high cycle rates, batch-to-batch melt flow shifts above 0.5 g/10 min can alter bubble removal and surface appearance; incoming lot consistency per ASTM D1238 is therefore part of process control. External mould release should be removed from the inner surface because organic residues degrade and cause pinholes.

Cooling rate after heating changes part crystallinity and shrinkage. Slow air cooling produces larger spherulites and higher modulus but may increase warpage; forced-air or water-fog cooling reduces cycle time but lowers crystallinity and can cause differential shrinkage in tight radii. Mould surface temperature during cooling should be monitored by infrared pyrometry; controlled cooling through 120 °C to 60 °C at 1 °C/min to 3 °C/min is typical for stress relief. Demoulding before the part reaches 60 °C may increase warpage in large flat panels. If the mould includes metal inserts, post-mould annealing at 80 °C for 1 h may reduce insert stress cracking after assembly.

At the nominal melt flow rate of 5.0 g/10 min, the zero-shear viscosity is lower than that of 2.0 g/10 min rotomoulding HDPE grades; this reduces the time for bubble dissolution but increases the risk of melt drool on overhead surfaces of complex moulds. The powder’s bulk density and particle-size distribution should be monitored because fines below 150 µm can segregate in zones of high airflow and produce thin corners. The material is supplied in powder form; pneumatic transfer should use dry air with a dew point below -40 °C to prevent condensation.

Dry-blending with high-density regrind should not be performed without evaluation of density and environmental stress crack resistance; adding HDPE regrind alters density and may reduce slow crack growth resistance significantly. The user must validate each blend ratio with ASTM D1505, ASTM D1693, and a full rotomoulded part test. Peroxide crosslinking additives are not required for this grade and should be avoided unless intentional network formation is part of the end-use specification.

When Food-Contact Status Is Required for Rotomoulded Containers

Food-contact suitability is not automatic for the compounded YEW 2517 product. The base olefin polymer may comply with FDA 21 CFR 177.1520 if end-use extraction tests are met, but the additive package may include pigments and processing stabilizers not listed in food-contact positive lists. Application-specific migration testing is required before use in food contact. For industrial chemical storage, chemical compatibility should be tested according to ASTM D543 for weight and dimensional change in the intended chemical at service temperature. Polyethylene has poor resistance to strong oxidizers; storage of concentrated hydrogen peroxide or nitric acid is outside the published service boundary for this grade unless supported by long-term immersion data.

Permeability to water vapour and oxygen is higher for this LLDPE than for HDPE because of lower crystallinity. Therefore the grade is less suitable for barrier packaging applications requiring low oxygen transmission; it remains acceptable for open-to-atmosphere liquid storage. If a moulded part requires lower permeability, a higher-density grade or a multi-layer structure with a barrier liner is used.

On rotomoulding lines producing agricultural sprayer tanks of 1,000 L to 3,000 L, wall thickness is typically 5 mm to 8 mm. Slow-cooling fixtures are used for the tank mouth to prevent ovaling after demoulding. If external thread inserts are moulded in, post-mould annealing at 80 °C for 1 h may reduce insert stress cracking after assembly. Rotomoulded parts made from this LLDPE grade require full sectioning of the first article to check for internal porosity at weld lines, rib intersections, and threaded bosses; destructive evaluation per ASTM D638 on specimens cut from product walls provides a better measure of part performance than plaque data alone.