LyondellBasell Icorene 3545 UV+ WHI 1101 Polyethylene, Linear Low Density is a rotational moulding powder supplied with an ultraviolet-stabilizer package and a white pigmentation system. The grade is identified by the UV+ modifier for weathering resistance and the WHI 1101 colour code for white pigmentation. It is manufactured for direct charging into rotational moulds rather than for extrusion or injection moulding. The base resin carries a nominal melt flow rate of 4.5 g/10 min measured at 190 °C and 2.16 kg in accordance with ISO 1133-1, and a nominal density of 0.935 g/cm³ measured in accordance with ISO 1183-1. These values place the material in the intermediate-flow linear low density polyethylene segment for rotational moulding, in which powder flow, cycle time, and low-temperature impact resistance are balanced. The product is not supplied as pellets; sieve retention and powder flow properties are controlled for rotomoulding and reported on the lot certificate. Single-layer and multi-layer moulded parts requiring outdoor exposure, opacity, and consistent white appearance are typical end uses. The grade is commonly specified for covers, enclosures, tanks, agricultural housings, and outdoor equipment panels. In multi-layer structures it may serve as the outer surface layer over a foamed or recycled core; published data for this specific configuration is limited.

How does this grade differ from unpigmented and non-UV LLDPE rotational moulding powders?

The UV+ designation indicates that the formulation contains a stabilizer system intended to reduce ultraviolet-induced chain scission and surface embrittlement. The WHI 1101 colour code indicates a white pigmentation package, typically based on titanium dioxide, that provides opacity and modifies the radiative heating behaviour of the powder. A significant processing difference is that white-pigmented powder absorbs radiant heat more slowly than dark-coloured powder under identical oven conditions. Oven setpoints or residence times are therefore adjusted, and the actual thermal history is confirmed by internal air thermocouple profiling rather than by matching the settings used for black or natural grades.

Compared with a non-UV LLDPE powder of similar density and melt flow rate, the UV+ grade is intended to retain tensile elongation at break and impact resistance for longer under outdoor weathering. Comparative weathering evaluations are typically conducted using ISO 4892-2 or ISO 4892-3; accelerated ageing tests use xenon-arc or fluorescent ultraviolet sources, and the results depend on irradiance, sample thickness, and test duration. Published data for this specific configuration is limited, and laboratory ageing results should not be extrapolated beyond the tested energy dose. Compared with a white-pigmented compound without the UV+ package, the primary difference is the presence of the additional light stabilizer system. Visual colour retention alone is not an adequate measure of mechanical durability.

The base polymer is a linear low density polyethylene produced from ethylene and an alpha-olefin comonomer, which introduces short-chain branching. This structure provides a different property balance than conventional high-pressure low density polyethylene and high-density polyethylene. Conventional LDPE of similar melt flow rate generally has lower environmental stress crack resistance and lower toughness; HDPE offers higher stiffness but lower ESCR and low-temperature impact resistance. The 0.935 g/cm³ density of this grade places it in the LLDPE/MDPE boundary region, favouring stress crack resistance and ductility over maximum tensile modulus.

On a carousel-type rotational moulding machine, the powder is charged into a closed mould, heated in an oven while the mould rotates biaxially, and then cooled with forced air and controlled water mist. Oven temperature is not the sole control parameter; peak internal air temperature is the more reliable indicator of sintering. For LLDPE powders in the 4.5 g/10 min melt flow band, peak internal air temperature is commonly targeted in the 190–205 °C range. The exact target is part-specific. If the value is too low, incomplete powder coalescence leaves pinholes and reduces impact strength; if it is too high, oxidative degradation and colour shift may increase. Because this grade is white-pigmented, oven temperature may need to be raised by 5–10 °C relative to a dark shade to reach the same peak internal air temperature in the same mould.

Mould rotation ratio and speed determine wall thickness uniformity. The optimal ratio is affected by part geometry and mould mounting; no single ratio applies to all articles. Shuttle machines may require different residence times than carousel machines because of differences in forced-air circulation and mould heat capacity. Powder pre-conditioning is also relevant. Cold powder brought into a warm mould room can develop surface condensation if the powder temperature is below the ambient dew point. The powder should be allowed to equilibrate or be stored in sealed containers above the dew point. Excessive fines generated by conveying can segregate at the mould surface and contribute to porosity.

Batch-to-batch processability of a rotomoulding powder is controlled through particle size distribution, bulk density, and dry flow time. A sieve stack from 500 µm to 150 µm is used to quantify the fraction retained on each screen. Fines below 150 µm can migrate and cause uneven wall build-up; coarse particles above 500 µm may require additional heat to melt. Powder dry flow time is measured with a funnel test; moisture or static charge can increase flow time and lead to non-uniform charging. Bulk density of rotational moulding powders in this class is commonly reported around 0.38–0.42 g/cm³ using ASTM D1895, but the lot certificate should be consulted for the accepted range. This bulk density value is not the same as polymer density and is relevant only to hopper fill and mould charging.

Reported mechanical and thermal values under ISO 527-2 and ISO 178

The values in the table are typical properties reported for the product and are not specification limits. They are generated from compression-moulded or rotomoulded specimens under laboratory conditions. Actual part performance is affected by wall thickness, cooling rate, and mould surface finish. Certificates of analysis for the specific lot should be referenced for conformance.

The flexural modulus value indicates short-term stiffness, while the low-temperature brittleness value from ASTM D746 is a comparative indicator rather than a guarantee of part performance under impact. Environmental stress crack resistance measured under ASTM D1693 condition B is relevant for moulded parts exposed to detergents, surfactants, or agricultural chemicals. The result is time-to-failure data; it does not establish chemical compatibility with every fluid. Chemical resistance for a candidate medium requires immersion testing at the end-use temperature and stress state.

Weathering performance of a white-pigmented UV-stabilized LLDPE part depends on stabilizer concentration, pigment dispersion, and part thickness. Outdoor failure usually appears as surface chalking, micro-cracking, and loss of tensile elongation. The UV+ package is intended to delay these mechanisms, but it does not eliminate them. Accelerated weathering using ISO 4892-2 or ISO 4892-3 allows comparative ranking of formulations; however, correlation with field exposure depends on geographic irradiance and temperature. Published data for this specific configuration is limited. Users should define acceptance criteria based on retained elongation at break or retained impact strength, not solely on colour change. Pigmented surfaces also respond differently under solar load; white surfaces remain cooler than dark surfaces, which can reduce the thermal oxidative contribution in outdoor service. That effect is beneficial but must not be confused with intrinsic UV resistance. Components installed in direct contact with strong acids, oxidizing agents, or certain solvents may require separate chemical-resistance validation; the stabilizer system is optimized for outdoor weathering, not for continuous immersion in aggressive fluids.

When peak internal air temperature drops below 185°C during rotomoulding

If internal air thermocouple profiling shows a peak below 185 °C, the powder bed may not complete sintering. The result is incomplete bubble removal, pinhole defects, and a rough inner surface. Low-temperature impact strength of the moulded article decreases disproportionately because voids act as stress concentrators. The corrective action is not always to raise oven temperature; oven residence time, mould mass, and rotation ratio must be reviewed together. A heavier mould or a thicker wall section consumes more heat, and a white-pigmented powder reflects more incident radiation than a dark powder, so the same oven setpoint may no longer reach the target. The oven setpoint should be increased in small increments, with peak internal air temperature re-profiled before production release.

Operators should also verify that the powder temperature is above the dew point. Condensation introduced from chilled powder storage creates steam during the heating cycle, leaving voids and surface defects. The powder should be held in sealed containers and equilibrated before charging. If the material is blended with regrind, the regrind particle size distribution must be controlled; coarse regrind melts later than fine virgin powder and can cause the same class of defect even when the internal air temperature appears adequate.

Compliance of the base olefin polymer with food-contact regulations may be assessed against 21 CFR 177.1520 or EU Regulation 10/2011, but the final rotomoulded article requires migration testing at the intended thickness and surface-to-volume ratio. The UV-stabilizer and white-pigmentation packages must be confirmed for use in food-contact applications through the supplier’s documentation; the grade is not automatically acceptable for all food-contact uses. For industrial products, the material is subject to the general conditions of REACH and RoHS, and restricted substance status should be verified against the safety data sheet and supplier declaration for the specific lot. If the article is painted or adhesively bonded, flame, corona, or plasma treatment may lower surface energy, but the treatment must be validated on rotomoulded surfaces because the mould release agent can affect adhesion.

Storage recommendations are part of the technical boundary. The powder should be kept in sealed containers, away from direct sunlight and moisture, and at temperatures below 40 °C. Avoid blending with unapproved additives or colour concentrates, because an additional carrier resin or stabilizer may shift the UV-stabilization balance. The grade is not intended for applications requiring continuous exposure to steam above its softening point, nor for contact with strong oxidizing chemicals without case-by-case evaluation.

Relative to high-density polyethylene rotational moulding grades, Icorene 3545 UV+ WHI 1101 has lower short-term flexural modulus and lower continuous-use temperature ceiling, but higher environmental stress crack resistance and better low-temperature impact strength. This trade-off makes it suitable for outdoor parts that must survive handling, freeze-thaw cycles, and occasional chemical exposure, rather than for structural foam or high-temperature tanks. Relative to crosslinked polyethylene rotomoulding grades, this linear low density product does not provide the creep resistance or elevated-temperature mechanical properties of a crosslinked network; however, it avoids the additional crosslinking chemistry and can be reprocessed as a thermoplastic. Selection among LLDPE, HDPE, and XLPE should be based on the end-use load, chemical environment, and required failure mode rather than on density alone. The final part design should avoid sharp corners and abrupt wall transitions, because these features reduce the effective low-temperature impact performance even when the resin itself has a ductile-brittle transition below -70 °C.