LyondellBasell Icorene 3546 UV+ PUR 5398 Polyethylene, Linear Low Density is a linear low-density polyethylene powder formulated for rotational molding. The trade designation identifies a UV-stabilised LLDPE base with the PUR 5398 color/additive formulation; the suffix is a product-formulation identifier, not a polyurethane or reactive modifier. The material is supplied as a free-flowing powder with controlled particle-size distribution to promote uniform melt coalescence on multi-axis tooling. Incoming resin evaluation normally records melt mass-flow rate under ISO 1133-1 at 190 °C and 2.16 kg, density under ISO 1183-1, bulk density under ISO 60, and dry flow under ISO 6186. Because the base polyethylene is a linear low-density ethylene copolymer, the short-chain branching distribution reduces post-mold warpage and improves low-temperature impact relative to a high-density polyethylene rotational molding resin of equivalent melt flow. Lot-specific release data for the PUR 5398 formulation should be obtained from the supplier’s certificate of analysis; published data for this specific color configuration is limited, and class-typical LLDPE data should not be substituted for grade qualification.

What material thresholds separate this grade from unmodified LLDPE and HDPE rotational molding powders?

Rotational molding polyethylene grades are differentiated by density, melt flow, flexural stiffness, low-temperature impact, and environmental stress crack resistance. Unmodified HDPE rotomolding powders typically provide higher flexural modulus and better top-load resistance, but they exhibit lower ESCR and a greater tendency toward brittle failure at sub-zero temperatures. A linear low-density ethylene copolymer such as the Icorene 3546 UV+ base resin retains ductile behavior under ISO 179-1/1eA notched impact conditions at -40 °C, while an HDPE of the same melt flow may fall below the ductile threshold. The UV-plus package is a second separation point: a standard colored HDPE rotomolding powder may contain only a pigment masterbatch, whereas the UV+ designation indicates a formulated light-stabilizer system intended to delay gloss loss, chalking, and tensile elongation loss in outdoor exposure. The PUR 5398 color/additive package does not alter the base resin density class, but pigment particle content and additive loading can shift melt stability and cycle time during rotational molding. Where creep resistance or maximum top-load stiffness is required, the material must be compared with HDPE rotomolding grades using ISO 899-1 creep data and ASTM D1693 ESCR data rather than by single-point tensile values alone. Published data for this specific configuration is limited; comparative ranking should therefore be confirmed on actual molded parts.

In shuttle and carousel rotational molding machines, heat transfer into the powder bed is governed by mold swing radius, oven setpoint, and the powder’s particle-size distribution. A free-flowing LLDPE powder with controlled dry flow under ISO 6186 enables uniform filling of deep ribs, vents, and thread inserts; poor dry flow causes particle bridging in narrow cavities and produces thin or voided walls. The powder is often processed at oven setpoints between 240 °C and 290 °C, while the peak internal air temperature is maintained in the region of 200 °C to 260 °C for linear low-density polyethylene. Molders monitor internal air temperature with shielded thermocouples and use that signal to terminate the heating cycle. Heating beyond the necessary peak internal air temperature accelerates oxidative degradation, increases melt adhesion to the mold surface, and discolors the internal wall. After fusion, the cooling phase is controlled by forced air, water mist, or full water spray; rapid cooling raises cycle rate but can increase part warpage and reduce low-temperature impact. In thick-section moldings, differential shrinkage between the outer mold-contact surface and the inner air-exposed surface produces residual stress that is evaluated by annealing trials or by measuring post-mold dimensional change after conditioning at 23 °C under ISO 291. Pigment packages such as PUR 5398 change infrared absorption characteristics; dark or saturated colors can reduce the time required to reach peak internal air temperature in comparison with natural powder. Production-scale line data should be established for the specific mold mass, wall thickness, and color because published data for this exact formulation is limited.

Mechanical property verification and incoming resin acceptance

Incoming resin acceptance for rotational molding powder is not limited to melt flow and density. Mechanical tests are performed on rotomolded plaques or compression-molded specimens prepared under controlled conditions. Typical laboratory methods include tensile testing under ISO 527-2 using type 1A specimens, flexural modulus under ISO 178, notched Charpy impact under ISO 179-1/1eA, and environmental stress crack resistance under ASTM D1693 condition B at 50 °C in 100% Igepal CO-630. The ESCR test is especially relevant for LLDPE service in contact with aggressive liquids; a higher ESCR value indicates a slower transition from hinge-area crazing to complete fracture. Oxidation resistance is screened by oxidative induction time under ISO 11357-6, with longer OIT values indicating greater retained stabilizer activity. The UV-plus package is further assessed by accelerated weathering in laboratory xenon-arc or fluorescent UV devices using ISO 4892-2 or ASTM G154 cycles. Color difference after weathering is measured according to ISO 11664-4 with a spectrophotometer and reported in CIELAB ΔE* units; gloss retention is measured at 60° under ISO 2813. Because the PUR 5398 pigment may itself affect spectral reflectance, weathering acceptance criteria for dark or saturated shades should be determined on molded plaques of the actual color rather than on natural resin samples. A complete property matrix is maintained in the supplier’s certificate of analysis and raw material release documentation; several test values are product-lot dependent and not fixed by the grade designation alone.

When outdoor weathering and ultraviolet aging dictate service life

Outdoor service life is governed by UV irradiance, moisture, temperature cycling, and the chemical environment. The UV-plus stabilization package in Icorene 3546 UV+ PUR 5398 is intended for applications in which the molded part is exposed to direct sunlight for extended periods. In accelerated weathering, the key response variables are tensile elongation loss, surface chalking, color change, and gloss loss. ISO 4892-2 xenon-arc testing with daylight filters and controlled irradiance of 0.51 W/m² at 340 nm is commonly used to simulate outdoor exposure; ASTM G154 fluorescent UV testing at 0.89 W/m² at 340 nm provides a lower-cost screening method but does not reproduce the full solar spectral distribution. The stabilization system can be depleted by surface water carry-off, contact with acidic or alkaline runoff, and high surface temperatures resulting from dark pigmentation. Because PUR 5398 is a formulated color package, the solar heat load of the final part must be measured on the actual color; a dark purple surface can exceed the surface temperature of a natural or white part by 20 °C to 40 °C under high solar irradiance, which accelerates oxidative stabilizer consumption. Parts intended for tropical or desert exposure should be tested under wet/dry cycling rather than continuous dry UV exposure alone. When gloss retention under ISO 2813 falls below 50% of the original 60° gloss value, visual appearance may still be acceptable for some applications, but tensile elongation loss should not exceed the end-user specification. Published comparative data for this exact PUR 5398 configuration is limited; outdoor validation on molded components is required for service-life claims.

Rotational molded parts within the performance window of this grade include outdoor playground components, agricultural hoppers and feed troughs, chemical storage tank liners, dock floats, and enclosures requiring a balance of impact strength and UV resistance. For playground components, the material is typically evaluated for low-temperature impact after conditioning at -20 °C and for extractable metals and phthalates according to regional toy safety requirements; compliance with regional toy regulations is not automatically established by polyethylene resin compliance alone. In agricultural tank applications, the resin’s ESCR response is tested under ASTM D1693 in 100% Igepal CO-630 at 50 °C, and the molded part is inspected for pinholes and thin-out around inserts. Chemical storage tank liners produced from LLDPE rotomolding powder resist stress cracking but are not universally compatible with oxidizing acids, aromatic hydrocarbons, and strong oxidizers; compatibility must be verified by immersion testing under ASTM D543 for the specific chemical, concentration, and service temperature. In water-contact applications such as dock floats or water storage liners, the resin may be evaluated against extraction limits under the applicable drinking-water standard. Because the PUR 5398 color package is integrated into the powder, additional pellet-color masterbatch dosing at the machine may not be required; however, the processor must verify that the target wall thickness and dry flow are maintained with the as-supplied powder. The absence of a post-machining blending step reduces the risk of dose-related color variation but also fixes the final pigment concentration at the supplier’s formulation.

Processing boundaries are set by powder rheology and the UV stabilizer package

The processing window is bounded by melt flow, oxidative stability, and the thermal sensitivity of the UV-plus stabilization system. The LLDPE base resin is not designed for injection molding, sheet extrusion, or blow molding; its molecular architecture and powder morphology are optimized for rotational molding. The stabilizer package imposes a maximum processing temperature above which discoloration, crosslinking, or volatile generation can occur. In practice, peak internal air temperature should be monitored and controlled; operation above the supplier’s maximum recommended value can deplete antioxidant and light stabilizer reserves before the part enters service. Under very high relative humidity, condensation on cold powder surfaces may produce surface defects; drying with warm air at 60 °C for 1–2 h is common if the powder has been stored outside the original sealed packaging. The powder should not be combined with copper-based pigments, pro-oxidant masterbatches, or reactive fillers that may deactivate hindered amine light stabilizers. Post-mold regrind addition can be used only if the regrind is free of oil, metal fines, and other rotational molding contamination; the addition rate is determined by dry flow and bulk density testing rather than by melt flow alone. If dark PUR 5398 powder is blended with natural or white resin, the resulting color and UV performance will shift; the blend ratio must be controlled gravimetrically. Processing data for this specific color on a particular machine is not universally transferable because mold thickness, oven air speed, and part mass change the thermal history.

Regulatory screening for the formulated product addresses polymer composition, colorant chemistry, and migration potential. The polyethylene base resin may be assigned a cell classification under ASTM D3350 for polyethylene pipe and fitting materials when tested in the unfilled, unpigmented condition; the PUR 5398 pigment package modifies the final classification and must be considered separately. For food-contact uses, the resin is assessed under FDA 21 CFR §177.1520 olefin polymers, but the finished article must meet the end-use limitations for fatty foods, alcoholic foods, and high-temperature service. European Union compliance is evaluated under REACH Regulation (EC) No 1907/2006 for registration and SVHC screening. RoHS Directive 2011/65/EU restrictions on lead, mercury, cadmium, hexavalent chromium, PBBs, and PBDEs are typically confirmed by supplier declaration and X-ray fluorescence screening. The table below summarizes the main screening layers; it is not a substitute for a written regulatory certificate for the specific PUR 5398 lot.

The presence of organic and inorganic pigments in PUR 5398 can influence density measurement; density should be determined on the formulated material, not on the translucent natural base resin. A lot-specific certificate of analysis should state which tests were performed on the final colored powder and which values are inherited from the unfilled base resin. The distinction is critical for release testing because a natural-powder value may not represent the molded colorformulation in outdoor service or in contact with aggressive media.