LyondellBasell Icorene 3546 G BLK 9001 is a black-pigmented linear low density polyethylene powder compound in the Icorene rotational molding range. The base polymer is an ethylene-alpha-olefin copolymer, and the grade code 3546 G distinguishes the melt-flow and density target within the LLDPE class; the suffix BLK 9001 denotes the black colorant and stabilizer package. The compound is supplied in pulverized form with a particle size distribution intended for dry-flow rotational molding processes, although lot-specific particle size data must be obtained from the current manufacturer’s certificate of analysis. Published data for this exact configuration is limited; therefore, class-level values used in this document must be verified against the current technical data sheet before mold design, process qualification, or material substitution.

Typical uses involve outdoor rotomolded parts requiring low-temperature ductility and environmental stress crack resistance: agricultural liquid-storage tanks, marine fenders, water-management chambers, industrial containers, and non-food outdoor housings. The compound may be processed on independent-arm, shuttle, and carousel rotational molding machines; however, the black pigmented surface modifies radiant heat absorption compared with natural LLDPE and therefore requires separate cycle development. Food-contact status is not assumed for the black pigmented grade. Where compliance is required, lot-specific certification under FDA 21 CFR 177.1520 or EU Regulation (EU) No 10/2011 should be requested because the pigment package may restrict direct food-contact approval.

How does the black 9001 pigment package alter oxidation induction and processing stability?

The incorporation of carbon black into an LLDPE matrix increases infrared absorption during radiant heating. In production-scale rotational molding on a shuttle machine with a 3.2-m swing capacity, black LLDPE powders commonly reach peak internal air temperature 3–5 °C earlier than unpigmented powders at the same oven setpoint. This shift must be compensated by reducing oven temperature or residence time; otherwise, the internal air temperature may overshoot above 210 °C and initiate oxidative chain scission. Thermal stability should be confirmed by oxidation induction time according to ASTM D3895-19, with a differential scanning calorimeter cell held at 200 °C under oxygen flow. For black LLDPE rotomolding grades, a minimum oxidation induction time of 30 min is commonly specified, although lot-specific values depend on stabilizer masterbatch composition and regrind history.

The suffix 9001 is not a published chemical formulation. It functions as the manufacturer’s internal code for a black colorant and ultraviolet stabilization system. Carbon black dispersion quality should be measured on compression-molded plaques under ISO 18553, with agglomerate sizes below 20 µm considered acceptable for uniform weather resistance. If dispersion is poor, localized oxidative instability may appear as surface chalking after 1000 h of accelerated weathering under ISO 4892-2:2023 using UV-A 340 lamps at a black-panel temperature of 60 °C. Because the exact stabilizer package has not been published, outdoor service life must be validated by part-specific weathering trials, not solely by resin type.

Quality release for Icorene 3546 G BLK 9001 is based on control of melt mass-flow rate, density, flexural modulus, tensile yield strength, environmental stress crack resistance, low-temperature impact, carbon black content, powder dry flow, and residual moisture. The following matrix lists the test methods and class-level acceptance windows for a black LLDPE rotational molding compound. These values are not a substitute for the manufacturer’s current sales specification and must be confirmed before material substitution.

Residual moisture is critical because steam generated during heating can produce pinholes and porosity at the inner surface of a rotomolded part. Pre-drying is recommended when storage relative humidity exceeds 60% or when regrind from outdoor storage is included. Drying in a desiccant hopper at 70–80 °C for 2 h typically restores dry flow. During incoming inspection, the powder should be sampled from multiple layers of the liner because fines and carbon black can segregate during transport. Apparent density according to ISO 60:2023 should be controlled at 0.32–0.42 g/cm³; values below this range indicate elevated fines or irregular particle shape and may cause poor powder flow in deep molds. Particle size distribution is commonly checked by ASTM D1921 or ISO 4610. For rotomolding, the fraction retained on a 500 µm sieve is generally less than 5%, and the mass fraction passing a 150 µm sieve is less than 15%, to maintain dry flow and avoid segregation.

Rotational molding process boundaries for black LLDPE powder

Cycle development for Icorene 3546 G BLK 9001 must account for both particle coalescence and pigment-induced heat absorption. The powder is charged into a cavity at ambient temperature and rotated biaxially inside an oven at air temperatures between 260 and 320 °C. The actual oven setpoint is adjusted by mold thickness, wall area, and arm ratio. The internal air temperature measured at the mold axis should reach 190–205 °C to complete alloying of the polymer particles; below 185 °C, residual particle boundaries may remain as microvoids and degrade low-temperature impact. Above 210 °C, black LLDPE tends to exhibit gloss loss, surface stickiness, and a measurable rise in the carbonyl index near 1715 cm⁻¹ when examined by Fourier transform infrared spectroscopy.

Heating time depends on mold wall thickness. For a 6-mm nominal wall section, the oven residence time is typically 18–24 min on a carousel machine with forced-air circulation at 280 °C. Thinner sections require shorter residence; thicker sections may also require reduced oven temperature to avoid surface degradation before the core reaches coalescence. The cooling phase affects warpage and shrinkage. Water spray cooling reduces cycle time but increases frozen-in stress and can reduce environmental stress crack resistance; forced-air cooling is preferred where high stress-crack resistance is the primary requirement. Mold release should be confirmed with the supplier if the grade is not specified as self-releasing.

Production-scale variability in dry flow of more than 10% relative standard deviation has been associated with wall-thickness variation in a 1000 L cylindrical tank mold. Such variation typically appears as thinning near the mold parting line and thickening at the lower polar regions. Therefore, dry flow and bulk density are not cosmetic parameters; they are direct indicators of uniform powder transport through the moving mold cavity.

If regrind ratios exceed 20% in shuttle-machine production, what changes in impact and ESCR are expected?

There is no published data for this exact configuration at high regrind levels. Industry practice for black LLDPE rotomolding compounds indicates that regrind addition up to 15–20 wt% can be used with moderate loss of low-temperature impact and a shift in dry flow. At regrind levels above 30 wt%, the powder may become more angular and less free-flowing, leading to uneven coverage in narrow ribs and kiss-off features. Each regrind pass increases the carbonyl concentration and lowers the high-molecular-weight tail, which can reduce environmental stress crack resistance by more than 30% after three passes. Therefore, regrind fractions should be validated by ASTM D1693 F50, ARM impact at −40 °C, and melt mass-flow rate before production. If regrind is used from parts that have undergone outdoor weathering, oxidation induction time must also be reassessed because the stabilizer package is partially consumed.

Differences from HDPE, LDPE, and metallocene LLDPE in rotomolded part design

Relative to high-density polyethylene, Icorene 3546 G BLK 9001 and similar LLDPE rotomolding grades exhibit lower flexural modulus and lower heat deflection temperature but superior environmental stress crack resistance and low-temperature ductility. HDPE may be selected for stiff-walled tanks with low impact demands, whereas LLDPE is preferred where local bending and crack propagation dominate. Relative to low-density polyethylene, LLDPE provides higher tensile yield strength, greater slow crack growth resistance, and a narrower processing window because of its higher crystalline plateau and more linear backbone. Metallocene LLDPE grades typically provide higher dart impact or ARM impact at comparable density, but they often require tighter peak internal air temperature control and show greater sensitivity to over-heating; processers may experience a processing window of ±5 °C for some mLLDPE rotomolding grades, compared with a wider window for conventional LLDPE. The specific positioning of Icorene 3546 G BLK 9001 within this matrix depends on the manufacturer’s comonomer type and molecular architecture, which have not been disclosed. If the grade is based on a butene comonomer, the ESCR and dart impact will be lower than for hexene- or octene-based LLDPE at the same density and melt index. The published datasheet should be checked for the comonomer designation; published data for this specific configuration is limited.

Outdoor chemical storage and marine fender tooling have demonstrated that black LLDPE rotomolding compounds can sustain continuous flexural fatigue when wall thickness is held above 5 mm and internal corners are radiused to at least 9 mm. Accelerated weathering under ISO 4892-2:2023 for 3000 h has been used to screen black formulations for loss of elongation; retention above 50% of original tensile elongation is often considered acceptable for nonstructural outdoor parts, but product-specific acceptance limits must be established. In all cases, lot-specific certification to REACH Annex XVII and food-contact requirements under EU Regulation (EU) No 10/2011 or FDA 21 CFR 177.1520 should be requested if applicable; the black pigment package may restrict direct food-contact status.