LyondellBasell Icorene 3545 RED 4740 is a pre-compounded, red-pigmented linear low density polyethylene powder formulated for rotational molding of single-layer articles. The designation RED 4740 identifies a supplier-specific color package incorporated into the melt before grinding; it is not a dry-blend masterbatch. The base resin has a nominal density of 0.934 g/cm³ determined according to ISO 1183-1 and a nominal melt flow rate of 4.5 g/10 min measured at 190 °C under 2.16 kg load according to ISO 1133-1. Components produced from this grade include chemical storage containers, agricultural floats, traffic control products, utility enclosures, and cladding panels requiring moderate flexural stiffness and stress-crack resistance. The material is not intended for blown film, high-speed injection molding, or high-pressure pipe extrusion without rheological revalidation.

Because the pigment is pre-dispersed, the molded article carries the color through the wall cross-section and avoids the weigh-scale variation, dust generation, and dispersion defects associated with dry-blended red masterbatch. However, the integrated color package also means that the user cannot adjust color intensity at the hopper. The color is controlled against a supplier master target; lot-to-lot consistency may be reported by CIELAB measurement under ISO 11664-4 or equivalent. A first-article appearance evaluation on the actual mold should be performed before production release.

What property envelope is reported for this grade?

The values in Table 1 are supplier-published representative data for the Icorene 3545 base LLDPE grade. The red-pigmented variant may show minor shifts in tensile, impact, and melt-flow values; the certificate of analysis for each lot is the controlling document.

The density of 0.934 g/cm³ places the material in the upper-density region of linear low density polyethylene and the lower-density edge of medium-density polyethylene, depending on the classification system used. Using a two-phase density model with amorphous polyethylene density of 0.853 g/cm³ and crystalline polyethylene density of 1.000 g/cm³, the estimated crystalline fraction is approximately 0.55. This crystallinity level contributes to the flexural modulus of 700 MPa while retaining a high tensile elongation at break of 800 % in compression-molded specimens. Actual rotomolded parts develop a crystallinity gradient through the wall because the outer surface cools faster than the inner surface. Consequently, tensile and flexural values from test plaques should not be used directly for finite-element analysis of a production component; part-specific tensile properties must be measured on specimens cut from a production article according to ISO 527-2.

The melt flow rate of 4.5 g/10 min is a melt-mass-flow index obtained under ISO 1133-1; it is not a direct viscosity measurement. For mold-fill simulation and bubble-removal analysis, capillary rheometry per ISO 11443 at 190 °C and shear rates representative of rotomolding coalescence is required. The environmental stress-crack resistance value of >1000 h under ASTM D1693 condition B reflects the behavior of the base resin under continuous stress in a wetting agent at 50 °C. Actual service failures often occur under intermittent load, temperature cycling, and aggressive fluids; therefore the ESCR value should not be extrapolated to strong detergents, chlorinated water, or constant-strain service without immersion testing under ISO 22088-1. Published data for the red-pigmented configuration under all of these methods may be limited, so qualification lots should be tested before product release.

Thermal transitions for LLDPE of this density, as measured by differential scanning calorimetry under ISO 11357-3, are typically in the range of 120 °C to 130 °C for the melting peak and 105 °C to 115 °C for the crystallization peak, depending on cooling rate. These transitions govern demolding behavior. If the inner surface is removed from the mold before it falls below the crystallization onset, post-demolding shrinkage and warpage can occur. Molders should establish cooling time by thermocouple trials on the production tool rather than by relying solely on plaque-derived thermal data.

Rotational molding of LLDPE depends on biaxial rotation, powder densification, bubble removal, and coalescence in a heated mold. Production-scale clamshell machines with a 4:1 major/minor axis speed ratio and aluminum molds are usually run with oven air temperatures of 280 °C to 320 °C for wall thicknesses between 4 mm and 12 mm. The peak internal air temperature should be established by thermocouple trials rather than inferred from oven set point. For LLDPE of 0.934 g/cm³ density, the optimum peak internal air temperature commonly falls between 200 °C and 220 °C; below this window, residual porosity may remain in the inner surface, while above 230 °C, oxidative degradation can shift molecular weight and color.

RED 4740 is a pre-compounded color package; therefore the pigmented powder may absorb radiant heat differently from natural powder. The processing team should map wall-thickness distribution with ultrasonic inspection at gate, sidewall, and rib positions for the first production trials. If the same oven residence time as natural powder produces a fine pinhole band or unmelted powder at the inner surface, the peak internal air temperature should be adjusted in steps of 5 °C before changing oven air temperature. Cooling rate is equally important: slow cooling in the oven or with insulated mold covers increases crystallinity and shrinkage, while water mist or forced-air cooling lowers crystallinity and can improve impact but increases distortion risk. The material should be characterized for warpage on the actual tool before mold shrink allowances are fixed.

Moisture on the powder surface is a separate source of defects. Polyethylene powder is not hygroscopic in the bulk sense, but cold powder moved into a warm, humid molding area can condense surface moisture. At relative humidity above 60 %, powder should be allowed to equilibrate to ambient temperature before mold charging. Surface moisture produces pinholes and low-gloss defects that cannot be corrected by extending the oven cycle without degrading the outer surface.

Steel molds have lower thermal conductivity than aluminum and require longer oven residence times at the same oven air temperature. If a mold is constructed from stainless steel, the thermal lag can shift the peak internal air temperature by more than 10 °C relative to an aluminum mold of equal wall thickness. Process technicians should not transfer an aluminum tool oven profile to a steel tool without thermocouple mapping. Mold release agents based on silicone or fluoropolymer can improve demolding but may affect post-molded painting, adhesive bonding, or surface gloss on red parts; release-agent level should be minimized and revalidated if the part is to be post-coated or joined.

Rotational molding powders are combustible dusts. Material handling systems should follow NFPA 652 and applicable ATEX provisions for dust explosion hazard management. The powder should be stored in unopened containers at temperatures below 40 °C and away from direct sunlight to avoid sintering and bulk-density changes. Contaminated powder from dirty hoppers, transfer lines, or grinding equipment can introduce black specks that are highly visible in red-pigmented parts.

Differences from HDPE, butene-based LLDPE, and natural powder

Compared with a high-density polyethylene rotomolding grade at 0.945 g/cm³ to 0.955 g/cm³, the 0.934 g/cm³ density of Icorene 3545 RED 4740 produces lower flexural stiffness and a larger failure strain. In return, the lower crystallinity usually improves stress-crack resistance and low-temperature impact. For structural tanks, pallets, or load-bearing frames, the smaller flexural modulus means that creep and top-load performance must be evaluated under the relevant part test rather than by comparing short-term flexural modulus alone. Creep modulus determined under ISO 899-2 at the expected service temperature is the appropriate design input. Published data for this specific red-pigmented configuration under long-term creep is limited.

Among linear low density polyethylene rotomolding grades, differences in comonomer type and distribution influence physical properties more than a small density difference. Butene-based LLDPE grades often show lower environmental stress-crack resistance at the same density; hexene-based grades may provide higher tie-molecule formation. However, the exact comonomer of Icorene 3545 RED 4740 should be confirmed from the supplier’s technical documentation before conclusions are drawn for comparative material selection. A processor who requires comonomer information for food-contact migration modeling should request the relevant disclosure; density and melt flow rate alone do not identify the alpha-olefin.

Compared with natural Icorene 3545, the pre-compounded RED 4740 eliminates dry-blend red masterbatch handling. The integrated pigment produces more uniform color and avoids the airborne dust and dispersion defects of dry blending, but it also removes the ability to adjust color level at the hopper. The red pigment may also alter perceived gloss, scratch behavior, and surface energy. For outdoor service, red coloration does not imply weathering stabilization; an outdoor application should be tested by ISO 4892-2 or ASTM D2565 at the intended wall thickness. Color shift, chalking, and loss of elongation are dose-dependent, and red pigments may mask early surface oxidation more than natural or black compounds.

The pigment class in RED 4740 is supplier-controlled. Inorganic iron oxide red pigments can act as nucleating agents and increase crystallization rate, while organic red pigments may have lesser nucleating effect but different thermal stability. If the color package is changed between lots or between equivalent grades, process changes should be validated by differential scanning calorimetry and mold trials. A shift in crystallization temperature of only a few degrees can alter demolding behavior and dimensional stability.

For food-contact use, the base polyethylene may fall under 21 CFR 177.1520 and EU 10/2011 positive-list provisions, but the red pigment package has a separate regulatory status. Food-contact clearances for natural resin do not automatically extend to the pre-compounded red article. If food-contact compliance is required, the rotomolder must obtain a written regulatory statement for the exact Icorene 3545 RED 4740 lot and confirm migration limits under the relevant food-simulant conditions. In industrial service, the grade may be subject to chemical control legislation such as REACH and RoHS; the red pigment system may contain metal-based or organic colorants that require specific SVHC screening under REACH, and end users should verify against the Safety Data Sheet and composition statement.

For potable water containers, raw-material compliance is not sufficient. Approvals such as NSF/ANSI 61 or BS 6920 apply to the final molded component with the specific colorant package and processing conditions. Published data for this specific configuration is limited; no raw-material certificate replaces component-level testing.

When component-level service conditions override generic material data

Generic property data are generated on compression-molded specimens and cannot represent every wall thickness, mold material, cooling rate, or regrind level. In applications where the molded part is exposed to aggressive fluids, elevated temperatures above 60 °C, or continuous stress, immersion testing under ISO 22088-1 and tensile testing of production-cut specimens under ISO 527-2 should be performed. For parts exposed to strong acids, bases, or chlorinated water, specific chemical resistance testing at the service temperature is required because the ESCR test uses a wetting agent and does not quantify swelling or reaction with the service fluid.

Regrind usage changes the heat history and may reduce environmental stress-crack resistance and color consistency. If regrind is used, its concentration and source must be fixed; each regrind ratio should be revalidated for density, melt flow rate, tensile strength, and ESCR before release. The maximum permissible regrind level is not a universal value for this grade; it depends on the rotomolding equipment, part wall thickness, and end-use regulatory requirements. Published data for this specific configuration is limited.

To avoid premature degradation, the powder should not be exposed to melt temperatures above 250 °C to 260 °C; localized hot spots may cause color shift, reduced ESCR, and generation of oxidized low-molecular-weight species. Aluminum molds with sharp internal corners can create local thermal transitions; tooling radius design and mold release agent selection should be included in process trials. If the part is to be post-coated, printed, or joined by welding, adhesion tests should follow the relevant ISO 4624 or DVS 2207 methods because the integrated color package may affect surface free energy and bond strength.