LyondellBasell Icorene 3546 NAT0000 is supplied as a natural-color linear low density polyethylene powder for rotational molding. The NAT0000 designation identifies the uncolored natural presentation without a compounded pigment masterbatch; the base polymer is an ethylene copolymer with short-chain branches introduced along the linear backbone to reduce crystalline density and increase tie-molecule formation relative to high-density polyethylene. Published typical values for the grade include a density of 0.935 g/cm³ when tested in accordance with ISO 1183-1:2019 and a melt flow rate of 4.6 g/10 min when determined at 190°C under a 2.16 kg load according to ISO 1133-1:2022. These two indicators place the material in the intermediate-density rotomolding segment: the density produces higher flexural modulus than conventional low-density polyethylene, while the moderate melt flow rate retains the long-chain relaxation behavior required for stress crack resistance in large hollow articles. The grade is not a high-pressure LDPE homopolymer and should not be substituted where the high melt strength and branched architecture of autoclave LDPE are specifically required.

The tabulated values are typical values reported in the product technical data sheet and are not to be interpreted as specification limits. Incoming resin verification for production use should reference the lot-specific certificate of analysis and the agreed specification under ISO 1872-1:2018 or equivalent grade designation.

How Does Icorene 3546 NAT0000 Differ from Higher-Flow LLDPE and HDPE Rotomolding Grades?

The melt flow rate of 4.6 g/10 min separates this product from injection molding grades of linear low density polyethylene that typically exhibit melt flow rates from 20 g/10 min to 50 g/10 min. High-flow LLDPE injection grades are designed for filling thin-wall molds under high shear; they possess lower average molecular weight, reduced chain entanglement density, and consequently shorter stress crack resistance. In rotational molding, shear is negligible and mold filling occurs by biaxial rotation of powder against a heated tool surface. The lower melt flow rate of Icorene 3546 NAT0000 permits the formation of a densified, void-free wall while retaining molecular weight sufficient for long-duration hydrostatic stress resistance. Compared with high-density polyethylene rotomolding grades at a density near 0.945 g/cm³, the 0.935 g/cm³ density of Icorene 3546 NAT0000 produces lower flexural modulus in exchange for higher impact toughness and improved environmental stress crack resistance. This trade-off is measured directly: the tensile yield strength of 17 MPa under ISO 527-2:2012 is below the yield strength commonly observed in HDPE rotomolding resins, while the >1000 h failure time under ASTM D1693-15 exceeds many HDPE grades with equivalent melt flow rate. Compared with lower-density LLDPE rotomolding powders, this grade provides greater stiffness and lower cold-temperature ductility; compared with higher-density grades, it provides greater resistance to slow crack growth in the presence of detergent solutions, alcohols, and weak acid environments.

The short-chain branching distribution of the grade also distinguishes it from conventional high-pressure LDPE. The linear backbone and controlled comonomer insertion produce a narrower molecular weight distribution and a different crystallization profile. In practice, this results in a melting peak of 127°C by ISO 11357-3:2018 and a Vicat softening temperature of 116°C by ISO 306:2022. These thermal indicators should not be used as continuous-use temperature limits. Processors comparing this grade with an LDPE homopolymer should note that linear low density polyethylene typically exhibits higher tensile strength at yield, higher puncture energy, and better environmental stress crack resistance, but lower melt strength and a narrower sintering window in the absence of pressure.

Peak Internal Air Temperature and Cooling-Rate Control

Rotational molding of Icorene 3546 NAT0000 requires attention to oven set point, peak internal air temperature, and cooling rate because the grade develops properties through particle coalescence and crystallization rather than through shear-induced homogenization. Published processing guides for intermediate-density LLDPE rotomolding powders commonly recommend an oven set point between 280°C and 315°C. The peak internal air temperature measured through the mold vent is typically controlled between 185°C and 205°C for this density range. If the peak internal air temperature is below 180°C, residual powder particles may persist at the inner wall surface, producing porosity and pinholing. If the peak internal air temperature exceeds 220°C, oxidative degradation may accelerate, reducing impact strength and causing discoloration even in the natural color grade. Production-scale clamshell and shuttle rotomolding machines with biaxial rotation ratios of 4:1 to 5:1 are commonly used; the exact ratio must be adjusted to part geometry and wall thickness distribution.

Cooling rate after the heating phase affects shrinkage, warpage, and slow crack growth resistance. Rapid forced-air cooling followed by water mist cools the mold surface and freezes the outer layer, but excessive cooling rate can generate internal residual stress and asymmetric shrinkage. Slow cooling through the crystallization plateau near 115°C to 120°C permits greater crystal perfection and reduces post-mold distortion, but may increase wall shrinkage. Demolding is typically initiated when the mold surface temperature falls below 70°C because premature ejection can distort thin unsupported sections. Precise grade-specific data for cooling-rate variation under production-scale tooling are limited in public technical literature; therefore mold trials should confirm shrinkage targets, wall thickness stability, and low-temperature impact results for each new tool geometry.

Powder particle characteristics also govern processing behavior. The powder form is suitable for direct charging into rotomolding molds without pellet compounding. Particle size distribution, bulk density, and powder flow affect the uniformity of the initial tack layer and the subsequent sintered wall. Incoming powder should be stored in dry conditions; prolonged exposure to high humidity can introduce surface moisture that forms steam bubbles during the heating cycle.

In tank and container applications, the resin is processed into double-wall and single-wall hollow articles including stationary water tanks, chemical storage vessels, agricultural sprayer tanks, and outdoor recreational shells. The grade is used where low-temperature impact strength and long-term stress crack resistance are required. Parts molded from this material may require post-mold trimming of vents and inserts; the natural color allows direct pigmentation by dry blending with a compatible polyethylene color masterbatch, but the masterbatch must be selected to avoid introducing a high-melt-index carrier that can reduce the effective stress crack resistance of the finished wall. Published data for masterbatch dilution effects on this specific configuration is limited; therefore addition rates above 2 wt% require verification of ASTM D1693-15 performance on molded plaques or cut specimens.

If Hydrostatic Stress Cracking Controls Tank Qualification

Environmental stress crack resistance is the critical selection property for agricultural and industrial tanks exposed to surfactants, detergents, and mild oxidizing solutions. The F50 failure time under ASTM D1693-15, condition B, in 100% Igepal CO-630 is reported as >1000 h for Icorene 3546 NAT0000. This test subjects notched polyethylene specimens to a constant strain in a heated surfactant bath; the F50 value is the time at which 50% of the test population exhibits visible cracking. The high ESCR of this grade arises from the linear low density architecture: lower crystallinity and higher tie-molecule density between lamellae provide resistance to slow crack growth that is not available in many high-density rotomolding grades at similar density and melt flow rate. Stress crack resistance is also influenced by mold cooling rate; rapid cooling can suppress spherulitic structure and alter tie-chain distribution, but may introduce residual stresses that act as crack initiation sites in service.

When evaluating this grade against hydrolytic or chemical exposure, the compatibility of polyethylene with the stored fluid should be confirmed under the expected service temperature. Polyethylene resists aqueous acids, alkalis, and polar solvents at ambient temperature, but it can swell and lose mechanical strength in contact with aromatic hydrocarbons, chlorinated solvents, and mineral oils at elevated temperature. Strong oxidizing acids such as concentrated nitric acid can cause oxidative attack. The resin should not be exposed to sustained service temperatures above 60°C under continuous load unless creep and oxidative induction time data for the specific part geometry are reviewed. For food-contact applications, compliance should be confirmed against FDA 21 CFR 177.1520 or European Commission Regulation (EU) 10/2011 using a current supplier compliance statement; the natural color designation does not by itself establish food-contact conformity. Outdoor service requires an appropriate UV stabilizer package or coating because prolonged ultraviolet exposure can embrittle natural polyethylene surfaces.