LyondellBasell Icorene 3545 WHI 1101 is designated as a polyethylene, linear low density (LLDPE) resin. The suffix code “WHI 1101” is a manufacturer colour/additive designation; in rotational moulding product families such coding commonly indicates a white pigmented powder, but the exact lot-specific formulation must be verified against the grade-specific technical data sheet and certificate of analysis. The following description therefore separates material-class behaviour from lot-specific certification. Where published data for this specific grade configuration are limited, that limitation is identified.

Classification of the polymer is governed by ISO 17855-1 and ISO 1043-1. The designation “linear low density” indicates a copolymer backbone with controlled short-chain branching from an alpha-olefin comonomer; 1-butene, 1-hexene, or 1-octene may be used. For LLDPE rotational moulding powders of this nominal class, density is generally determined according to ISO 1183-1, and melt mass-flow rate is determined according to ISO 1133-1:2022 at 190 °C under 2.16 kg. Typical class values fall within 0.920 g/cm³ to 0.940 g/cm³ and 3 g/10 min to 6 g/10 min, respectively; these ranges are not a substitute for grade-specific values.

The absence of a publicly disclosed comonomer type for Icorene 3545 WHI 1101 prevents a definitive statement on its environmental stress-cracking resistance relative to hexene- or octene-based LLDPE. Published data for this specific configuration is limited; comparative selection should use the manufacturer’s current datasheet and, where possible, instrumented mould trials on the intended cavity.

What Process Window Governs Rotational Moulding Powders of This Class?

The applicable processing window for an LLDPE rotomoulding powder is narrower than for a conventional high-pressure LDPE powder at the same oven setpoint. On a four-arm carousel machine with forced-air oven and a steel or cast-aluminium mould, oven residence time is typically set to bring the internal mould atmosphere to a peak of 180 °C to 200 °C. Prolonged exposure above 230 °C can produce oxidative discoloration, surface tack defects, and brittle failure in thin-wall sections. The exact endpoint inside a closed mould is monitored with an internal air thermocouple or infrared pyrometer, not by oven air temperature alone.

Part removal and cooling are part of the processing window. Demoulding while the polymer is too hot produces warpage and post-mould shrinkage, while excessively slow cooling through the crystallisation range can increase shrinkage anisotropy. A two-stage cooling sequence, forced-air cooling to 80–90 °C followed by ambient cooling to 40 °C or lower, is used on many industrial carousels to balance cycle time against dimensional stability. Air flow distribution and mould rotation ratio, commonly 4:1 or 5:1, must be maintained because static surface overheating is a known failure mode in pigmented LLDPE powders.

Melt flow rate is an input-control parameter; it does not fully predict rotomoulding behaviour. Particle-size distribution, bulk density, and dry-flow time determine mould charging and densification. These powder properties are measured by ISO 60, ISO 6186, and ASTM D1895. A supplier’s certificate of analysis normally reports these values for each lot. A change in pulverising conditions can alter the top cut and fines fraction without changing the polymer’s melt flow rate; this is a common root cause of intermittent pinholes and surface porosity on a production line.

Powder Dry-Flow, Particle-Size Distribution, and Mould Charging Reproducibility

Rotational moulding powder is not pelletised. The powder must flow uniformly into complex mould features and densify without voids. Dry-flow behaviour is assessed by ISO 6186 or equivalent; bulk density is determined by ISO 60 or ASTM D1895. A rotomoulding powder of this class typically has a nominal top cut near 35 mesh (500 µm) and a controlled fines fraction. Excessive fines below 74 µm can cause localised over-densification and airborne dust during charging; insufficient fine material can slow sintering and reduce surface detail reproducibility.

Moisture management is a process boundary. Powders stored in unlined bags or in high-humidity areas can pick up surface moisture. Pre-drying is required at relative humidity above 60% or when visible condensation on a cold mould is observed. A desiccant or hot-air drying step at 70–80 °C for 2–4 h is typical for polyolefin powders, but drying must not exceed the powder’s sintering onset or agglomeration will occur.

During the early heating phase, powder particles adhere to the mould surface. The tumbling action distributes material through a sequence of tack melting, densification, and bubble elimination. Bubble elimination is not complete at peak temperature if the internal air thermocouple is placed in a cold spot; a plateau of 120–180 s at peak internal air temperature is often used. The required plateau must be developed on the production tool, because cavity wall thickness, parting-line geometry, and mould release surface alter the thermal profile.

When White Titanium Dioxide Pigmentation Alters Radiant Heat Transfer

The white colour package in Icorene 3545 WHI 1101 is not a passive aesthetic variable. Titanium dioxide increases opacity and can reduce the rate of infrared absorption in the initial stage of oven heating compared with a black or natural pigmentation. The practical result on a rotating mould is a lag in early melt film formation; oven residence may need to be extended or the oven setpoint raised by a small amount relative to an unpigmented grade. The magnitude of the shift is equipment-dependent and must be established by instrumented mould trials; published data for this specific configuration is limited.

Titanium dioxide agglomerates can also act as nucleation sites during cooling, changing spherulite size and shrinkage behaviour in pigmented parts. This is relevant when a white LLDPE part is moulded in the same tool as a black or coloured part. Dimensional acceptance should be based on the pigmented compound, not on a natural-powder benchmark. The pigment dispersion quality should be checked by filter pressure rise or optical microscopy on thin sections; poor dispersion can produce surface specks and local embrittlement.

Because the dense white pigment raises the compounded polymer density slightly, a formulated density value should be taken from the certificate of analysis rather than recalculated from a natural-powder datasheet. The difference is usually small, but it can affect part weight calculations and shipping-cost estimates in large tanks or containers.

Comparing Icorene 3545 WHI 1101 with LDPE, HDPE, and Higher Alpha-Olefin LLDPE

Compared with high-pressure low-density polyethylene, LLDPE of this class generally exhibits higher tensile strength, higher puncture resistance, and higher environmental stress-cracking resistance at equivalent density, but lower melt-flow processability and lower clarity. Compared with high-density polyethylene, LLDPE has lower stiffness, lower heat deflection temperature, and higher low-temperature toughness. For rotomoulding tanks and vessels, the ESCR improvement of LLDPE over LDPE is the primary selection driver under ASTM D1693 or ISO 16770 testing.

Within LLDPE, comonomer length modifies mechanical performance. 1-hexene and 1-octene copolymers generally provide higher dart impact and greater ESCR than 1-butene copolymers at similar density and melt flow, but at higher cost and sometimes with slower crystallisation. The difference in dart impact can exceed 20–30% in thin-wall parts depending on comonomer content and moulding conditions. If the Icorene 3545 WHI 1101 datasheet identifies the comonomer as butene, hexene, or octene, that designation is critical for tank and containment applications; if it is not disclosed, the manufacturer should be consulted before substitution.

For design calculation, tensile properties are determined by ASTM D638-14 or ISO 527-2, flexural modulus by ISO 178 or ASTM D790-17, and low-temperature impact resistance by a falling-weight method such as ISO 6603-2 or ASTM D5276 depending on part geometry. The modulus of an LLDPE rotomoulding powder is frequently in the 550 MPa to 750 MPa range at 23 °C, placing it between typical LDPE and HDPE. This intermediate stiffness allows unsupported tank sidewalls to withstand hydrostatic load without cracking but requires ribbing or wall thickness increases when long spans are designed.

Regulatory Status Under Olefin Polymer Food-Contact and REACH Frameworks

Food-contact use is not automatic by polymer class. If Icorene 3545 WHI 1101 is considered for food-contact articles in the United States, the olefin polymer provisions of 21 CFR 177.1520(c) may apply, subject to the conditions of use and migration assumptions in 21 CFR 176.170(c). In the European Union, compliance with Regulation (EU) No 10/2011 requires verification of overall migration below 10 mg/dm² and specific migration limits for authorised additives and monomers. The white pigment package must itself be authorised; titanium dioxide as a colourant is subject to specific purity and migration requirements. REACH Regulation (EC) No 1907/2006 imposes registration and communication obligations on the supplier, while European Directive 2011/65/EU RoHS thresholds apply only when the material is incorporated into electrical and electronic equipment.

On production-scale rotational moulding lines, a recurring defect with white LLDPE powders is incomplete sintering at the parting line when the mould charge is distributed unevenly across long, thin cavities. The resulting knit line is not a weld line in the injection-moulding sense but a low-density region with reduced impact resistance. Instruments used to detect this include thermal imaging of the mould surface after oven exit and automated weight checks of trimmed flash. Another observed failure mode is gas-induced porosity when moisture or volatile additives vaporise during the 180–200 °C densification stage. The corrective action is pre-drying and, where necessary, venting of the mould cavity at the parting line to allow gas escape without resin leakage.