LyondellBasell Icorene 3560 GRN 6121 Polyethylene, Linear Low Density is a linear low-density polyethylene (LLDPE) rotational moulding grade supplied as green-pigmented powder. The base resin carries a nominal density of 0.935 g/cm³ when tested in accordance with ISO 1183-1:2019 and a melt flow rate of 5.5 g/10 min at 190°C/2.16 kg when tested in accordance with ISO 1133-1:2022. The suffix GRN 6121 identifies a green colour package rather than a separate base-resin identifier. Published data for this exact pigmented configuration are limited; supplier documentation for Icorene 3560 should therefore be used as the primary reference, with batch-specific properties confirmed against the certificate of analysis.

Molecularly, the LLDPE backbone carries short-chain branches introduced by an alpha-olefin comonomer. These branches limit chain folding and reduce crystallinity relative to high-density polyethylene while preserving linear chain continuity that separates the material from branched low-density polyethylene. The density of 0.935 g/cm³ places the grade in the medium-density portion of the LLDPE range, which influences stiffness, impact resistance, and environmental stress crack resistance in rotationally moulded parts.

What separates the molecular architecture of Icorene 3560 GRN 6121 from conventional LDPE and HDPE rotational moulding powders?

Compared with a branched LDPE rotomoulding powder of similar melt flow rate, the linear backbone and short-chain branching of Icorene 3560 GRN 6121 typically produce higher tensile yield stress and higher flexural modulus. Representative supplier-documented values include tensile yield stress of 15 MPa measured to ISO 527-2:2012, flexural modulus of 600 MPa measured to ISO 178:2019, and environmental stress crack resistance F50 exceeding 500 h under ASTM D1693-21. These mechanical values support specification of the material for rotationally moulded agricultural tanks, small craft components, outdoor equipment enclosures, and portable water tanks where slow crack growth resistance is part of the design requirement.

Compared with HDPE rotomoulding grades having density between 0.940 g/cm³ and 0.955 g/cm³, the lower crystalline content of Icorene 3560 GRN 6121 reduces flexural modulus and increases elongation. Compared with conventional LDPE rotomoulding grades, the linear architecture raises yield stress and environmental stress crack resistance. These differences are summarised in the following representative comparison.

Additional thermal and hardness values support demoulding and surface specification. Typical Vicat softening temperature is 117°C under ISO 306, Shore D hardness is 61 under ISO 868, and tensile elongation at break exceeds 800% under ISO 527-2:2012. At density 0.935 g/cm³, the crystalline fraction is estimated at 45–55% using the density method with amorphous and crystalline reference densities of 0.855 g/cm³ and 1.000 g/cm³. Differential scanning calorimetry of LLDPE with this density typically shows a peak melting temperature of 118–124°C under ISO 11357-3:2018; published data for this specific green variant are limited.

Metallocene-catalysed LLDPE grades may differ from conventional LLDPE of this type in molecular weight distribution and impact at sub-zero temperatures. A broader molecular weight distribution often favours bubble release during rotational moulding, but low-temperature dart impact may be lower than metallocene alternatives. Published comparative data for this specific green variant are limited, so evaluation by the converter is required for parts exposed to dynamic impact below −20°C.

Environmental stress crack resistance in LLDPE arises from tie-molecule population and reduced lamellar thickness. Under ASTM D1693-21, a notched specimen is exposed to a stress-cracking fluid such as 100% Igepal CO-630 at 50°C. F50 values above 500 h indicate resistance to slow crack growth, but part design and moulded-in stress can reduce performance. Sharp corners, metal inserts, and rapid water quenching can create local stress concentrations that negate the resin advantage.

Outdoor service performance depends on UV stabiliser loading and part design. The green pigment package should not be assumed to provide long-term UV protection unless the supplier confirms a UV stabiliser package. Accelerated weathering should be verified by ISO 4892-2:2013 cycles and evaluated for colour shift and tensile property retention.

Peak internal air temperature, moisture, and particle-flow boundaries in rotational moulding

In production-scale rotational moulding machines with biaxial rotational ratios of 3:1 or 4:1, oven setpoints for LLDPE powder of this density are commonly set between 260°C and 300°C, but the controlling variable is the internal air temperature inside the mould. Measured internal air temperature should reach a peak between 190°C and 220°C for a wall section of 6 mm; below 190°C, incomplete particle coalescence, pinholes, and internal voids may persist. Above 220°C, thermo-oxidative degradation can reduce ESCR and shift the green colour toward yellow. The optimum peak temperature must be mapped for each mould and machine because wall thickness, mould material, and part mass alter heat transfer.

During the heating phase, the powder passes through particle coalescence, densification, and bubble removal stages. A melt flow rate of 5.5 g/10 min provides sufficient melt mobility at 190–220°C to eliminate air bubbles; however, bubble removal rate is governed by resin viscosity, surface tension, and local pressure. In moulds with complex geometry, air pockets can become trapped in rib areas if rotation speed is insufficient. Multi-axis machines may use rotation ratios from 3:1 to 5:1 depending on part shape.

Cooling rate is a further process boundary. Demoulding above 100°C can generate warpage in flat panels; forced-air cooling followed by controlled water mist is common, but rapid water quench can increase residual stress. Parts with variable wall thickness should be cooled at a rate that limits differential shrinkage, particularly in moulds with metal inserts or abrupt thickness transitions.

Moisture control is normally not required because polyethylene absorbs less than 0.01% moisture by mass at 23°C and 50% relative humidity. Surface condensation is nevertheless a boundary condition: powder stored below dew point or moved into a warm moulding bay at relative humidity above 60% can carry water on the particle surface. Steam generated during heating can create pinholes and internal porosity. Powder should be equilibrated to ambient temperature above dew point before charging into the mould.

Particle size distribution should be checked to ASTM D1921-18 because fines can promote hopper bridging and dust generation. A shift in melt flow rate greater than ±0.5 g/10 min from the target should initiate a process review, because oven cycle time and wall-thickness distribution in deep ribs or thin channels are sensitive to melt flow rate. The medium flow rate of 5.5 g/10 min is generally suited to wall sections between 3 mm and 10 mm; sections above 10 mm may require a lower-melt-flow grade to reduce internal void formation, while sections below 3 mm may require a higher-melt-flow grade for complete fill.

Chemical resistance follows the LLDPE profile for nonpolar semicrystalline polyolefins. The material is suitable for aqueous solutions, dilute acids, alkalis, and many polar solvents at service temperatures below 50°C, but chlorinated hydrocarbons, strong oxidising acids, and aromatic solvents can swell or degrade the surface. Compatibility for a particular fluid should be tested by immersion under ASTM D543-21 at the expected service temperature.

The green pigment may shift the melt flow rate and reduce tensile elongation because pigment agglomerates act as stress concentrators. Dispersion quality affects surface appearance and impact. Batch-to-batch colour variation can be monitored by spectrophotometric CIELAB values to ASTM D2244-21. If the moulded product is subjected to repeated impact, pigment dispersion should be checked by microscopic examination or by comparing notched impact results with unpigmented resin data.

If the converted article is intended for food contact or outdoor electrical service, migration and compliance boundaries apply

Base olefin polymers may comply with FDA 21 CFR 177.1520 when the finished article is used within the conditions of use specified in that section. Pigments and stabilisers, including the green colour package, must meet their own applicable clearances or be evaluated through migration testing under EU 10/2011. The moulded article should be tested for overall migration and specific migration of pigment-related metals before food-contact use.

For electrical and electronic equipment, the pigment package should be confirmed as compliant with the maximum concentration values in Directive 2011/65/EU Annex II. For industrial use, the powder should be handled as a combustible dust; control of electrostatic discharge and dust concentration during silo transfer is required. The material should not be melt blended with condensation polymers such as polyamide or polycarbonate at processing temperatures above 250°C because trace moisture and incompatible melt phases can create surface defects and local degradation.

Incompatibility with strongly oxidising media and excessive oven residence time represent the principal operational limits. Processors should establish a maximum oven residence time for each mould by comparing internal air temperature, part colour, and ESCR retention after moulding. If ESCR retention after moulding falls below the design requirement, the oven setpoint or peak internal air temperature should be reduced rather than increasing stabiliser levels without supplier verification.