LyondellBasell Icorene 3560 AO+ ATC 9816 Polyethylene, Linear Low Density is a pelletized linear low-density ethylene polymer supplied with the AO+ antioxidant system and the ATC 9816 additive package. The grade is positioned for rotational moulding and associated powder processing lines where a moderate melt flow, adequate melt consolidation, and resistance to environmental stress cracking are required. Public technical data for the base resin lists a nominal density of 0.936 g/cm³ under ISO 1183-1 and a melt flow rate of 5.0 g/10 min at 190 °C/2.16 kg using ISO 1133-1:2022. The exact chemical identity of the ATC 9816 component is not disclosed in the publicly available datasheet; the combination is represented as a process and light-stabilization package intended for extended oven residence and outdoor exposure.

Representative values are drawn from publicly available datasheet summaries. Final lot-specific certificates of analysis govern for production use, and the tabulated data do not replace testing on the finished moulded article.

What separates the 3560 AO+ ATC 9816 grade from conventional butene linear low-density polyethylene?

The primary differentiation lies in the combination of melt flow rate, additive load, and intended rotomoulding utility rather than in a single molecular parameter. Conventional butene LLDPE grades of similar density and melt flow are available with lower stabilization packages; the AO+/ATC 9816 configuration extends processing latitude by reducing oxidative chain scission during repeated heat histories. The molecular architecture of the base polymer remains an ethylenic backbone with short-chain branches. The public datasheet does not specify comonomer type, so direct branching comparisons must be made by the processor using crystallisation elution fractionation or thermal rising elution fractionation if that level of resolution is required.

In standard laboratory testing, the grade’s linear structure produces a higher tensile yield strength than branched LDPE of equivalent density. The yield stress under ISO 527-2 is approximately 16.0 MPa, while many rotational moulding LDPE formulations yield between 8 MPa and 12 MPa at comparable density. The difference is attributable to the absence of long-chain branching and the presence of load-bearing tie chains in the semicrystalline network. For applications requiring stiffness, the flexural modulus measured by ISO 178 is approximately 0.55 GPa, a value that exceeds soft LDPE but remains below HDPE. The trade-off against LDPE is lower melt elasticity and reduced bubble stability in extrusion processes; the grade is therefore not specified for blow moulding or cast film lines where high melt strength is required.

On a carousel-type rotational moulding machine, the resin is dry-blended or ground to a nominal 35 mesh (500 µm) particle size before charging into the mould. The heating phase is controlled by peak internal air temperature rather than by oven set-point alone. For this melt-flow class, typical peak internal air temperatures fall between 200 °C and 220 °C. Incomplete particle coalescence appears as pinholes or bubble-like porosity on the inner wall if the peak temperature is not reached; excessive residence time above the upper bound produces yellowness and a measurable reduction in elongation at break. Heating time to reach peak internal air temperature depends on mould mass, oven temperature, and arm ratio. On a 2.4 m offset arm with a 4:1 secondary-to-primary speed ratio, cycle time is governed by the thickest mould section.

Mould release is influenced by the grade’s low-temperature ductility and shrinkage. Demoulding at wall temperatures below 60 °C is common to reduce distortion, but rapid quenching can increase residual stress and lower impact toughness. Forced-air cooling followed by water mist is used when cycle time reduction is prioritised; the resulting crystallinity profile through the wall is not uniform, and the outer layer can exhibit higher flexural modulus than the inner layer. The processor should verify the grade’s powder bulk density and dry-flow time under ASTM D1895 because fines generated during grinding alter flow into deep ribs and narrow bosses. Lot-to-lot variation in melt flow rate is controlled by the supplier’s release limits, but powder flow after grinding is more affected by regrind composition and moisture pickup.

Relative to low-density polyethylene, the short-chain branching distribution alters environmental stress crack resistance and stiffness.

The structural difference between linear low-density and high-pressure LDPE is measurable in environmental stress crack resistance. Under ASTM D1693 condition B, 10% Igepal CO-630, crack propagation in the linear grade is slower because the short-chain branches form tie molecules that bridge adjacent lamellae. The public datasheet value for the base resin is above 1000 h at F50, compared to typical LDPE rotomoulding grades that commonly fall below 100 h under the same condition. That difference is significant for flat-sided tanks but is not a substitute for chemical compatibility testing under ISO 175 or ASTM D543; stress cracking agents used in ESCR testing are not universal chemical simulants.

The stiffness increase relative to LDPE is accompanied by a narrower sintering window and higher melt viscosity at equivalent processing temperature. This changes the heat-transfer response in the mould: the powder bed takes longer to consolidate because the linear chains require more thermal energy to reach the same level of molecular mobility as branched LDPE. Processors switching from LDPE should not simply transfer oven residence times; peak internal air temperature must be revalidated against void formation and colour retention. The grade’s higher tensile yield strength also allows wall-thickness reduction in stiff tanks, but the reduction must be validated by full-scale drop impact and burst testing.

Oxidative stability is governed by the AO+ system and by the thermal history accumulated during processing. Long-term oven aging of moulded plaques at 100 °C in air under ISO 4577 can be used to compare the time to 50% loss of elongation at break; published data for this specific ATC 9816 configuration are limited, and the result is wall-thickness dependent. The ATC 9816 component contributes to light stability in outdoor exposure. Accelerated weathering is conducted under ISO 4892-2 method A with a xenon arc source and a 0.35 W/m² irradiance at 340 nm. A change in colour or a drop in tensile elongation after 2000 h does not automatically predict a service lifetime in a specific climate.

The stabilized resin should not be dry blended with transition-metal salt pigments or acidic fillers without first confirming oxidation induction time stability by ISO 11357-6; such additives can deplete the phenolic and phosphitic components of the AO+ package. Combination with additional hindered amine light stabilizers in masterbatch form requires verification of interaction because the base stabilization package is already formulated for outdoor exposure, and additional amine additives can shift the oxidation induction time unpredictably. If recompounding is attempted on a co-rotating twin-screw extruder with L/D 40:1, the screw design should avoid high-shear mixing zones that raise local melt temperature excessively; the AO+ package is consumed more rapidly at elevated temperature. Published fracture mechanics data for this specific additive-modified grade under cyclic fatigue loading are limited; design verification should rely on application-specific weld-line testing rather than extrapolation from standard ESCR data.

Rotomoulding heat-transfer and powder-flow constraints

Powder particle-size distribution controls the sintering rate and bubble removal. A bimodal distribution with a median particle size of 300–500 µm and a maximum of 1.0 mm is typical for stable wall formation, but the manufacturer does not publish a fixed sieve specification because final grinding is carried out at the moulding plant. Bulk density of the ground powder is measured by ASTM D1895 method A; values below 0.32 g/cm³ indicate excessive fines or moisture pickup and are associated with feed bridging in narrow channels. Heating rate inside the mould is limited by the thermal conductivity of the polymer powder bed, which remains below 0.25 W/m·K until sintering closes porosity. Pinhole-free consolidation is obtained only after the internal air reaches the final temperature and the polymer melt viscosity is low enough to allow trapped gas to diffuse; the relationship between viscosity and temperature is available from the supplier’s capillary rheometry data, not from the melt flow rate alone.

Moisture uptake before moulding is a process risk. At relative humidity above 60%, pre-drying of the ground powder is recommended because surface moisture creates steam bubbles during the early heating phase. Drying should be performed in a dehumidified hopper dryer at a resin temperature not exceeding 60 °C to avoid particle sticking. The grade is not specified for direct submersion in hot aqueous chemical environments without prior chemical resistance testing. Incompatibility with amine-based additive systems should be avoided unless the combination has been screened by oxidation induction time measurements and colour stability trials.

Regulatory status for the base ethylene polymer is routinely assessed under FDA 21 CFR 177.1520 and EU Commission Regulation (EU) No 10/2011. The clearances apply to the polymer component and are subject to migration limits and additive restrictions in the finished article. The ATC 9816 package must be examined separately because its components are not automatically covered by the base polymer listing. For electrical and electronic goods, the finished article must conform to EU Directive 2011/65/EU (RoHS Recast) for lead, cadmium, mercury, hexavalent chromium, PBB, and PBDE; the resin supplier does not issue a finished-article RoHS certificate without end-use processing data. The product is not intended for medical implant applications, and no ISO 10993 biocompatibility data are provided in the public technical file.

When specifying the grade for chemical storage tanks, what standard test data govern?

Chemical storage tank specification requires data sets that are not captured by the standard property table. For a vertical cylindrical tank operating at ambient temperature and a design hoop stress below 5 MPa, the critical tests are full-thickness tensile elongation at break after moulding under ISO 527-2, environmental stress crack resistance under ASTM D1693 condition B, and drop impact at the intended minimum service temperature. Notched Charpy impact according to ISO 179-1/1eA at -40 °C provides an additional comparison against brittleness. Published data for the base grade indicate low-temperature ductility is retained to -76 °C by ASTM D746; however, the result is obtained on a compression-moulded plaque and does not account for weld lines, gate regions, or inserts in a rotomoulded tank. Burst testing on the finished article is mandatory because failure under constant internal pressure is governed by seam quality and wall-thickness distribution.