LyondellBasell HDPE L5045 is a high-density polyethylene injection moulding grade supplied in pellet form, characterized by a nominal density of 0.950 g/cm³ and a melt flow rate of 4.5 g/10 min when measured at 190 °C under a 2.16 kg load. The grade is positioned for rigid packaging and industrial articles in which medium melt flow provides a compromise between injection pressure and long-term stress crack resistance. Applications commonly associated with the product include pails, crates, housewares, caps and closures, and material-handling components. Within the producer’s HDPE portfolio the 4.5 g/10 min flow class sits between high-flow thin-wall grades above 12 g/10 min and fractional-melt blow moulding or sheet grades below 1.0 g/10 min; the position is a processing boundary that determines fill pressure, gate freeze time, and environmental stress crack resistance in the finished article.

What physical property envelope is reported for HDPE L5045?

The following representative values are compiled from published supplier technical literature and are not specification limits. Converters should request the certificate of analysis for the production lot. Density is determined in accordance with ISO 1183-1:2019 or ASTM D1505; melt flow rate is measured under ISO 1133-1:2022 or ASTM D1238 using a 2.16 kg weight at 190 °C.

The representative values are generated from injection-moulded or compression-moulded specimens conditioned at 23 ± 2 °C and 50 ± 10 % relative humidity. They are neither minimum sales specifications nor maximum design limits; a production certificate of analysis should be requested because individual lots may vary around the nominal values. For load-bearing articles, the tensile yield stress and flexural modulus must be translated into design values using safety factors specified by the relevant end-use standard rather than applied directly from the material datasheet.

Processors evaluating L5045 for multi-cavity closure or crate tools often begin with spiral flow testing, because the melt flow rate is measured at low shear and does not predict injection behavior. A spiral-flow mould at 190 °C, 220 °C, and 240 °C with a mould temperature of 40 °C typically shows flow-length values rising from approximately 40 cm to 65 cm as the melt temperature increases from 190 °C to 240 °C. The data are tool-specific; gate diameter, injection velocity, and cavity thickness change the result. Published data for this specific configuration is limited, so converters should develop internal spiral-flow curves using their own mould geometry rather than relying on a datasheet value.

For gate design, the apparent viscosity of medium-flow HDPE under injection moulding shear rates is more useful than melt flow rate. Capillary rheometry data for similar density and melt flow materials typically show apparent viscosity declining from the low-shear plateau to roughly 200–400 Pa·s at 1,000 s⁻¹ and 190 °C; the actual L5045 lot may differ. High-flow grades with 20 g/10 min may drop below 150 Pa·s at the same condition, which explains their easier filling but lower stress crack resistance. Fractional-melt HDPE with 0.3 g/10 min can exceed 800 Pa·s at 1,000 s⁻¹, producing excessive pressure drop in thin-wall injection tooling.

At the conversion stage, L5045 is typically evaluated on injection moulding machines with general-purpose or polyolefin screws. A screw L/D of 20:1 to 22:1 and a compression ratio of 2.5:1 to 3.5:1 are common for this melt flow class. Barrel temperature profiles are usually set from 190 °C in the rear zone to 230 °C at the nozzle, with a melt temperature between 210 °C and 240 °C. Mould temperature is normally maintained between 20 °C and 50 °C; higher mould temperatures reduce weld-line depth and improve surface gloss at the cost of longer cooling time.

Because HDPE is non-hygroscopic, pre-drying is not normally required. However, pellets stored below 5 °C and transferred into a warm, high-humidity production hall may acquire surface condensation. If splay or surface defects are observed, a hot-air hopper dryer at 70–80 °C for 1–2 h is adequate to remove surface moisture. Thermal-oxidative degradation becomes significant above 260 °C; at that melt temperature, residence time should not exceed 5 min. On a typical 20 L pail tool with a shot weight near 850 g, a barrel capacity of 1.2–1.6 kg maintains shot size between 55 % and 70 % of maximum. Shot sizes below 20 % increase residence time and may cause yellowing, while shot sizes above 80 % can destabilize screw recovery and produce short shots.

When high-flow injection grades sacrifice stress crack resistance in detergent pails

Compared with high-flow HDPE grades having melt flow rates above 20 g/10 min, L5045 retains a higher molecular weight fraction that generally improves resistance to environmental stress cracking under detergent, oil, and surfactant exposure. The penalty is higher filling pressure. For a 20 L pail with a nominal sidewall of 1.8 mm, filling pressure with L5045 may run 10–20 % higher than a 20 g/10 min grade at the same melt temperature; however, the lower-MFR material typically offers greater margin in stacking tests with stress crack agents. Screening is conventionally performed under ASTM D1693 Condition B with 100 % Igepal at 50 °C, but published data for this specific configuration is limited, and part-level testing remains necessary because moulded-in stress is not captured by pellet or compression-moulded specimens. A bent-strip method such as ISO 22088-3 is more representative for a moulded sidewall subjected to external load.

Differences from other products should not be inferred from melt flow rate alone. Two HDPE grades with the same 4.5 g/10 min value can exhibit different ESCR if one has a bimodal molecular weight distribution and the other is unimodal. The single-point melt flow measurement does not quantify molecular weight distribution, long-chain branching, or comonomer placement. Where detergent resistance is critical, the comparison should include ESCR data generated on the same tool and the same lot, not only the supplier datasheet.

Controlling Mould Shrinkage in Thick-Wall Industrial Articles

Mould shrinkage for HDPE L5045 is typically in the range of 1.5–2.5 % when determined according to ASTM D955 or ISO 294-4. The lower values occur in fast-cooled thin sections with high packing pressure; the upper values occur in thick bosses, ribs, and gate regions that cool slowly. Tool designers for crates and pails should not apply a single global shrink factor. A rib with a thickness of 4 mm attached to a nominal wall of 2 mm can produce sink marks if the rib-to-wall ratio exceeds 0.6, and the local shrinkage difference can exceed 0.5 %. The phenomenon is a geometry-dependent processing limitation rather than a defect in the resin.

Post-mould crystallization continues after ejection; dimensional checks should be delayed for at least 24–48 h at ambient temperature. For stackable crates, premature measurement immediately after ejection commonly produces acceptance errors because the part may shrink an additional 0.2–0.4 % as crystallinity equilibrates.

Incoming lot verification for L5045 typically includes melt flow rate, density, and visual pellet inspection. A deviation of more than ±0.3 g/10 min from the reference lot is often used as an internal alert for injection moulding because it may indicate a lot-to-lot shift in shear viscosity. Density is checked by gradient column or compression-moulded density per ISO 1183-1:2019 or ASTM D1505. For colour-critical housewares and caps, oxidation induction time measured by ISO 11357-6 or ASTM D3895 can identify thermally degraded regrind; an OIT below 20 min at 200 °C may indicate excessive recycled content or processing history. Pellet size distribution should also be monitored because variation in pellet geometry can stratify in the feed throat and produce screw starvation on high-speed machines.

Food-contact status for HDPE L5045 must be confirmed with the specific supplier declaration for the production lot. The base olefin polymer is typically manufactured to satisfy FDA 21 CFR 177.1520 and may meet the overall migration requirements of EU Regulation 10/2011 under specified food simulants, but the finished article compliance is converter-dependent. Colour concentrates, regrind, and processing aids can change specific migration values. REACH and RoHS declarations for the neat resin do not automatically cover the coloured or filled compound. The resin should not be blended with unapproved metallic stearates or unknown post-consumer HDPE if the article is intended for food contact or long-term detergent storage; metallic residues can accelerate thermo-oxidative degradation.

For non-food industrial applications, clean post-industrial regrind from sprues and rejected pails may be reintroduced at 20–30 % by weight if the regrind has not undergone thermal damage. The pellet feed system should be adjusted to prevent bridging when a blend of virgin and regrind is used because differences in bulk density can cause screw starvation.

On a production line producing stackable crates from HDPE L5045, a frequent failure mode is premature ejection during cooling. If the cooling time is set below 12 s for a 3 mm wall, the part may deform when transferred to hot stacking. Processing guides for high-density polyethylene injection moulding recommend cooling times proportional to the square of wall thickness; a 2 mm wall may cool in 8–12 s, while a 4 mm wall may require 30–45 s at a mould temperature of 35 °C. The use of closed-loop process control on hydraulic or electric injection units is recommended to maintain hold pressure within ±0.5 MPa of the set point and to limit lot-to-lot part mass variation.