LyondellBasell HDPE M5410 is an injection-moulding-grade high-density polyethylene homopolymer supplied in pellet form. The resin is characterised by a nominal melt flow rate of 10.0 g/10 min at 190°C under 2.16 kg load when tested to ASTM D1238 or ISO 1133-1:2022, and a density of 0.954 g/cm³ when tested to ASTM D1505 or ISO 1183-1. These two values define the grade as a comparatively high-flow HDPE homopolymer for thin-wall injection moulding, not a high-molecular-weight extrusion or blow-moulding resin. The higher melt flow reduces injection pressure and improves cavity filling in multicavity tooling, but it also lowers melt strength and environmental stress crack resistance relative to fractional-melt HDPE. Typical application areas reported in technical literature include closures, overcaps, thin-walled packaging, pails, and general housewares. The grade should not be selected for pressure pipe, blow-moulded chemical bottles, or aggressive detergent packaging unless the finished article has passed the relevant stress-cracking test programme.

The manufacturer’s current datasheet should be consulted for lot-specific values. The typical values below are representative of the grade as published for injection-moulding evaluation; they are not specification limits. Where a grade-specific value is unavailable, published data for that specific configuration should be requested from the supplier rather than inferred from similar HDPE products.

The notched Izod value indicates that M5410 is a rigid material with limited ductility under notch-sensitive loading. Sharp corners, gate blush, and moulded-in weld lines reduce this further; load-bearing sections should therefore use generously radiused transitions not below 0.5 mm. The high elongation at break under ASTM D638 does not imply high environmental stress crack resistance, because elongation is measured in a short-time tensile mode without the aggressive surfactant environment required by ASTM D1693.

What Processing Limits Emerge in Thin-Wall Injection Moulding?

For thin-wall containers with nominal wall thickness between 0.6 mm and 1.5 mm, barrel temperature settings are normally 180–220°C in the rear zone, 200–230°C in the centre zone, and 210–240°C at the front and nozzle. Melt temperatures should not exceed 250°C; residence time at 250°C or above should remain below 5 min because chain scission raises the melt flow rate and reduces impact strength. A general-purpose polyolefin screw with L/D of 20:1 to 24:1 and compression ratio of 2.0:1 to 2.8:1 is appropriate; high-shear barrier screws are unnecessary for this unimodal homopolymer. Back pressure should be set at 0.5–1.0 MPa hydraulic, just sufficient to disperse colour concentrate. Injection speed is a more sensitive variable: the cavity should fill within 0.5–1.5 s, with maximum shear rates below 50,000 s⁻¹ in gates. Higher shear rates can produce splay and surface melt fracture; lower speeds may cause short shots or oriented weld lines.

Mould temperature is commonly 15–30°C for rapid solidification. Mould temperatures up to 50°C improve gloss and reduce moulded-in stress but increase cooling time. Hold pressure in the range of 55–75% of peak injection pressure is maintained until gate freeze, which is confirmed by stabilised part mass. If part mass continues to increase after additional 0.5 s hold-time increments, the gate has not sealed. Pre-drying is usually unnecessary if pellets remain below 0.05 wt% moisture, but condensation from ambient air above 60% RH can cause surface splay; a desiccant hopper at 80°C for 2 h removes surface water without introducing significant thermal history. A vented barrel is not required for this grade.

Thermal Degradation and Chemical Stress Cracking Constraints

HDPE M5410 is not intended for sustained contact with strong oxidising acids, aromatic hydrocarbons, or chlorinated solvents. Aromatic and aliphatic solvents can cause swelling and stress cracking in moulded-in stress zones. For any chemical-contact application, the converter should expose stressed plaques or finished parts to the target fluid at 23°C or 40°C under a method aligned with ASTM D1693 or ISO 22088-3, with applied strain no greater than 2%. If the stress-cracking time falls below the intended service duration, the material should not be used without redesign to reduce moulded-in strain. Oxidative stability can be screened by oxidation induction time under ASTM D3895 or ISO 11357-6; unstabilised HDPE should not be specified for continuous service above 85°C. Outdoor use requires an effective UV stabiliser package, and weathering programmes under ASTM D4329 or ISO 4892-3 should be tied to end-use failure criteria rather than colour change alone.

For coloured or recycled-content versions, thermal and chemical performance may shift. Addition of calcium carbonate or talc fillers lowers mould shrinkage and raises flexural modulus but can reduce notched impact. Lubricant packages used for demoulding can also affect surface printing and lid sealing. These variables are not captured by a base-resin datasheet and must be validated on production tooling.

When M5410 Is Benchmarked Against Bimodal Pipeline and Blow-Moulding HDPE

Relative to fractional-melt HDPE blow-moulding grades with melt flow rates from 0.15 g/10 min to 0.5 g/10 min, M5410 has significantly lower viscosity at shear rates typical of injection filling, so it fills long flow paths at lower melt temperature or injection pressure. The trade-off is lower melt strength and lower environmental stress crack resistance. Fractional-melt grades are preferred for continuous parison extrusion and blow moulding but are not suitable for injection moulding thin-wall parts without excessive pressure drop. In comparison with bimodal PE100 pipe resins, M5410 lacks the high-molecular-weight tail and slow crack growth resistance required by ISO 9080 and ISO 12162; it must not be substituted in pressure pipe or fittings. Against a 4.0 g/10 min HDPE injection homopolymer, M5410 offers improved flow length and shorter fill time, but the lower average molecular weight gives lower notched impact and ESCR. In cap and closure tools with flow-length-to-wall-thickness ratios above 150:1, the improved high-shear flow is beneficial; in thick-section parts where sink-mark control and ESCR dominate, a lower-MFR grade is usually more robust.

Differences from polypropylene impact copolymers are also relevant. HDPE M5410 has a flexural modulus in the range of 1.2–1.4 GPa, which is higher than some PP impact copolymers but below many homopolymer PP grades. Its heat deflection temperature under 0.46 MPa is near 74°C, and its Vicat softening point is near 126°C; steam sterilisation at 121°C exceeds the practical service range for this resin. M5410 is therefore not a direct substitute for PP in hot-fill or sterilised applications.

Food-contact evaluations for HDPE M5410 are based on FDA 21 CFR 177.1520 or Commission Regulation (EU) No 10/2011. A base olefin polymer may conform to these provisions, but the final article must be tested for overall migration and, where applicable, specific migration of additives. REACH compliance is usually documented by the supplier under Regulation (EC) No 1907/2006. RoHS status under 2011/65/EU applies only to the four restricted heavy metals and two brominated flame retardant classes; it does not imply food-contact or medical approval. Medical or pharmaceutical use should not proceed without ISO 10993 biocompatibility assessment and relevant pharmacopoeia testing.

Gate Freeze, Hold Pressure, and Shrinkage Control in Multicavity Moulds

In multicavity closure and cap tools, the main dimensional difficulty is mould shrinkage. The published mould shrinkage range of 0.018–0.022 mm/mm under ASTM D955 means that a 100 mm part dimension can vary by 0.4 mm across cavity positions if hold pressure and gate freeze are inconsistent. Cavity-to-cavity filling imbalance above 5% by mass causes variable shrinkage; the correction is runner balancing or gate-land adjustment rather than an overall increase in melt temperature. When post-mould ovality occurs in pail lids or overcaps, it is often the result of premature hold-pressure release before gate seal. Hold pressure should be maintained until the part-mass curve plateaus; premature release starves the cavity near the gate and leaves underpacked regions that shrink more after ejection. Overpacking at the gate can be avoided by reducing hold pressure in a stepped profile after gate freeze. For parts with sink-prone ribs or bosses, nominal wall thickness should not exceed 3.0 mm without coring, because thick sections extend cooling time and induce sink marks. Cooling time is governed by the square of wall thickness; a 2.0 mm wall may require 8–12 s of cooling in a 20°C mould, while a 3.0 mm wall may require 18–25 s under the same conditions. These values are starting points, not process guarantees, and should be optimised by part-weight curve and dimensional capability studies.

When regrind is introduced, the melt flow rate can shift upward with repeated extrusion cycles. In production, a regrind level above 20% can narrow the processing window and reduce notched impact in the finished part. The regrind fraction should therefore be limited and its particle size controlled to avoid bridging in the hopper. If colour or additive masterbatch is used, the carrier resin should be a compatible HDPE with a melt flow rate within ±3.0 g/10 min of M5410 to avoid local viscosity mismatch and streaking.