LyondellBasell HDPE M6020

The resin identified as LyondellBasell HDPE M6020 is a high-density polyethylene supplied as pellets for injection moulding. The grade is characterised by a nominal density of 0.960 g/cm³ when tested to ISO 1183-1:2019 and by a nominal melt flow rate of 20 g/10 min when tested at 190 °C under a 2.16 kg load according to ISO 1133-1:2022. These two values place the resin in the high-flow, high-stiffness segment of the HDPE injection moulding portfolio. The product is not a high-molecular-weight blow-moulding or pipe resin; its high melt-flow index reduces pressure loss in multi-cavity tools but also reduces environmental stress-cracking resistance relative to HDPE grades with melt flow rates below 2 g/10 min. In normal covered storage, predrying is not required because polyethylene is not hydrolytically sensitive. If surface moisture from condensation is observed, drying at 80 °C for 2 h in a desiccant dryer is sufficient; prolonged exposure above 250 °C should be avoided because oxidative chain scission increases gel formation and odour.

Because HDPE M6020 is not hydrolytically sensitive, the primary material-handling risk is not moisture uptake but cross-contamination by polypropylene, polycarbonate, or PET pellets in shared conveying systems. These incompatible resins can produce discrete micro-domains in moulded parts and delamination at knit lines. Pneumatic conveying should use dry, oil-free air, and regrind should be limited to 20 % by mass unless the moulder has established higher levels through lot testing. Regrind accumulation from multiple heat histories can reduce impact strength and increase gel specks.

What nominal property set defines HDPE M6020 under ISO conditioning?

Design calculations for this grade commonly use supplier typical property values generated on injection-moulded ISO plaques conditioned at 23 °C and 50 % RH for 40 h unless otherwise stated. The values are not a guarantee of lot-to-lot identity, but they define the stiffness/impact balance that distinguishes HDPE M6020 from lower-density polyethylene grades. The table below summarises typical values from supplier technical literature; safety-critical design should use first-party testing on the actual moulded part.

In thin-wall container tooling with nominal wall stock at 0.8–1.2 mm, the 20 g/10 min MFR enables filling at lower melt pressure than a 10 g/10 min HDPE of similar density. On production-scale toggle-clamp machines of 80–120 t, moulders have observed reduced hydraulic filling pressure in multi-cavity closure tools when melt temperature is held at 220 °C and mould cooling water is maintained at 15 °C. The lower pressure demand allows a smaller clamp-force margin, but gate geometry and hot-runner balance must be validated by short-shot studies because the grade can produce a sharper viscosity change as the melt approaches gate freeze. Thin-wall parts moulded from HDPE M6020 typically exhibit mould shrinkage of 1.5–2.5 % parallel to flow and 1.0–2.0 % perpendicular to flow when measured after 24 h at 23 °C; these values depend on holding pressure, gate dimensions, and wall thickness more than on melt flow rate alone.

Weld lines formed at the melt-front junction in multi-gate tools are a common failure mode on production lines. Because HDPE M6020 has a high melt-flow rate, the melt front may cool before complete molecular diffusion across the weld interface, producing a weak plane with tensile strength retention below that of the bulk material. In a multi-gated rectangular tray moulded at 220 °C, the weld-line force at break may be 30–50 % lower than the un-welded value when tested according to ISO 527-2:2012. Gate positions should therefore be arranged to reduce weld-line length or place the weld in a low-stress region. This limitation is aggravated when melt temperature is run at the lower edge of the processing window and when the mould surface is below 10 °C.

When gate freeze and low residual stress control cycle time

On production-scale injection machines with reciprocating screws of 20:1–24:1 L/D and compression ratio between 2.2:1 and 2.8:1, HDPE M6020 is processed at melt temperatures of 200–230 °C and mould skin temperatures of 10–30 °C. Back pressure is held at 0.5–1.5 MPa hydraulic to prevent screw slip while avoiding excessive shear heating in the metering zone. Injection velocity is set high enough to fill the cavity before gate freeze, but not so high that jetting occurs; a common starting point is 100–200 mm/s screw advance speed depending on machine size. Holding pressure is applied until gate freeze, and cooling time is governed by the square of the maximum wall thickness. Because HDPE M6020 has a high melt index, the gate freeze time is shorter than that of a 5 g/10 min grade at the same gate diameter, which lowers cycle time but reduces the time available for packing out sink marks. Screw decompression of 2–5 mm after recovery reduces nozzle drool. Melt temperatures above 240 °C are not recommended for thin-wall tools, and processing above 250 °C increases oxidative gel formation. Hot-runner residence time should not exceed 10 min at 230 °C; stagnation zones can produce intermittent black specks in the finished part.

The melt viscosity of HDPE M6020 at 200 °C and a shear rate of 1000 s⁻¹ is substantially below that of a 5 g/10 min HDPE; process engineers commonly estimate injection pressure requirements by capillary rheometry or spiral flow trials rather than relying on MFR alone. The MFR value is a single-point measurement and does not capture the high-shear viscosity crossover observed in injection moulding. On a 50 mm screw, the use of a high-flow grade may reduce the melt pressure at the machine nozzle by 20–30 MPa compared with a lower-flow grade in the same tool; however, actual pressure differences depend on gate size, runner diameter, and mould temperature.

Comparative differentiation against lower-flow HDPE categories

Relative to a lower-flow blow-moulding HDPE with an MFR of 0.3 g/10 min, HDPE M6020 displays significantly lower zero-shear viscosity and lower notched impact, although flexural modulus may be similar because density is similar. The higher flow rate permits injection moulding of thin walls at lower pressure, whereas the blow-moulding grade would freeze prematurely at the gate. Compared with general-purpose injection HDPE of 8 g/10 min, HDPE M6020 reduces fill pressure but also reduces environmental stress-cracking resistance under ASTM D1693 conditions, particularly in the presence of polar organics or household surfactants. The ESCR ranking is directionally predictable from melt flow rate and density, but exact condition-specific values require testing because comonomer distribution and catalyst residuals influence crack resistance independently of MFR.

Closures and overcaps benefit from the high stiffness of the 0.960 g/cm³ density. In a continuous-thread closure with a thread depth of 1.2 mm, the resin has sufficient flexural modulus to prevent excessive strip torque loss after repeated use. However, if a closure is exposed to bleach-containing media, environmental stress-cracking performance must be assessed by exposing moulded samples to a 10 % solution of nonylphenol ethoxylate at 50 °C according to ASTM D1693, because high-flow HDPE grades can fail more rapidly than lower-flow grades under these conditions.

High-flow HDPE grades of this density are not the preferred choice for continuous exposure to chlorinated disinfectants, terpenes, or aggressive detergents at elevated stress. The environmental stress-cracking resistance under ASTM D1693, condition B, may be lower than that of lower-flow injection grades, and published data for this specific configuration is limited. If a moulded article is to be used with strong oxidizers or aromatic hydrocarbons, chemical resistance tests should be performed on finished parts because moulded-in stress and part thickness can produce failures that do not occur in standard tensile plaques.

For food-contact applications, regulatory evaluation is performed under FDA 21 CFR 177.1520 for olefin polymers and under Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food. Overall migration limits are typically assessed at 10 mg/dm² using food simulants specified by the regulation; the relevant simulant, contact time, and temperature determine whether a particular moulded article is compliant. The resin is not formulated with lead, cadmium, mercury, or hexavalent chromium above the maximum concentration values set in RoHS Directive 2011/65/EU, and its status under REACH is declared by the supplier through safety data sheet and product compliance documentation. These regulatory statements apply to the unpigmented pellet; the end-article must be reassessed if masterbatch, printable coatings, or adhesives are introduced.