LyondellBasell HDPE M6028 is supplied as a high-density polyethylene injection-molding resin in pellet form. The product is classified as a high-flow grade within the polyethylene family and is employed in thin-wall rigid packaging, closures, caps, housewares, and general-purpose injection-molded articles. The numerical designation is read in industrial practice as a nominal density of 0.960 g/cm³ and a nominal melt flow rate of 28 g/10 min when determined under ISO 1133-1:2022, Condition 190 °C / 2.16 kg. The resin is supplied in bulk, octabin, or lined paper bags depending on logistics route, with typical pellet bulk density in the range of 0.55 g/cm³ to 0.60 g/cm³. Incoming resin should be certified for melt flow rate and density against the supplier’s certificate of analysis; lot-to-lot drift in these two parameters can shift fill behavior in multi-cavity tools even when other processing variables remain unchanged.

The property profile in Table 1 summarizes representative values for standard injection-molded specimens. These values are not product specifications and may vary with lot, pigmentation, and specimen preparation method.

The density of 0.960 g/cm³ places the product in the higher-crystallinity segment of high-density polyethylene, which contributes to flexural modulus and hardness. Melt flow rate of 28 g/10 min is a low-pressure indicator, not a complete rheological characterization; capillary rheometry across shear rates typical of injection molding is needed for accurate mold-filling simulation. The single-point MFR value should be used together with melt temperature and injection speed to establish the processing window. When comparing polymer data, values generated under ISO 527-2 and ASTM D638-14 may differ because of specimen type, extensometer gauge length, and testing speed. Density values from ISO 1183-1 and ASTM D1505 are comparable but may show minor differences due to sample preparation. Users should not mix ASTM and ISO datasets for engineering calculations without correcting for geometry and conditioning state.

Will the 28 g/10 min melt flow rate alter injection pressure requirements in multi-cavity tooling?

At 28 g/10 min, the melt viscosity is substantially lower than that of HDPE injection grades in the 8 g/10 min to 20 g/10 min range. The apparent viscosity reduction occurs at shear rates typical of injection mold filling, generally 100 s⁻¹ to 10,000 s⁻¹. In thin-wall tools with nominal wall sections below 1.2 mm, the lower viscosity reduces peak injection pressure and improves cavity-to-cavity balance, provided that runner diameters and gate geometries are uniform. The effect is more pronounced when the flow-path-to-wall-thickness ratio exceeds 150:1. However, melt-flow rate alone does not determine pressure requirements; the exact pressure-velocity relationship must be established on the target mold because gate freezing and shear heating depend on part geometry. Processors should not extrapolate single-point MFR values to predict clamp force. For preliminary clamp-force estimation, a projected-area loading of 3 kN/cm² to 4 kN/cm² is used for unfilled HDPE thin-wall parts, but published data for this specific configuration is limited; the final force must be confirmed by cavity-pressure monitoring.

On production-scale injection molding machines with 20:1 to 25:1 L/D general-purpose polyolefin screws, the resin is processed at melt temperatures of 200 °C to 240 °C. Hot-runner systems with valve-gated nozzles normally use the upper portion of this range to prevent premature gate freeze-off. Mold temperatures from 15 °C to 40 °C supply adequate solidification rates; lower mold temperatures may reduce cycle time but increase differential shrinkage and frozen-in stress. Screw speeds of 50 rpm to 120 rpm and back pressures of 0.5 MPa to 1.5 MPa are typical for this melt-flow class. Shot size should be maintained between 40% and 70% of barrel capacity to limit residence time and prevent molecular weight breakdown. The material does not require desiccant drying for normal pellet handling, but surface moisture from storage above 60% relative humidity can produce splay. Pre-drying at 80 °C for 2 h is sufficient to remove surface condensate. During production interruptions longer than 15 min to 20 min, the barrel should be purged with a neutral polyolefin purge compound to avoid thermal degradation of stagnant material.

When thin-wall container tooling demands packing consistency at reduced cycle time

When wall thickness drops below 1.2 mm, gate-seal time becomes the controlling parameter. The melt must be packed to compensate for solidification shrinkage before gate freeze; otherwise sink marks, voids, and warpage result. Packing pressures in the range of 40 MPa to 80 MPa are commonly applied for HDPE M6028, with hold time adjusted to achieve gate seal. Overpacking at excessive pressure can increase molecular orientation and raise molded-in stress, while underpacking results in dimensional instability. Differential shrinkage between flow and transverse directions, measured under ASTM D955-21, is typically 1.5% to 2.5% for unfilled HDPE; tooling dimensions must compensate accordingly. A melt temperature above 260 °C should be avoided because oxidative degradation causes discoloration and reduces mechanical integrity. If cycle time is constrained, mold cooling channels should be placed within 10 mm to 15 mm of the cavity surface and sized to maintain a cooling-water Reynolds number above 10,000 for turbulent heat transfer; this configuration is a conventional production-scale setup for thin-wall polyolefin packaging.

Environmental stress crack resistance and chemical exposure limits

Environmental stress crack resistance is measured under ASTM D1693-15 in a bent-strip configuration exposed to 10% Igepal CO-630 solution at 50 °C. High-density polyethylene with a 0.960 g/cm³ density and 28 g/10 min melt flow rate has relatively high crystallinity and a shorter average molecular chain length than medium-flow or high-molecular-weight HDPE grades. The result is lower tie-molecule concentration across lamellar boundaries, which reduces ESCR compared with lower-flow grades. The material should therefore be used in short-cycle rigid packaging where environmental stress cracking is not the primary failure mechanism. For applications involving detergents, surfactants, alcohols, or oxidizing agents, the specific ESCR value on the supplier’s certificate of analysis must be evaluated against the service condition. Polyethylene is inherently resistant to water, dilute inorganic acids, and alkaline solutions at ambient temperature; however, aromatic hydrocarbons, chlorinated solvents, and certain vegetable oils can swell or stress-crack the polymer. Published data for HDPE M6028 in specific thin-wall closure geometries is limited; plant trials with the intended lid or cap design and service fluid are required before commercial release.

Regulatory positioning for unfilled HDPE grade M6028 is assessed under 21 CFR 177.1520(c) for olefin polymers when food-contact use is contemplated. The finished article must comply with the extraction limits specified in that section and with applicable good manufacturing practices. Under the European framework, Commission Regulation (EC) No 10/2011 is relevant for plastic food-contact materials; migration testing of the finished article is required because processing aids, masterbatch colorants, and converting conditions influence overall migration and specific migration limits. The base polyolefin is outside the restricted substances of Directive 2011/65/EU for lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and selected polybrominated diphenyl ethers; however, finished components containing colorants or additives must be assessed separately. Under UL 94, unfilled HDPE of this type is commonly rated HB at 1.5 mm thickness; a grade-specific UL Yellow Card should be confirmed for the final product. Compliance with Regulation (EC) No 1907/2006 concerning REACH is communicated through the supplier’s safety data sheet and product stewardship documentation.

Comparative positioning against lower-flow high-density polyethylene grades

The nearest processing analogues are HDPE injection grades with melt flow rates of 8 g/10 min to 20 g/10 min at the same nominal density. Relative to those grades, HDPE M6028 shifts the processing envelope toward shorter fill times, lower peak injection pressure, and easier filling of long flow paths in thin sections. The trade-off is reduced toughness and environmental stress crack resistance, as reflected in notched impact testing under ISO 180/A or tensile impact testing under ISO 8256. Grades with melt flow rates above 50 g/10 min may provide still lower injection pressure but can show greater molecular orientation, reduced tensile strength, and higher susceptibility to warpage. The 0.960 g/cm³ density class maintains higher stiffness than lower-density HDPE copolymer grades in the 0.940 g/cm³ to 0.950 g/cm³ range but typically exhibits lower notched impact strength. Extrusion blow-molding grades with melt flow rates below 0.5 g/10 min are not interchangeable with M6028 because their high melt strength is required for parison stability; M6028 does not provide sufficient melt strength for extrusion blow molding or large-part thermoforming. Within the same supplier series, numeric suffix changes correspond to differences in nominal melt flow rate and, in some grades, density; actual design values should be taken from the certificate of analysis rather than inferred from the grade number alone.

For cap and closure applications, HDPE M6028 is typically selected when a high cavitation count or thin-wall stack mold is used; a lower-flow HDPE may be selected when the cap requires improved hinge durability or ESCR. The choice is not based solely on MFR but on the balance of injection pressure, environmental stress crack resistance, and dimensional stability required by the part.