LyondellBasell HDPE H5220 is an injection-molding-grade high-density polyethylene supplied in pellet form. The resin is specified for thin-wall rigid packaging, closures, and high-speed injection-molding operations in which a high melt flow rate lowers filling pressure and shortens cycle time. Under ASTM D1238-23 at 190°C with a 2.16 kg load, the melt flow rate is reported as 52 g/10 min. Density by ASTM D1505 is reported as 0.952 g/cm³. The polymer is a linear ethylene resin with a narrow molecular weight distribution; this architecture determines the observed shear-thinning response and the processing restrictions that follow.

The published property profile places H5220 among high-flow HDPE grades rather than general-purpose injection or blow-molding resins. Tensile yield strength under ASTM D638 is reported at 26 MPa, elongation at break at 10%, flexural modulus under ASTM D790 at 1070 MPa, Shore D hardness under ASTM D2240 at 68, and Vicat softening temperature under ASTM D1525 at 124°C. The low elongation at break relative to high-molecular-weight HDPE indicates reduced plastic deformation before failure. That distinction matters when H5220 is substituted for a lower-melt-flow grade in latching hinges or cold-chain closures because the impact resistance of the finished article is governed by the same short-chain relaxation processes that lower the melt viscosity.

The melt flow rate of 52 g/10 min is far above the 0.2–0.7 g/10 min range common for blow-molding HDPE and above the 7–20 g/10 min range used in many general-purpose thin-wall injection grades. Consequently, H5220 is not interchangeable with blow-molding or sheet-extrusion polyethylene. Low melt strength leads to parison sag in blow molding and poor melt-fracture control in cast-film and sheet lines. In injection molding, however, the reduced viscosity permits short flow paths to be filled through restrictive gates at lower hydraulic pressure.

Why is H5220 specified for multi-cavity thin-wall molds instead of a general-purpose HDPE injection grade?

The principal selection driver is pressure drop. In a multi-cavity cold-runner tool with wall stock below 1.2 mm, the high melt flow rate reduces the hydraulic pressure required to fill the runner system and cavity. A processor running a 32-cavity tool can expect a shorter injection time than with a 20 g/10 min HDPE; however, published data for this specific configuration is limited, and the actual gain depends on gate diameter, runner balance, core deflection, and melt temperature. The lower melt viscosity also reduces shear heating during plastication, which can help maintain a lower melt temperature at the nozzle and reduce odour development in high-speed food-container production.

For a general-purpose polyolefin screw of 20:1 to 24:1 L/D, barrel settings from rear to front of 170–190°C, 180–200°C, 190–210°C, and nozzle 190–220°C provide a stable plastication range for H5220. Mold temperature should be kept between 10°C and 30°C for cold-runner tools; the upper portion of that range improves surface replication but can extend cycle time. In valve-gated hot-runner systems, manifold temperatures above 230°C are not recommended because extended residence time at elevated temperature can produce yellowing or black specks, particularly with long production stops.

The resin is not hygroscopic. Pre-drying is normally unnecessary when pellets are stored in sealed containers at ambient conditions. If storage humidity exceeds 60% relative humidity or if condensed moisture is visible, drying in a desiccant dryer at 80°C for 2 h removes surface moisture and reduces splay. Hopper magnets and screen packs should be inspected frequently because high-throughput regrind streams can introduce metallic fines that cause hot-runner gate wear.

The shear-viscosity curve of H5220 is typical of highly linear high-density polyethylene: a broad Newtonian plateau at shear rates below 10 s⁻¹ and a sharp shear-thinning transition above 100 s⁻¹. Cavity-filling analysis using a single melt flow rate value therefore does not capture the full pressure requirement. Mold simulation with Cross-WLF parameters is recommended for thin-wall tools below 0.8 mm. For short flow lengths, the high melt flow rate may reduce injection pressure by up to 30% relative to a 20 g/10 min HDPE; for longer flow lengths with a frozen layer, the benefit is smaller because conductive cooling limits flow advance.

Regulatory status and the boundary between a resin certification and finished-article compliance

Supplier documentation lists HDPE H5220 under FDA 21 CFR 177.1520 for olefin polymers in food-contact applications. That citation does not by itself clear a finished article; the converter must verify that any colour concentrates, processing aids, and levels of regrind conform to the intended conditions of use. For the European Union, compliance is assessed under Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm² for food-contact plastics. REACH obligations under Regulation (EC) No 1907/2006 apply, with Candidate List substances of very high concern limited to 0.1% w/w per article. Electrical and electronic applications require evaluation under Directive 2011/65/EU (RoHS). Packaging applications may also require heavy metal concentration limits under Directive 94/62/EC.

Regulatory statements apply to the base resin as supplied; they do not remove the need for migration testing on the finished part. If H5220 is used in a microwave or hot-fill container, the condition-of-use classification under FDA 21 CFR 177.1520 must be confirmed for the actual temperature and food simulant. Long-chain migration data for this specific high-flow HDPE in fatty food simulants is often not published in vendor bulletins; therefore, converters must generate data for the finished geometry.

When regrind content exceeds 40 wt% without adjustment to hold pressure

Regrind loading in high-speed thin-wall production is an operational boundary because the melt flow rate of post-industrial HDPE regrind can drift upward with repeated heat history. If a converter blends 40 wt% regrind into H5220 without reducing hold pressure or transfer position, overpacking can occur in flash-prone areas, especially around core pins and slide faces. The lower melt viscosity of regrind-rich blends also reduces the pressure drop through the runner, so cavity pressure may exceed the set point even when the screw transfer position remains unchanged. The recommended corrective action is to use cavity-pressure sensors and to reduce hold pressure in increments of 10–15 bar while monitoring part weight and sink depth. Batch-to-batch melt flow testing under ISO 1133-1:2022 is advised at the hopper for blends containing more than 20 wt% regrind, because density alone does not capture chain scission.

Molding shrinkage is anisotropic for this high-density polyethylene. Thin flat lids molded at a nominal wall of 1.0 mm frequently exhibit shrinkage in the flow direction of 1.5–2.0% and transverse shrinkage of 1.5–2.5% after 24 h at 23°C. Actual shrinkage varies with gate layout, packing pressure, and cooling time. For round containers with a central sprue, radial shrinkage may dominate and produce ovality if the core and cavity are not pre-distorted. Dimensional checks should be delayed by 24 h to allow post-molding crystallisation to stabilise.

Gate diameter should be at least 0.8 mm for a 1.0 mm wall; subgates below 0.5 mm can freeze prematurely and produce short shots even at the high melt flow rate. Land lengths should be kept under 1.0 mm to limit pressure loss. Tunnel gates are possible for high-cavitation closures, but gate locations should be placed away from visible surfaces because the low melt viscosity can generate jetting if the gate enters directly into a thick section.

Thin-wall dairy cups, margarine tubs, lids, overcaps, and general housewares represent the primary application field for H5220. In these tools, nominal wall thickness often ranges from 0.8 mm to 1.5 mm, and the part frequently contains a hinged area or a snap-fit lip. Tooling with a single-face cold runner or a valve-gated hot runner is typical. When multi-cavity molds exceed 16 cavities, runner balance becomes critical because the low melt viscosity has less self-correcting melt-front advancement than a higher-viscosity HDPE. Venting depth should be maintained at 0.015–0.025 mm on the parting line to prevent trapped air and short shots.

Compared with a medium-flow injection HDPE of 20 g/10 min, H5220 generally requires lower injection pressure and can fill a longer spiral-flow length at the same melt temperature. The trade-off is lower notched impact resistance and lower environmental stress crack resistance under ASTM D1693. It is therefore not specified for detergent bottle closures or fuel tank components that require long-term stress crack resistance under aggression from surface-active fluids. In applications with high impact at freezing temperature, a lower-MFR HDPE or an impact copolymer polypropylene may be selected instead.

The grade is not recommended for blow molding, blown film, or pipe extrusion because the melt strength is insufficient to maintain a stable parison or bubble. Prolonged outdoor exposure is outside the base resin’s designed use; continuous UV exposure requires a carbon black or stabilizer pre-compound. Strong oxidising acids, chlorinated solvents, and aromatic hydrocarbons can soften or stress-crack the polymer. Continuous service above 80°C may produce distortion, and steam sterilization at 121°C is outside the Vicat-based thermal boundary.

Low odour and taste are important for dairy packaging; however, the base resin does not contain an antioxidant package optimised for organoleptic performance unless specified by the supplier. Processors should avoid barrel residence times above 12 min and purge after production stops to prevent the formation of oxidised material. Head-space gas chromatography on finished articles is used to verify sensory limits.

On high-speed injection lines, H5220 is used for thin-wall lids and dairy cups with wall thickness below 1.0 mm. The high melt flow rate permits shorter injection-time segments than a lower-MFR HDPE, but cavity-to-cavity consistency is dominated by the check ring and cushion control. A cushion variation above 5 mm on a 48-cavity tool generally indicates check-ring leakage or regrind accumulation and produces part weight drift. In-mold labelling applications benefit from the fast fill and low viscosity, but static charge on polypropylene labels requires corona treatment or ionized air at the mold face to maintain label placement. Published data for this specific configuration is limited, and tool trials remain the final arbiter of cycle time, part weight stability, and dimensional repeatability.