LyondellBasell HDPE H5650 is a high-density polyethylene injection-moulding grade supplied in pellet form and intended for rigid packaging applications such as industrial pails, stackable crates, tote bins, and structural closures. The manufacturer’s published data characterises the material by a melt flow rate of 5.0 g/10 min at 190 °C under a 2.16 kg load according to ISO 1133-1:2022, and by a density of 0.956 g/cm³ according to ISO 1183-1:2019. These values are typical datasheet values, not contractual specification limits unless separately agreed with the supplier. The grade is therefore not a direct substitute for extrusion blow-moulding or film HDPE grades, which are normally designed with lower melt flow rates to maintain parison melt strength or film bubble stability.

Routine drying of H5650 is not required under normal handling conditions. Surface condensation can occur when cold pellets are moved into a high-humidity processing hall, particularly at relative humidities above 60 %. If splay or silver streaks appear in moulded parts, a hot-air drying step at 70 °C to 80 °C for 2 h to 4 h is sufficient. Prolonged drying at higher temperatures is unnecessary and may cause pellet sticking in hopper dryers.

Does the Melt Flow Rate of H5650 Create a Thin-Wall Moulding Advantage?

At 5.0 g/10 min, H5650 occupies the medium-flow segment of high-density polyethylene. The melt flow rate is high enough to reduce injection pressure in thin-walled industrial packaging, but not so high that molecular weight is sacrificed to the level observed in 20 g/10 min to 80 g/10 min thin-wall grades. A moulded crate or pail with wall sections of 1.5 mm to 3.0 mm can typically be filled on clamping units of 1,500 kN to 5,000 kN without requiring extreme melt temperatures.

Barrel setpoints for a general-purpose screw with L/D of 20:1 to 24:1 and a compression ratio of 2.0:1 to 2.5:1 generally range from 180 °C at the feed zone to 220 °C at the metering zone. The nozzle should be held between 210 °C and 240 °C. Mould surface temperature directly affects surface gloss, weld-line strength, and cycle time; a range of 10 °C to 40 °C is used, with the lower band favouring shorter cycle times and the upper band improving appearance and knit-line impact resistance. Holding pressure is commonly set at 40 MPa to 80 MPa, while back pressure is limited to 0.5 MPa to 1.5 MPa to avoid excessive shear heating. Although high-density polyethylene is shear-thinning, melt temperature should not be used as the primary means to improve flow. Temperatures above 260 °C and residence times beyond 5 min can reduce notched impact resistance and produce discolouration.

Cooling time is usually the limiting factor in pails and crates. The cooling phase increases approximately with the square of wall thickness. At constant mould temperature, an increase from 2.0 mm to 2.5 mm can raise cooling time by roughly 40 % to 60 %. Ejection temperatures for HDPE are generally maintained between 60 °C and 80 °C to avoid distortion and sink marks. If parts are ejected hotter, dimensional stability can fall outside the tolerance bands required for lid or closure fitments.

Spiral flow data obtained under ASTM D3123 can be used for comparative tool design, but spiral-flow length depends on injection speed, melt temperature, and mould temperature. A medium-flow HDPE of this class typically produces a spiral flow length between 30 cm and 40 cm at 230 °C and 80 MPa. Published spiral-flow data specific to H5650 should be requested from the supplier rather than estimated from grade-class averages.

The following table summarises typical characterisation data reported for the grade. The values are not design minima; users should obtain the current certificate of analysis and the supplier’s specification for critical products.

The tensile yield stress and flexural modulus in Table 1 are consistent with a density of 0.956 g/cm³. These properties are influenced by moulding conditions. Rapid cooling at a mould temperature of 20 °C reduces crystallinity relative to slow cooling and can lower the density of a moulded skin by roughly 0.001 g/cm³ to 0.003 g/cm³, with a corresponding small decrease in modulus. For critical top-load specifications, measurements should be made on moulded parts or plaques under ISO 527-2:2012 and ISO 178:2019 rather than on annealed laboratory specimens. Lot-to-lot control should include melt flow rate by ISO 1133-1:2022 and density by ISO 1183-1:2019, because even a variation of 0.5 g/10 min in melt flow rate can alter injection pressure and cycle time in thin sections.

Processors blending H5650 with post-industrial regrind should limit regrind addition to 20 % to 30 % unless the application accepts reduced impact strength and increased warpage. Higher regrind ratios increase the risk of black specks and viscosity shift because the material has undergone one or more heat histories. The practical upper limit depends on regrind particle size, contamination level, and the mechanical requirements of the moulded part.

The comparison table below positions H5650 relative to common high-density polyethylene flow classes used in industrial packaging. The classifications are process-family generalisations and do not replace grade-specific comparative data.

The two comparison lines show the central trade-offs. A low-melt-flow HDPE with high environmental stress crack resistance often cannot be injection moulded at the same wall thickness and cycle time. A high-flow grade may fill thinner sections but may fail to retain top-load stiffness and stress-crack resistance. H5650 is selected where the part is thick enough for a medium-flow grade but complex enough to require better mould filling than a blow-moulding resin.

When H5650 Replaces a Low-Melt-Flow HDPE in Crates and Pails

The substitution of a fractional-melt HDPE with H5650 requires adjustment of tooling and processing parameters. Because H5650 has a higher melt flow rate, injection pressure for an identical fill time typically decreases, and the packing phase may be shortened because the gate freezes earlier. However, the same property reduces melt strength, so wall-thickness distribution in complex parts may become more sensitive to gate location and flow balance. In direct comparisons, the lower molecular-weight tail of the medium-flow grade reduces slow crack growth resistance under sustained load with aggressive fluids. A crate continuously exposed to detergent, oil, or agricultural chemicals should therefore be tested under ASTM D1693 condition B or ISO 16770 to confirm adequate environmental stress crack resistance. Published data for this specific configuration is limited; users should request supplier data for the intended chemical environment.

When replacing a low-flow grade in an existing tool, screw recovery speed and back pressure may need to be reduced to prevent over-shearing. The cushion size should be maintained at 5 mm to 10 mm to ensure stable holding pressure. Cooling time may be shorter than that of a fractional-melt HDPE because the lower molecular weight can permit ejection at a slightly lower temperature without excessive warpage. These effects are process-dependent and should not be treated as fixed reductions. Direct cycle-time comparisons specific to H5650 should be qualified on the production line rather than extrapolated from melt flow rate alone.

Differences with polypropylene impact copolymers are relevant for packaging engineers. H5650 has lower density and generally better environmental stress crack resistance in many detergent and oil-based environments, but polypropylene impact copolymers provide higher flexural modulus at elevated temperatures and better shape retention in hot-fill or dishwasher applications. For outdoor crates exposed to UV, both polymer classes require stabilisation. Unstabilised HDPE loses surface gloss and develops surface cracks more readily than stabilised grades under ISO 4892-2 weathering conditions.

Typical application routes include pails from 5 L to 25 L, stack/nest crates, tote bins, and large-diameter industrial closures. In pail moulding, central gates or hot-runner sequences are used to avoid weld lines near the handle region. Drop-impact testing of filled pails should follow ASTM D2463 or ISO 2248 at the intended service temperature. Low-temperature drop tests at -20 °C are recommended for freezer or cold-warehouse distribution. For closures, dimensional tolerance after moulding is controlled by shrinkage of 1.5 % to 2.5 %, depending on wall thickness and packing pressure. Tool designers should verify shrinkage anisotropy with ISO 294-4 or ASTM D955 before cutting steel.

For food-contact packaging, compliance must be verified under FDA 21 CFR 177.1520 in the United States and under Commission Regulation (EU) No 10/2011 in the European Union, including migration testing according to EN 1186-1:2002. The base resin does not confer automatic compliance for finished articles; colorants and processing aids must also be authorised. The grade is subject to REACH, and downstream users must confirm that no substance of very high concern is introduced at article level. For toys, the finished article must meet the relevant parts of EN 71 or ASTM F963, where applicable.

The material should not be specified for pressurised pipe, gas distribution, or hot-water service. PE100 pipe grades with bimodal high-density copolymers and hydrostatic testing under ISO 4427 are required for such applications. H5650 is also unsuited to prolonged immersion in strong oxidising acids, chlorinated solvents, or hot water above 80 °C because oxidative degradation and environmental stress cracking may occur. When outdoor service is required, a UV-stabilised package must be selected and validated by accelerated weathering under ISO 4892-2 or ASTM D2565; unstabilised material is not recommended for continuous outdoor exposure.