LyondellBasell HDPE L5800I is a high-flow, high-density polyethylene injection molding resin supplied as a narrow-molecular-weight-distribution grade. The melt mass-flow rate is specified at 80 g/10 min under ISO 1133-1, equivalent to ASTM D1238, at 190 °C with a 2.16 kg load. Density is specified at 0.953 g/cm³ under ISO 1183-1 or ASTM D1505. The material is selected for thin-wall packaging, closures, housewares, and rigid consumer articles where high injection speed, low residual stress, and short cooling time are dominant process requirements. The L5800I designation separates the grade from lower-flow HDPE resins used in extrusion blow molding, sheet extrusion, and moderate-flow injection molding.

At the molecular level, the 80 g/10 min melt mass-flow rate corresponds to a lower weight-average molecular weight and a narrower molecular weight distribution than is typical of HDPE grades with melt flow rates below 10 g/10 min. This architecture reduces chain entanglement and lowers zero-shear viscosity, but it also reduces tie-chain concentration. The result is a stiffness–toughness balance shifted toward stiffness: tensile stress at yield is reported at 26.2 MPa under ISO 527-2 or ASTM D638, flexural modulus at 1,380 MPa under ISO 178 or ASTM D790, and notched Izod impact at 21 J/m under ASTM D256 at 23 °C. Reported tensile strain at break is 10% under ISO 527-2. Vicat softening point A50 is 127 °C under ISO 306 or ASTM D1525. The density of 0.953 g/cm³ corresponds to a crystalline fraction in the range of 60–70% as measured by differential scanning calorimetry under ISO 11357-3, using 293 J/g as the heat of fusion reference for fully crystalline polyethylene. Because the high melt flow rate reduces molecular weight, environmental stress-crack resistance and notched impact are expected to be lower than those of high-molecular-weight HDPE; comparison data should be obtained from ASTM D1693 or ISO 22088-3 when stress cracking is a concern.

How Does L5800I Compare With Lower-Melt-Flow HDPE Resins?

Compared with intermediate-flow HDPE injection grades in the 10–40 g/10 min range, L5800I reduces injection pressure and improves filling of thin sections, but sacrifices environmental stress-crack resistance and notched impact. In closure applications where fatty acids, surfactants, or aggressive liquid formulations are packaged, lower-flow HDPE grades or molecularly bimodal resins with melt mass-flow rates below 20 g/10 min are usually evaluated before L5800I. Extrusion blow molding HDPE grades with melt flow rates of 0.2–0.8 g/10 min are not direct substitutes in injection molding because their higher molecular weight and melt elasticity increase injection pressure, can produce jetting, and may require higher clamp force.

Within the Alathon L-series, the 80 g/10 min melt mass-flow rate of L5800I is positioned above intermediate-flow injection grades that are typically cited at 20–40 g/10 min; however, exact grade comparison must be confirmed against the current manufacturer data sheet because nomenclature and specifications are subject to revision. High-density polyethylene grades with comparable melt flow but lower density, such as ethylene-butene or ethylene-hexene copolymers, can exhibit lower flexural modulus and higher impact. L5800I, specified at 1,380 MPa flexural modulus, is positioned among the stiffer high-flow HDPE grades. Lower comonomer content commonly reduces environmental stress-crack resistance relative to high-flow copolymer HDPE. For dairy closures requiring hinge flexibility, a high-flow HDPE copolymer or a bimodal high-flow grade may be selected instead. For disposable thin-wall containers where stiffness and stacking strength dominate, the denser, stiffer architecture of L5800I is more suitable.

Production-scale injection molding of L5800I is typically performed on reciprocating-screw machines with L/D ratios from 20:1 to 25:1 and compression ratios between 2.5:1 and 3.5:1. The resin is not hygroscopic; predrying is not mandatory when storage is dry and ambient relative humidity remains below 60%. Condensation on cold pellets, however, can produce surface splay and must be eliminated. If predrying is needed, a desiccant dryer set to 80 °C for 1–2 h with a dew point below −20 °C is sufficient.

Melt temperature is maintained between 200 °C and 260 °C, with a preferred processing window of 220–240 °C. Barrel zones are typically profiled from 180–200 °C at the feed throat to 220–240 °C at the metering zone, with nozzle setpoints between 220 °C and 250 °C. Sustained melt temperatures above 280 °C increase oxidative degradation risk and can shift the melt flow rate. Mold temperature is generally held at 20–40 °C to accelerate crystallization and shorten cycle time; increasing mold temperature up to 60 °C can improve surface gloss and reduce flow lines but increases cooling time and may enlarge post-mold shrinkage. Back pressure is limited to 0.5–1.5 MPa. Injection speed is set high enough to fill before gate freeze-off, but excessive velocity can produce gate blush or melt fracture at hot runner gates. Cavity pressure is commonly held below 60 MPa after switchover; clamp force is calculated from total projected area and the expected cavity pressure rather than from shot volume.

Shot size should be maintained between 30% and 70% of barrel capacity to avoid excessive residence time. Total melt residence time is preferably below 5 min at melt temperatures above 240 °C; longer times can shift the melt flow rate and increase gel formation. A non-return valve in good condition is necessary because high-flow HDPE can exhibit leakage at low back pressure and affect shot weight consistency. Regrind content up to 20 wt% is used in many non-appearance injection molding operations; higher levels may shift the melt flow rate and reduce notched impact. Masterbatch carriers should have melt flow rates of at least 20 g/10 min to minimize localized flow variation in thin-wall sections. Weld-line strength in high-flow HDPE can be lower than in lower-melt-flow HDPE; gate location and melt front convergence must be managed in part design, particularly for snap-fit features.

Property Data and Test Method Alignment

The tabulated values are representative data from the manufacturer’s published injection molding grade information and are not release limits. Results on production parts may differ because of pigment package, regrind content, and processing history.

Because HDPE is a semi-crystalline polymer, the mechanical values in the table are not intrinsic constants. Test speed, specimen thickness, and molding orientation shift the results. Notched Izod values are sensitive to gate location and weld-line position; specimens cut from oriented regions may show higher or lower values. Mold shrinkage for unfilled HDPE in this density class is typically 1.5–2.5%, but the value must be established on the tool and for the specific gate and cooling layout. No single datasheet value is sufficient for tool steel allowance.

When Thin-Wall Injection Molding Demands Short Fill Times and Reduced Clamp Pressure

Thin-wall containers with nominal wall thickness below 0.5 mm impose a severe pressure-drop requirement. L5800I at 80 g/10 min melt mass-flow rate permits filling flow-length-to-wall-thickness ratios approaching 200:1 at lower injection pressure than a 20 g/10 min HDPE under the same tool geometry. Hot-runner systems with valve gates and small nozzle tips benefit from the lower viscosity, but gate diameter should not be reduced below 0.8 mm without filling simulation because gate freeze-off occurs rapidly in high-melt-flow HDPE. Hold pressure after filling is typically maintained at 30–50 MPa until gate freeze-off to limit sink marks; however, extended hold time increases residence time at melt temperature and can reduce impact retention.

Fill time in thin-wall applications is often below 0.5 s, and the velocity profile is ramped to prevent pressure spikes. Cavity pressure sensors are used for switchover from velocity to pressure control at 95–98% of part volume, rather than by screw position alone. This practice reduces flash and improves shot-to-shot consistency in high-flow HDPE. Multi-cavity tools with 32 and 64 cavities have been used for high-flow HDPE closures and thin-wall containers; published data for L5800I in every tool configuration is limited, and process capability should be verified by mold-flow simulation and first-article inspection. Asymmetric cooling can cause warpage in flat lids because high-density polyethylene crystallizes rapidly and shrinks anisotropically. Mold cooling circuits should be operated in turbulent flow; a Reynolds number above 10,000 is the standard design target to maximize heat removal and minimize mold temperature variation.

Melt Rheology and Crystallization Rate Distinctions

The melt rheology of L5800I is pseudoplastic. The high melt mass-flow rate under 2.16 kg does not imply Newtonian behavior under injection molding shear rates. At shear rates in the range of 10³–10⁵ s⁻¹, the viscosity of high-flow HDPE is significantly lower than at the 2.16 kg melt flow condition; however, the exact shear viscosity for L5800I should be measured by capillary rheometry according to ISO 11443 before constructing flow simulation models. The manufacturer data sheet does not publish full Power Law constants. Published data for this specific configuration is limited.

The narrow molecular weight distribution reduces shear-thinning relative to broad-molecular-weight-distribution high-density polyethylene, so the advantage in low-shear flow may be less pronounced at very high shear rates. Crystallization is rapid; the density of 0.953 g/cm³ and the narrow molecular weight distribution support a short cooling time but also produce higher shrinkage anisotropy than lower-density polyethylenes. The differential scanning calorimetry trace under ISO 11357-3 shows a narrow crystallization exotherm, which is expected for a high-flow HDPE grade. This thermal behavior shortens cooling time but requires careful mold-temperature control to avoid differential shrinkage and warpage.

For food-contact applications in the United States, the base resin is represented as complying with 21 CFR 177.1520(c) for olefin polymers when the finished article is used under conditions specified in the regulation. In the European Union, compliance is typically addressed under Regulation (EU) No 10/2011 and its amendments; finished-article migration testing is performed according to EN 1186-1 or equivalent. The grade is manufactured under an ISO 9001-aligned quality system. REACH registration for the substance is applicable in the European Economic Area. Unfilled HDPE formulations generally satisfy RoHS 2011/65/EU heavy-metal restrictions, but converters must confirm with the supplier for each pigment package.

The material is not inherently UV-stabilized for outdoor exposure; long-term weathering requires an appropriate UV stabilizer package or carbon black content of 2–3 wt% for opaque applications. Unfilled HDPE typically carries a UL 94 HB rating at a thickness of 1.5 mm or greater; the final article must be tested at the end-use thickness because the rating is thickness-dependent. Sustained contact with strong oxidizing acids, aromatic hydrocarbons, or halogenated solvents is outside the normal service envelope and must be validated by ASTM D543 immersion testing. Continuous load-bearing use above 80 °C reduces mechanical stiffness and accelerates creep; stress-cracking susceptibility must be evaluated under ISO 22088 when surface-active chemicals or mineral oils are present. Avoid combination with metal stearates that are not thermally stabilized at processing temperatures above 240 °C; additive-related degradation can produce localized discoloration. The HDPE should not be stored in direct contact with copper or copper alloys at elevated processing temperatures because copper ions can catalyze oxidative chain scission.