LyondellBasell HDPE M6080WC is an injection-grade high-density polyethylene with a nominal melt flow rate of 8.0 g/10 min when measured at 190 °C/2.16 kg in accordance with ASTM D1238-20 and ISO 1133-1:2022. The nominal density is 0.960 g/cm³ when tested according to ASTM D1505 or ISO 1183-1:2019. The grade is supplied in pellet form and is specified for rigid packaging, caps, closures, housewares, and thin-wall technical moldings in which fast cycle time, high stiffness, and acceptable impact resistance are required. Typical property data from injection-molded specimens are summarized below; these values are not supply specifications and vary by lot, specimen preparation, and test laboratory.

The melt flow rate of 8.0 g/10 min positions the grade in the intermediate-flow segment of the LyondellBasell HDPE injection-molding portfolio. Compared with extrusion blow-molding or film grades, this product has a molecular weight distribution and rheology more suited to high-shear filling of multi-cavity tools. Melt flow rate and density are the primary release parameters on the certificate of analysis; mechanical property data are collated from standardized specimens but are not guaranteed for every molding geometry.

What processing window governs HDPE M6080WC in reciprocating-screw injection molding?

Injection molding of an 8.0 g/10 min HDPE grade typically uses a general-purpose polyolefin screw with an L/D ratio from 18:1 to 24:1 and a compression ratio from 2.0:1 to 3.0:1. Barrel settings from 200 °C to 250 °C from feed throat to nozzle are common; the feed throat should remain below 60 °C to prevent pellet bridging. The mold temperature is maintained between 10 °C and 30 °C to balance cycle time and surface finish. Injection pressure is adjusted to fill 95–98% of the cavity at transfer; holding pressure is then applied at 50–70% of injection pressure. Back pressure between 0.5 MPa and 1.5 MPa is used to maintain melt homogeneity without excessive shear heating. Screw surface speed should not exceed 0.3 m/s for this grade; higher speeds may increase shear heating and cause uncontrolled temperature rise. Hot-runner systems should be fitted with thermocouple control at each nozzle and set below 280 °C to avoid thermal degradation. On electric toggle presses, clamp force recommendations are typically 3.0–4.5 kN/cm² of projected area for thin-wall containers. Melt temperature should be verified with a needle pyrometer at the nozzle; melt temperatures above 260 °C do not improve mold filling and increase the formation of oxidative degradation products. Residence time should be controlled to the shortest interval that achieves uniform melt temperature; total residence time above 10 minutes at 250 °C is not recommended.

In thin-wall closure production, HDPE M6080WC is processed in high-cavitation molds where flow length-to-wall thickness ratios commonly exceed 150:1. The 8.0 g/10 min melt flow rate allows filling of 0.6–1.0 mm wall sections at injection velocities above 200 mm/s on hydraulic accumulator presses. The narrow molecular weight distribution reduces melt elasticity and die swell, which contributes to consistent part mass and lower dimensional variation in tamper-evident bands. However, because the grade has lower molecular weight than HDPE M6060, molded-in stress relaxation is faster, and closure side-wall cracking under stress-cracking agents may occur earlier if the part contains sharp corners or weld lines. Draft angles of 0.5–1.0° per side, gate vestige control, and radiused transitions help maintain strip torque and leak performance. Published data for specific closure designs with M6080WC is limited; design qualification requires application-specific testing.

Differences from HDPE M6060 and M6210 in injection molding

LyondellBasell M6060 is a lower-melt-flow grade with a nominal melt flow rate of 6.0 g/10 min and similar density; it provides higher notched Izod impact and environmental stress-crack resistance but demands higher injection pressure and longer cooling time. M6210 is a higher-melt-flow grade with a nominal melt flow rate of 19 g/10 min; it fills thin-wall geometries at lower pressure but trades tensile strength and impact resistance. M6080WC sits between these products: its 8.0 g/10 min melt flow rate reduces injection pressure by approximately 10–15% relative to M6060 in identical tooling, while retaining better stiffness than M6210. The specific additive package associated with the WC suffix may influence color acceptance and weatherability; converters should request the lot-specific certificate of analysis because additive concentration can shift melt flow rate by ±0.5 g/10 min and alter notched impact performance.

The grade is not intended as a direct substitute for extrusion blow-molding, film, or rotational-molding HDPE grades. The lower molecular weight distribution of M6080WC reduces melt strength and die swell, which is advantageous for injection mold filling but limits parison stability in blow molding. In applications requiring high environmental stress-crack resistance, a bimodal or high-molecular-weight HDPE grade should be evaluated instead.

When M6080WC replaces a lower-melt-flow grade in existing tooling

When M6080WC replaces HDPE M6060 in existing tooling, gate pressure and fill time should be revalidated rather than assumed linear. The lower melt viscosity of M6080WC, reflected in the higher melt flow rate, can reduce gate pressure by 10–15% and may allow a reduction in holding pressure of 5–10%; however, the same viscosity reduction can lower cushion stability in machines with worn check rings, leading to shot weight variation above 0.3%. If the tool has hot runners sized for 6.0 g/10 min material, the higher flow may cause premature cavity filling at the same screw velocity, producing flash in vents exceeding 0.02 mm depth. Conversely, in cold-runner tools with long flow paths, the improvement in shear-thinning behavior is less pronounced and should not be used to justify removing mold release or decreasing draft. The lower molecular weight of M6080WC may also reduce weld-line strength by 10–20% relative to M6060 in unreinforced applications; notched Izod impact testing according to ASTM D256-23 is recommended on weld-line specimens before substitution.

Regulatory compliance is governed by thermoplastic olefin food-contact standards.

HDPE M6080WC, like other high-density polyethylene grades, is eligible for food-contact use in the United States under 21 CFR 177.1520 when the polymer meets the prescribed density and extractables limits and when the finished article meets end-use limitations. In the European Union, compliance must be evaluated under Regulation (EU) No 10/2011 and its amendments, including overall migration limits of 10 mg/dm² and specific migration limits for additives. The supplier’s compliance statement, not generic statements, governs a given lot. Under REACH Regulation (EC) No 1907/2006, the grade must be supplied with a safety data sheet indicating any substances of very high concern above 0.1% w/w; typical polyethylene grades do not require SVHC declaration. Heavy metals and restricted phthalates are not expected; however, RoHS Directive 2011/65/EU applicability depends on the finished electrical or electronic component, not the polymer resin alone. No ISO 10993 or USP Class VI claim applies to this industrial grade unless explicitly certified.

Operational boundaries for HDPE M6080WC are most often exceeded during color change or start-up. If pellets are stored below 10 °C and moved into a warm plant, surface condensation can raise moisture above 0.05 wt%, producing splay and poor gate appearance. Drying in a desiccant dryer at 80 °C for 2 h is recommended under these conditions. Avoid blending with polypropylene or low-density polyethylene at levels above 5 wt% without technical review; incompatible blends reduce notched Izod impact and create delamination in multi-layer parts. The grade should not be exposed to prolonged outdoor weathering without adequate UV stabilizer addition; unstabilized HDPE undergoes chain scission and embrittlement. Contact with strong oxidizing agents, chlorinated solvents, or aromatic hydrocarbons can degrade surface finish and mechanical properties. In stress-cracking environments involving nonylphenol ethoxylates, mineral oils, or specific surfactants, molded-in stress must be reduced by annealing at 80–90 °C for 2 h or by increasing radii. Published data for specific stress-cracking resistance of M6080WC is limited; users should conduct ESCR testing per ASTM D1693 or ISO 22088-3 under the actual chemical environment.