LyondellBasell HDPE M5562

LyondellBasell HDPE M5562 is supplied as a pelletized high-density polyethylene for injection-molding applications requiring a nominal density of 0.956 g/cm³ and a nominal melt flow rate of 6.2 g/10 min at 190 °C under 2.16 kg. The density is determined by ASTM D1505; the melt flow rate is determined by ASTM D1238. This combination places the material in the medium-flow HDPE segment, where moderate molecular weight reduces injection pressure while the high density provides flexural stiffness. The resin is used in crates, totes, trays, thin-wall pails, caps, and housewares, but the final part design must account for the lower melt strength and lower environmental stress-crack resistance that accompany a higher-melt-flow injection grade.

For batch evaluation, the certificate of analysis should be checked against the current grade specification because typical values are not absolute limits. The resin is supplied with an antioxidant stabilization package intended for normal injection-molding heat histories. Any later addition of color masterbatch, nucleating agents, or regrind can shift crystallization behavior, melt flow, and impact response; therefore, the final compound should be characterized on molded specimens rather than inferred from neat resin data.

Specification Profile Under ASTM D1238, D1505, and D638

These values are generated on standard test specimens and should not be read as direct part-performance predictions. The tensile yield and flexural modulus indicate a stiff, crystalline HDPE rather than a flexible LLDPE or LDPE. The 0.956 g/cm³ density reflects a relatively high crystalline fraction after standard cooling, and the 1,310 MPa flexural modulus is generally above blow-molding HDPE grades of lower density. The notched Izod value is a laboratory crack-initiation measurement; it does not predict the drop-impact resistance of a finished container, which is controlled by wall thickness, weld lines, gate location, and molded-in residual stress.

Processing behavior cannot be inferred from 6.2 g/10 min alone because the melt flow rate is measured at low shear. Capillary rheometry at 190 °C and shear rates between 100 s⁻¹ and 1,000 s⁻¹ shows that HDPE injection grades exhibit pseudoplastic viscosity reduction; the reduction is less pronounced in narrow-molecular-weight resins than in broad-molecular-weight blow-molding grades. Mold-filling simulations for thin-wall containers should use an experimentally derived viscosity model, such as a Cross-WLF fit, rather than a single MFR point.

What separates a 6.2 g/10 min injection grade from extrusion HDPE?

Pipe and extrusion blow-molding HDPE grades typically exhibit melt flow rates of 0.2 g/10 min to 1.0 g/10 min under 190 °C/2.16 kg. The higher melt flow rate of M5562 lowers melt viscosity at processing shear rates, which reduces fill pressure and allows longer flow in multi-cavity molds. The trade-off is a reduction in extrudate melt strength and higher susceptibility to drawdown; M5562 is not suitable for continuous parison blow molding or large-part extrusion where melt strength controls wall uniformity. The density of 0.956 g/cm³ also places M5562 above many general-purpose blow-molding grades, yielding higher flexural modulus but lower intrinsic impact absorption.

Compared with a lower-flow injection grade such as a nominal 3.5 g/10 min HDPE, M5562 generally allows shorter fill times and lower hydraulic pressure at the same part weight. However, the molecular weight difference may reduce notched Izod and environmental stress-crack resistance. Published grade-specific ESCR data under ASTM D1693 Condition B is limited for this product; detergent, oil, or agricultural chemical containers should be validated by finished-part exposure, not by generic resin selection.

Within the LyondellBasell injection-molding slate, a relevant benchmark is the lower-flow HDPE grade M5350, historically described with nominal density 0.953 g/cm³ and nominal melt flow rate 5.0 g/10 min. The difference of 0.003 g/cm³ in density and 1.2 g/10 min in melt flow means that M5562 will typically fill thin sections at slightly lower pressure but can exhibit higher injection-molded shrinkage because of higher crystallinity. The exact property difference should be read from the current data sheets for the grades being compared, not from historical values alone.

Compared with polypropylene, M5562 has lower continuous heat deflection: its 78 °C DTUL at 0.455 MPa under ASTM D648 is lower than typical PP homopolymer values often above 100 °C. Polypropylene also provides better flexural fatigue resistance, but M5562 offers better low-temperature ductility and lower density. The choice in thin-wall packaging is therefore governed by stacking temperature, cold storage, and chemical compatibility.

On production-scale reciprocating-screw injection machines with 20:1 to 24:1 L/D general-purpose screws, a barrel profile of 180 °C at the feed zone, 190 °C to 210 °C in the middle zones, and 210 °C to 220 °C at the nozzle is commonly used for M5562. Nozzle melt temperature should be held between 200 °C and 230 °C; prolonged residence above 250 °C causes chain scission, increases melt flow rate, and can produce yellowing or silver streaks. Coolant temperature is maintained at 10 °C to 30 °C. Higher mold temperatures may improve weld-line strength but increase cycle time and differential shrinkage.

At high screw speeds above 0.3 m/s peripheral velocity or plasticating back pressure above 15 bar, melt temperature can increase beyond the set barrel temperature because of viscous dissipation. Therefore, barrel setpoints above 220 °C can produce actual melt temperatures near 250 °C in extended high-speed cycles; the nozzle melt temperature should be checked with a pyrometer rather than inferred from machine setpoints.

Pre-drying is not normally required for virgin HDPE stored below 60% relative humidity. If pellets are exposed to wet conditions or high levels of dusty regrind are added, a hot-air dryer at 80 °C for 1 h to 2 h removes surface moisture. Barrel decompression and screw-back settings should be minimized to avoid air entrapment and melt feed variations.

When wall thickness falls below 1.5 mm, flow length becomes the controlling variable

Thin-wall containers molded from M5562 at nominal wall thickness of 0.8 mm to 1.2 mm require high injection velocity and well-balanced hot-runner or cold-runner channels. Because the material freezes quickly in cold molds, gate freeze-off can halt packing before the part reaches full crystallization shrinkage compensation. Short gates with diameter below 0.8 mm may freeze before sufficient hold pressure is applied, producing sink marks and dimensional variation. Molders often increase gate thickness to 1.0 mm to 1.5 mm for parts in this wall range and use multiple gates to keep flow paths within the pressure capability of the selected injection unit.

Inadequate venting of thin-wall cavities can cause burn marks on flow fronts and pressure loss; vents should be provided at the end of fill and at weld lines, with land lengths of 0.02 mm to 0.03 mm and widths appropriate for the cavity perimeter. Vacuum venting may be required for very fast cycles. For thin-wall pails and trays, cavity-pressure sensors should be used to set velocity-to-pressure switchover and to maintain cavity pressure during packing between 300 bar and 500 bar, depending on part geometry.

Linear mold shrinkage for M5562 is typically in the range 0.018 mm/mm to 0.025 mm/mm when measured after 24 h on standard injection-molded plaques. Shrinkage is anisotropic: flow-direction shrinkage is often lower than transverse shrinkage because of molecular orientation, while thicker sections shrink more than thin sections. Differential cooling between the mold surfaces causes warpage in flat lids and trays. Uniform wall thickness, balanced gates, and adequate hold time reduce warpage. Use of regrind above 20 wt% can alter the molecular weight distribution and increase shrinkage variability; for critical dimensions, regrind content should be kept below 15 wt% unless process capability data demonstrate otherwise.

Thermal Oxidative Degradation Boundaries in HDPE M5562 Processing

The thermal stability of HDPE M5562 is governed by the antioxidant package added during pelletization. In normal injection molding, the melt can be processed at 200 °C to 230 °C without measurable viscosity shift. Start-up after shutdown should follow a purging procedure with a compatible polyethylene or a commercial purging compound; idle times above 10 min at melt temperature can initiate oxidation, especially at hot-runner tips and screw surfaces. Repeated recycling of hot-runner scrap or sprues at 100% regrind can increase the melt flow rate and lower notched Izod; the magnitude depends on the number of heat histories and should be measured by ASTM D1238 and ASTM D256 on molded specimens.

Combustion of HDPE releases carbon monoxide, carbon dioxide, and incompletely oxidized hydrocarbons; processing should maintain melt temperatures below 260 °C to minimize degradation products. The resin should not be mixed with amine-based additives or strongly oxidizing agents that may interfere with the stabilizer package. Contact with copper or brass tooling at high temperature may accelerate oxidation; steel molds and machine surfaces are preferred.

Whether M5562 satisfies 21 CFR 177.1520 depends on grade-specific clearance

As an unfilled high-density polyethylene, HDPE M5562 falls within the scope of FDA 21 CFR 177.1520 for olefin polymers. This regulation permits the use of olefin polymers in contact with food only when the resin meets specified density, extractables, and end-use limitations for the relevant food type and temperature condition. A grade-specific food-contact letter from LyondellBasell must be obtained for each lot or formulation; the base resin designation alone does not establish compliance. For EU applications, migration testing under EU Regulation 10/2011 is required on the finished article, particularly for fatty foods and for repeated-use packaging.

For nonfood articles covered by the RoHS Directive 2011/65/EU, an unfilled HDPE without heavy-metal pigments is not expected to exceed the 0.1 wt% homogeneous material threshold for lead, mercury, hexavalent chromium, PBBs, or PBDEs or the 0.01 wt% limit for cadmium. However, color masterbatches, regrind, and processing aids must be separately verified. REACH SVHC screening is required at the article level because the base resin does not address substances introduced by converters.

In returnable distribution trays and pails, M5562 is commonly selected for the balance of top-load stiffness and injection cycle time. The 1,310 MPa flexural modulus under ASTM D790 supports stack load in dry ambient conditions, but sustained loading above 45 °C under high humidity should be evaluated by creep testing because the 78 °C DTUL at 0.455 MPa is a short-term thermal property and does not predict long-term deflection. For detergent and agricultural chemical packaging, stress-crack resistance is the limiting variable; finished containers should be tested under ASTM D1693 Condition B or ASTM D2561 with the intended chemical agent, because high-flow injection HDPE grades may not match the ESCR of high-molecular-weight blow-molding grades. For cold-chain use, drop testing at -20 °C or -40 °C on the finished part is necessary because notched Izod does not represent full-container impact response.