LyondellBasell HDPE 50-0350 is a high-molecular-weight high-density polyethylene homopolymer intended for extrusion blow moulding and heavy-gauge sheet extrusion. The grade carries a nominal melt flow rate of 0.35 g/10 min at 190 °C/2.16 kg per ASTM D1238 and a nominal density of 0.950 g/cm³ per ASTM D1505. The product is stabilised for conventional melt processing and is not formulated with fillers or nucleating agents. All numerical values in this document are typical published values and are not contractual sales specifications.

How Does the Molecular Architecture of 50-0350 Affect Parison Sag and Stress Crack Resistance?

The broad molecular weight distribution of 50-0350 increases melt elasticity and elongational viscosity, which controls parison sag during interrupted extrusion blow moulding. On shuttle-type blow moulders, the parison hang time for a 25 L container body is typically shorter than for a narrow-MWD HDPE of equivalent melt flow rate. The high-molecular-weight fraction contributes strain-hardening behaviour that resists length extension and diameter reduction before mould closure. In slow crack growth testing under ASTM D1693, Condition B, using 100 % Igepal CO-630, typical F50 values above 600 h are reported. These results are sensitive to specimen thickness, notch depth, cooling rate and moulded-in stress; compression-moulded test plaques do not fully represent blow-moulded part performance.

Extrusion blow moulding of 50-0350 is typically operated at melt temperatures between 180 °C and 220 °C. On a 65 mm grooved-barrel extruder with an L/D of 24:1, a compression ratio of 2.5:1 to 3.0:1 and a Maddock mixing section are used to homogenise the melt. Parison die gaps of 1.0 mm to 2.5 mm are common for shot weights up to 5 kg. Narrower die gaps increase shear rate and may trigger melt fracture when the die land temperature is below 190 °C. Mould temperatures of 10 °C to 30 °C are employed for rapid cooling; higher temperatures reduce warpage in thick-walled portions. Blow air pressure is normally set between 0.6 MPa and 1.0 MPa. Insufficient air pressure produces poor pinch-off definition at seam areas. Screw speed is adjusted to keep extruder head pressure below 35 MPa; sustained operation above this value increases shear heating and gel formation. Pre-drying at 80 °C for 2 h in a desiccant hopper dryer is recommended when storage relative humidity exceeds 60 % or when surface moisture causes splay. Published data for this specific equipment configuration is limited beyond general processing guidelines.

The following property profile is used for preliminary material selection and should not replace production lot certification.

Heavy-gauge sheet extrusion of 50-0350 is performed on a barrier screw with 30:1 L/D, melt temperatures between 200 °C and 230 °C, and roll stack temperatures of 60 °C to 90 °C. Because the high molecular weight of the grade increases extruder back-pressure, a screen pack of 40/60/80 mesh and a gear pump are used to stabilise output and isolate downstream pressure fluctuations. The thermoforming window is broad, but radiant heating must be controlled to avoid surface blistering above 180 °C. Formed parts retain higher residual stress than amorphous thermoplastics; chemical stress crack testing should be performed under ASTM D1693 or a notched constant tensile load method such as ISO 16770. The grade is not optimised for cast film or oriented film processes because its viscosity and melt strength exceed the typical operating limits of narrow-gap film dies. Published data for specific heating profiles is limited.

When 50-0350 Replaces a 0.944 g/cm³ HDPE in Industrial Packaging

When a converter considers replacement of a 0.944 g/cm³ HDPE by 50-0350 in a blow-moulded industrial container, the density increase from 0.944 g/cm³ to 0.950 g/cm³ raises flexural modulus from roughly 900–1,000 MPa to a typical 1,100 MPa. This stiffness gain may permit wall thickness reduction if the part is top-load limited, but the exact reduction must be calculated from part geometry and compression strength requirements. The same density increase reduces slow crack growth resistance relative to lower-density copolymers. In detergent, agricultural chemical and surfactant packaging, field cracking is often attributed to environmental stress cracking rather than insufficient stiffness; in such cases a lower-density or medium-density grade with ESCR above 1,000 h may be preferred. If stack load and deformation control dominate, 50-0350 is selected. For chemicals with high stress-cracking potential, converters may blend 50-0350 with a lower-density HDPE to balance stiffness and ESCR; published compounding data for specific blend ratios is limited.

Relative to a 0.30 g/10 min HMW-HDPE used for large fuel tank shells, 50-0350 has a slightly higher melt flow rate and lower molecular weight, which reduces extruder head pressure and permits higher output on a 90 mm single-screw extruder. Its parison sag resistance is lower than that of a 0.20 g/10 min HMW-HDPE, limiting very large parisons with long hang times. Compared with a 0.7 g/10 min blow moulding HDPE, 50-0350 requires higher melt temperature or higher head pressure to achieve equivalent output, but it produces fewer weld-line failures and better pinch-off strength. The density of 0.950 g/cm³ distinguishes 50-0350 from 0.960 g/cm³ HDPE used in thin-wall bottles where oxygen and hydrocarbon vapour permeation resistance is critical. The lower density of 50-0350 provides a modest improvement in ESCR at the expense of slightly higher permeability. Comparative oxygen transmission rate testing is performed under ASTM D3985; published data for this specific configuration is limited.

The grade is not intended for injection moulding. Its 0.35 g/10 min melt flow rate is below the typical range of 2–20 g/10 min used for HDPE injection moulding, and the high molecular weight increases filling pressure and cooling time in thin-walled moulds. When injection moulding is unavoidable, barrel temperatures above 230 °C and injection pressures above 140 MPa are generally required; these conditions increase the risk of molecular degradation and colour shift. This property profile positions 50-0350 within extrusion blow moulding and heavy-gauge sheet extrusion rather than high-speed injection moulding applications.

Chemical Compatibility, Drying Boundaries, and Regulatory Status

The resin is resistant to aqueous acids, alkalis and saline solutions at ambient temperature, consistent with semi-crystalline polyethylene. Continuous contact with strong oxidising acids above 60 °C, aromatic hydrocarbons or chlorinated solvents is not recommended because these agents plasticise or swell the matrix. For dangerous goods packaging, compatibility testing should follow UN 6.1 and UN 6.3 protocols. The grade is stabilised for multiple extrusion heat histories, but reprocessing levels above 30 % regrind may reduce ESCR through molecular weight degradation and gel formation. Pre-drying is required at relative humidity above 60 %. Food-contact compliance for the United States is typically addressed under FDA 21 CFR 177.1520; for the European Union, migration testing under EU 10/2011 is required. The grade is typically aligned with REACH and RoHS heavy metal restrictions, but application-specific certification must be obtained from the supplier.