LyondellBasell HDPE L4907 is a high-density polyethylene extrusion grade supplied as stabilized pellets for extrusion blow molding and thick-sheet thermoforming. Representative technical datasheet values place density at 0.949 g/cm³ per ASTM D1505, which corresponds to DIN EN ISO 1183-1:2019, and melt flow index at 0.75 g/10 min per ASTM D1238 at 190°C with a 2.16 kg load, which corresponds to ISO 1133-1:2022 method A. Tensile yield strength of 26 MPa per ASTM D638 and flexural modulus of 1,100 MPa per ASTM D790 characterize the grade as a medium-stiffness HDPE with sufficient load-bearing capacity for industrial containers. The molecular weight distribution is controlled to provide parison melt strength while maintaining environmental stress crack resistance under ASTM D1693 condition B. The resin is stabilized with an antioxidant and acid-scavenger package typical of HDPE blow molding grades and is sold as natural or pre-colored pellets depending on the production site.

On shuttle blow molding lines with 24:1 to 30:1 L/D single-screw extruders and barrier screws, L4907 processes at melt temperatures of 190°C to 210°C. Barrel temperature profiles typically begin at 160°C in the feed throat, rise to 185°C in the compression zone, and hold at 190°C to 195°C in the metering zone. Die head temperatures are held within 5°C of the melt set point. At melt temperatures above 215°C, surface haze, odor, and parison sag become measurable; below 180°C, head pressure increases and sharkskin may appear on the parison. Die gaps of 1.5 mm to 2.5 mm and blow-up ratios of 2.0:1 to 3.0:1 are used for 20 L to 30 L industrial containers. On a 60 mm barrier screw, sustained screw speeds above 60 rpm can generate melt pressure oscillations above ±3% of setpoint unless barrel cooling is increased. These processing limits reflect production-scale behavior of medium-high molecular weight HDPE rather than a single laboratory sample.

How Does L4907 Differ from High-Flow Injection Molding HDPE Grades?

High-flow injection molding HDPE grades typically exhibit melt flow index values greater than 20 g/10 min per ASTM D1238 and narrow molecular weight distributions. L4907 at 0.75 g/10 min falls into the extrusion blow molding range; its melt viscosity at low shear is one to two orders of magnitude higher than a 20 g/10 min injection grade. This difference makes L4907 unsuitable for injection filling paths with wall thicknesses below 1.5 mm because the melt front freezes before cavity filling completes. The lower density of 0.949 g/cm³ compared with 0.960 g/cm³ high-flow injection HDPE reduces tensile yield strength and flexural modulus by approximately 10% to 15% but improves environmental stress crack resistance under ASTM D1693 condition B. Flow-length tests in a 2 mm spiral mold at 220°C show that L4907 reaches substantially shorter lengths than high-flow injection grades; published spiral flow data specific to L4907 are limited. Compared with a high-load melt-index HDPE film grade of similar density, L4907 has lower melt flow index and higher die swell, which shifts its suitability away from high-stalk blown film and toward extrusion blow molding where parison thickness uniformity is critical. In extrusion blow molding, the high melt strength of L4907 permits larger unsupported parison lengths and reduces drawdown, whereas high-flow injection grades cannot sustain a stable parison.

When the Melt Temperature Window Narrows Below ±5°C Around the 195°C Set Point

Polyethylene melt flow near 190°C follows an Arrhenius relationship with reported activation energies between 25 kJ/mol and 30 kJ/mol. For L4907, a 5°C increase from 195°C to 200°C reduces apparent viscosity by approximately 5% to 7%; a 5°C decrease increases viscosity by a similar amount. In a 1.8 mm land length annular die head, this viscosity shift can alter parison weight by 2% to 4% when the extruder operates without closed-loop melt temperature control. Blow molders running multi-cavity shuttles have observed parison length differences above 15 mm as melt temperature drifts from 195°C to 203°C across a 5-minute accumulator cycle. At parison die exit shear rates below 100 s⁻¹, melt strength and sag resistance are highly temperature-sensitive; at 1,000 s⁻¹, shear thinning reduces the effective viscosity difference. Controlling the die head with PID loops and thermocouple time constants below 2 s is required to keep parison weight variation within 5%. When ambient temperature changes across a 12-hour shift, feed-throat cooling water may need a 2°C to 3°C adjustment to maintain stable barrel zone overrides.

Capillary rheometry according to ASTM D3835 at 190°C characterizes L4907 as a pseudoplastic melt with a power-law index below 0.4 in the shear rate range of 100 s⁻¹ to 1,000 s⁻¹. The low-shear viscosity plateau, reported only in scattered technical literature for this grade, controls parison sag; the high-shear thinning controls extruder backpressure and melt pump load. In multilayer blow molding, L4907 is commonly paired with EVOH barrier layers. The melt viscosity ratio between L4907 and the EVOH grade must be kept below approximately 3:1 at the shear rates prevailing in the coextrusion feedblock to avoid interfacial instability. Tie-layer selection based on anhydride-grafted polyethylene with melt flow index between 1.0 g/10 min and 2.0 g/10 min is standard practice. The melt pump suction pressure should not exceed 15 MPa on an 80 mm extruder to prevent excessive shear heating and loss of parison melt strength. These limits derive from general HDPE coextrusion practice; published data for L4907 in specific EVOH structures is limited.

Die Swell, Parison Sag, and Accumulator Head Behavior

Die swell for L4907 at 195°C and shear rates below 100 s⁻¹ is typically reported in the range of 1.4:1 to 1.6:1. This requires die diameter reductions of 15% to 25% relative to container outside diameter to maintain wall thickness. Parison sag lengths of 300 mm can be held within ±5% if melt temperature is controlled within ±3°C and accumulator shot time is kept below 10 s. On single-station machines with 80 mm extruders and 15 L accumulator heads, the first-in-first-out flow pattern of the accumulator head must be purged after any shutdown longer than 15 minutes because stagnant resin can develop gel particles and black specks. If the head is not purged, surface defects may appear on the first 20 to 30 containers after restart. Shuttle clamp force for 20 L to 30 L containers typically ranges from 300 kN to 500 kN depending on mold parting area and blow ratio. These process values reflect HDPE blow molding equipment practice and should be validated on the specific line.

Assessing ESCR in Aggressive Surfactant Environments

Environmental stress crack resistance of L4907 is measured according to ASTM D1693 condition B in 100% Igepal CO-630 at 50°C. The lower density of 0.949 g/cm³ and medium-high molecular weight combine to produce ESCR values above 40 h; high-density injection grades with 0.960 g/cm³ density often fall below 10 h under identical conditions. Compared with higher-density blow molding HDPE grades at 0.954 g/cm³ to 0.960 g/cm³, L4907 exchanges some top-load stiffness for improved ESCR and easier parison pinch-off welding. For high stack-load containers, a higher-density grade may be required. Containers for agricultural chemicals, detergents, and industrial liquids should also be tested under filled stacking load at 60°C for 30 days because ASTM D1693 provides a relative ranking, not a service-life prediction. For fluorinated or sulfonated surface treatments used to improve barrier properties, L4907 must be processed in a dedicated fluorination line and the treated article re-tested because polar surface modification can alter stress-crack initiation at closure weld lines. The weld-line region in blow molded handles is the critical point for ESCR failure; parison programming should prevent thinning below 60% of nominal wall thickness at the handle pinch-off zone.

Regulatory status: Under FDA 21 CFR 177.1520(c), L4907 may be used as a component of food-contact articles for all food types provided the finished article meets extraction limits in FDA 21 CFR 177.1520(d). For EU applications, the finished article must comply with Regulation (EU) No 10/2011 overall migration limit of 10 mg/dm² and specific migration limits for any additives used. The base polymer is not intentionally formulated with bisphenol A, phthalates, or heavy metals above 0.1 wt% under REACH Annex XVII. RoHS Directive 2011/65/EU heavy-metal restrictions for electrical and electronic equipment packaging are met at the base-resin level, but flame-retardant or colored masterbatch additives must be verified separately. Pre-drying is not required for L4907 if stored in closed containers at relative humidity below 60%. If condensation is present, pellets should be dried at 60°C for 2 h in a desiccant dryer; hot-air drying above 90°C may cause additive migration and should be avoided. Avoid blending with polypropylene homopolymer above 5 wt% in regrind streams because incompatible phase domains reduce impact strength and create delamination in multilayer parisons.

Typical applications include extrusion blow molded containers for household and industrial chemicals, agricultural chemical bottles, and large-format water-cooler bottles where environmental stress crack resistance and parison stability are required. The grade is also used in sheet extrusion for thermoformed packaging that requires a balance of stiffness and toughness. In these applications, the resin is processed at melt temperatures of 190°C to 210°C, with mold cooling at 20°C to 40°C to achieve acceptable cycle time. Published data for L4907 in thermoforming is limited; processors should validate draw ratio, sag resistance, and mold shrinkage with their own tooling before production. In coextrusion blow molding, the tie-layer and barrier-layer melt temperatures must be matched to L4907 within ±5°C to prevent interfacial instability.