LyondellBasell HDPE L5645 is supplied as a high-density polyethylene copolymer pellet for continuous extrusion blow moulding. The typical density reported in supplier technical literature is 0.956 g/cm³ when measured to ISO 1183-1:2019. The typical melt flow rate is 0.45 g/10 min when measured at 190 °C under 2.16 kg load to ISO 1133-1:2022. These values identify a high-molecular-weight polyethylene with a density above that of medium-density blow-moulding resins, which typically span 0.930 g/cm³ to 0.941 g/cm³, and below that of high-rigidity HDPE grades near 0.964 g/cm³. On production-scale blow-moulding lines, this combination is observed as longer parison hang time, higher melt strength, and greater resistance to parison sag than injection-moulding HDPE grades with melt flow rates above 20 g/10 min.

Unlike a narrow-molecular-weight unimodal HDPE of identical density and melt flow rate, L5645 is selected for accumulator-head and rotary-wheel blow-moulding operations where cycle times exceed 20 s and the parison must remain stable before mould closure. The resin is not intended for thin-wall injection moulding; published spiral flow length, injection pressure, and mouldability index data for this specific configuration are limited. This product therefore occupies a blow-moulding-specific position among HDPE grades.

What Separates HDPE L5645 from Other Blow-Moulding Polyethylenes with Comparable Density?

The differentiation from other blow-moulding HDPE grades arises from molecular weight distribution, comonomer placement, and shear response. The melt flow rate of 0.45 g/10 min places the product below the 1.0 g/10 min range at which parison sag on large accumulator heads becomes a routine production defect. A die gap of 1 mm to 3 mm combined with die swell in the range 1.2 to 1.4 is typical for high-molecular-weight HDPE blow-moulding grades; converters use these values to set parison diameter relative to neck and flash pocket dimensions. If die swell is below 1.2, the parison may fail to fill the neck insert; if it exceeds 1.4, flash volume increases. The exact die swell for L5645 is not always published in a public datasheet and should be confirmed on the moulding line.

The comonomer type used in L5645 is not disclosed in the public supplier datasheet. The density of 0.956 g/cm³ indicates that short-chain alpha-olefin incorporation is moderate, which reduces crystallinity compared with homopolymer HDPE. Molecular weight distribution broadens the shear-thinning response, allowing extrusion at manageable head pressure while retaining low-shear viscosity for parison stability. Compared with a higher-molecular-weight HDPE blow-moulding grade with melt flow rate 0.30 g/10 min, L5645 may show lower head pressure and slightly lower melt strength; compared with a lower-molecular-weight grade with melt flow rate 0.80 g/10 min, it may show greater sag resistance. These relative differences are inferred from standard melt-flow principles, not from published L5645 rheology, which is limited.

In dynamic oscillatory shear at 190 °C, a high-molecular-weight HDPE with melt flow rate 0.45 g/10 min typically shows a zero-shear viscosity in the range 1.5×10⁵ Pa·s to 4.0×10⁵ Pa·s. During extrusion through a parison die at apparent wall shear rates of 10 s⁻¹ to 100 s⁻¹, shear thinning reduces the apparent viscosity to a range that permits continuous parison formation. The crossover frequency of storage and loss modulus is lower for broad-molecular-weight-distribution HDPE than for narrow-molecular-weight unimodal grades, indicating a wider relaxation time spectrum. This spectrum contributes to die swell and sag resistance. Published rheological data specifically for L5645 is limited, so these values should be understood as class behaviour for high-molecular-weight HDPE blow-moulding resins.

On rotary blow-moulding machines equipped with grooved-feed extruders of 25:1 to 30:1 L/D, barrel temperature settings for L5645 typically progress from 170 °C in the feed section to 210 °C in the metering zone and 200 °C at the die head. The melt temperature at the die should remain from 200 °C to 220 °C. Sustained melt temperature below 190 °C can produce sharkskin melt fracture at high extrusion rates; sustained melt temperature above 230 °C can generate gels, colour shift, and odour from oxidative chain scission. Screen pack pressure on a 60 mm grooved-feed extruder should remain below 50 bar, because higher pressure indicates melt filtration blockage and may increase shear heating. Pre-drying is unnecessary at storage relative humidity below 60 %; when hopper condensation appears, hopper heating at 60 °C to 80 °C for 1 h to 2 h removes surface moisture. Blow mould temperature is held at 10 °C to 30 °C for dimensional stability. Thick sections above 6 mm require internal cooling air at 0.2 bar to 0.5 bar until the outer wall is below 60 °C.

Start-up failure modes observed on production-scale blow-moulding lines with this product class include parison curvature caused by non-uniform die temperature, pinch-off weld lines that fail top-load testing because of cold mould surfaces, and die lines from degraded material at the die lip. Corrective actions include raising die-head temperature uniformity, increasing mould temperature above 15 °C, and purging the head after any shutdown exceeding 30 min. When L5645 is compounded with colour masterbatch or regrind, co-rotating twin-screw extruders with L/D 40:1 and low-shear screw elements are used to minimise melt-temperature rise. Batch-to-batch variation in regrind content above 20 wt% can shift parison sag because regrind reduces molecular weight and increases MFR; converters therefore limit regrind addition to below 20 wt% unless rheology is verified after blending.

When Environmental Stress Crack Resistance Governs Container Life

Containers for household cleaning formulations, agricultural adjuvants, and aqueous surfactant systems are evaluated for environmental stress crack resistance under ASTM D1693-15. High-molecular-weight HDPE blow-moulding copolymers with density near 0.956 g/cm³ are generally selected where F50 failure times above 100 h are required. The exact ESCR value for L5645 is lot-dependent and must be read from the certificate of analysis, because comonomer distribution, not density alone, controls slow crack growth. The material occupies a middle position: chemical permeation resistance and top-load strength are higher than MDPE blow-moulding grades, while stress-crack resistance is generally better than high-density grades above 0.960 g/cm³.

Drop-impact testing for containers above 5 L is commonly conducted under ASTM D2463-15 or the UN packaging drop sequence at −18 °C. L5645 can be evaluated for UN-certified packaging, provided the complete closure, handle geometry, wall thickness distribution, and pinch-off integrity are certified on the production line. Continuous contact with aromatic solvents, chlorinated hydrocarbons, or strong oxidizers should be excluded unless validated by ASTM D543-21 chemical resistance testing, because these agents permeate polyethylene and lower stress-crack resistance. Additive systems containing peroxides above 0.1 wt% should be avoided unless intentionally used for controlled rheology modification, because peroxide-induced branching changes die swell and can generate gels.

When compared with HDPE blow-moulding grades of density 0.960 g/cm³ or higher, L5645 has a lower density that is selected for improved low-temperature impact and environmental stress crack resistance. The trade-off is a reduction in top-load stiffness of approximately 5–15 % when sidewall thickness is held constant. When compared with MDPE blow-moulding grades of density 0.934 g/cm³ to 0.941 g/cm³, L5645 provides higher tensile yield, lower permeation to aliphatic solvents, and greater top-load strength, but lower low-temperature impact toughness. These differences follow from density-property relationships for polyethylene and should not replace part-specific testing.

In cosmetic and pharmaceutical bottle production, blow ratios below 3:1 and die gaps between 1 mm and 3 mm are used to maintain wall thickness uniformity. Top-load strength measured on empty containers according to ASTM D2659-11 is governed by wall thickness distribution and corner radii rather than by resin density alone. For a 1 L round bottle with nominal wall thickness of 1.5 mm, top-load values above 200 N are attainable on well-tuned tooling, but production lots must be verified because pinch-off and handle zones create stress concentrations. In agricultural chemical containers, post-cooling fixtures that hold internal air pressure at 0.2 bar to 0.5 bar until the outer surface is below 60 °C reduce shrinkage and warpage. These process values are standard high-molecular-weight HDPE blow-moulding practice, not unique to L5645.

Mechanical property values from technical literature are generated under ISO 527-2:2012 tensile testing at 23 °C and 50 mm/min test speed and under ISO 1183-1:2019 after standard conditioning. These values should not be used for finite element analysis without true stress-strain data at the service temperature and strain rate. Creep modulus at 60 °C is lower than the room-temperature value by up to 30–40 % for HDPE, depending on crystallinity and load duration. For continuous-load design, stress values should be based on ISO 9080:2012 regression curves or equivalent long-term data, not on short-term tensile data. Published data for this specific configuration is limited.

Regulatory Compliance Matrix for the Polyolefin Polymer Class

The regulatory status of an article made from L5645 is determined by the final formulation, additives, and end-use conditions, not by the base resin alone. The following instruments are applicable to olefin polymers and should be confirmed against the supplier certificate for the specific lot.