Extrusion blow moulding of LyondellBasell HDPE L4904LSC into 5 L detergent and agrochemical containers is run on a single-station shuttle blow moulder with an 80 mm grooved-barrel extruder, 24:1 L/D barrier screw, and a 2.5 L accumulator head. Pellets stored in outdoor silos or conveyed through unheated lines at relative humidity above 60% are pre-dried at 60°C for 2 h because surface condensation produces parison pinholes and splay. Barrel zones from hopper to die are set at 170°C, 190°C, 200°C, 205°C, 210°C, 205°C, with melt temperature measured by an immersion thermocouple at 209–213°C. A 25-point parison programmer is used to blow a nominal wall of 1.0 mm across the side panel, thickening to 1.6 mm at the pinch-off zone and 1.8 mm at the handle bridge. Die gap is maintained at 2.0–3.5 mm, blow air pressure is 6–8 bar, and mould cooling water is held at 10–20°C. Cycle time for a 5 L container is 35–45 s depending on hydraulic clamping and operator part removal. Top-load compression is measured to ISO 12048:1994 with a fixed platen crosshead speed of 10 mm/min, and drop impact is assessed at 0°C after 24 h conditioning following ISO 16495:2022, with the container filled to 90% water and dropped from 1.2 m onto a steel plate. Fractures initiating at pinch-off flash are classified as weld-line failure. Post-industrial regrind from flash, tails, and non-conforming bottles is re-extruded at a maximum 20 wt% when the container is used for UN 3H1 certified liquids; above this fraction the environmental stress crack resistance measured by ASTM D1693-15 condition B, 100% Igepal, becomes batch-dependent and must be revalidated on the production line.

Can Fluorination Deliver Solvent Barrier Improvement in HDPE L4904LSC Jerry Cans?

Surface fluorination of blow moulded HDPE L4904LSC jerry cans is performed in a gas-tight stainless steel chamber after the container has cooled to room temperature and been purged of residual process air. A gas mixture of 0.5%–1.5% fluorine in nitrogen is introduced at 20–30°C for 30–120 s; the fluorine concentration is controlled to ±0.1% because excursions above 2.0% cause wall darkening, reduced pinch-off toughness, and accelerated surface haze. The inner wall is fluorinated to a depth of 5–20 µm, which reduces solvent permeation for toluene, xylene, and aliphatic hydrocarbon mixtures by interrupting the amorphous free-volume pathway at the surface. Barrier performance is measured gravimetrically by a container weight-loss procedure at 40°C for 14 days; containers with a wall thickness of 3–5 mm must show a weight loss not exceeding the converter’s validated maximum for the intended solvent class. Post-fluorination purging uses 4–6 air exchanges with an aqueous potassium hydroxide scrubber to neutralize hydrogen fluoride; residual fluorine in the chamber is monitored electrochemically before the doors open. Hot-tip welding of fluorinated pinch-off zones is not performed because the fluorinated surface layer can inhibit melt fusion; welds are restricted to unfluorinated outer zones or produced before fluorination. Published data for fluorination of this specific grade is limited; production-scale validation is required for each container geometry and solvent class.

A 120 mm barrier screw extruder running LyondellBasell HDPE L4904LSC at 620 kg/h feeds a gear pump and a 1300 mm flexible-lip sheet die with a 100 µm woven screen pack. Barrel temperatures are set from 180°C at the feed throat to 210°C at the adapter, melt temperature is controlled at 208–215°C, and the gear pump inlet pressure is kept at 120–150 bar to stabilize throughput. The three-roll stack is set at 80°C, 90°C, and 85°C; sheet thickness from 2 mm to 8 mm is maintained with a gauge variation of ±1.5%. Heavy-gauge sheet is thermoformed on a plug-assisted forming station with the sheet core temperature at 165–175°C and aluminium tooling held at 25°C. The resulting trays and dunnage platforms are tested for flexural modulus by ISO 178:2019 at 2 mm/min, tensile yield stress by ISO 527-2:2012, and deflection temperature under load by ISO 75-2:2013 method B at 0.45 MPa. Edge trim and skeletal scrap are granulated and re-introduced at up to 15 wt%; higher regrind fractions shift the melt flow rate enough to require adjustment of the gear pump speed and lip gap. HDPE L4904LSC sheet is not suitable for continuous service above 65°C in heavy load-bearing dunnage because the creep modulus at that temperature falls below the design limit for stacking loads.

When Cold Impact Requirements Push Blow Moulded Automotive Reservoirs Below -30°C

For automotive washer reservoirs moulded at a 4.5 L shot weight, the accumulator head is programmed with a parison length calibration that compensates for a die swell of 30–40% at an extrusion rate of 150 kg/h. The mould contains a blow pin with a 110 mm stroke and three undercut inserts for pump brackets; insert temperatures are kept within ±5°C of the mould coolant temperature to avoid local thinning at the insert periphery. The extruder is a 90 mm grooved-barrel machine with a 24:1 L/D screw, and barrel zones are held at 175°C, 190°C, 200°C, 205°C, 200°C, with the die at 195°C. Wall thickness at the reservoir’s lowest corner is monitored by ultrasonic thickness gauge with a lower reject limit of 2.0 mm; parts below this threshold fail the OEM cold-drop test at -30°C. Charpy notched specimens milled from the flat sidewall are tested to ISO 179-1:2010 at -30°C with a 2 J hammer. Low-temperature fracture often initiates at the pinch-off tail where frozen-in stress from the mould close is highest; tail flash is therefore trimmed to less than 1.0 mm after deflashing. Continuous exposure to ethylene glycol coolant is not permitted because the molecular weight and ESCR of HDPE L4904LSC are not designed for hot pressurized coolant service above 80°C; the reservoir is specified for washer fluid only. Published data for L4904LSC in this specific blow moulded geometry is limited, so OEM validation is required on the actual production tool.

In masterbatch compounding, LyondellBasell HDPE L4904LSC is metered as a pellet into the main feed throat of a co-rotating twin-screw extruder with a 40:1 L/D barrel and 58 mm screw diameter. The base resin is combined with 40–60 wt% pigment, for example phthalocyanine blue or carbon black, and 0.5–1.0 wt% wax dispersant. Barrel zone temperatures are set from 160°C in zone 1 to 200°C at the die plate; screw speed is maintained between 500 rpm and 900 rpm, and specific mechanical energy input is held at 0.25–0.35 kWh/kg to achieve pigment particle size reduction to 5–20 µm. Vacuum devolatilisation at -0.8 bar is applied downstream of the mixing zone to remove moisture and low-volatile decomposition products; a melt filter with 100 µm mesh screens is placed before the die to detect agglomerates. Strand pelletising follows a water bath at 25°C and air knife, with pellet temperature below 50°C during bagging to avoid pellet blocking. Dispersion quality is checked by filter pressure value, ash content to ISO 3451-1:2019, and capillary viscosity to ISO 11443:2021 at apparent shear rates from 100 s⁻¹ to 1000 s⁻¹. Use of this carrier resin above 60 wt% pigment loading may lead to torque spikes and granule fracture; published data for L4904LSC in carbon black masterbatch at the upper loading limit is limited and must be confirmed on the specific twin-screw line.

Blow Moulded Water Storage Tank Wall Sections and Hydrostatic Failure Limits

Large water storage tanks blow moulded from HDPE L4904LSC require an accumulator head with shot capacity not less than 8 kg, a 100 mm extruder with 30:1 L/D, and a die gap of 4–8 mm. Parison wall thickness is programmed from 4.5 mm at the top closure to 7.0 mm at the bottom corner; the pinch-off zone is reinforced to a minimum 8.0 mm because hydrostatic pressure concentrates at the weld line. Mould cooling channels are drilled for water at 10–15°C, but the total cooling time is not less than 90 s for a 30 L tank; premature demoulding results in panel deformation and reduced top-load capacity. Hydrostatic testing is performed by filling the tank to 100% water and pressurising to 20 kPa for 1 h with no leakage; additional cyclic pressure testing to 10 kPa for 1000 cycles is used for potable water tank certification. Dimensional stability is checked after 48 h at 40°C and 90% relative humidity; shrinkage of more than 1.0% in the top thread region is a cause for rejection. Long-term hydrostatic strength of HDPE L4904LSC is not a substitute for PE 80 or PE 100 pipe-grade resin; the material is not approved for pressurised plumbing lines. Surface oxidation during processing is minimised by keeping melt temperature below 220°C and by purging with inert gas during shutdown; prolonged residence time above 10 min at 230°C produces gel particles and parison surface roughness.