For industrial container blow moulding, Sumitomo Chemical HDPE B2555 is processed on shuttle presses equipped with a 25:1 L/D barrier screw and a 4.5 kg accumulator head. The melt temperature is maintained between 190°C and 210°C, while the die head is held at 195°C to 205°C to limit parison sag. Blow pressure is set at 0.7 MPa to 0.9 MPa with a mould temperature of 8°C to 18°C. A 10-point axial parison programming profile is required because the high molecular weight distribution produces 35% to 45% die swell. For a 220 L open-head drum weighing 9.2 kg, the minimum formed sidewall thickness is 1.9 mm, and the cycle time typically ranges from 125 s to 150 s depending on cooling water temperature. Virgin pellets do not require desiccant drying; however, when post-wash regrind exceeds 30 wt%, a vented extruder is necessary because surface moisture above 0.05 wt% generates pinholes in the pinch-off zone. The material contributes a tensile yield stress of 29 MPa when tested to ISO 527-2, a flexural modulus of 1250 MPa when tested to ISO 178, and an environmental stress crack resistance greater than 1000 h under ASTM D1693 condition B with 10% Igepal at 50°C. These properties support revalidation of UN 1H1 drums, but the pinch-off tail must be trimmed cleanly because residual flash exceeding 2 mm at the mould parting line reduces drop-test reproducibility.

What Limits the Accumulator Head Programme for High-Molecular-Weight HDPE Fuel Tank Shells?

Six-layer coextrusion lines combine B2555 skins with a central EVOH barrier layer and maleic anhydride grafted PE tie layers. The HDPE extruders run at 200°C to 220°C; the EVOH extruder is limited to 205°C to 215°C because residence above 230°C produces gel particles at the layer interface. EVOH pellets are pre-dried at 80°C for 4 h to a moisture content below 0.3%, while B2555 requires no desiccant drying. The accumulator head is held at 210°C, and the die gap is set between 1.8 mm and 2.4 mm. For a 60 L diesel tank shell weighing 8.5 kg, the parison programmer increases the thickness to 4.0 mm at the pinch-off corners and reduces it to 2.2 mm in the sidewall. Blow pressure is 0.6 MPa to 0.8 MPa. A critical process conflict is shear heating from the high-viscosity B2555 layer: an undersized extruder below 90 mm diameter can push the melt above 230°C at the screw tip even when barrel setpoints remain conservative, causing EVOH degradation and delamination. Layer adhesion should be revalidated by ISO 10365 peel testing; published data for this specific six-layer configuration using B2555 is limited, so bonding must be confirmed on the production line before serial moulding. B2555 reduces parison sag due to its 0.25 g/10 min melt flow rate, but the trade-off is higher head pressure and slower extruder recovery. The mould clamp must hold 800 kN to 1,000 kN during blowing to prevent flash at the pinch-off. Fuel permeation performance is evaluated by ECE R34 or SAE J1737; the EVOH layer, not B2555, controls hydrocarbon permeation, so the B2555 layer is selected primarily for impact toughness and environmental stress crack resistance.

When flat die extrusion over a three-roll polishing stack converts HDPE B2555 into secondary containment liners, sheet thickness is controlled between 2.0 mm and 4.0 mm, with the melt temperature held at 195°C to 210°C. The polishing roll surface temperature is set at 70°C to 85°C to limit frozen-in orientation. Heating for thermoforming uses a twin-sided quartz oven with a surface temperature of 125°C to 135°C, measured by pyrometer, before a syntactic foam plug assists pre-stretching. A draw ratio of 2:1 is typical for basin dimensions up to 1.2 m × 1.0 m × 0.4 m. High melt strength is required to avoid sheet sag during oven dwell; B2555 with its low melt flow rate maintains a sag deflection below 5 mm for a 3.0 mm sheet over a 400 mm unsupported span. The mould is maintained at 50°C to 70°C to reduce thermoforming stress. Welded corners are completed by hot-gas extrusion welding, and weld factors are validated by DVS 2207-1. Immersion testing under ASTM D543 is required for the specific acid or alkaline medium; B2555 shows broad resistance to 30% sulfuric acid, 10% sodium hydroxide, and 5% sodium chloride, but aromatic solvents and strong oxidizers are outside the continuous-use envelope. The operational boundary is 60°C; above this temperature, the flexural modulus decays sufficiently to produce creep under hydrostatic pressure, and polypropylene or engineering thermoplastics should be considered instead of HDPE.

When HDPE B2555 Replaces Lower-Molecular-Weight Grades in IBC Inner Bottles

The substitution becomes technically binding only after revalidation of the mould filling phase because the lower melt flow rate changes pinch-off wall thickness distribution. A 1,000 L composite IBC inner bottle is blow moulded on a machine with a 15 kg accumulator head and a clamp force of 1,200 kN to 1,500 kN. The melt temperature is set at 200°C to 210°C, and the die head is held at 205°C to 215°C. The bottle weight is 14 kg to 15 kg, with minimum corner wall thickness of 3.0 mm and body wall thickness of 2.5 mm. Because B2555 exhibits 35% to 45% die swell, the parison is programmed shorter than with a 0.5 g/10 min grade; failure to reduce parison length produces thick flash and extends cycle time beyond 240 s. Blow pressure is 0.8 MPa. The pinch-off weld must be tested by ASTM D638-14 on a specimen cut across the weld; a weld factor above 0.85 is required for UN 31H1 qualification. Environmental stress crack resistance is evaluated by ASTM D1693 condition C in 100% Igepal, and B2555 normally exceeds 1,000 h without failure. Regrind use is limited to 20 wt% because higher levels broaden molecular weight distribution and reduce top-load buckling resistance. Mold temperature is kept at 10°C to 20°C to control cooling shrinkage; uneven cooling of the 1,000 L bottle can cause sidewall warpage exceeding 5 mm, which complicates cage assembly. The bottle must pass hydraulic pressure testing at 100 kPa for 10 min and a drop test at -18°C from 1.2 m according to UN Model Regulations.

Drop-impact failure modes in 20 L stack-moulded jerrycans

Cumulative damage from repeated pallet stacking is simulated by ASTM D5276 drop tests at -18°C after conditioning for 48 h. A 20 L jerrycan is blow moulded at 850 g with a minimum sidewall thickness of 2.0 mm and a top and bottom pinch-off thickness of 3.5 mm. The accumulator head is set at 200°C to 215°C, and the mould temperature is held at 8°C to 15°C. Cycle time is 55 s to 75 s per two-cavity mould. B2555 is selected because conventional 0.5 g/10 min HDPE grades fail after prolonged contact with organophosphate ester-based crop protection formulations; the high molecular weight fraction of B2555 delays crack initiation at moulded-in stress concentrations. However, low-temperature impact is sensitive to pinch-off flash, and a flash line remaining above 1.5 mm from the parting surface acts as a crack initiator. Post-moulding fluorination is used for solvent barrier improvement; the fluorine concentration must not exceed 1.0% surface atomic fluorine because higher levels create a brittle skin layer that reduces drop impact by more than 30%. The jerrycans are closed with an UN 3H1 certified closure and tested under UN Model Regulations chapter 6.1.5 for drop, leakproofness, and hydraulic pressure. Leakproofness is evaluated at 30 kPa for 5 min for packing group II; B2555 allows consistent pinch-off weld quality when the flash is removed within 2 s of mould opening, before the weld zone cools below 120°C.

Reservoir Shells Exhibit Methanol-Induced Stress Cracking at Weld Lines

Because reservoir geometries include offset fill necks and pump sockets that require curved parison placement, B2555 is processed on a 3D blow moulding line with a parison manipulator. Extrusion blow moulding of automotive washer fluid reservoirs uses B2555 for its resistance to stress cracking in methanol and ethanol blends at temperatures from -30°C to 60°C. Melt temperature is 200°C to 210°C, die head temperature 205°C, and blow pressure 0.5 MPa to 0.7 MPa. The reservoir shell weight is 600 g to 900 g, with wall thickness of 2.0 mm to 2.5 mm. A mould clamp of 500 kN to 700 kN is adequate for single-cavity tools. The material is not dried; however, reclaimed internal skeleton scrap must be dried at 80°C for 2 h if stored above 70% relative humidity to prevent internal porosity at weld lines. Resistance to washer fluid containing 30% methanol and 10% ethanol is verified by immersion at 60°C for 500 h followed by ISO 527-2 tensile retention above 85%. Burst testing is performed at 250 kPa internal pressure for 60 s without visible swelling or leakage. The main incompatibility is with concentrated brake fluid or hot engine coolant, which can exceed the 60°C continuous-use boundary and should be directed to polypropylene or polyamide reservoirs.