Alathon H5618 is a high-molecular-weight high-density polyethylene with density 0.956 g/cm³ under ASTM D1505 and melt flow rate 0.18 g/10 min at 190 °C/2.16 kg under ASTM D1238. The resin is specified for extrusion blow moulding and heavy-gauge sheet where environmental stress-crack resistance, impact strength and melt stability are process-limiting variables.

Where 220-L L-ring drums are produced for UN-certified liquids transport, H5618 is blended at 70–85 wt% virgin resin with 15–30 wt% post-industrial regrind generated from the same blow moulding line. The regrind fraction is limited to 30 wt% because drop-impact energy at -18 °C under 49 CFR §178.603 and stack-load deformation under 49 CFR §178.606 become inconsistent above this threshold. Colour masterbatch is added at 1.5–3.0 wt%; antistatic masterbatch is introduced at 0.5–1.0 wt% only when the packed liquid conductivity is below 10⁴ pS/m and ignition risk is identified. The containers are produced on accumulator-head extrusion blow moulding machines with screw L/D ratios of 24:1 to 30:1, shot capacities of 5–20 kg, parison programmers controlling wall thickness from 4–8 mm, melt temperature 185–210 °C, die gap 8–15 mm, and mould cooling at 10–20 °C. Blow air pressure is maintained at 0.6–1.0 MPa. Parison sag on large-diameter heads is controlled by reducing accumulator shoot time below 3 s. Finished product types include 20–30 L jerricans, 60 L open-head drums, 220 L L-ring drums and 1000 L intermediate bulk container inner bottles. Compliance is assessed against ADR 6.1.3, IMDG Code Chapter 6.1, 49 CFR §178.503 and ISO 16101:2004 for compatibility with hazardous liquid formulations.

Does Coextruded EVOH Provide Lower Permeation Than Post-Cycle Fluorination in HDPE Fuel Tank Shells?

The selection between coextruded EVOH and post-cycle fluorination for H5618 fuel tank shells is controlled by evaporative emission limits rather than by a single mechanical property. In a six-layer coextruded structure, the outer H5618 layer is held at 30–50 wt% of total wall thickness, structural regrind at 20–40 wt%, adhesive tie layers each at 1.5–3.0 wt%, EVOH barrier at 2–4 wt%, and the inner H5618 layer at 20–35 wt%. The EVOH layer is maintained above 1.5 wt% because intermittent layer breakup below that level creates permeation spikes. The process uses six-extruder coextrusion blow moulding with HDPE melt temperature 190–225 °C, die gap 10–25 mm, parison programming to distribute wall thickness across pinch zones, and mould cooling at 8–15 °C. Post-cycle fluorination, where selected for monolayer shells, uses a 0.5–2.0% fluorine in nitrogen mixture at 20–50 °C for 10–30 min. This route reduces barrier-layer adhesion complexity but introduces surface polarity that can interfere with adhesive bonding of brackets; published permeation data for H5618 after fluorination is limited and requires tank-level validation. Finished product types include 40–80 L gasoline and diesel tanks, fuel filler necks and carbon canister housings. Regulatory compliance anchors to ECE R34 Annex 5 for fire resistance, 40 CFR Part 86 evaporative emission schedules, CARB LEV III limits and EU Regulation (EU) 2017/1151.

Diesel exhaust fluid reservoirs fabricated from H5618 are specified where aqueous urea solution at 32.5 wt% and storage temperatures from -11 °C to 50 °C must not be contaminated by metal ion release. The resin is processed at 90–100 wt% virgin; regrind is limited to 15 wt% and must be free of copper-based stabilizer residues because copper concentration above 0.2 mg/kg can degrade DEF quality as specified in ISO 22241-3:2017. Carbon black is added at 1.5–2.5 wt% when outdoor UV exposure is expected. The blow moulding process for tank shells uses a 24:1 to 30:1 L/D extruder, melt temperature 180–210 °C, mould cooling 10–18 °C, and leak testing at 0.05 MPa after post-mould cooling. Wall thickness is held between 2.5–6.0 mm, with weld-line pinch zones thickened by parison programming to prevent stress cracking at the mould parting line. Finished products include 5–30 L vehicle DEF tanks, 100 L mobile dispensing containers and 220 L bulk urea solution containers. Compliance additionally requires material marking under ISO 11469 and resistance to alkaline hydrolysis under ASTM D543.

Heavy-Gauge Sheet Extrusion and Fusion Welding Window for Fabricated Chemical Containment

At 8–25 mm thickness, sheet produced from H5618 is converted into fabricated chemical containment, transport dunnage and secondary spill trays. The extrusion line uses a single-screw extruder with L/D 30:1, barrier screw, melt temperature 190–220 °C, screen pack 40/60/80 mesh for gel removal, and a die gap of 1.2× final sheet thickness. The sheet is calendered on a three-roll stack at 60–110 °C; surface temperature above 110 °C causes blocking, while below 60 °C produces residual stress that manifests as warpage in thermoforming. Formulation is 90–100 wt% virgin H5618 with up to 20 wt% in-house sheet regrind; for outdoor service, UV inhibitor masterbatch is added at 0.5–1.0 wt% and carbon black at 2.0–2.5 wt%. Thermoforming is run at 165–185 °C surface temperature using plug-assisted vacuum or pressure forming; mould shrinkage in the range 1.5–2.5% must be factored into tool dimensions. Fabricated containers are butt-fused at 210 °C using welding procedures validated to ISO 11414; weld seam tensile reduction is held below 10% of parent material. Finished product types include 100–5000 L chemical process liners, secondary containment basins, battery spill trays and transport dunnage. Material compliance is anchored to ASTM D4976-12a, REACH Regulation (EC) No 1907/2006, and RoHS Directive 2011/65/EU.

After persistent ESCR failures in mono-layer HDPE exposed to xylene-containing emulsifiable concentrates, containers for pesticide and herbicide formulations are qualified with H5618 in coextruded barrier structures. The structural H5618 layer is used at 80–95 wt% of total wall thickness, with regrind limited to 15 wt% and a polyamide barrier inner layer at 3–5 wt% when active ingredients exceed 100 g/L solvent concentration and vapour pressure exceeds 0.1 Pa at 20 °C. Surface fluorination is applied as an alternative at 0.5–2.0 wt% fluorine uptake on the inner surface to reduce hydrocarbon permeation. The coextrusion blow moulding process uses die gap 10–20 mm, melt temperature 185–210 °C, and parison programming to maintain barrier layer continuity at pinch-off weld lines. Containers are tested for drop impact at -18 °C, internal pressure and stacking under 49 CFR Part 178 Subpart M; ESCR is monitored under ASTM D1693 Condition C. Finished products include 1–20 L crop-protection bottles, 220 L drums and 1000 L IBC inner bottles. Additional regulatory compliance includes 40 CFR §165.20 for child-resistant packaging where required and ISO 16101:2004 for chemical compatibility testing.

Long-Term Hoop Stress Retention in Large-Diameter Blow Molded Storage Tanks After Outdoor UV Aging

For vertical storage of aggressive aqueous solutions, large-diameter blow moulded tanks manufactured from H5618 are specified where hoop stress and UV resistance are controlling variables. Tank bodies are produced on large accumulator-head blow moulding machines with shot capacity 80–150 kg, melt temperature 185–210 °C, die gap 20–50 mm, and mould cooling at 8–15 °C. Wall thickness is programmed from 5–15 mm to compensate for parison thinning at the lower sidewall; the pinch-off weld is reinforced to at least 1.5× nominal wall thickness. Formulation is 100 wt% virgin H5618 for potable water contact; regrind is limited to 10 wt% for non-potable chemical tanks and must be generated from the same tank production run. Outdoor service requires carbon black at 2.0–2.5 wt% or a UV stabilizer package at 0.5–1.0 wt%; carbon black dispersion must meet ISO 18553 to avoid impact-strength loss from agglomerates. Structural design and testing follow ASTM D1998-21 for polyethylene upright storage tanks and EN 12573-1 for welded thermoplastic tanks when fabricated from sheet. Compliance for potable water requires verification against NSF/ANSI/CAN 61:2023; published data for H5618 under this specific standard is limited, and batch-level certification is required before shipment. Finished product types include 500–5000 L vertical cylindrical tanks, conical-bottom processing tanks and open-top chemical baths.