For the blow moulding of UN-certified open-head drums and tight-head jerricans, TPC (Japan) HDPE KL370C is processed on an accumulator-head extrusion blow moulding line with barrel zone setpoints between 180°C and 210°C, the die head held 5–10°C below the rear zone to increase melt strength and stabilise parison hang. The formulation addition ratio is typically 96.5–98.0 wt% KL370C, 2.0–2.5 wt% carbon black masterbatch of 50% carbon black loading, 0.05–0.10 wt% hindered phenolic antioxidant, and 0.05–0.10 wt% calcium stearate acid scavenger. The downstream production process uses parison programming with 30-point axial wall thickness control; in the 220 L open-head drum body, wall thickness is maintained between 1.8 mm and 2.6 mm, while the pinch-off zone must cool below 80°C before demoulding to avoid weld-line splitting. The terminal products are 220 L open-head drums compliant with UN 1H2/Y, and 5–30 L tight-head jerricans compliant with UN 3H1/Y; containers are tested under 49 CFR Part 178.603 and ADR/RID Chapter 6.1, with packaging group II liquids requiring no rupture after a 1.2 m drop at -18°C. At mould temperatures below 8°C or relative humidity above 70%, condensation on the mould surface can generate pitting; when changing from a carbon black formulation to an unpigmented food-contact batch, the accumulator head must be purged with nitrogen to prevent gel contamination.

What Controls Parison Sag in Six-Layer HDPE Fuel Tank Coextrusion?

Parison sag on a six-layer coextrusion line equipped with six 25:1 L/D extruders feeding a spiral mandrel die is governed by the apparent melt viscosity of KL370C under low-shear sag conditions; processors typically maintain the high-load melt flow index at 21.6 kg and 190°C within the datasheet range and measure sag length at a fixed drop time of 20–40 s on accumulator heads with clamp force between 3,500 kN and 5,000 kN. The formulation addition ratio is expressed as layer mass distribution rather than masterbatch let-down: HDPE outer skin 35–40 wt%, regrind layer 30–40 wt%, maleic anhydride-grafted PE tie layer 1.5–2.5 wt%, EVOH barrier 1.5–3.0 wt%, second tie layer 1.5–2.5 wt%, and HDPE inner skin 20–25 wt%. In the regrind layer, KL370C is blended with up to 20 wt% post-industrial fuel tank trim, while the outer and inner skins are produced from 100% virgin KL370C. The downstream coextrusion process must hold EVOH at 195–215°C and purge at shutdown to avoid thermal degradation; a 10°C overshoot above the EVOH upper limit will generate black specks and odour. Compliance is anchored to UN ECE R34.03 Annex 4 fire resistance and Annex 5 impact, plus ASTM D638-14 for tensile yield not less than 20 MPa and ASTM D790-17 for flexural modulus characterisation. Blow moulds are textured with 25–50 µm depth venting grooves to prevent air entrapment, and pinch-off flash is recycled only after two passes through a 100 µm screen changer. The terminal products are 45–80 L coextruded fuel tanks for passenger vehicles and off-road equipment. Published data for KL370C in cyclic CNG fuel tank service is limited, and the grade is not specified for contact with fuel blends exceeding 10 vol% alcohol without barrier validation.

Where composite IBC liners are produced for chemical distribution, KL370C is blow moulded into 1,000 L inner bottles on a high-output accumulator machine with a 120 mm screw diameter, 30:1 L/D, and a 125 kg melt reservoir. The formulation addition ratio for the IBC liner is 97.7–99.0 wt% KL370C, 0.05–0.10 wt% hindered phenolic antioxidant, 0.02–0.05 wt% phosphite process stabiliser, and 2.0–2.5 wt% carbon black masterbatch where UV exposure during outdoor storage is anticipated; unpigmented liners for food contact omit carbon black and rely on 0.15–0.25 wt% HALS. Downstream, the bottle is cooled in a temperature-controlled fixture at 20–25°C to maintain wall thickness at the top and bottom chimes of 2.0–3.0 mm and sidewall of 1.5–2.0 mm; chime-radius thinning below 1.5 mm can reduce top-load resistance below the 8,000 N value commonly specified by buyers for 3-high rail shipment. The terminal product is the inner receptacle of a UN 31HA1/Y composite IBC, tested under ADR/RID Chapter 6.5 for leakproofness at 20 kPa air pressure and hydraulic pressure at 100 kPa for 10 minutes. Accumulator-head machines running KL370C at 190–200°C exhibit a drop in parison hang strength if melt temperature exceeds 210°C, causing bottom-thinning beyond the 2.0 mm minimum in heavier-wall designs.

If Fluorination Is Specified for Solvent Barrier Performance

Post-mould fluorination of KL370C containers using a 1.0–2.5 vol% fluorine-in-nitrogen mixture at 40–60°C for 10–30 minutes reduces permeation of xylene and aromatic solvents by converting surface polyethylene to a fluoropolymer barrier less than 0.5 µm thick. For agrochemical sprayer tanks and 10–25 L narrow-mouth jugs, the bulk formulation addition ratio is 96.0–97.5 wt% KL370C, 2.0–2.5 wt% carbon black masterbatch, 0.15–0.30 wt% HALS UV stabiliser, 0.05–0.10 wt% antioxidant, and 0.05–0.10 wt% calcium stearate; amine-based antistatic agents are excluded because amine functionality can retard surface fluorination by competing for reactive sites. Downstream production uses a two-station shuttle blow moulding machine with parison programming and a fluorine barrier treatment line. The terminal product is a fluorinated UN 3H1/Y or UN 3H2/Y container; compliance includes ASTM D1998-21 for moulded tank design stress and 49 CFR Part 178.603 drop testing at -18°C with a 1.2 m drop height. The fluorination process must be followed by a 30-minute post-treatment purge with nitrogen to remove residual fluorine before unloading; operators must verify surface fluorine-to-carbon ratio by X-ray photoelectron spectroscopy at 1.0–1.5 rather than relying on post-hoc permeation tests. For tanks holding aqueous formulations with pH below 3.0, published field data indicates surface fluorination may reduce stress cracking but does not replace chemical resistance validation.

Marine Buoyancy Structures and Low-Temperature Impact Response

Marine buoyancy shells blown from KL370C require an extrusion blow moulding line with a 90 mm screw, 25:1 L/D, and a 40 kg accumulator head to maintain a parison drop length of 2.5–3.0 m without sag-induced bottom thinning. The formulation addition ratio for marine fenders and mooring buoys is 96.5–97.5 wt% KL370C, 2.0–2.5 wt% carbon black masterbatch with 50% carbon black content, 0.30–0.45 wt% hindered amine light stabiliser, 0.05–0.10 wt% phosphite antioxidant, and 0.02–0.05 wt% processing aid. The terminal products are cylindrical buoyancy modules, dock fenders, and channel marker floats produced in wall thicknesses of 4–12 mm. Compliance for UV exposure is assessed under ISO 4892-3:2016 with a 2,000 h exposure cycle and a ΔE target below 4.0, while low-temperature impact verification follows ASTM D1998-21 at -20°C; marine-specific certification is not universal and is often buyer-specified. The process risk is cooling-time-induced shrinkage: wall thickness above 10 mm may require 15–25 minutes of in-mould cooling at 15–20°C mould water temperature to limit volumetric shrinkage below 2.5% and to avoid sink marks at stiffener intersections. Adding more than 0.45 wt% HALS in unpigmented marine service can exude to the surface at mould temperatures above 20°C, causing visible bloom and potential solvent wipe failure.

When sheet gauge exceeds 8 mm, extrusion of KL370C into 8–25 mm thick sheet for thermoformed pallets and separator dunnage uses a 120 mm single-screw extruder with a barrier screw and melt pump, running at 190–210°C, then passes through a three-roll stack with roll temperatures of 30–60°C. The formulation addition ratio for sheet is 99.5–99.8 wt% KL370C, 0.03–0.08 wt% hindered phenolic antioxidant, 0.02–0.05 wt% phosphite process stabiliser, and 0.02–0.05 wt% external lubricant; carbon black is not added unless electrostatic discharge protection is specified for electronics dunnage. Thermoforming is conducted on twin-sheet equipment at a sheet surface temperature of 165–175°C, with plug depth set to avoid thinning below 20% of the original sheet gauge in the corner radii. The terminal products are twin-sheet pallets, separator sheets, and dunnage trays used in automated warehousing. Compliance for pallet load capacity is tested under ISO 8611-1:2011, while tensile elongation at yield is measured to ASTM D638-14; material in dunnage service is not specified for direct food contact unless separately cleared under FDA 21 CFR 177.1520. At sheet thickness above 25 mm, published process data is limited, and cooling capacity rather than extruder output becomes the controlling limitation.

Blow Moulding Double-Wall Panels for Outdoor Storage and Enclosures

Double-wall outdoor enclosure panels produced from KL370C are blow moulded on a single-station machine with a 100 mm extruder, 24:1 L/D, and a 75 kg shot accumulator; the mould closing speed is set below 300 mm/s to avoid tearing the parison when pinch-off area exceeds 1,200 cm². The formulation addition ratio for UV-stabilised outdoor panels is 97.2–98.0 wt% KL370C, 0.20–0.30 wt% HALS, 0.05–0.10 wt% antioxidant, 1.0–2.0 wt% pigment masterbatch or 2.0–2.5 wt% carbon black masterbatch, and 0.02 wt% processing aid. The terminal products are door panels, shed wall panels, and enclosure panels with 20–40 mm double-wall cross-sections. Compliance for weathering and mechanical properties follows ISO 4892-2:2013 for xenon-arc exposure and ASTM D790-17 for flexural creep; structural panel assemblies are not regulated under a single global standard and are tested to customer-defined load cases. At the transition from the solid pinch-off weld to the hollow double-wall section, low mould temperature and excessive clamping speed are known failure sites, and Charpy impact strength must be verified according to ISO 179-1:2010 at -30°C. Post-mould fixturing for 24–48 h is required to stabilise panel bow to below 3 mm per 1,000 mm span before assembly.

Water Storage Vessels and the NSF/ANSI/CAN 61 Extraction Boundary

In potable water service, vertical storage tanks produced from KL370C are blow moulded as single-piece shells with wall thickness 6–15 mm and capacities of 500–10,000 L, using an accumulator-head machine with a 120 mm screw and 40:1 L/D to maintain homogeneous melt at 185–200°C. The formulation addition ratio for potable-water contact is 99.7–99.9 wt% KL370C, 0.05–0.10 wt% hindered phenolic antioxidant, and 0.02–0.05 wt% phosphite process stabiliser; carbon black and HALS are omitted unless the unit is designated for outdoor non-potable water storage, in which case 2.0–2.5 wt% carbon black and 0.25–0.35 wt% HALS are charged. The terminal products are cylindrical vertical storage tanks and conical-bottom dosing tanks for water treatment plants. Compliance is established through NSF/ANSI/CAN 61 by the terminal fabricator, not by the resin supplier, because extraction test results depend on the moulded surface-to-volume ratio and post-mould cleaning; EU drinking water compliance is assessed under Directive (EU) 2020/2184 and national migration limits. The process must avoid zinc stearate in the additive package because zinc-containing residues can elevate extraction test metals above detectable thresholds. A resin moisture content above 0.03% can produce surface splay at the vented mould surface; published data for KL370C at wall thickness above 15 mm is limited.