TPC (Japan) HDPE KL471A is processed by extrusion blow moulding for UN-certified large packagings in the 50 L to 220 L range. The grade is characterised by a nominal melt flow rate of 0.36 g/10 min when tested to ISO 1133-1:2022 at 190 °C under 2.16 kg load, and a density of 0.947 g/cm³ to ISO 1183-1:2019. These values position the resin for high parison melt strength and sufficient die swell during accumulator blow moulding. On a typical 200 L tight-head drum line, the extruder is a 90 mm or 120 mm barrier screw with L/D 25–30, barrel temperatures from feed to metering set at 170–190 °C, and head/die temperatures at 190–210 °C. The accumulator head drops a parison weighing 4.2–5.5 kg; the mould closes at a clamping force of 800–1,200 kN; blow air is delivered at 0.6–0.8 MPa with a blow time of 25–45 s for a wall thickness of 2.5–4.0 mm. Processors add 0.3–0.5 wt% of a high-density polyethylene-compatible carbon black masterbatch when outdoor storage is specified, and 0.1–0.2 wt% of a fluoropolymer processing aid to reduce melt fracture at the die lip. The finished 1H1 closed-head drum must pass the UN 6.1.5.2 drop test at −18 °C from 1.8 m for Packing Group II liquids with a relative density not exceeding 1.2, the hydraulic internal pressure test at 100 kPa for 30 min to UN 6.1.5.5, and the stacking test at 40 °C for 28 days to UN 6.1.5.6. Wall-thickness distribution is measured ultrasonically to maintain a minimum of 2.0 mm at the chime and 2.8 mm in the sidewall. Failure modes observed on production lines include parison fold welding defects at the pinch-off zone when the mould temperature drops below 8 °C, and environmental stress cracking at the closure area when the drum is filled with non-ionic surfactants at 50 °C. The resin’s ESCR value, tested to ASTM D1693-21 condition B, is typically above 100 h, which is a critical release criterion for this pack type.

Co-extruded Automotive Fuel Tank Base Layers and Adhesive Tie Resins

Co-extruded six-layer automotive fuel tank construction uses HDPE KL471A as the structural cap and inner base layers. The layer sequence is HDPE/tie/EVOH/tie/regrind/HDPE. The EVOH barrier layer is typically 2.5–4.0 wt% of total wall thickness, with tie layers at 1.5–2.5 wt%. The total wall thickness is 4.0–6.5 mm, varying at pinch-off and insert areas. The HDPE layers provide impact resistance and weld strength; the EVOH layer reduces hydrocarbon permeation. Processing is performed on a six-extruder co-extrusion blow moulding machine with accumulator head. Barrel temperatures for HDPE layers are 200–220 °C; EVOH is 195–215 °C; tie resin is 200–220 °C. Head and die temperatures are 210–230 °C. Parison drop time is 8–20 s, blow air is 0.7–0.9 MPa, and mould temperature is 10–25 °C. Cycle time for a 60 L tank is 120–180 s. After demoulding, the tank is cooled on a fixture to minimise shrinkage; leak testing is performed at 30 kPa for 60 s; permeation is tested per 40 CFR 86.1813-17 or ECE R34. Fuel tanks must meet fire resistance, impact after preconditioning at −40 °C, and tensile impact of welds. The table below gives a representative layer distribution for a 60 L multi-layer fuel tank.

During extrusion blow moulding of HDPE KL471A for agricultural chemical containers, in-line fluorination is applied to the inner surface to reduce solvent permeation. The process uses fluorine gas diluted in nitrogen at 0.1–0.5 vol% F₂, introduced into the parison while the mould is open or after moulding. The fluorine atoms replace hydrogen on the polyethylene chain, forming a 50–150 nm fluorinated barrier layer. This reduces permeation of non-polar solvents such as xylene and cyclohexanone by a factor of 10–100 compared with untreated HDPE. Container sizes range from 1 L to 25 L, with wall thickness 1.2–3.0 mm. The blow moulding machine uses a 65–80 mm extruder, melt temperature 185–205 °C, blow air 0.5–0.7 MPa, and mould temperature 8–20 °C. The resin is typically blended with 0.2–0.4 wt% hindered amine light stabiliser masterbatch for UV resistance when containers are stored outdoors. Fluorination must be controlled to avoid excessive surface roughness; the treated inner surface should have a surface energy of 25–35 mN/m. Compliance is required to UN 6.1.5.2.1 for Packing Group II and III liquids, EPA FIFRA container standards, and FAO/WHO guidelines where relevant. The finished containers are bottom-gripped in drop tests at −18 °C from 1.2 m. Production bottlenecks include fluorine gas feed pulsation causing uneven barrier thickness, and parison weld lines at the handle area failing at low temperatures.

HDPE KL471A is extruded into sheet of 2.0–10.0 mm thickness for thermoformed secondary containment basins and chemical tank liners. The sheet line uses a 90–120 mm single-screw extruder with L/D 30–33, a flat die with adjustable lip, and a three-roll stack at 70–90 °C. Melt temperature at the die is 195–215 °C. Sheet is then thermoformed at 130–150 °C surface temperature with plug assist into basins of 0.5–2.0 m³ capacity. Welding of sheet sections is performed by hot-gas or extrusion welding with HDPE welding rod at 220–240 °C melt temperature. The finished liner is tested for spark testing at 15–30 kV to detect pinholes and hydrostatic leak testing for 24 h to EN 13361:2018 or ASTM D4437/D4437M-16 for geomembranes. Chemical compatibility is determined by immersion testing in 98% sulfuric acid and 30% sodium hydroxide at 23 °C for 7 days with change in tensile properties less than 10%. Processing addition: 1.5–2.5 wt% carbon black masterbatch is added when the liner is used in outdoor installations to meet ISO 16871 weathering. End product is used as secondary containment under chemical storage tanks, with a design leak rate below 1 × 10⁻⁶ m³/m²/day. Failure modes include weld cracking at the corner folds when the sheet is thermoformed below 120 °C, and environmental stress cracking in contact with wetting agents when the liner is under constant strain.

What Limits Parison Wall Uniformity in 1,000 L IBC Inner Bottle Moulding?

In blow moulding of 1,000 L IBC inner bottles, the limiting process variables are parison sag, die swell, and accumulator head pressure. HDPE KL471A provides a melt flow rate of 0.36 g/10 min to ISO 1133-1:2022, which maintains parison integrity over the 1,000–1,400 mm parison length. The accumulator head on a 120–150 mm extruder delivers a shot weight of 12–18 kg in 8–15 s; head pressure is 25–35 MPa. The mould clamping force is 3,000–6,000 kN; blow air is 0.6–0.8 MPa; mould temperature is 10–20 °C. Wall-thickness programming adjusts die gap from 1.0 mm at the top to 6.0 mm at the bottom corners. The finished inner bottle has a nominal wall thickness of 1.5–3.5 mm and a weight of 10–14 kg. Dimensional stability is checked by 3D scanning; the bottom outlet boss must remain within ±2 mm of true position. Compliance for composite IBCs is UN 31H1 for intermediate bulk containers; the inner bottle is drop-tested inside its steel cage from 1.2 m after conditioning at −18 °C. Hydraulic internal pressure test is performed at 70 kPa for 10 min to UN 6.5.4.8.5. Processing difficulties arise when the parison temperature drops below 185 °C at the lower edge, causing weld-line thinning at the bottom pinch-off; this is controlled by maintaining die exit temperature at 205–215 °C and closing the mould within 12 s of parison drop. Published data for this specific configuration is limited for some accumulator head geometries.