Blow moulding of 25–60 L tight-head jerry cans for UN dangerous-goods packaging uses PetroChina Dushanzi HDPE 5502XA in monolayer construction. The formulation is normally 98.0–99.5 wt% virgin pellets, 0.5–2.0 wt% pre-dried plant regrind, and 0.15–0.30 wt% lubricant or process aid where surface finish is specified. Extruder configuration is a 24:1–30:1 L/D barrier screw with a mixing section; barrel temperature profile is 175–190 °C in the feed zone, 185–200 °C in the compression zone, and 195–210 °C in the metering zone. Die head temperature is held at 190–210 °C. Blow air pressure is set at 0.65–0.85 MPa. Mould cooling water is maintained at 12–25 °C. The parison drop time must be kept below 8 s. In this window the resin is processed without drying under normal indoor storage; if pellet surface condensation occurs after outdoor storage at relative humidity above 75%, dry-air hopper exposure at 50–60 °C for 1–2 h reduces surface splay. Monolayer jerry cans qualify for UN certification under UN Model Regulations Chapter 6.1.5 for packaging group II and III liquids when the minimum wall thickness is not less than 2.5 mm on the flat sidewall and 3.0 mm at the closure boss. The resin meets the ESCR requirement because 5502XA typically exceeds 300 h F50 under ASTM D1693-15 Condition B. Tensile yield stress measured on specimens machined from blow-moulded sidewalls is not less than 24 MPa under ASTM D638-14. Flexural modulus is in the range 1,000–1,200 MPa under ISO 178:2019. End-use jerry cans for petrol, diesel, aqueous agrochemicals, and lubricant additives are produced at 20 L, 25 L, 30 L, and 60 L nominal capacity. If the packaged liquid is petrol or solvent-based, the inner surface is fluorinated inline at 0.1–0.3% fluorine in nitrogen for 10–30 s; this reduces permeation through the HDPE wall and prevents panel collapse or label lifting.

Why Does Die Swell in 5502XA Constrain Hourly Output in 200 L Drum Lines?

In 200 L drum production, the primary constraint is not screw output. The high molecular mass distribution of 5502XA produces pronounced die swell, typically 35–55% when measured as cross-sectional area increase at shear rates of 100–400 s⁻¹ and 200 °C under ISO 11443:2021 capillary rheometry. Die swell forces the tooling designer to use a die aperture 30–40% smaller than the target parison diameter; if the die is too wide, the parison diameter exceeds the split mould and pinch-off flash becomes uncontrollable. On 100–120 mm accumulator-head extruders with 28:1–32:1 L/D grooved-feed screws, 5502XA lines run at 350–550 kg/h only when the melt temperature at the die exit is held between 195 °C and 205 °C. Below 185 °C, sharkskin melt fracture appears at the die lips and causes micro-voids along the parison surface. Above 210 °C, the parison sag rate increases; a 6 kg parison for a 200 L L-ring drum sags by more than 15% in 6–8 s and the wall-thickness distribution cannot be corrected by parison programming alone. Programmable die gap profiles are set with 20–30 radial wall-thickness points; the die gap is reduced to 1.4–1.8 mm at the pinch-off zone and opened to 3.0–3.5 mm at the top chime. Blow pressure is 0.60–0.80 MPa. Mould water temperature is 12–20 °C. The clamping unit must provide 400–600 kN of closing force for a 200 L drum. The die swell behaviour is also affected by die land length; a land length of 12–18 mm is used to damp the elastic recovery of the melt. The output limitation is therefore a quality constraint: the extruder may be capable of 600–650 kg/h, but increasing screw speed above the shear-rate threshold causes melt fracture and unacceptable surface roughness. The production bottleneck is documented on manufacturing lines where the accumulator head volume is 15–25 L; filling and extrusion must be balanced so that the parison is delivered before cooling starts in the mould.

Multi-layer Coextrusion of 120–220 L L-Ring Drums for Hazardous Solvents

Multi-layer coextrusion of 120–220 L L-ring drums for Class 3, Class 5.1, and Class 8 materials uses 5502XA as the inner and outer virgin layers because its high-molecular-mass structure resists environmental stress cracking at the weld lines and closure chimes. The layer structure is typically three layers: 20–30% virgin 5502XA inner layer, 40–60% plant regrind core, and 15–25% outer layer of 5502XA compounded with 1.5–2.5% carbon black or colour masterbatch. Coextrusion die head temperature is kept at 190–205 °C. The inner virgin layer thickness must not be less than 0.8 mm at any point after wall-thickness programming. For aggressive chlorinated solvents and some ketones, unfluorinated HDPE is not an adequate barrier. Inline fluorination of the inner surface with 0.1–1.0% fluorine in nitrogen for 20–40 s at ambient temperature reduces permeation and improves container integrity. For coextrusions with a polyamide or EVOH barrier layer, an adhesive tie layer is required; 5502XA is then used only as the structural outer and inner skin, not as the barrier. The design wall thickness for a 200 L drum is 2.2–3.0 mm on the sidewall and 3.5–4.5 mm at the top and bottom chimes. The drum must pass the UN hydraulic pressure test under UN Model Regulations Chapter 6.1.5.5 without leakage at the specified pressure for the packaging group. ESCR retention at the chime weld is verified before commercial release by sampling three drums per shift and performing ASTM D1693-15 Condition B F50 on sidewall coupons cut at 12 o'clock and 6 o'clock positions. The regrind core is limited to 60 wt% because higher levels reduce the F50 value to below 150 h and increase the chance of environmental stress cracking at the L-ring junction after 6–12 months of filled storage.

For non-road diesel and hydraulic-fluid reservoirs produced on single-head accumulator machines, 5502XA is processed at a melt temperature of 190–205 °C with a 25:1–30:1 L/D extruder and a 4–6 L accumulator head. A 40 L tank uses a parison weight of 2.4–3.2 kg; wall thickness is 3.5–5.0 mm at the tank body and 6.0–8.0 mm at the filler neck. The mould cooling water is held at 18–25 °C. Demoulded tanks are placed in a water-cooled or air-cooled fixture for 90–180 s to prevent shrinkage warpage. The resin is suitable where the OEM specification accepts an HDPE structural shell with fluorinated or sulphonated inner wall for hydrocarbon retention. Vibration welding of injection-moulded HDPE filler necks to the blow-moulded shell is performed at 1.0–1.5 mm amplitude, 200–240 Hz frequency, and 0.5–1.5 MPa weld pressure. Welded joint strength of 85–95% of parent material is obtained if the weld joint is a shear rib with 0.5–1.0 mm interference. Open-flame or hot-plate welding is not recommended above 230 °C because extended residence time causes depolymerization at the weld bead. Drop impact at -20 °C is specified by end users for cold-climate machinery; the tank is conditioned for 24 h at -20 °C and impact-tested under ISO 6603-2 with a 20 J striker. Published data for this specific configuration is limited; batch validation is therefore performed by the moulder using the end-user's own drop height and fill medium.

Post-Consumer Regrind Blends in Non-Regulated Household Chemical Packaging

Post-consumer HDPE regrind is blended with 5502XA at 20–50 wt% for non-food household chemical bottles and industrial pails where UN dangerous-goods certification is not required. The PCR must be melt-filtered through 100–150 mesh screens and dried to below 300 ppm moisture before blending. Extrusion blow moulding is performed at the same barrel profile as virgin 5502XA: 175–200 °C feed-to-compression, 195–210 °C metering, and 190–205 °C die. At 30 wt% PCR, the blend retains approximately 60–70% of the virgin ESCR value because the high-molecular-mass fraction in 5502XA compensates for the reduced tie-molecule density of the recycled material. Above 50 wt% PCR, the ESCR F50 under ASTM D1693-15 Condition B falls below 100 h, and the notched Izod impact under ISO 179-1:2020 drops below 15 kJ/m². For such blends, 0.05–0.15 wt% of a hindered phenol/phosphite antioxidant masterbatch is added to reduce further degradation during the additional heat history. The resulting containers are limited to non-food applications because FDA 21 CFR 177.1520(c) permits recycled olefin polymers only when a premarket notification demonstrates contamination control. This application does not satisfy EU No 10/2011 food-contact migration limits unless the entire supply chain is food-grade and tested on the finished article under Regulation (EU) 2022/1616.

When 5502XA Is Blow-Moulded into Marine Fenders and Buoyancy Shells

When 5502XA is blow-moulded into marine fender shells, dock floats, and buoyancy modules, the specification changes from chemical compatibility to long-term weathering and impact. The compound contains 2.0–3.0 wt% carbon black masterbatch; other UV stabilizer systems are used only where colour matching is required. The wall thickness is 5–10 mm for fender shells that are filled with closed-cell polyurethane foam after moulding. Extrusion is performed at 190–210 °C melt temperature on an accumulator head with 60–100 L shot capacity for large parts. Mould temperature is 20–30 °C. Cooling time is 180–300 s. The blow-moulded shell must pass ISO 4892-2:2013 xenon-arc exposure for 2,000 h with tensile elongation retention not less than 70%; carbon black at the specified loading provides the necessary UV absorption. Seawater exposure requires ESCR testing after 1,200 h immersion in 10% Igepal at 50 °C under ASTM D1693-15 Condition C; typical failure time for 5502XA-based black shells exceeds 500 h. The moulded part is inspected for pinch-line thinning; the pinch-off area must be trimmed to leave a flash bead not more than 2 mm and not less than 0.5 mm to prevent stress concentration at the seam. Fastener inserts are not overmoulded because thermal expansion and water ingress at the insert-HDPE interface can initiate stress cracks; instead, the foam-filled shell is post-drilled and fitted with stainless steel backing plates. The application is limited to service temperatures above -20 °C; below that threshold, impact crack propagation at flash lines increases.