Yanchang China Coal Yulin (Shaanxi) HDPE 5502S enters the industrial packaging route as an extrusion blow moulding resin with a manufacturer-published typical melt flow rate of 0.35 g/10 min at 190°C/2.16 kg and a typical density of 0.955 g/cm³. The grade is processed on accumulator-head machines for 5–60 L jerrycans and tight-head drums, where parison melt strength and environmental stress crack resistance determine the useful processing window. The extruder barrel is maintained at 180–210°C from feed throat to die head, the accumulator tooling is heated to 190–205°C, and the mould temperature is held at 10–25°C to balance cooling time against surface finish. Wall thickness programming uses a parison programmer with 20–100 points around the circumference; the die gap is adjusted between 1.2 mm and 3.5 mm to produce a final sidewall thickness of 1.8–3.0 mm depending on container size and UN transport classification. Blow air is introduced at 0.55–0.80 MPa through a calibrated blow pin. The parison is pre-clamped before final mould closure to centre the pinch-off line and to prevent off-centre weld displacement. Flash thickness at the pinch-off is controlled to 0.2–0.5 mm; thicker flash indicates insufficient clamp force or excessive die gap, while thinner flash creates a cold weld that fails in drop testing. For outdoor storage, 0.5–2 wt% of a UV-stabilized polyethylene masterbatch is added; the masterbatch must be dried if packaging has been exposed to high humidity, although HDPE itself does not require pre-drying below 60% RH. The finished jerrycan is typically marked as a UN 3H1 package. Drop testing is conducted after conditioning at -18°C per the UN Model Regulations Chapter 6.1.5. The pinch-off weld is the highest-risk zone. Burst strength is measured at 0.25–0.35 MPa, and the weld-to-sidewall thickness ratio should be at least 0.6 for dangerous goods containers. Environmental stress crack resistance is screened under ASTM D1693-15 Condition B in 100% Igepal CO-630; acceptance values are set by the end-user, and published data for this specific grade should be verified against each production lot because minor lot-to-lot variation in comonomer distribution can shift the F50 value.

What Limits Pinch-Off Weld Integrity in Detergent Bottle Production?

In shuttle and rotary wheel extrusion blow moulding lines producing 0.5–5 L detergent and household chemical bottles, the critical quality limit is the bottom pinch-off weld rather than sidewall thickness. HDPE 5502S is blended with a PE-based colour masterbatch at 1–3 wt% and, when surface slip is required, with a slip/antiblock masterbatch at 0.5–1.5 wt%. The barrel profile is normally 180–210°C, the die head is held at 190–205°C, and the mould is cooled to 8–20°C. The pinch-off insert is machined to an included angle of 30–45° with a land width of 0.3–0.8 mm. Correct clamp force limits flash to 0.2–0.5 mm; insufficient clamp pressure produces a thick flash hinge and a weak weld, while excessive pressure thins the weld line and reduces top-load capacity. Top-load strength is measured according to ASTM D2659-16 or ISO 12048:1994, with typical 1 L bottle values in the 150–300 N range. Bleach-containing products require screening under ASTM D1693-15 because hypochlorite accelerates stress cracking at the pinch-off line; the F50 time in 100% Igepal CO-630 is the normal release criterion. A documented production failure on shuttle machines is off-centre pinch-off when the parison is not mechanically pre-centred before mould closure. This shifts the weld line into the bottle base and lowers drop impact resistance. The defect is detected by sectioning the base, measuring weld displacement, and comparing it to a maximum offset of 0.5 mm. The final bottle is a hollow, narrow-neck container with a screw-thread finish and a snap-on or child-resistant closure.

Food-Contact Bottles Are Governed by Migration Thresholds

Under FDA 21 CFR 177.1520(c) 2.1, olefin polymers with a density not below 0.94 g/cm³ are cleared for food-contact use, subject to the condition that the finished article is tested for end-use migration. In the European Union, Regulation (EU) No 10/2011 applies an overall migration limit of 10 mg/dm² for plastic food-contact materials. For HDPE 5502S, the food-contact converter typically runs the resin unmodified or with a food-grade masterbatch at 0.5–2 wt%. The melt temperature is held at 200–220°C, but residence time above 220°C is limited to avoid oxidative degradation products that alter organoleptic neutrality. The parison drop time is minimized to 1.5–3.5 s, and the mould closes in 0.5–1.5 s to limit cooling of the parison skin before inflation. Blow air is filtered to remove oil and moisture. The mould cavity is vented at 0.02–0.05 mm to prevent air entrapment at the bottle shoulder. Cold-fill dairy and juice bottles in the 0.5–2 L range are commonly produced with wall thicknesses of 0.8–1.5 mm. Top-load testing follows ASTM D2659-16 with a target of 150–300 N for a 1 L bottle. Migration testing is performed on the final bottle under EU 10/2011 Annex V, using simulant D1 for aqueous foods and simulant D2 for fatty foods if the bottle is used for oil-containing products. Compliance of the resin as supplied does not automatically confer compliance on the blow-moulded article because processing aids, colourants, or recycled content can change migration behaviour. The finished product is a lightweight, squeezable or semi-rigid food bottle with an aluminium induction-seal or polypropylene closure.

Agrochemical Container Permeation and In-Line Fluorination Confinement

Agricultural chemical containers from 0.5 L to 20 L require a permeation barrier when the packaged solvent is aromatic, chlorinated, or ketonic. Untreated HDPE 5502S has high permeability to such solvents. Container permeation is measured gravimetrically according to ASTM D2684-18, using the actual formulation and storage temperature. In-line fluorination is introduced during blow moulding by injecting fluorine gas into the parison at 0.1–2.0 vol% in nitrogen. The fluorine reacts with the inner surface to form a fluorinated barrier layer several nanometres thick, reducing solvent loss and panel deformation. The process requires explosion-proof gas handling, continuous fluorine monitoring at 0.5–1.0 vol%, and purge cycles that reduce workstation fluorine concentration below 1 ppm before operator access. The formulation includes 1–2 wt% of a UV-stabilized PE masterbatch for outdoor storage. Amine-based additives are excluded because they deactivate the fluorinated surface. The extrusion line is run at 185–205°C melt temperature, with the parison inflating at 0.6 MPa after mould closure. Wall thickness is programmed from 1.5 mm at the shoulder to 2.5 mm at the base to support the weight of induction-sealed closures and stacking loads. The finished article is a tight-head container with a fluorinated inner barrier, a screw neck with induction-sealed foil cap, and UN marking as 3H1. Drop testing is performed at -18°C, and permeation testing at 40°C for 28 days is typical for qualification. The barrier is a surface treatment; deep scratches in the neck or shoulder remove the fluorinated layer and expose raw HDPE to solvent migration.

When Diesel Exhaust Fluid Containers Are Blow-Moulded from Unmodified HDPE

Diesel exhaust fluid (DEF) is an aqueous urea solution regulated by ISO 22241-1:2019. Packaging must not release metal ions, plasticizer, or other extractables into the fluid. HDPE 5502S is evaluated in unmodified form or with a low-ash PE masterbatch below 1 wt%. The blow moulding line for a 10 L DEF canister runs at a melt temperature of 190–210°C, with the mould at 10–18°C and wall thickness set at 1.5–2.5 mm. The container permeation to water vapour is assessed gravimetrically at 23°C and 50% RH under ASTM D2684-18. Typical HDPE water vapour transmission through a 2 mm wall is in the 0.2–0.8 g/(m²·day) range, but published data for this specific configuration is limited and must be confirmed on the finished canister. The closure is an induction-sealed PE-foam liner inside a polypropylene screw cap. Filled canisters are drop-tested at -10°C from 0.3 m without leakage. Stacking strength after 48 h at 40°C is measured under ISO 12048:1994. The product must be protected from direct sunlight during storage because UV exposure degrades the outer surface and reduces molecular weight at the skin.

Large open-head drums and water storage vessels from 60 L to 220 L form a separate downstream route for HDPE 5502S. The conversion line is an accumulator-head machine with multi-parison capability, capable of producing one or two open-headed parisons per cycle. For a 120 L open-top drum, the wall thickness is programmed from 3.0 mm at the base to 4.5 mm at the rim to prevent bulging under hydrostatic load. The material is blended with 0.5–1.5 wt% carbon black masterbatch for UV resistance. Outdoor weathering is assessed by ASTM D2565-23 or ISO 4892-2:2013, with the acceptance criterion normally being a specified property retention after a defined xenon-arc exposure. The mould temperature is held at 10–20°C, and internal cooling of the part is continued until the pinch-off zone reaches below 90°C before ejection to prevent post-mould warpage. Stacking performance is evaluated at 40°C for 28 days under a load equivalent to 1,000 kg on the bottom drum. Hydrostatic burst testing is conducted at 0.1–0.2 MPa to confirm sidewall integrity. The drum is fitted with a steel clamp ring and a gasketed lid; the gasket compression set is not a property of HDPE but influences the closure integrity. The end product is used for non-hazardous liquids, powdered chemical intermediates, and as a food-contact liner within a rigid outer packaging. Rotational moulding is not a suitable conversion route for this grade because the pellet form and parison-optimized molecular architecture are not designed for low-shear densification.

Cosmetic bottles blow-moulded from HDPE 5502S are usually in the 100 mL–1 L range and require a high-gloss outer surface free from weld lines, flow marks, and die lines. The resin is processed on continuous rotary wheel or intermittent shuttle machines at 185–205°C. The mould cavity is polished to SPI A-1 or A-2 to achieve reflectance. Formulation includes a pearlescent or colour masterbatch at 1–4 wt%; the masterbatch carrier must be PE-compatible and free from particles that create visible fish-eyes. The parison is pre-inflated at 0.05–0.15 MPa to lift it from the die before mould close and to spread residual die lines. A two-stage blow profile is used: first stage at 0.4 MPa for 1–2 s establishes the bottle silhouette, second stage at 0.7 MPa for 5–10 s consolidates wall thickness and replicates the cavity polish. The blow pin is kept at 25–35°C to calibrate the neck without forming a cold neck ring. Post-mould shrinkage of 1.5–2.5% over 24 h is applied to cavity dimensions. The end product is a single-layer cosmetic bottle with a screw-thread finish, decorated by screen printing or labels. Because the bottle is not pressurised and is intended for ambient storage, hydrostatic testing is not required; dimensional and drop resistance testing are conducted instead.

Why Blow-Moulded Automotive Reservoirs Demand High ESCR at Low Temperatures

Automotive washer fluid reservoirs from 2 L to 5 L are produced from HDPE 5502S when the design requires a lightweight, integrated tank with pump grommets and level-sensor bosses. The reservoir is blow-moulded at 195–215°C melt temperature, with wall thickness 2.5–4.0 mm to resist engine-compartment heat and stone impact. The mould includes inserts for the pump grommet and sensor boss; these inserts are kept at 80–100°C to ensure adequate material consolidation around the grommet seat. Formulation normally includes 1–2 wt% carbon black or grey masterbatch with heat stabilizers. Low-temperature impact resistance is assessed by drop testing at -30°C after conditioning. Environmental stress crack resistance is evaluated under ASTM D1693-15 Condition B, because methanol and ethylene glycol blends in washer fluid can accelerate microcracking at the pinch-off and grommet regions. Heat aging is performed at 100°C for 7 days under ASTM D3045-18; the retained tensile elongation is compared with the unaged value. The reservoir is not a pressure vessel and is not suitable for fuel or brake fluid. The final part includes snap-fit mounts, a pump grommet seal, and a level-sensor port. Leak testing is performed at 0.03–0.05 MPa air pressure under water to detect pinholing at weld lines.