Sinopec Shanghai HDPE CH2802 enters monolayer extrusion blow moulding operations as a high-density polyethylene with a nominal density of 0.958 g/cm³ to ISO 1183-1:2019 and a reference melt mass-flow rate of 0.28 g/10 min at 190 °C under 2.16 kg to ISO 1133-1:2022. In detergent, personal-care and lubricating-oil packaging, the resin is converted without pre-drying when storage relative humidity is below 60% RH; at higher humidity, surface condensation on cold granulate can generate melt-stream voids and pinholing at the die exit. The standard formulation for an opaque 1 L to 25 L stackable jerrican includes 100 parts virgin CH2802, 2–5 wt% titanium-dioxide-based white masterbatch, and 0–25 wt% post-industrial flash regrind for non-dangerous-goods service. Processing is carried out on single-head shuttle blow moulders with 24:1 to 30:1 L/D barrier screws. Barrel zones are profiled from 160 °C at the feed throat to 205 °C at the die head, and melt temperature is held between 195 °C and 215 °C. Parison programming is used to narrow the die gap 10–15% at the pinch-off zone and to widen it 8–12% at the base chime. Mould cooling water is maintained at 10–18 °C, blow pressure is set at 0.6–0.8 MPa, and pre-blow delay is 0.3–0.7 s. The finished articles are stackable jerricans with calibrated neck finishes for screw-cap or foil-seal closures, drop-tested to ASTM D2463-15 and leak-tested at 20–30 kPa pneumatic pressure. CH2802 is not a general-purpose injection-moulding grade; converters should not substitute the resin into hot-runner piston machines without first confirming melt-index compatibility to ISO 1133-1:2022.

What Causes Environmental Stress Cracking in Tight-Head Agrochemical Jerricans?

In tight-head agrochemical jerricans, environmental stress cracking is governed by residual hoop stress at the pinch-off weld, wall-thickness distribution at the bottom chime, and the polar association of ester, ketone, or amide solvent constituents with polyethylene tie chains. For CH2802 in agrochemical service, the resin is compounded with 2–3 wt% carbon black masterbatch to provide ultraviolet screening at 0.2–0.4 mm wall stock; the masterbatch carrier is LLDPE-based to limit melt-index drift during repeated heat histories. The blow-moulding operation uses an accumulator head with 10–25 L shot capacity, a diverging die gap of 1.5–2.5 mm, and parison programming adjusted to maintain corner wall thickness above 0.8 mm in the handle area and above 1.2 mm at the bottom chime. Melt temperature must not exceed 215 °C to avoid chain scission and ESCR decay; barrel residence time is limited to 6–8 minutes. Mould cooling at 12–15 °C is maintained until demoulded surface temperature is below 65 °C, because hot parts ejected into stacking bins retain weld-line stress. The finished article is a 1 L, 5 L, or 20 L UN-certified jerrican for pesticide concentrates and plant-growth regulators. Transport conformance is evaluated under the UN Manual of Tests and Criteria, Part III, section 21 drop test at 1.2 m for packing group II, a hydraulic pressure test at 250 kPa for 30 minutes, and a stack test for 28 days at 40 °C under ADR Chapter 6.1. Low-temperature drop claims require conditioning at -18 °C before the impact cycle. Not every lot automatically satisfies UN certification; batch-specific ESCR values to ASTM D1693-15, condition B, 100% Igepal CO-630, 50 °C, must be tabulated against minimum wall thickness before release.

Coextruded Barrier Skins: CH2802 Around an EVOH Core

Coextruded barrier containers for solvent-based agricultural formulations use CH2802 in the outer and inner skin layers, while an ethylene-vinyl alcohol copolymer core suppresses permeation of xylene, cyclohexanone, and mixed aromatic solvents. A typical six-layer structure is 45 wt% outer CH2802, 3 wt% maleic-anhydride-grafted polyethylene tie resin, 3 wt% EVOH, 3 wt% tie resin, 25 wt% post-industrial CH2802 regrind, and 21 wt% inner CH2802. Coextrusion is performed on a six-extruder blow moulder with layer sequencing controlled by a spiral mandrel die; HDPE skin extruders are set from 190 °C to 215 °C, while EVOH is processed at 185–205 °C within its thermal stability window. The die head is held at 205 °C and the melt curtain is inflated at 0.65 MPa blow pressure. The terminal product is a 1 L, 5 L, or 10 L multi-layer bottle for xylene-based or ketone-based agricultural adjuvants. Barrier performance is characterised by gravimetric solvent-loss testing at 40 °C for 28 days; dimensional stability is checked by GB/T 13508-2011 and drop impact by ASTM D2463-15. EVOH layers are moisture-sensitive; pre-drying at 80 °C for 4–6 hours is mandatory when ambient relative humidity exceeds 40% RH. Direct food-contact use is not automatic; a food-contact compliance certificate to GB 4806.7-2016 or EU 10/2011 must be obtained from the resin supplier before such claims are made.

On accumulator-head machines, open-top pails produced from CH2802 are processed when the part weight exceeds 600 g. The formulation for a water-based paint or adhesive pail is 100 parts CH2802, 4–6 wt% white masterbatch for light-blocking walls, and up to 35 wt% in-house regrind from trimmed rims and rejected pail walls, provided the product is not regulated as dangerous goods. For pails intended to hold flammable or corrosive preparations, regrind addition is limited to 15 wt% unless the re-qualified blend has been tested under the relevant transport regulation. The mould is a tapered bucket with rim, body, and base wall thicknesses held at 1.8 mm, 1.4 mm, and 1.2 mm respectively. Accumulator-head shot size is matched to the pail volume with a fill-to-shot ratio of 1.1:1 to 1.2:1; blowing pressure is 0.7–0.8 MPa. The terminal articles are 10 L, 20 L, and 30 L open-top pails with gasketed lids and steel locking rings for water-based coatings, adhesives, and construction admixtures. Top-load and stacking qualification uses ISO 12048:1994; pneumatic leakproofness is checked at 20 kPa with the lid locked.

When Regrind Fractions Exceed 30 wt% in Monolayer Wall Stock

When post-industrial flash and rejected container walls are re-extruded into monolayer wall stock, the critical variable is not melt index alone but the shift in die swell and parison sag caused by sheared and re-sheared polyethylene chains. At regrind fractions above 30 wt%, CH2802 wall stock exhibits measurable reductions in die swell at constant die gap, requiring an increase in die gap of 0.2–0.5 mm to maintain the same parison diameter. Melt pressure in the accumulator head falls by 5–15% as the molecular weight distribution narrows under repeated shear; operators compensate by lowering screw speed 10–20 rpm and raising the barrel temperature profile by 5–8 °C. The risk area is ESCR at the pinch-off weld: regrind-rich domains develop lamellar orientation that is less resistant to Igepal CO-630 stress cracking, so the addition rate for UN-certified jerricans is capped at the value specified in the certification test, commonly 20 wt% or lower. The process specification calls for granulator screens with 8–10 mm apertures, a densifier for spider-web flash, and blend homogeneity checks by melt index sampling per ISO 1133-1:2022. Published data for this specific configuration is limited; processors should run a 20-batch regrind stability trial measuring die swell, melt temperature uniformity, and drop impact under ASTM D2463-15 before releasing production.

Diesel exhaust fluid containers demand a wall-thickness tolerance that prevents deformation during sealed hot-fill and subsequent cooling. CH2802 is converted into 5 L, 10 L, and 20 L automotive AUS 32 containers on shuttle blow moulders with 10–20 L shot capacity. The blowing grade is processed at 195–210 °C melt temperature and 12–18 °C mould temperature; the parison programmer is set to hold flat-panel walls above 0.7 mm and welded corners above 0.9 mm. The resin formulation for AUS 32 service uses 2–4 wt% of a blue masterbatch that does not contain amine, phenolic, or mineral-oil residues because leachates can poison selective catalytic reduction catalyst systems. Only in-house regrind from diesel exhaust fluid containers is permitted; regrind from lubricant or agrochemical containers is excluded because residual hydrocarbons cannot be washed from porous regrind surfaces. Containers are tested for leakproofness at 30 kPa, burst resistance above 100 kPa, and drop impact under ASTM D2463-15 after conditioning at -10 °C. The finished product is a closed-loop AUS 32 container with a tamper-evident neck, handled under ISO 22241-3:2017 guidance for handling and transport of NOx reduction agent.