HD1100J is typically converted by shuttle or accumulator-head extrusion blow moulding for tight-head jerrycans with nominal capacities from 5 L to 30 L. The melt flow rate is normally specified below 1.0 g/10 min at 190 °C under 2.16 kg, and the density is maintained above 0.948 g/cm³ to provide panel stiffness. In production, barrel set temperatures are ramped from 180 °C at the feed throat to 215 °C at the accumulator head, with the die exit melt temperature held between 205 °C and 220 °C. A 70 mm single-screw extruder with a 25:1 L/D ratio and a barrier screw is adequate for a 0.9 kg shot on a 20 L container; shot-to-shot variation remains below 1.5% when the screw recovery time is set longer than the mould cooling time. Parison programming is essential because the pinch-off base and integrally moulded handle require thicker walls than the side panels. Typical programmed wall thicknesses are 1.6 mm to 2.0 mm on the sidewall, 2.4 mm to 2.8 mm at the handle bridge, and 3.0 mm to 3.5 mm at the pinch-off weld. Blow air pressure is set at 0.6 MPa to 0.9 MPa, with a pre-blow step of 0.1 MPa to 0.3 MPa for controlled parison inflation. Cooling times of 20 s to 30 s are typical with chilled mould water at 8 °C to 15 °C. At die temperatures above 220 °C, the parison becomes prone to drawdown and diameter variation; below 190 °C, melt fracture at the die lip creates shark-skin on the inner surface. The practical processing window is therefore approximately ±5 °C around 205 °C when a 1.4 mm die gap is used. Extruder head pressure should remain below 25 MPa to avoid excessive shear heating, while backpressure at the screen pack is maintained between 5 MPa and 10 MPa to stabilise output.

The critical weld at the base is formed by trimming flash between the mould halves; insufficient pinch-off compression produces a cold crack path that lowers drop-test survival. For UN certification under ADR 6.1.5.3.4, the filled container must resist a 1.2 m drop at -18 °C after conditioning. Blow-moulded parts from HD1100J are also tested for environmental stress crack resistance using ASTM D1693 Condition B, 100% Igepal CO-630; the plaque F50 value is not sufficient for qualification because orientation and pinch-off stress can reduce the actual bottle ESCR by 30% to 50%. Regrind content in the parison is limited to 20 wt% to 35 wt% for UN-approved jerrycans; lot-to-lot regrind from the same production campaign is preferred because foreign HDPE grades with different melt viscosity cause parison ovality and weld-line delamination. If the regrind fraction exceeds 35 wt%, melt strength drops, die swell becomes unstable, and the hydraulic pressure test required by UN 6.1.5.3.5 may show leakage at the base pinch-off. Wall thickness distribution is verified by ultrasonic scanning in the range 5 MHz with a 10 mm transducer; sidewall variation greater than 0.4 mm outside the programmed map indicates parison drift and requires immediate recalibration of the accumulator stroke.

What Limits Environmental Stress Crack Resistance in Hypochlorite Bleach Bottles at the Pinch-Off Weld?

In monolayer extrusion blow moulding of detergent and hypochlorite bleach bottles from HD1100J, the most frequent failure is not burst but environmental stress cracking that initiates at the base pinch-off or the flash trim line. A 750 mL bottle with a 38 mm neck finish is run on a continuous shuttle machine with a 55 mm extruder, 24:1 L/D, and a converging die gap of 0.8 mm to 1.2 mm. The melt temperature is usually held near 195 °C to 210 °C; lower melt temperatures increase molecular orientation but also elevate injection pressure and die swell, which can shift the pinch-off weld location. Bottles for sodium hypochlorite at 5% to 6% active chlorine must pass a cap-torque retention sequence with 2 N·m to 3 N·m initial closure. Stress cracking at the thread roots is evaluated by ASTM D1693 Condition C or a bottle-specific 28-day contact test at 50 °C. The tie between parison wall thickness and ESCR is nonlinear: lowering the sidewall from 0.9 mm to 0.6 mm to reduce weight raises the surface stress under internal pressure and shortens time to craze initiation. Thickness at the pinch-off weld must remain above 2.2 mm for a filled 750 mL bottle because the weld is the region with the lowest ESCR after trimming. Regrind addition at 15 wt% to 25 wt% is standard for cost control, but higher regrind fractions increase the coefficient of variation in parison length by 3% to 6% and produce translucent weld lines. TiO₂ masterbatch at 2 wt% to 3 wt% is added for opacity; the masterbatch carrier must have a melt flow rate within 0.5 g/10 min of the base resin to avoid die swell instability. The cap-to-neck interface is formed with calibrated blow pins or post-mould reaming; neck ovality above 0.4 mm causes torque loss and leak failure after hot filling or squeeze testing.

Co-Extruded Barrier Layer Sequencing and the Polyolefin Tie-Layer Interface

Agrochemical bottles produced from HD1100J are typically co-extruded in six-layer configurations: virgin HDPE outer skin, maleic anhydride-grafted polyolefin tie, ethylene vinyl alcohol barrier, maleic anhydride-grafted polyolefin tie, regrind core, and virgin HDPE inner skin. Layer distribution is controlled at the die feedback with outer skins together in the range 30 wt% to 40 wt%, tie layers 2 wt% to 3 wt% each, and EVOH at 2 wt% to 5 wt%. The regrind core, consisting of trimmed flash and off-spec bottle flake, is limited to 30 wt% to 40 wt% because higher core fractions increase back pressure at the feedback and can disturb layer uniformity. Feedblock and spiral mandrel dies are operated at 210 °C to 230 °C; EVOH and tie layers require pre-drying to below 0.1% moisture, otherwise pinhole gels and interlayer delamination occur at the die lip. Solvent-based formulations based on xylene, cyclohexanone, or chlorothalonil require permeation testing on the finished bottle, not on compression-moulded sheet, because wall thickness in the corners drops to 60% to 70% of the nominal sidewall and accelerates permeation. The bottle must meet the hydraulic pressure test under UN 6.1.5.3.5 and a stack-load test for 28 days at 40 °C without leakage when filled with the actual formulation. A problematic failure observed on production lines is delamination at the tie-HDPE interface after solvent immersion for 72 h at 50 °C, indicating that tie-layer coverage was discontinuous due to an oversized regrind fraction or excessive moisture in the tie resin. The rework window is therefore narrower than monolayer packaging: any change of more than 5 wt% in regrind content requires re-validation of the bottle wall thickness map and weld strength. EVOH layer thickness is targeted between 0.05 mm and 0.10 mm; below 0.03 mm, oxygen barrier performance degrades sharply due to layer breakup and flow instability in the feedback selector plug.

When Coolant Expansion Tanks Need Creep Data at 120 °C

Extrusion blow moulded coolant expansion tanks and windscreen washer reservoirs made from HD1100J are validated to long-term hydrostatic creep and ethylene glycol resistance, not solely burst. A 2.5 L expansion tank is blow moulded on an accumulator-head machine with parison programming that shifts wall thickness to the two mounting bosses and the hose barb; the sidewall remains between 1.5 mm and 2.0 mm. The material is exposed to 50/50 ethylene glycol/water at 120 °C and an internal pressure of 1.0 bar to 1.5 bar for 1,000 h in a pressure cycling rig. Creep rupture is evaluated under ASTM D2990 or a comparable OEM standard; published data for this specific configuration is limited, so part-level validation is required. The failure mode seen on production lines is not brittle fracture but softening at the hose barb, where local wall thickness can fall to 1.2 mm and the hoop stress increases. The hoop stress at the barb root is calculated from the Barlow equation; a wall thickness below 1.2 mm at the barb is rejected during ultrasonic thickness scanning. For windscreen washer reservoirs, a methanol-water mixture at 35% methanol is tested for 500 h at 60 °C; the main concern is stress cracking at weld lines and inserts. HD1100J’s melt flow below 1.0 g/10 min allows deep-draw parison inflation without excessive sag, but moisture on the mould surface above 60% relative humidity causes surface defects and must be controlled with mould temperature above the dew point. Mould temperature is maintained between 40 °C and 60 °C for adequate surface replication of mounting boss ribs; lower mould temperatures reduce gloss and create incomplete forming at the hose-barb base. Pre-blow and main blow pressures are profiled at 0.05 MPa to 0.15 MPa and 0.6 MPa to 0.8 MPa, respectively, to prevent folded weld lines in the handle transition.

Open-head pails from 10 L to 25 L are blow moulded from HD1100J on single-station shuttle machines with a 60 mm extruder and a blow pressure of 0.6 MPa to 0.8 MPa; the melt strength permits accumulator-free parison formation at shot weights up to 0.7 kg.

Twin-sheet thermoforming of HDPE dunnage trays and machine guards begins with sheet extrusion from HD1100J at melt temperatures of 220 °C to 240 °C, using a 90 mm extruder and a 30:1 L/D screw with a barrier profile. The sheet is polished on three-roll stack rolls at 80 °C to 95 °C. A twin-sheet forming line then heats the sheet to 165 °C to 180 °C surface temperature, with vacuum holes and plug assist forming the two halves before compression welding at the flange. The lower melt flow index of HD1100J provides high melt strength during radiant heating and reduces sag, but sheet output is lower than injection-moulding grades by 10% to 20% at the same screw speed. The formed tray is assessed for dart impact according to ISO 6603-2, with failure energy typically above 20 J at -20 °C for a 3 mm sheet. Process problems occur when sheet temperature exceeds 180 °C; the sheet thins non-uniformly at the plug assist and creates weld flash at the flange that reduces the part’s load-bearing capacity. This application is secondary to blow moulding and should not be used for structural returnable pallets without additional creep testing under ISO 899-2.