EQUATE HDPE EGDM-6888 is specified for extrusion blow moulding of industrial, agrochemical, and intermediate bulk containers where the primary process variables are parison melt strength, resistance to slow crack growth, and dimensional stability under stacked transport loads. The resin is characterized by a nominal density of 0.954 g/cm³ when measured according to ISO 1183-1, and a high-load melt index in the 7–9 g/10 min range under ISO 1133-1:2022 at 190 °C/21.6 kg. That high-load melt index places the grade in the high-molecular-weight blow-moulding segment, where accumulator-head production of containers from 5 L to 220 L is feasible without excessive parison sag. On production-scale single-screw extruders with screw diameters between 60 mm and 120 mm and 24:1–30:1 L/D ratios, melt temperatures are maintained at 190–210 °C; higher settings reduce melt viscosity and increase the risk of thin-wall banding, while lower settings raise backpressure and generate unmelted gel particles at throughputs above 180 kg/h. Accumulator-head die temperatures should be held within 5 °C of the adapter temperature to avoid parison curl. Because high-density polyethylene is not hygroscopic, pre-drying is not required for resin taken directly from sealed packaging; however, cold pellets stored at ambient relative humidity above 60% can develop surface condensation that produces pinhead porosity in the pinch-off seam. A hopper purge with dry air is therefore required when condensation is visible. The addition of low-viscosity hydrocarbon waxes above 0.5 wt% is not recommended for this resin because those additives depress melt elasticity and increase parison sag in large-sheet parison configurations.

220-L Tight-Head Drum Line: Pinch-Off Integrity and Wall Thickness Distribution

In extrusion blow moulding of 220-L tight-head drums, EGDM-6888 is processed on accumulator-head machines with die diameters in the 250–350 mm range and parison programming that ramps wall thickness from the top closure to the bottom chime. The limiting defect is pinch-off flash splitting at the bottom seam, where two semi-molten parison surfaces are welded under clamp force before blowing; insufficient melt temperature or excessive mould closing speed produces a cold weld line with low interdiffusion across the parison interface. On a two-platen shuttle press with clamp force above 800 kN, blow pressure is set at 0.7–1.0 MPa, and pinch-off bar temperature is held at 40–60 °C to prevent quench cracking in the flash. Wall thickness is controlled non-uniformly: the bottom chime is programmed to 3.5–4.5 mm, the sidewall to 2.0–2.8 mm, and the top shoulder to 3.0–3.5 mm because the top closure must withstand drop impact without distortion. Thickness distribution is verified by ultrasonic gauge with a minimum single-wall tolerance of 2.0 mm at the sidewall. Drop testing is performed under 49 CFR 178.509 with a 0.6 m drop height and 100% fill at −18 °C; the bottom chime must not show stress whitening or through-cracking. The high-molecular-weight tail of EGDM-6888 improves slow crack growth resistance at the pinch-off seam; however, the use of regrind above 30 wt% narrows the melt-temperature window and increases the incidence of parison sag under accumulator-head conditions.

Batch-to-batch variation in high-load melt index should be monitored because a shift of 0.5 g/10 min changes the parison elongation rate at the same die gap. Screw speed is normally set to 30–50 rpm on a 90 mm extruder, giving a melt pressure of 18–25 MPa at the die entrance; higher melt pressure indicates insufficient melt homogeneity or a blocked screen pack. The screen pack is normally 20/40/60 mesh to remove carbonized particles from recycled material. The base resin should meet environmental stress cracking resistance testing according to ASTM D1693-21, condition A, with F50 above 200 h in 100% Igepal CO-630; if F50 falls below 150 h, seam cracks are likely after UN stacking tests. For each batch of drums, a hydraulic proof test at 250 kPa internal pressure is common before top-handling impact evaluation.

For 15–20-L agricultural chemical jerry cans, the controlling process variable shifts from pinch-off integrity to resistance against cyclic internal pressure and stacking deformation. These containers are produced with an integrated handle pinch-off, and the handle attachment area must maintain a minimum wall thickness of 1.5–2.0 mm to prevent premature stress cracking when the container is subjected to repeated toggling between −5 °C and 35 °C. Mould closing speed and pinch bar temperature determine the degree of polymer orientation at the handle pinch; slow closing creates thicker flash but increases residual stress. The container is tested under ASTM D2463-20b drop impact using 3–5 specimens per cavity at 1.2 m drop height. The finished container must also pass UN packaging certification under 49 CFR 178.506 for stack pressure, which places a load of 400 kg over 28 days at 40 °C without yielding. EGDM-6888 provides a balance between swell ratio and die swell uniformity; the parison weight for a 15-L jerry can is normally 260–300 g, with a wall thickness of 1.2–1.5 mm over the sidewalls. The cap neck is normally compression moulded or injection moulded from a lower-melt-index HDPE, and the weld line of the neck insert carries a potential failure locus if insufficient melt temperature is applied at the insert.

What Limits Drop Impact Resistance in 25-L Stackable Carboys at Sub-Zero Ambient Storage?

Drop impact resistance of 25-L stackable carboys produced from EGDM-6888 is governed not only by base resin toughness but also by the residual stress distribution frozen into the sidewall during mould cooling. The ductile-to-brittle transition of high-density polyethylene in notched impact testing is typically below −40 °C, but moulded-in stresses can raise the apparent transition temperature to −10 °C or higher in the top shoulder and bottom chime. Carboys stored at sub-zero ambient temperatures must meet drop tests from 1.2–1.5 m at −18 °C with water or glycol-water mixture fills; the failure mode observed on production lines is usually a circumferential crack at the top shoulder where the parison was stretched over the blow pin. To reduce this risk, the blow pin is heated to 60–80 °C, and mould cooling water temperature is set at 10–15 °C for the pinch-off and chime areas while the sidewall is cooled at 20–25 °C. The resulting crystallinity gradient reduces residual stress at the shoulder. Impact testing is supplemented by ISO 6603-2 puncture impact at −20 °C and by slow crack propagation evaluation according to ISO 16770 with a notch depth of 1.0 mm. Published data for EGDM-6888 under ISO 16770 is limited, so container-level drop testing remains mandatory.

Batch-to-batch variation in comonomer distribution affects low-temperature impact response more than high-load melt index variation. Processors should request a comonomer type and distribution statement from the supplier; for EGDM-6888, the high-molecular-weight fraction is the main carrier of short-chain branching, which controls tie-molecule density. When regenerated material is added above 20 wt%, tie-molecule population is reduced by chain scission in the high-molecular-weight fraction, and low-temperature drop failures become more frequent even when high-load melt index and density remain within specification. A practical control limit is to keep regrind particle size above 8 mm and to screen out fines below 3 mm before re-extrusion. Container wall thickness at the shoulder of a 25-L carboy is normally held at 2.0–2.5 mm; if the shoulder thins below 1.8 mm, impact failure probability increases non-linearly under sub-zero conditions.

Across Multi-Parison Die Heads for 5-L Narrow-Neck Bottles

Multi-parison extrusion blow moulding of 5-L narrow-neck bottles places a different demand on EGDM-6888: uniform parison length and thickness across two to four cavities. On a rotary wheel machine with 4 to 8 stations, the parison drop time is shorter than in accumulator-head processing, and the melt must retain enough elasticity to resist sag during the transfer step. Melt temperature is set at 200–215 °C, slightly higher than in large drums, to ensure flow through the manifold fills all die heads at equal pressure. Die gap is usually 1.0–1.5 mm, and parison programming adjusts each cavity to compensate for manifold pressure drop. The main processing defect is unequal shot weight; a variation above 2% between cavities produces thin-wall areas that can fail leak testing at 30 kPa internal pressure. Because the bottle dimension is small, mould closing speed is high and the pinch-off line is narrow; this requires a resin with a controlled melt flow ratio between 190 °C/5 kg and 190 °C/21.6 kg to maintain melt strength. Drop impact for these bottles is normally conducted at 1.5 m on the flat side and the bottom seam at 23 °C according to ASTM D2463-20b.

When Barrier-Layer Coextrusion Demands High Parison Melt Strength

In coextruded barrier containers for solvent-based agrochemicals or industrial fluids, EGDM-6888 serves as the structural high-density polyethylene layer, while a polyamide or EVOH barrier layer provides reduced solvent permeation. The process is more demanding than monolayer because the parison consists of 3–6 layers with different melt viscosities and because interfacial instabilities produce layer breakup or weld line separation. The HDPE skin layer is set to 50–70% of total wall thickness, with tie layers at 4–8% each and the barrier layer at 3–8% depending on the target permeation rate. Melt temperature of EGDM-6888 in this coextrusion is held at 200–210 °C, while the barrier layer is run at its own recommended temperature; the die head must be designed for layer thickness programming over a parison length of 0.8–1.2 m. Published data for EGDM-6888 specifically in EVOH coextruded structures is limited; processors should verify layer adhesion on a pilot line before committing to full moulds. The main HDPE-related failure mode is parison sag in the centre of the drop, which thins the HDPE outer layer and exposes the barrier layer to impact damage. A wall-thickness profile that increases sidewall thickness to 1.8–2.2 mm reduces this risk. Permeation testing uses ASTM D3985 or DIN 53380-3 depending on the target chemical.

For 1000-L intermediate bulk container inner bottles, the processing window for EGDM-6888 is defined by parison programming across a drop length of 1.5–2.0 m and by the need for a uniform sidewall thickness near 3.0–4.0 mm. The bottle is typically moulded as a one-shot blown liner on a large-platen shuttle press with clamp force above 2500 kN, and mould cooling water is maintained at 8–15 °C to obtain a cycle time near 180–240 s. The main defect is localised thinning at the top corner radius where the parison stretches before contact with the mould; this area is programmed to 4.5–5.5 mm using a 50-point parison programmer. After moulding, the liner must pass a leak test at 20 kPa and a hydraulic burst test above 350 kPa. Because the liner is later placed inside a galvanised steel frame, surface damage from folding or insertion can initiate slow crack growth; resistance to that damage is evaluated by environmental stress cracking resistance on notched specimens according to ASTM D1693-21, condition A, with an F50 above 500 h being desirable. Regrind content is normally limited to 10–15 wt% for intermediate bulk container liners because of the thickness and long-term contact with aggressive chemicals.