Braskem HDPE GD5160 is a high-density polyethylene extrusion blow moulding resin with a manufacturer designation that places it in the rigid container segment. The grade is supplied as pellets and is processed on accumulator-head and continuous shuttle machines to produce containers with capacities commonly between 5 L and 60 L. Table 1 summarises the nominal property profile as transcribed from the manufacturer’s technical bulletin; the values are not unilateral specification limits unless incorporated into a purchase contract.

The melt flow rate of 0.35 g/10 min under 190 °C/2.16 kg is low relative to injection-moulding HDPE grades. The density of 0.956 g/cm³ contributes to wall stiffness and top-load strength, while the low melt index increases parison hang time. These properties define the processing envelope: high density raises crystallinity and modulus but narrows the low-temperature impact window, and low melt flow rate improves melt strength but increases extruder back pressure and residence-time sensitivity.

What Property Profile Distinguishes GD5160 from Other HDPE Blow Molding Resins?

The differentiation is primarily a function of rheological and crystallisation behaviour. A melt flow rate of 0.35 g/10 min measured by ASTM D1238-20 places GD5160 among high-molecular-weight HDPE blow moulding grades, while the density of 0.956 g/cm³ provides a balance between top-load strength and environmental stress crack resistance. At higher density above 0.960 g/cm³, ESCR tends to decline sharply for a given melt flow rate. The Vicat softening temperature of 129 °C under ASTM D1525-17 imposes a practical upper service temperature for unfilled HDPE containers; sustained exposure above this value produces distortion under load. Compared with HDPE grades used for small bottle blow moulding, GD5160 has higher die swell and parison hang strength, which are required for long parisons and heavy shot weights. The notched Izod impact value of 6.0 kJ/m² at 23 °C is moderate for this density class; low-temperature impact remains dependent on pinch-off weld integrity and processing conditions rather than resin alone.

The crystallisation temperature of HDPE of this density is typically between 116 °C and 120 °C under a cooling rate of 10 °C/min in differential scanning calorimetry per ISO 11357-3:2018. This influences mould cooling time and shrinkage. A slower cooling rate increases crystalline perfection and reduces impact toughness. In terms of molecular architecture, the broad molecular weight distribution typical of such blow moulding resins increases shear thinning at high die shear rates but also increases die swell. This behaviour is measured indirectly by melt flow ratio between 2.16 kg and 21.6 kg loads, although the manufacturer’s bulletin does not always report the high-load melt index. The laboratory should therefore measure melt viscosity at angular frequencies relevant to die flow using a capillary rheometer according to ISO 11443:2021 before tool transfer. Published rheological master curves for this specific configuration are limited; equipment-specific trials are recommended for initial die gap settings.

On continuous shuttle blow moulding machines, barrel temperature profiles are typically divided into five or six zones. A grooved-barrel extruder with an L/D ratio of 30:1 and a barrier screw is preferred for homogeneous melt quality at high throughput. Zone set points from feed to metering are commonly 170 °C, 180 °C, 190 °C, 200 °C, and 210 °C, with the die head set at 200–220 °C. Melt temperature at the die exit is measured with an insertion thermocouple and maintained between 185 °C and 215 °C; the maximum safe continuous melt temperature is 240 °C, above which chain scission and crosslinking yield black specks and gel-like inclusions. In production, extrusion back pressure increases when the melt temperature is below 180 °C, and motor amperage rises; this condition may overload a 60 mm extruder gearbox if sustained. In contrast, melt temperatures above 220 °C cause parison drawdown and uneven wall thickness in parts longer than 300 mm. Melt pressure at the die head is commonly 15–35 MPa depending on die gap and throughput; sustained melt pressure above 40 MPa can lead to melt fracture and parison surface roughness. Within the recommended melt temperature span, a deviation of ±5 °C shifts parison sag rate by an observable amount. For a parison length of 350 mm, lowering melt temperature by 5 °C can reduce parison drawdown but requires an increase in die gap of 0.2–0.4 mm.

Table 2 lists the processing ranges used as preliminary set points. Actual settings are tool-specific and are established through design of experiments on the target machine.

Blow air pressure is adjusted according to part size and wall thickness. For containers with volumes from 1 L to 5 L, 0.4–0.6 MPa is usually sufficient; for 20 L jerrycans with wall thickness above 1.2 mm, 0.8–1.0 MPa is typical. Mould temperature is controlled with closed-loop water units at 10–30 °C; lower mould temperatures shorten cycle time but increase frozen-in stress and may warp flat panels. Regrind from the same grade is commonly added at 0–20% by weight; higher percentages reduce ESCR and increase black speck risk due to repeated heat history. All regrind should be dedusted and screened for tramp metal before gravimetric blending.

When GD5160 Is Processed on Accumulator-Head Blow Molders

In accumulator-head machines, molten polymer is collected in a cylindrical accumulator and then forced through the die by a ram. This process subjects GD5160 to intermittent shear and potential residence time at temperature. Accumulator capacity should be sized so that shot weight represents at least 40% of the accumulator volume; prolonged residence at 220 °C beyond 15 min increases gel formation. A melt pump may be installed between the extruder and accumulator to stabilise pressure, but it is not always required for this grade. The die head design, including spiral mandrel or side-fed annular dies, affects melt temperature uniformity and wall thickness consistency. Parison programming is required: the die gap is varied during extrusion to compensate for parison drawdown and mould geometry. A typical program for a 20 L jerrycan has 100 programming points; the first 10% of parison length is often extruded with a narrower die gap to maintain top thickness, while the lower body uses wider gaps to achieve bottom pinch-off.

During accumulator discharge, melt is forced through the die at high shear rate. The resulting die swell can increase parison diameter by 20–40% depending on die gap, draw ratio, and melt temperature. Operators compensate by selecting a die diameter smaller than the mould opening. Die swell measurements should be recorded at start-up: a change in die swell from 25% to 15% at constant settings may indicate resin lot variation, contamination, or moisture. Batch-to-batch changes in melt flow rate of ±0.03 g/10 min are within typical production tolerance but can shift die swell enough to require parison program adjustment. For that reason, the incoming resin is tested by ISO 1133-1:2022 before release to production, and the data are used to preset the die gap. For large containers, the mould halves must close against the inflated parison. Clamp force requirements for a 20 L jerrycan are typically in the range of 100–300 kN, depending on mould size and blow pressure. Inadequate clamp force leads to flash at the parting line and dimensional variation.

Environmental stress crack resistance is the primary long-term failure mechanism in rigid HDPE containers exposed to surfactants, agrochemicals, and certain oils. The F50 value of >500 h under ASTM D1693-15 condition A indicates resistance to crack growth under constant flexural strain in a 100% Igepal CO-630 solution at 50 °C. This test is sensitive to specimen thickness, notch quality, and annealing history; results from moulded containers may differ from compression-moulded plaques. The ESCR test has high scatter; F50 values are best compared using a minimum of ten specimens per condition. For containers holding emulsifiable concentrates, ESCR at 50 °C alone may not predict field failure; full-scale container stress-crack testing under ASTM D2561-17 is necessary. The resin is not recommended for continuous contact with strong oxidising acids, aromatic solvents, or low-molecular-weight ketones unless permeability and environmental stress crack resistance are validated on the finished article. Swelling behaviour is assessed by immersion testing under ISO 175:2010; if no published data are available for a specific liquid, a 28-day immersion trial at the maximum service temperature is used to measure weight change and tensile retention.

At storage relative humidity above 60%, surface moisture on virgin pellets is uncommon but possible in high-humidity coastal plants; pre-drying in a dehumidifying hopper at 80 °C for 2–4 h is recommended when surface haze or splay appears. Regrind should be dried under the same conditions before blending above 20%. HDPE is not hygroscopic in the same manner as polyamide, but surface moisture affects melt quality at the die lip and can produce elongated air pockets at the parison wall.

Dimensional Stability and Wall Thickness Distribution in Hazardous-Liquid Containers

Wall thickness distribution is controlled not only by parison programming but also by mould alignment, blow pressure ramp rate, and cooling uniformity. For a 20 L jerrycan, the target minimum wall thickness is usually specified on the container drawing; typical designs require no region below 0.8 mm for non-regulated liquids and 1.0–1.2 mm for UN hazardous-goods packaging. Thickness is verified with ultrasonic gauges or by sectioning and optical microscopy. Shrinkage of GD5160 after demoulding is anisotropic and depends on mould temperature; for gas-phase HDPE of this density, measured linear mould shrinkage commonly falls between 1.5% and 2.5% along flow and 0.8% and 1.2% across flow. These values are not singular material constants; they must be established for the specific tool geometry and cooling layout. Mould shrinkage is measured after 48 h conditioning at 23 ± 2 °C and 50 ± 5% relative humidity per ASTM D955-08(2014) or ISO 294-4:2018.

Top-load strength is measured on empty, conditioned containers at 23 °C using a compression tester at a crosshead speed of 10 mm/min; values for 20 L jerrycans are commonly specified in the range of 1.5–2.5 kN, but the specification depends on design and wall thickness. Drop impact resistance is evaluated at -18 °C after a minimum conditioning period of 24 h; failure at the pinch-off weld is a known limitation of extrusion blow moulded HDPE. Pinch-off failure is minimised by increasing melt temperature, ensuring adequate pinch-off land pressure, and avoiding regrind percentages above 20%. Low-temperature cracks propagate preferentially at sharp corners and weld lines; part radii should be maximised where possible. Low-temperature drop test results for HDPE depend on density; for each 0.001 g/cm³ increase in density, the ductile-to-brittle transition temperature may shift upward by several degrees Celsius.

Compared with injection-moulding HDPE grades with melt flow rates above 5 g/10 min, GD5160 is not intended for thin-wall injection moulding; its high melt viscosity requires elevated injection pressures and can cause short shots in sections below 1.5 mm. Compared with low-density HDPE blow moulding grades used for personal-care and dairy bottles, GD5160 provides higher stiffness and top-load strength at equivalent wall thickness but lower low-temperature impact toughness in very thin sections. Compared with bimodal high-molecular-weight HDPE grades, GD5160 may show lower ESCR at equal density and melt flow rate; bimodal resin architecture separates high molar mass chains from low molar mass chains to improve stress-crack resistance while retaining processability. The selection between GD5160 and a bimodal grade is therefore determined by the chemical aggressiveness of the packaged liquid, drop test severity, and container wall thickness. In direct substitution trials, tooling changes may be required because die swell and parison hang time differ; wall-thickness deviations of 0.2 mm or more are observed if parison programming is not re-optimised.

Regulatory Compliance and Food Contact Considerations Under FDA 21 CFR and REACH.

For food contact applications in the United States, the base resin may be evaluated under FDA 21 CFR 177.1520(c) 3.1a for polyolefin polymers, subject to specifications on density, melting point, and extractables. End-use migration testing is the responsibility of the converter or brand owner. In the European Union, food contact compliance is evaluated under Regulation (EU) No 10/2011 as amended; the overall migration limit for the finished plastic article is 10 mg/dm², and specific migration limits apply to any intentionally added substances. The manufacturer’s declaration should identify the monomer basis and any dual-use additives. Under REACH 1907/2006, the supplier is required to provide a safety data sheet and communicate any substances of very high concern present above 0.1% by weight. RoHS 2011/65/EU compliance is normally confirmed by a material declaration showing absence of lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE above the permitted maximum concentration values. For UN hazardous goods packaging, the finished container must pass design type testing, including drop, leakproofness, hydraulic pressure, and stacking tests under the applicable modal regulations; the raw resin grade alone does not confer UN certification.