PCC (Iran) HDPE HD5620 is a high-density polyethylene extrusion blow-moulding grade supplied in pellet form for industrial and consumer rigid packaging. The nominal Melt Flow Rate is 0.20 g/10 min at 190 °C under a 2.16 kg load when measured to ISO 1133-1:2022, and the base density is 0.956 g/cm³ when measured to ISO 1183-1:2019. These values place the grade in the high-molecular-weight segment of HDPE, where melt strength, parison sag resistance and environmental stress cracking resistance are prioritised over low-viscosity flow. The product is intended for extrusion blow moulding on accumulator-head machines and long-stroke reciprocating-screw blow moulders, not for thin-wall injection moulding. Typical application articles include industrial containers, jerrycans, detergent bottles, automotive fluid reservoirs and agricultural chemical packaging from approximately 1 L to more than 1,000 L. The material is differentiated from general-purpose HDPE bottle grades by its low MFR, which reduces parison drawdown in large parts, and from high-flow injection grades by its inability to fill long flow paths under conventional injection pressures. Published data for pellet colour, slip and anti-block additives should be obtained from the supplier’s technical datasheet.

What separates high-molecular-weight blow-moulding HDPE from thin-wall bottle grades?

In thin-wall shuttle blow moulding of bottles, processors often select HDPE with Melt Flow Rate values between 0.8 g/10 min and 1.2 g/10 min and densities between 0.950 g/cm³ and 0.954 g/cm³. These lower-viscosity grades permit faster parison extrusion, shorter clamping cycles and reduced extruder motor load. HD5620, with Melt Flow Rate near 0.20 g/10 min, exhibits higher melt viscosity and therefore greater resistance to parison sag when shot weight exceeds about 500 g or target wall thickness exceeds 1.5 mm. The practical difference is most evident on large accumulator machines producing containers above 20 L: a thin-wall bottle grade begins to show visible parison drawdown before mould closing, resulting in thin top corners, thick pinch-off areas and a wider wall-thickness distribution. The high-molecular-weight fraction in HD5620 contributes to zero-shear viscosity and parison elastic recovery. Resin lots should be checked for Melt Flow Rate stability because a shift from 0.20 g/10 min to 0.25 g/10 min may require die-gap or melt-temperature correction to avoid wall thickness drift.

On a production-scale accumulator blow moulder with an 80 mm barrier screw and 25:1 length/diameter ratio, HD5620 is typically started at barrel temperature settings from 170 °C in the feed section to 195–205 °C at the accumulator head. The measured melt temperature at the die is held between 190 °C and 205 °C; lower temperatures can produce sharkskin on the parison, while higher temperatures lower melt strength and increase cooling time. Mould surface temperature is maintained between 10 °C and 30 °C to accelerate skin solidification and stabilise the pinch-off. Blow air pressure is set between 0.6 MPa and 1.0 MPa. For containers above 10 L, parison programming is required: die-gap changes of 30–40% around the set point are used to produce a tapered parison that compensates for sag and mould shape. Heat-soak studies on similar HMW-HDPE grades indicate that exposure above 230 °C for longer than 20 min can initiate thermo-oxidative degradation that reduces environmental stress crack resistance and increases gel formation. Pre-drying is not routinely required because HDPE has low hygroscopicity, but surface moisture from outdoor silo storage at relative humidity above 70% should be removed by drying at 80 °C for 4 h before extrusion.

Mechanical, elevated-temperature and environmental stress crack resistance data for container validation

Design calculations for industrial containers and jerrycans typically use tensile stress at yield and flexural modulus. For HD5620, tensile stress at yield is commonly reported near 25 MPa with elongation at break above 600% when tested on ISO 527-2/1B specimens at 50 mm/min. Flexural modulus is commonly reported between 1,000 MPa and 1,200 MPa under ISO 178:2019. The material softens progressively above 60 °C; Vicat softening temperature is typically reported near 123 °C using ISO 306/A120. Environmental stress cracking resistance is the main performance differentiator for household and industrial chemical containers. The method ASTM D1693-15, condition B with 100% Igepal CO-630 at 50 °C, is used to compare high-molecular-weight blow-moulding grades with lower-viscosity bottle resins. Published ESCR values for HMW-HDPE grades with Melt Flow Rate near 0.2 g/10 min commonly exceed 600 h F50, while general-purpose bottle grades can fail between 20 h and 200 h under the same condition. Purchasers should request lot-specific certificates for ESCR because the result is influenced by comonomer type, molecular weight distribution, catalyst residue and stabilizer level.

Compared with a general-purpose blow-moulding HDPE of Melt Flow Rate 0.8–1.2 g/10 min, HD5620 produces a more stable parison for large containers but requires higher extruder drive energy. On the same screw speed and temperature profile, motor amperage may increase by 10–20% relative to a lower-viscosity blow-moulding grade. Compared with an injection moulding grade such as PCC (Iran) HDPE HD5218, which is designed for thin-wall closures and crates, HD5620 has a much lower Melt Flow Rate and is not suitable for injection moulds requiring long flow paths. Compared with a pipe-grade PE100 resin, HD5620 is not classified for sustained internal pressure over 50 years under ISO 9080; pipe resins carry a separate hydrostatic design basis and stabilizer package. Compared with recycled HDPE, HD5620 offers starting-polymer consistency, because post-consumer recyclate can introduce mixed comonomer chemistry, non-polyolefin contamination and gels that reduce ESCR and form pin-holes in blow-moulded walls.

When dangerous-goods or food-contact demands are placed on the packaging, formal certification governs the use of HD5620

For dangerous-goods jerrycans and bottles, the container is tested as a complete system, not the resin alone. Under 49 CFR 178.603 drop test and 49 CFR 178.606 stack test, the blow-moulded container must withstand specified drop heights at various fill levels and conditioning temperatures. HD5620 is often selected because high-molecular-weight HDPE generally passes conditioning at -18 °C with fewer cracks than lower-molecular-weight bottle grades, but published data for this specific product in UN-certified designs is limited and must be generated by the converter. Food-contact status is not automatically guaranteed by the resin type. The converter must verify compliance with 21 CFR 177.1520 for olefin polymers and EU Regulation 10/2011, with migration limits expressed in mg/kg food or mg/dm² contact surface. The supplier’s statement should cover monomer residues, catalyst neutralizers and processing antioxidants. Without this documentation, the resin should be restricted to non-food industrial packaging.

Heavy-metal and hazardous-substance compliance is normally declared under REACH Article 33 for substances of very high concern above 0.1% w/w and under RoHS II 2011/65/EU if the container is used in electrical and electronic equipment. Packaging waste limits for lead, cadmium, mercury and chromium VI are assessed under Directive 94/62/EC, with a combined limit of 100 mg/kg by weight. Because HD5620 is a natural high-density polyethylene, these elements are expected to be below detection limits, but batch certification should be retained. For outdoor UV resistance, the unmodified grade should not be used for prolonged outdoor storage unless stabilized; carbon black masterbatch or hindered amine stabilizers must be evaluated under ISO 4892-2:2013 and ISO 4892-3:2016 to establish an exposure class. Since HDPE is electrically insulating, static discharge risks during storage and transfer should be controlled by earthing and bonding of silos and bagging stations; this is standard for powder and pellet handling systems.

Incoming inspection matrix and lot certification practice

The following acceptance windows are typical for production-quality control and should be confirmed against the supplier’s certificate of analysis for the specific lot.

Common processing defects observed on production lines include melt fracture at low melt temperatures, underweight containers from excessive parison sag, and weak pinch-off lines from insufficient melt temperature or low blow pressure. Melt fracture appears as fine ridges or sharkskin on the outer surface when die shear stress exceeds the critical limit; increasing the die gap or raising melt temperature to the upper end of the range is used to correct it. Underweight containers can be corrected by parison programming and by stabilising die-head temperature within ±2 °C. Weak pinch-offs may be caused by mould temperatures below 10 °C or excessive clamp closing speed. Published data for HD5620-specific defect thresholds is limited; process validation is performed on the converter’s own tooling.

HD5620 is also used as the structural layer in multilayer blow-moulded containers when EVOH or polyamide barrier layers are incorporated. The tie layer must be compatible with both HDPE and the barrier resin; adhesion is evaluated on flat sections cut from the container, and the HDPE layer is processed at 190–210 °C while the barrier layer is kept below 240 °C to prevent thermal instability. In such structures, layer thickness ratios are often set to 85–90% HDPE structural layer, 3–5% tie layer and 5–10% barrier layer, but the final distribution must be verified by layer-thickness microscopy. The use of HD5620 as the structural layer does not eliminate the need for a dedicated pinching and welding study because high molecular weight HDPE can develop weak weld lines in moulds with insufficient pinch-off land flatness; the pinch-off area should be inspected under transmitted light after sectioning to detect porosity and cold welds.

Chemical compatibility for agricultural and automotive fluids should be evaluated by immersion tests based on ISO 175:2010 or environmental stress cracking tests based on ISO 22088-2:2016. A container for diesel or kerosene may pass hydrocarbon exposure when wall thickness is increased, but continuous contact with high concentrations of aromatic solvents can plasticize HDPE, reduce tensile strength and shorten service life. The maximum continuous service temperature should be verified with the actual fluid and closure system, because chemical resistance is temperature dependent. Published data for HD5620 in aggressive oxygenated solvents is limited; testing on the finished container with actual filling goods is required when the intended service temperature exceeds 40 °C.

Pellets should be stored in closed silos or original bags at temperatures below 50 °C and protected from direct sunlight. Prolonged storage at high temperature can consume the phenolic antioxidant and reduce oxidation induction time. Oxidation induction time is measured by ISO 11357-6:2024 or ASTM D3895-19; a minimum value of 20 min at 200 °C is commonly used for incoming inspection of stabilised HDPE, but the supplier’s specification should be followed. Ultraviolet exposure of uncovered pellets can degrade the polymer surface and produce gels. Cross-contamination with polypropylene or low-density polyethylene should be avoided because even small fractions can alter melt viscosity, reduce ESCR and create visible swirl defects in blow-moulded containers. Equipment changeovers should be verified by purge count and clear transition procedures.

In injection blow moulding or injection stretch blow moulding, HD5620 is generally unsuitable because the low Melt Flow Rate does not permit the rapid injection phase and precise molecular orientation required for those processes. In extrusion blow moulding, accumulator head purging should be performed at the upper melt-temperature limit after shutdown from coloured or filled formulations. The starting purge may require up to 3–5% of the barrel volume to remove degraded polymer after prolonged idle time. These are practical limits observed on production-scale equipment and must be adjusted for machine size and residence time distribution.

Post-mould shrinkage of HDPE containers is time-dependent and should be accounted for in gauge control. For HD5620, dimensional changes of 1–3% may occur within 24 h depending on part thickness and cooling rate. Thicker sections shrink more because they cool more slowly and undergo higher crystallinity development. Published data for this specific product and part geometry is limited; converters should conduct a shrinkage study on the actual mould and verify dimensions after conditioning for 48 h at 23 °C and 50% relative humidity.