Borealis HDPE HE2581-PH is a blow-moulding high-density polyethylene supplied for rigid pharmaceutical, diagnostic, and personal-care packaging. The grade designation HE2581 identifies the polymer class and melt-flow segment; the -PH suffix denotes a pharmaceutical-grade formulation in which intentionally added slip and antiblock additives are minimised to reduce low-molecular-weight extractable compounds. Melt flow rate is 2.1 g/10 min at 190 °C with a 2.16 kg load when measured by ISO 1133-1:2022. Density is 958 kg/m³ by ISO 1183-1:2019. The resin therefore occupies a medium-viscosity blow-moulding segment with a density high enough to impart stiffness and moisture-vapour resistance but not so high that low-temperature impact is sacrificed. In pharmaceutical packaging operations the material is processed by extrusion blow moulding into narrow-mouth and wide-mouth bottles used for liquid oral dosage forms, dry oral dosage closures, diagnostic reagents, and healthcare containers. Comparative positioning against general-purpose HDPE blow-moulding grades rests on a narrower specification for extractables, improved environmental stress-crack resistance, and stable parison melt strength during die-swell-sensitive operations.

What separates pharmaceutical blow-moulding HDPE from conventional unimodal grades?

Conventional unimodal HDPE blow-moulding resins with equivalent melt flow rate and density are often formulated with slip agents, antiblock agents, or processing aids that can increase total organic carbon in aqueous extraction tests. HE2581-PH is supplied under a formulation policy that avoids these additives in the base blend; the result is a lower pellet-surface additive layer and reduced migration of lubricant species into filled containers. The absence of slip agent has a processing consequence: the coefficient of friction between finished bottles is higher than that of general-purpose grades, and unscrambling or conveying equipment may require contact-surface adjustments. In addition, the resin is not colour- or antioxidant-loaded in a way that masks variability in the base polymer under sensory testing.

The polymer architecture of HE2581-PH is controlled for a balance of stress-crack resistance and stiffness. Environmental stress-crack resistance is measured under ASTM D1693 in a 100 % Igepal solution at 50 °C; reported typical values exceed 300 h, which is above many unimodal HDPE blow-moulding grades of comparable 958 kg/m³ density. Notched Charpy impact strength is reported at 8.0 kJ/m² at 23 °C according to ISO 179-1:2023. Tensile yield stress is 28 MPa under ISO 527-2:2012, and flexural modulus is 1250 MPa under ISO 178:2019. These properties are interrelated: an increase in density would raise flexural modulus and moisture-vapour barrier but reduce stress-crack resistance and low-temperature impact; a decrease in melt flow rate would improve ESCR but reduce extruder output and increase shear heating. The selected balance is relevant to pharmaceutical containers that require drop resistance after filling and resistance to crazing when exposed to aggressive soaps, alcohols, or diagnostic reagents.

In comparison with polypropylene random copolymers used for pharmaceutical bottles, HE2581-PH has higher moisture-vapour barrier and higher environmental stress-crack resistance but lower optical clarity and lower resistance to autoclave sterilisation. In comparison with polyethylene terephthalate, the HDPE grade has lower modulus and lower oxygen barrier but provides better ESCR and a more ductile failure mode under squeeze-to-dispense use. Within Borealis high-density polyethylene blow-moulding grades, the -PH version is differentiated by extractables control rather than by an increase in melt-flow or density; a non-PH grade with the same 2.1 g/10 min MFR may be unsuitable for pharmacopoeial packaging because its additive package is not qualified for highly purified, low-migration containers.

A representative property profile compiled from publicly available manufacturer technical literature is presented below. Values are typical and do not constitute a release specification; exact limits are controlled by the current datasheet and quality agreement.

From the table, density is a critical control parameter. A shift of 0.002 g/cm³ upward moves the grade closer to the high-density stiffening knee where stress-crack resistance declines, while a similar downward shift reduces top-load strength in lightweight bottles. The melt flow rate of 2.1 g/10 min gives moderate screw back-pressure during blow moulding; the shear viscosity under ISO 11443 capillary testing is not routinely supplied but is implied by the MFR and the known high-density polyethylene molecular weight distribution. The notched Charpy value of 8.0 kJ/m² at 23 °C should not be extrapolated to filled-container drop performance because wall thickness, pinch-off weld integrity, and stress concentration at the neck–shoulder transition dominate failure. Bottle drop testing is therefore required under ASTM D2463 or equivalent filled-container protocols. Similarly, top-load testing of finished bottles should follow ASTM D2659 or an agreed crush-test procedure, because top-load strength depends on sidewall geometry, distribution, and mould cooling history.

The Vicat softening temperature of 127 °C under ISO 306/A50 is a short-term thermal index; it does not imply continuous operational use at that temperature. For HDPE containers under load, continuous use is typically restricted to below 80 °C, and even short excursions above 100 °C can produce dimensional distortion without reaching the Vicat point. This distinction is relevant for filling lines that may use hot-water rinses or tunnel drying.

When parison programming shifts from general-purpose containers to narrow-mouth pharmaceutical bottles

Extrusion blow moulding of HE2581-PH is performed at melt temperatures between 180 °C and 220 °C. The lower bound is set by melt viscosity and screw torque; the upper bound is set by thermal degradation and parison sag. Production lines typically use single-screw extruders with barrier screws and L/D 24:1 to 30:1. Head pressure in the accumulator or continuous die depends on die gap, output, and melt temperature; a representative range is 100 bar to 350 bar. Pressures above 350 bar have been associated with gel formation or insufficient melting, while pressures below 100 bar may indicate worn screw or barrel clearances. Published data for a specific line configuration are limited, and these values are general blow-moulding operating windows rather than product-specific guarantees.

Because die-swell characteristics are controlled by the molecular weight distribution, grade change from a general-purpose HDPE to HE2581-PH requires re-setting the die gap and reprogramming the parison wall profile. The change can shift sidewall thickness in the waist region and move the pinch-off line. A die-gap increase of 5 % to 10 % is the typical initial correction on shuttle machines, but the final setting is bottle-geometry dependent. Wall-thickness distributions should be measured by ultrasonic or magnified sectioning before committing to process validation. The pinch-off weld is a critical failure site; insufficient clamp force or a badly programmed tail flash can produce weld-line notches that act as impact initiation points. Blow moulds are typically run at 10 °C to 30 °C to freeze the parison surface rapidly. A mould temperature below 10 °C can cause surface defects and condensation; above 35 °C, cycle time increases and wall crystallinity may rise, lowering impact toughness.

Pre-drying is not normally required. The polymer is hydrophobic, but surface moisture picked up in high-humidity storage can generate splay and voids. When relative humidity exceeds 60 %, a desiccant hopper set at 80 °C for 2 h is sufficient. Regrind use in pharmaceutical packaging is qualification-dependent. Clean, uncontaminated in-house regrind up to 20 wt% is often acceptable in non-sterile packaging lines, but many pharmaceutical validations limit regrind to lower levels or require documented heat histories. Degraded regrind from multiple heat cycles reduces ESCR and increases gel count; it should not be used in high-gloss or high-impact applications. Colour masterbatch loading for opaque white or pastel pharmaceutical bottles is typically 2 wt% to 4 wt%; higher inorganic pigment loadings can reduce ESCR by creating stress concentrations at pigment agglomerates, and the carrier resin must be compatible with the -PH extractables profile.

Compliance of the raw material with pharmaceutical and food-contact regulations is listed below. The resin supplier supports these standards at the pellet level, but finished container compliance remains the responsibility of the converter and marketer.

The pharmacopoeial standards do not provide blanket approval of the resin. They define extractable-metal limits, total organic carbon, and identity tests on the packaged article. The -PH formulation is intended to support low extractable profiles, but the converter must verify that the combination of blow-moulding temperature, regrind, and colourant does not change the profile. Raw-resin lot data cannot replace finished-container stability studies under ICH Q1A where the package holds a pharmaceutical product. Similarly, ISO 10993 testing is a finished-device requirement; the resin alone is not a medical device, and the conversion process, sterilisation, and leachables from tooling may introduce new risks.

Residual metal control, organoleptic neutrality, and steam sterilisation boundaries

The -PH designation imposes restrictions on residual transition-metal and ash content because these species can migrate into liquid formulations under acidic or chelating conditions. Organoleptic neutrality is evaluated by odour and taste transfer tests on blow-moulded containers; the base resin is formulated to avoid volatile species that impart off-taste. This does not remove all off-taste risk: oxygenated degradation products generated by excessive melt temperature or by repeated regrind can still contaminate packaged contents. Melt temperature should therefore remain below 220 °C to limit thermo-oxidative product formation. Odour and taste transfer can be measured by ASTM E1870 or equivalent sensory methods; the -PH formulation is designed for low taint, but final container sensory performance depends on process history and masterbatch choice.

The resin is not suitable for steam sterilisation at 121 °C. The Vicat softening temperature of 127 °C under ISO 306/A50 is a short-term heat-distortion indicator, but the actual continuous-use temperature of HDPE is lower, and autoclave load produces irreversible deformation. Suitable sterilisation routes for this polyolefin are limited to ethylene oxide at 55 °C or lower, electron-beam irradiation, or gamma irradiation under controlled dose. Gamma doses above 25 kGy can increase carbonyl formation and reduce notched impact strength; dose mapping is required because the radiation response of finished bottles depends on wall thickness and antioxidant package. Dry heat above 80 °C is not recommended. The grade should not be blended with unqualified amine-based antioxidant masterbatches or processing aids that raise extractable nitrogen species, because such additions can invalidate organoleptic and pharmacopoeial qualification.

Production-scale qualification of HE2581-PH for pharmaceutical oral-dosage containers includes top-load, drop-impact, and extraction studies. Top-load values are bottle-geometry dependent but generally rise with density and sidewall thickness; the 958 kg/m³ density provides a stiffness baseline for 100 mL to 250 mL bottles. Drop-impact acceptance testing is usually performed at 4 °C or room temperature after conditioning according to ASTM D2463; the resin-level notched Charpy value of 8.0 kJ/m² at 23 °C does not replace this test. Sealing integrity of induction-sealed and child-resistant closures must be tested separately because the absence of slip agents changes cap-on-bottle torque and liner adhesion. For containers exposed to dilute soaps, alcohol-based hand rubs, or diagnostic reagents, stress-crack testing on filled bottles is preferred over resin-level ESCR data alone; the final bottle should be tested under the specific contact medium and temperature conditions of use.