PetroChina Dushanzi HDPE 6095 is a high-molecular-weight high-density polyethylene supplied in pellet form by Dushanzi Petrochemical Company, PetroChina Company Limited. The grade is positioned in the producer’s published technical data for blown-film extrusion where high melt strength, low melt flow under low load, and a broad molar mass distribution are required for downgauging. The density is reported as 0.949 g/cm³ under ISO 1183-1:2019. This places the material at the lower-density end of the high-density polyethylene range and reduces the equilibrium crystalline fraction relative to 0.955–0.962 g/cm³ HDPE film grades. The lower crystalline fraction contributes to toughness but lowers modulus and oxygen barrier. The melt mass-flow rate measured at 190 °C and 5.0 kg is 0.90 g/10 min under ISO 1133-1:2022, while the high-load 21.6 kg value is approximately 9.5 g/10 min. The resulting high-load/low-load ratio indicates a high-molecular-weight tail that is not present to the same extent in conventional unimodal film resins.

Which property values differentiate HDPE 6095 from 0.955–0.962 g/cm³ high-density film resins?

These values are typical lot-average values from the manufacturer’s published data; release limits may differ. The melt-flow ratio between 21.6 kg and 5.0 kg is not always specified, but it is monitored as an indirect index of the high-molecular-weight fraction. A ratio near 10–12 is characteristic for this grade, whereas typical unimodal high-density film resins often fall between 6 and 8. The lower nominal density of 0.949 g/cm³ relative to a standard high-density film of 0.958 g/cm³ enhances dart impact and environmental stress-cracking resistance but reduces tensile modulus and oxygen barrier. Typical published environmental stress-cracking resistance F50 under ASTM D1693-15, condition B, exceeds 600 h, but converters should verify the value against production-compounded regrind because stress-cracking resistance is sensitive to additive and regrind loading. Since the melt-flow ratio is not a complete descriptor of processability, converters may run dynamic oscillatory measurements under ISO 6721-10:2015 at 190 °C. A characteristic feature of HDPE 6095 is a longer terminal relaxation time than conventional unimodal film HDPE; the cross-over frequency at which storage modulus equals loss modulus occurs at lower frequency because of the high-molecular-weight component. That rheological signature is directly relevant to bubble stability and tear resistance. Published lot-to-lot crossover-frequency data are not normally supplied on certificates of analysis; the producer instead controls the specification through density and melt-flow-rate limits.

Extruder configuration and blown-film processing limits

On production-scale grooved-feed extruders with screw L/D from 25:1 to 30:1 and water-cooled feed sections, HDPE 6095 is processed with feed-zone temperatures near 160 °C and adapter/die temperatures of 190–210 °C. The recommended die gap for monolayer film between 12 µm and 80 µm is 0.8–1.2 mm. A blow-up ratio of 3:1 to 5:1 and a frost-line height of 6–10 die diameters are used to balance machine-direction and cross-direction tear anisotropy. Because the grade exhibits high extensional viscosity, bubble stability is sensitive to frost-line height; operation with a frost line below 5 die diameters can increase haze and reduce machine-direction tear, while operation above 10 die diameters increases the risk of bubble oscillation. A melt temperature above 230 °C is not recommended; prolonged residence time at higher temperatures can degrade the high-molecular-weight fraction and generate gel defects. Screen-pack configurations of 20/40/20 or 80/120/80 mesh are used depending on die pressure; backpressure on 65–75 mm grooved-feed extruders is commonly 250–400 bar at screw speeds above 80 min⁻¹, though the value depends on screw compression and screen condition.

At high output, two process conflicts arise. First, raising screw speed to increase output decreases residence time but raises shear heating; the melt film in the metering zone can exceed the set-point barrel temperature by 10–15 °C on 25:1 screws. Second, reducing die gap to improve gauge uniformity raises die pressure and melt-fracture risk. The resolution is usually a compromise between die gap and melt temperature: a die gap of 0.8 mm can maintain gauge control at 12 µm with acceptable bubble stability if the die temperature is held at 195–205 °C. When die pressure exceeds 400 bar, the screen pack should be changed or a higher-pressure die body used; sustained operation above the thrust-assembly rating is a failure mode observed on older 65 mm lines. Process-aid addition at 400–1000 ppm is used to postpone melt fracture at high shear rates. In high-output dies with restrictive die gaps, the onset of sharkskin may occur at lower screw speeds than with unimodal film HDPE. Polymeric processing aids can shift the critical shear rate upward, but excess loading above 1500 ppm can reduce film surface energy and complicate post-film corona treatment. Die-lip cleanliness is critical; the high-molecular-weight tail can accumulate as oxidatively degraded deposits at the die exit if the die lips are overheated or if the extruder is stopped with melt in the die.

Film-converting experience with HDPE 6095 is concentrated in thin-gauge consumer and industrial packaging. The grade is used for shopping bags, refuse sacks, and industrial liners where a thickness reduction from 25 µm to 12 µm is required without a proportional loss in tear resistance. In comparative converting trials, the F50 dart impact at equal thickness can increase from approximately 60 g to 100 g when HDPE 6095 replaces a conventional 0.958 g/cm³ unimodal HDPE film grade, but the magnitude depends on film gauge, die gap, and frost-line conditions. Published data for this specific configuration is limited, and converters should run comparative evaluations on their own lines. The improvement is associated with the high-molecular-weight chain fraction that resists crack propagation and tear growth. In punched-grip carrier bags, the same chain fraction reduces tear initiation at the punch perimeter. For food-contact packaging, the finished film must comply with FDA 21 CFR 177.1520 and applicable migration limits; compliance depends on the complete additive package and conversion conditions, not only on the base resin. HDPE 6095 is not automatically food-contact-certified from the resin producer unless a specific grade certificate is issued for the delivered lot.

When film thickness drops below 15 µm in high-stalk bubble geometries

Bubble stability governs the process window more strongly than plastication. At blow-up ratios above 4:1 and frost-line heights above 8 die diameters, the grade may exhibit periodic bubble-diameter oscillation if internal bubble pressure is not controlled within ±10% of setpoint. Published data for this specific configuration is limited; production lines typically reduce the die gap to 0.6–0.8 mm, lower melt temperature to 180–190 °C, and increase internal bubble cooling to fix the frost line. Compared with fractional-melt HDPE of density 0.960 g/cm³, HDPE 6095 has a broader processing latitude because of its lower density and broader molecular-weight distribution; compared with LLDPE-rich blends, it has a narrower bubble-stability window and higher die pressure. In ultra-thin high-stalk film, the limiting defect is often thickness variation caused by bubble breathing, not extruder output. Calibration of the air-ring geometry and internal bubble pressure against the actual melt extensional viscosity of the lot is necessary because batch-to-batch variation in high-load melt flow can shift the stable operating point.

HDPE 6095 is not a direct substitute for blow-moulding or pipe HDPE grades. A blow-moulding HDPE with density 0.955 g/cm³ and melt mass-flow rate of 0.35 g/10 min at 2.16 kg exhibits higher density and lower high-load flow; replacing it with HDPE 6095 in extrusion blow moulding changes die swell and parison sag, and can produce wall-thickness distribution shifts in small containers. Conversely, in film applications, the blow-moulding grade typically shows higher tensile modulus and lower dart impact. Compared with carbon-black-filled HDPE pipe grades of similar density, HDPE 6095 is unpigmented and is not tested for long-term hydrostatic strength under ISO 9080; it is therefore unsuitable for pressure-pipe or fittings where hydrostatic design data are required. Compared with cast-film HDPE, HDPE 6095 is optimized for blown-film extrusion; its high melt strength and high backpressure can reduce output in narrow-die cast-film lines, while its broader molecular-weight distribution helps bubble stability but not chill-roll clarity. In film-to-film substitution, HDPE 6095 differs from commodity HDPE film resins in its high-load flow and low density. The combination permits downgauging but also reduces modulus and may increase oxygen permeation; the oxygen permeability of HDPE at 0.949 g/cm³ is intrinsically higher than at 0.960 g/cm³. If a packaging structure requires the same oxygen barrier after downgauging from 25 µm to 12 µm, the barrier loss from thickness alone may exceed the change from density; HDPE 6095 is not a barrier-improvement grade. For barrier-critical applications, simultaneous coextrusion with EVOH or PA is required, but HDPE 6095 in a core or skin layer may impose higher viscosity mismatch against EVOH or PA. In such structures, the melt streams are combined at 190–210 °C; the sharp difference in melt viscosities requires careful design of the feedblock to avoid interfacial instabilities.

Storage and handling boundaries apply to lot-to-lot reproducibility. Pellets should be kept dry; surface moisture from outdoor storage or condensation at relative humidity above 60% can cause film bubbles and surface defects unless the pellets are dried in a desiccant hopper at 60–70 °C for 2–4 h. Regrind addition should be controlled below 20% by mass in critical thin-film products; higher regrind loadings can shift bubble stability and reduce dart impact. Certain amine-based slip or antistatic concentrates reduce oxidative induction time at temperatures above 210 °C and must be evaluated before use with HDPE 6095. Antifog or antistatic additive packages must also be confirmed for thermal stability at the intended 190–210 °C processing temperature. Because the high-molecular-weight fraction is viscosity-determining, resupply from an alternate reactor lot should be qualified through a short production trial, not solely through melt-flow-rate and density certificates.