Mehr Petrochemical (Iran) HDPE 7000F is a high-molecular-weight, high-density polyethylene film resin in which the terminal “F” designation places the material in blown-film extrusion rather than injection moulding or blow moulding. The numerical designation 7000F is not a universal polymer classification; it identifies a specific supplier film grade and should not be substituted with other regional 7000F grades without examination of the full technical datasheet. The grade is positioned for converters requiring a nominal density of 0.954 g/cm³ when measured under ISO 1183-1:2019 and a melt mass-flow rate approaching 0.04 g/10 min at 190 °C with a 2.16 kg piston load under ISO 1133-1:2022. These two values identify a fractional-melt, high-molecular-weight film resin whose processing behaviour differs from general-purpose high-density polyethylene grades with melt flow rates above 0.3 g/10 min. Because supplier datasheets can vary by production campaign and the grade may be sold under different revision dates, the manufacturer’s certificate of analysis for each lot is the governing document; published data for this specific configuration is limited and should be verified before line trials.

In blown-film conversion, the viscosity of HDPE 7000F translates into melt-pressure demands that exceed those of medium-molecular-weight HDPE grades. A 45 mm single-screw extruder with a 24:1 L/D barrel and a 1.2 mm die gap may require melt pressure of 180–260 bar during stable operation at a 3:1 blow-up ratio, but the actual value depends on screw condition, screen-pack loading, melt temperature, and die geometry. This planning range is drawn from common fractional-MFR HDPE film line behaviour; exact values for the Mehr Petrochemical grade on a specific line are not available without converter measurements. Barrel temperature profiles are typically set from 160 °C in the feed section to 210 °C at the adapter, with melt temperature held below 220 °C to avoid oxidative chain scission and gel formation. Pre-drying is generally not required at ambient silo conditions below 60% relative humidity; if regrind or condensed moisture is present, drying at 70 °C for 2 h in a desiccant dryer reduces bubble instability caused by surface moisture.

What Limits the Processing Window in Low-MFR HDPE Film Extrusion?

The narrow processing window of HDPE 7000F is governed by the interaction of high molecular weight, shear viscosity, and melt temperature. Because the melt mass-flow rate is below 0.1 g/10 min, the resin retains considerable elastic character during bubble formation; this improves bubble stability but reduces tolerance to excessive shear heating. If screw speed is increased without a corresponding rise in die temperature, shear heat can produce localized melt temperatures above 230 °C, initiating chain scission and creating small oxidized gel particles that appear as lens-shaped defects in films of 15–25 µm. Converters mitigate this by using a barrier screw with a low compression ratio and by installing screen packs no finer than 80 mesh to avoid excessive back-pressure. The maximum recommended regrind addition is commonly 20 wt%; above that level, changes in molecular weight distribution and the introduction of contaminants increase bubble flutter and reduce dart impact retention.

For high-stalk bubble configurations, HDPE 7000F permits a stalk height above the die of approximately 6–8 die diameters before frost-line contact because its melt strength resists gravitational melt stretching. This high-stalk operation produces a balanced orientation that raises machine-direction tear strength while retaining transverse-direction elongation; however, frost-line height control must remain within ±20 mm to prevent cyclic bubble diameter oscillation. Data from blown-film trials on fractional-MFR HDPE resins show that frost-line movement is frequently caused by ambient air currents; therefore, side shielding of the bubble is used in production environments where draughts exceed 0.5 m/s.

Downgauging to 12–18 µm for T-shirt bags or bin liners requires a die gap of at least 1.2 mm if the film is to retain impact toughness. When a narrow die gap is used to increase output, the film may be trapped in a highly oriented state and dart impact values under ASTM D1709 fall sharply. On a 50 mm grooved-feed extruder with 30:1 L/D, stable bubble operation is generally observed when the melt temperature at the die is maintained between 200 °C and 215 °C; operation below 190 °C increases melt pressure and can trigger shark-skin melt fracture on the outer film surface. These boundaries are operational planning values, not supplier-certified limits, and must be adjusted for local equipment.

Shark-skin melt fracture in HDPE film is suppressed by die land length and die temperature. For HDPE 7000F, increasing die gap from 1.2 mm to 1.6 mm or raising die temperature by 5 °C often delays the condition; adding a fluoropolymer processing aid at 500–1000 ppm reduces die pressure and eliminates surface melt fracture. These interventions must be validated because high processing-aid levels can reduce the coefficient of friction below the range needed for bag opening, measured under ISO 8295:1995. Die-lip deposit control on high-molecular-weight film lines is achieved by maintaining lip-temperature uniformity within ±2 °C; when the lip is colder than the melt, low-molecular-weight fractions and external lubricants condense and create die lines. Production records from multilayer lines show that die-cleaning intervals can range from 7–30 days depending on ambient humidity and additive loading, but this interval is line-specific and not a supplier guarantee.

When Dart Impact Resistance Governs Film Grade Selection

In thin-gauge HDPE T-shirt bag and bin-liner production, the choice of HDPE 7000F over lower-density LLDPE or lower-molecular-weight HDPE is driven by impact toughness at reduced thickness. Dart impact testing under ASTM D1709 Method A on a 20 µm monolayer film typically shows higher values than a conventional HDPE blow-moulding grade converted at the same gauge because the high-molecular-weight fraction increases resistance to crack initiation. The same property is sensitive to die-gap and frost-line conditions: films produced with a die gap below 1.0 mm and high draw-down can lose dart impact because orientation freezes before adequate chain relaxation. Elmendorf tear strength under ASTM D1922 and tensile properties under ISO 527-2:2012 display a characteristic trade-off: as molecular weight rises at constant density, machine-direction tear strength increases, but transverse-direction tear strength can decrease if high-stalk processing is not balanced. Published numerical dart impact values for this specific Mehr grade are limited, so converter-specific testing on the target film structure is required before commercial acceptance.

A key differentiation is that the density near 0.954 g/cm³ provides lower stiffness than high-density injection-moulding grades with density above 0.965 g/cm³, but higher modulus than linear low-density films. The resulting film has sufficient dead-fold and tensile strength for thin bag applications without the excessive yield strength that complicates downstream slitting. The addition of standard colour masterbatches should be limited to let-down ratios between 2 wt% and 4 wt%; higher loadings of carrier resin with lower viscosity can reduce melt pressure and degrade bubble stability when the masterbatch carrier is an LLDPE with a melt flow above 2 g/10 min.

Food-contact compliance with FDA 21 CFR 177.1520 or EU Regulation 10/2011 is not automatic for all lots of HDPE 7000F. Converters producing food-contact bags must request a written compliance statement from Mehr Petrochemical or the export distributor, and migration testing under EU Regulation 10/2011 Annex V is required for specific food simulants if the grade is used in direct contact with fatty or aqueous foods. The absence of such a statement should be treated as a compliance risk, not as a technical defect, because the underlying olefin polymer may still meet the basic compositional requirements but the supply chain documentation may be incomplete.

Barrier and Permeation Boundaries

HDPE 7000F is not a barrier resin in the manner of EVOH or polyamide. Its water-vapour transmission rate is typical of high-density polyethylene with a density near 0.954 g/cm³; at 25 µm and 38 °C/90% relative humidity, published WVTR values for HDPE films generally fall in the range of 6–10 g/(m²·day) when measured under ISO 15106-3:2005, but exact values for this grade are limited. Gas barrier is not a primary selection criterion. When moisture or gas barrier demands increase, coextrusion with a barrier layer or replacement by a higher-density HDPE grade is considered. Contact with detergents, polar liquids, or wetting agents alters the environmental stress-cracking balance; environmental stress-cracking resistance under ASTM D1693 Conditions A or B should be reviewed for applications involving such exposure.

Concerning differences from other products, HDPE 7000F differs from HDPE injection grades in melt viscosity and molecular weight distribution. Injection grades with melt flow rates of 5–20 g/10 min cannot form stable blown-film bubbles without substantial LDPE addition; blow-moulding grades with melt flow rates of 0.3–0.8 g/10 min deliver lower die pressure and better surface appearance in bottle walls but do not provide the same thin-gauge bubble toughness. The following positioning compares the grade with generic adjacent HDPE families rather than specific named products, because structural differences between suppliers make direct brand comparison unreliable.

Incoming quality control for HDPE 7000F should include melt flow verification under ISO 1133-1:2022 and density under ISO 1183-1:2019, because batch-to-batch changes in molecular weight distribution can shift die head pressure by ±10% even within the same grade. A melt rheometer operating at 190 °C with oscillatory shear can reveal differences in the high-frequency storage modulus that are not visible from the low-shear MFR value alone. When the resin is received with surface dust from bulk handling, it is screened through a 100 µm sieve before hopper transfer to prevent feed-throat bridging and inconsistent intake. This is standard practice for fractional-MFR HDPE film grades and is not unique to Mehr Petrochemical material.

The melt-flow value alone does not capture the molecular weight distribution. Two fractional-MFR HDPE film grades with identical melt mass-flow rate can show different bubble stability if the high-molecular-weight tails differ. For HDPE 7000F, converting trials should record die pressure at constant screw speed and melt temperature; a shift of more than 8% at constant conditions suggests lot-to-lot variation in molecular architecture or contamination. This is because shear viscosity at a given MFR is affected by the high-molecular-weight tail content, not only by the average molecular weight.

Chemical incompatibility is limited because HDPE is a nonpolar polyolefin; however, the converter should avoid combining HDPE 7000F with strongly acidic or oxidizing purge compounds, and it should not be stored adjacent to aromatic solvents or ketones that can absorb and later volatilize during extrusion. Additive packages containing high levels of migratory slip agents can alter surface coefficient of friction under ISO 8295:1995; therefore, masterbatch compatibility with the base resin should be tested at the intended let-down before full production.

During multilayer coextrusion, HDPE 7000F may be used as a core layer or as a skin layer only after evaluating adjacent LLDPE or LDPE layers for melt-flow compatibility. Interfacial instability, gauge variation, and die-lip build-up are observed when the adjacent layer has a melt flow rate more than 10 times higher, unless the melt temperatures are matched at the feedblock. The grade is typically brought into the die at 200–215 °C, and the die lip temperature is held 10–15 °C above the body temperature to delay lip frost and reduce die-lip deposit formation.