Shandong Yulong HDPE HD-7000F is a high-molecular-weight high-density polyethylene blown-film extrusion resin produced by Shandong Yulong Petrochemical Co., Ltd. The grade is designated for unsupported thin-gauge film and as a stiffness-contributing layer in coextruded structures. Its nominal melt flow rate is 0.04 g/10 min at 190 °C under a 2.16 kg load according to ISO 1133-1:2022, and the annealed density is 0.947 g/cm³ according to ISO 1183-1:2019. The low MFR indicates a substantial high-molecular-weight fraction, which contributes to elevated melt strength during bubble inflation, while the density places the resin in the medium-stiffness segment of the HDPE film class. The primary operational consequence is that screw torque, melt pressure, and bubble stability differ from those of general-purpose HDPE film grades with higher MFR and from lower-molecular-weight blow-molding resins. The following sections define the property envelope, processing restrictions, and regulatory boundaries that distinguish HD-7000F from adjacent polyethylene grades.

Material and Rheological Profile for HD-7000F

The melt flow rate of 0.04 g/10 min under ISO 1133-1:2022 is approximately three to eight times lower than that of conventional HDPE blown-film resins, which commonly occupy a range of 0.08–0.12 g/10 min. The annealed density of 0.947 g/cm³ under ISO 1183-1:2019 is lower than that of 0.955 g/cm³ high-stiffness HDPE film grades, reducing flexural modulus but increasing low-temperature impact resistance and environmental stress crack resistance. Melt flow ratio data, which would define the molecular weight distribution more precisely, is not published in all regional technical data sheets; published data for this specific configuration is limited, and capillary rheometer characterization is recommended for die design. The resin’s high-viscosity response is consistent with a high-molecular-weight polyethylene; a broad or bimodal molecular weight distribution is typical for high-molecular-weight film grades of this class. On a rotational rheometer, the low-frequency storage modulus is elevated relative to general-purpose HDPE, indicating higher melt elasticity and greater resistance to bubble sag. The material should not be processed through low-torque extruders sized for MFR values above 0.5 g/10 min, because the pressure drop across a conventional die is substantially higher at equivalent output.

How Does HD-7000F Compare With Lower-Molecular-Weight HDPE Blown-Film Resins?

The differentiation from a general-purpose HDPE blown-film resin is primarily rheological and mechanical rather than constitutional: both are high-density polyethylenes, but the molecular weight and density balances differ. The table below summarizes comparative values commonly cited for these classes. Values for the general-purpose comparator are representative of a 0.952 g/cm³ HDPE film resin with MFR between 0.08 g/10 min and 0.12 g/10 min.

The lower MFR of HD-7000F translates into a lower melt index and a higher pressure requirement at the same screw speed. In blown-film operations, this raises bubble stability and permits thinner gauges, but it also increases the risk of overloading an extruder drive that was not designed for high-viscosity polyolefin processing. The lower density of HD-7000F relative to the 0.952–0.955 g/cm³ comparator reduces film stiffness moderately while improving dart impact and ESCR. Direct substitution on an existing general-purpose film line without verification of screw torque and die pressure limits is not recommended.

On high-stalk blown-film lines equipped with a 55 mm single-screw extruder with a 30:1 L/D barrier screw, HD-7000F is processed with barrel temperatures from 180 °C to 220 °C and a die temperature near 210 °C. A die gap of 1.2 mm and a blow-up ratio between 3.0:1 and 4.5:1 are typical for thin-gauge film; frost line height is adjusted to maintain bubble stability without exceeding the cooling capacity of the air ring. At a throughput of 80 kg/h, head pressures above 300 bar have been reported on some lines; this exceeds the pressure limit of certain single-layer die bodies rated for 250 bar, so die pressure verification is necessary before commissioning. On a 45 mm single-screw extruder with a 25:1 L/D general-purpose screw, output may be constrained to 40–55 kg/h because the high viscosity triggers over-torque before barrel temperature limits are reached. The same screw may produce 60–75 kg/h with a conventional 0.10 g/10 min HDPE film resin. Barrel zones above 230 °C should be avoided unless the stabilizer formulation is confirmed for higher temperatures, because oxidation and chain scission can increase low-molecular-weight species that affect organoleptic performance. Die gaps below 1.0 mm are generally avoided for high-molecular-weight HDPE because the wall shear stress can exceed the critical value for sharkskin melt fracture. Pre-drying is not normally required for unopened, moisture-protected pellets. If outdoor silo storage is used and the ambient dew point exceeds 20 °C, surface condensation on cold pellets can occur during pneumatic conveying, increasing the risk of feed-bridge formation and pellet clumping. Screen packs at 60/80/100 mesh are commonly installed to remove 100 µm gel defects; pressure drop across the screen pack should be monitored to avoid excessive melt temperature rise. The material is sensitive to high-shear, high-temperature stagnation at the die lip, which can promote die-lip buildup; periodic lip cleaning is recommended for runs longer than 24 h.

When Shandong Yulong HD-7000F Is Coextruded with LLDPE Sealant Layers

In coextruded film structures, HD-7000F is typically positioned as the core or exterior layer to provide stiffness, heat resistance, and low-cost bulk, while a linear low-density polyethylene or metallocene LLDPE sealant layer supplies a lower seal initiation temperature and improved hot-tack. The viscosity ratio between HD-7000F and a typical LLDPE sealant with MFR near 1.0 g/10 min can exceed 3:1 at typical processing shear rates. In feedblock systems, such viscosity disparity can produce interfacial instability when the HD-7000F layer is less than 10% of the total film thickness. Layer ratio adjustments and selective use of lower-viscosity LLDPE grades are required to maintain stable interfaces. The melt temperature of the outer HD-7000F layer is often maintained below 220 °C to minimize thermal degradation, while the sealant layer is processed at 220–240 °C to ensure sealant flow. This thermal separation is best achieved with multi-zone die bodies or separate extruder melt pipes. A die gap of 1.8–2.5 mm is typical for coextrusion, and blow-up ratios of 3.0:1 to 4.0:1 reduce film curl caused by differential shrinkage between the HDPE and LLDPE layers.

Compression-molded specimens of HD-7000F tested under ISO 527-2:2012 show a tensile yield stress of approximately 23 MPa and elongation at break exceeding 600%. These values provide a quality-control benchmark but do not directly predict blown-film puncture resistance because molecular orientation and cooling history in the bubble alter crystalline morphology. Dart drop impact measured under ISO 7765-1:1988 is reported at approximately 150 g on 25 µm film, and environmental stress crack resistance under ASTM D1693-15 Condition B is reported to exceed 400 h. Elmendorf tear resistance in machine and transverse directions is highly dependent on frost line height and blow-up ratio; published data for this specific configuration is limited. The film is not a barrier resin: water vapor transmission rate and oxygen transmission rate are governed by density and will be higher than those of 0.955 g/cm³ HDPE or ethylene-vinyl alcohol copolymer structures. Ultraviolet stability is not inherent; outdoor-grade films require carbon black at 2–3% or a hindered amine light stabilizer masterbatch at a loading specified by the additive supplier. Slip and antiblock additives are normally required at 0.1–0.3% when line speeds exceed 150 m/min to control blocking and converting friction.

Typical application contexts for HD-7000F include thin-gauge T-shirt bags, freezer film, lamination base films, and agricultural stretch film where a balance of stiffness, ESCR, and bubble stability is required. In freezer film, the resin retains sufficient low-temperature toughness because the density is lower than 0.952 g/cm³; however, the film thickness should be selected according to actual drop-test requirements rather than assumed impact performance. In lamination base film, the surface should be corona-treated to a wetting tension of at least 38 mN/m within 24 h of coating or printing. Corona treatment levels above 48 mN/m may leave low-molecular-weight oxidation species that can interfere with adhesive lamination. For T-shirt bag production, the high melt strength permits gauge reduction, but sealing temperature and dwell time must be adjusted because HD-7000F has a higher melt temperature than LLDPE-rich bag films. Published data for specific bag conversion lines is limited; line trials are necessary to set sealing parameters.

Compliance and Migration Boundaries for Food-Contact Service

Regulatory declarations for HD-7000F are supplied in the manufacturer’s product compliance statement or batch certificate. The matrix below summarizes the applicable regulatory framework for unpigmented monolayer film intended for food contact, based on the legislation itself rather than a specific production lot. Processors must verify that colorants, processing aids, and recycled content meet the same requirements.

For fatty food simulants and high-temperature exposure, the overall migration result for HD-7000F should be verified on the finished film rather than inferred from pellet testing. The use of post-consumer recycled HDPE in food-contact structures is outside the scope of the virgin-grade compliance matrix and requires separate authorization or functional barrier validation.

The most consequential difference from other Shandong Yulong HDPE grades appears in the melt flow rate. Blow-molding and injection-molding grades with MFR values above 0.3 g/10 min are designed for low-pressure flow into closed molds, whereas HD-7000F is a blown-film extrusion grade whose low MFR supports a stable bubble under draw. Compared with a 0.955 g/cm³ HDPE monofilament or pipe grade, HD-7000F has lower density and therefore lower tensile modulus, but improved dart impact and ESCR. Compared with metallocene-catalyzed LLDPE film resins, HD-7000F exhibits greater stiffness and heat resistance but lower puncture resistance and lower tensile elongation. The processing boundary is also different: HD-7000F should be run on extruders with drives capable of sustained high torque, and the die body pressure rating should be checked before replacing a general-purpose HDPE film resin. Addition of post-consumer recycle beyond 10% without compatibility testing can reduce ESCR and create gel-related film defects. The resin should not be combined with high-acid regrind streams, unneutralized catalyst residues, or incompatible polyamide regrind unless a tie-layer design and controlled devolatilization are present. In downstream conversion, slitting and sealing operations should be adjusted for the higher heat resistance of HD-7000F; seal bars set for LLDPE may require a temperature increase of 15–25 °C to achieve comparable seal strength on monolayer HD-7000F film.