Lotte Chemical HDPE 7000F is a high-molecular-weight, high-density polyethylene resin intended for blown film extrusion. The grade is characterized by a nominal melt mass-flow rate of 0.04 g/10 min at 190 °C under 2.16 kg load, determined in accordance with ISO 1133-1:2022, and a nominal density of 0.950 g/cm³ determined under ISO 1183-1:2019. These values place the material in the HMW-HDPE film segment, where low melt index, high melt strength, and bubble stability control process economics. The resin is converted on high-stalk blown film lines with grooved feed extruders and is specified for drawdown-sensitive formats such as 10 µm to 70 µm T-shirt bags, refuse sacks, and industrial liners.

What Are the Core Physical Properties That Differentiate 7000F from Lower-Molecular-Weight HDPE Film Grades?

In converting practice, the 0.04 g/10 min melt index correlates with high zero-shear viscosity and pronounced shear thinning. The property profile positions 7000F between conventional HDPE film resins and high-viscosity blow molding grades. Batch-to-batch changes in melt index can shift bubble height and head pressure; incoming resin lots should be checked against certificate-of-analysis limits before introduction to a continuous line.

Capillary rheometry of HMW-HDPE film grades with an ISO 1133-1 melt index of 0.04 g/10 min shows strong shear thinning. Steady-shear viscosity at 190 °C typically falls by more than one order of magnitude between 1 s⁻¹ and 1000 s⁻¹. The resulting viscosity profile supports bubble stability at low shear rates while limiting head pressure at typical die shear rates. Die-wall shear stress should remain below the critical value for gross melt fracture; if sharkskin appears at the die lip, increasing the die gap from 1.4 mm to 2.0 mm or raising the die temperature within the 210 °C limit often reduces the surface defect.

When Bubble Geometry and Frost Line Position Determine Final Film Properties

On production-scale blown film lines equipped with 25:1 to 33:1 L/D single-screw extruders and grooved feed sections, 7000F is processed at melt temperatures of 180 °C to 210 °C. Die gaps commonly range from 1.4 mm to 2.0 mm, and blow-up ratios of 3:1 to 5:1 are used to balance machine-direction and transverse-direction orientation. In high-stalk mode, the frost line is maintained 8 to 12 die diameters above the die face. This configuration increases melt tension before crystallization, which improves machine-direction tear strength under ASTM D1922. If the frost line is lowered below 4 die diameters, the film may show increased transverse-direction orientation and shifted dart impact under ASTM D1709.

Die pressure and melt temperature response require monitoring at high screw speeds. The low melt index of 0.04 g/10 min produces a steeper head-pressure response than 0.2 g/10 min to 0.5 g/10 min general-purpose HDPE film grades; pressure-limiting safeguards should be set below the die-head mechanical rating, commonly 35 MPa to 45 MPa. Barrel Zone 2 temperatures that are 5 °C to 10 °C lower than the feed zone set point improve feed stability on grooved-barrel extruders. Published data for this specific configuration is limited and line trials are required to establish target parameters.

On internally cooled blown film lines, cooling air temperature between 15 °C and 25 °C typically supports stable high-stalk operation at output rates of 120 kg/h to 220 kg/h per die head. Higher outputs may require adjustment of the air ring and internal bubble cooling to prevent bubble flutter. Bubble instability below 0.05 g/10 min melt index is more pronounced on short L/D extruders; therefore 20:1 L/D or shorter machines are not recommended for 7000F without a grooved barrel and intensive mixing section.

In T-shirt bag production, 7000F is extruded at gauges between 18 µm and 25 µm. The high melt strength and 0.950 g/cm³ density permit downgauging of 5 µm to 10 µm relative to a lower-molecular-weight HDPE film grade without equivalent dart impact loss in converter laboratory testing under ASTM D1709. Industrial liners are produced at 50 µm to 70 µm, where environmental stress crack resistance under ASTM D1693 is relevant for wet or surfactant-containing waste. Film tensile properties should be measured according to ASTM D882 or ISO 527-3 because the plaque values from ISO 527-2 do not represent oriented film behavior.

Under ASTM D1693, environmental stress crack resistance in 10% Igepal CO-630 at 50 °C is used to compare slow crack growth performance. 7000F generally provides higher ESCR than high-density grades with density above 0.955 g/cm³ because the lower density is associated with higher short-chain branching content and because the high molecular weight fraction delays brittle crack propagation. In refuse sacks exposed to waste streams containing cleaning agents, this resistance becomes a critical limitation against lower-molecular-weight HDPE film resins.

Converter-Reported Processing Boundaries and Incompatibilities

Operational boundaries for 7000F include a maximum melt temperature of 210 °C; excursions above this threshold increase the probability of oxidative chain scission, gel formation at the die lip, and film appearance defects. The resin is compatible with conventional polyethylene processing aids, but amine-based additives can inhibit the performance of fluoropolymer processing aids and should be evaluated before addition to the masterbatch stream. Edge trim and startup scrap can be reintroduced at loadings up to 20 wt% when the recycle stream is homogenized and protected with a screen pack of 100 mesh or finer. Shutdown procedures should use a purge resin with a melt index of 1.0 g/10 min to 2.0 g/10 min to displace high-viscosity 7000F from the die and adapter before cooling.

On coextruded blown film lines, 7000F may be positioned as a core layer to provide stiffness and load capacity. Outer sealant layers should be selected to match the viscosity of the core at the die shear rate. A large melt-index mismatch, such as a sealant layer above 0.5 g/10 min, can cause interfacial instability and gauge variation. In these structures, die lip temperature and die gap adjustments are made to keep wall shear stress below the critical melt fracture limit of the highest-viscosity layer.

Relative to HDPE grades formulated for injection molding with melt indices above 1.0 g/10 min, 7000F is unsuitable for filling thin-wall molds through narrow gates because the high viscosity requires excessive injection pressure. Relative to HDPE blow molding grades with densities above 0.955 g/cm³, 7000F provides lower stiffness but improved stress crack resistance under ASTM D1693 and greater bubble stability in film extrusion. Relative to LDPE film grades, 7000F has higher stiffness and tensile strength under ISO 527-2 but requires higher melt temperature and a wider die gap to avoid melt fracture.

Melt strength is not specified directly in the standard datasheet. It can be measured by a melt tension tester at strand take-up speeds from 10 mm/s to 200 mm/s or by extensional rheometry. Values for 7000F are expected to be higher than for 0.2 g/10 min HDPE film grades because of the lower melt index and broad molecular weight distribution; however, published data for this specific configuration is limited and comparisons must be made on the same instrument and specimen geometry.

Addition of post-consumer recyclate to 7000F affects dart impact and ESCR more than melt index. Contaminants such as polypropylene, paper labels, and polar barrier layers reduce interfacial adhesion and create pinhole defects. Recyclate loads above 15 wt% should be limited unless melt filtration at 80 mesh to 100 mesh and compatibility testing under ASTM D1709 confirm acceptable film quality. The presence of polypropylene at levels above 2 wt% can create visible gels and tear anisotropy that is measurable under ASTM D1922.

Gauge uniformity for 7000F depends on die gap, melt temperature, and bubble cooling. On a 1.6 mm die gap line with automatic gauge control, film thickness variation of ±5% is achievable over the web width. When die gaps are narrowed below 1.2 mm, melt fracture becomes more likely and head pressure rises; therefore the practical lower die gap limit for 7000F is 1.4 mm on most grooved-barrel extruders. Automatic gauge control systems should be tuned for the higher head pressure and slower melt-flow response of HMW-HDPE.

For film quality control, the dart impact test under ASTM D1709 should be performed on a minimum of 10 specimens per production run to reduce statistical scatter associated with gauge variation. Low-strength outliers often originate from pinholes or localized thickness defects rather than resin property variation. Optical inspection at 10 µm to 25 µm gauges should be used to detect gel counts because high melt temperatures above 210 °C increase oxidative gel formation.

These standards define regulatory pathways rather than intrinsic resin performance. A migration test result or food-contact certification is specific to the film construction and conversion conditions; converters should not rely solely on the resin grade designation. For applications requiring food-contact status, neat 7000F may be evaluated under FDA 21 CFR 177.1520(c) as an olefin polymer. Conformance must be confirmed with the film converter because colorants, processing aids, and multilayer structures can change the regulatory status. Under European Union Regulation (EU) No 10/2011, specific migration testing is required for the intended food simulant and film thickness; no resin grade alone provides unconditional approval. Polyolefin moisture uptake is below 0.01 wt% at 23 °C and 50% relative humidity, so pre-drying is unnecessary unless surface condensation occurs; if needed, a hopper dryer at 60 °C to 70 °C for 2 h to 4 h removes surface water. Extended storage above 50 °C or direct sunlight exposure may degrade the stabilizer package.