For high-stalk blown film operations producing die-cut handle sacks and bottom-seal grocery sacks, Hanwha HDPE 870F is run on a grooved-feed single-screw extruder with an L/D of 25:1 to 30:1 and a barrier screw fitted with a Maddock mixing section. The feedstock is not hygroscopic under normal silo storage; if the resin is exposed to condensation or stored above 60% RH, surface moisture must be removed with a hopper dryer at 60–70 °C for 1–2 h before processing to avoid pinholes and bubble breakage. Barrel temperatures are profiled from 180–190 °C in the feed zone to 220–225 °C in the metering zone, with the die held at 210–220 °C. A die gap of 1.5–2.0 mm is maintained for film gauges between 18 and 35 µm, using a blow-up ratio of 4:1 to 5:1 and a stalk height of 6–8 die diameters. The high-stalk bubble shape is critical for HDPE because it balances transverse-direction stiffness and tear without the low melt strength that causes pocket collapse in LLDPE. At 25 µm, machine-direction tensile yield strength measured under ASTM D882-18 is typically in the range 22–28 MPa, transverse-direction yield strength is 18–24 MPa, and elongation at break is above 400%. Slip and antiblock masterbatches are added at 1.0–3.0 wt% to achieve a kinetic coefficient of friction of 0.15–0.25 under ASTM D1894-21, which is necessary for bag opening in high-speed wicket lines. For food-contact grocery sacks, the converter must document compliance with FDA 21 CFR 177.1520(c) olefin polymer conditions and EU Regulation (EU) No 10/2011, with overall migration limited to 10 mg/dm² using EN 1186-14. Finished articles are die-cut handled sacks, bottom-seal T-shirt sacks, and reversible soft-loop bags used in retail, meat-to-go, and pharmacy pick-up.

What Shifts in Tear Balance When HDPE 870F Replaces a 0.948-Density Grade in Sleeve-Type Bag Film?

The main process shift when substituting Hanwha HDPE 870F for a 0.948 g/cm³ HDPE in a sleeve-type bag line is a measurable loss in impact-related properties and an increase in tensile modulus. The density increase from 0.948 to 0.956 g/cm³ raises 1% secant modulus under ASTM D882-18 by approximately 15–25%, but reduces dart impact under ASTM D1709-16a and Elmendorf tear under ASTM D1922-15 by 20–40% when the film is compared at equal thickness. This effect is intrinsic to higher-density polyethylene crystallisation and cannot be fully offset by processing alone. On production lines, the loss is managed by increasing the blow-up ratio to 5:1 and raising the frost line height to 8 die diameters, which reorients the bubble and partially recovers transverse-direction tear. The melt temperature is kept in the 210–225 °C band to avoid excessive crystallinity gradient at the die lip. For food-contact sleeve bags, the same regulatory documentation under FDA 21 CFR 177.1520(c) and EU Regulation (EU) No 10/2011 applies, and the addition of a PPA process aid at 400–800 ppm is permitted if the final migration screening under EN 1186-14 remains below 10 mg/dm². Terminal articles include heavier T-shirt sacks, die-cut handle sack stacks for fast-food carry-out, and protective sleeve bags for clothing and textile pick-up.

In coextruded dry food liners and bag-in-box webs, HDPE 870F is specified as the outer skin layers at 10–15 wt% per side, with the remaining 70–80 wt% core composed of a lower-viscosity LLDPE or metallocene LLDPE sealing layer. The HDPE skins contribute stiffness for web transport, reduced elongation under tension, and lower water vapour transmission through the composite. A five-layer spiral mandrel die is normally used, and the layer distribution accuracy should be held within ±3% to prevent curl and asymmetric seal initiation. Melt temperatures are set at 205–225 °C for the HDPE skins and 190–210 °C for the LLDPE core, because the melt viscosity ratio between the two materials is close enough to avoid interfacial instability when the HDPE fraction remains below 20 wt%. For a 50 µm composite liner, water vapour transmission rate under ASTM F1249-20 at 38 °C and 90% RH is commonly 20–30% lower than an equal-thickness LLDPE mono-layer, but the absolute value must be measured because seal layer type and processing orientation affect the result. Layer tie resins are not required between HDPE and ethylene-based LLDPE if the melt streams merge above 200 °C, but if EVOH or nylon oxygen barrier layers are added, maleic anhydride-grafted tie layers must be placed between the non-olefin barrier and the HDPE skins. The final structures are used in cereal box liners, cracker sleeves, dry soup powder sachets, and bag-in-box liners for liquid packaging where the outer HDPE layer provides abrasion resistance during case packing.

When This Grade Is Run Below 15 µm on High-Speed Form-Fill-Seal Lines, Bubble Stability Becomes the Limiting Variable

Downgauging HDPE 870F film below 15 µm on a high-speed form-fill-seal line transfers the critical control point from tensile strength to bubble stability and gauge uniformity. The high-stalk bubble used for HDPE becomes increasingly sensitive to room air turbulence and die-lip contamination as the wall thickness drops, with bubble flutter feeding directly into gauge bands that exceed ±10%. On a 350 mm die, the die gap is typically reduced from 1.5–2.0 mm to 1.2–1.4 mm, and the blow-up ratio is narrowed to 3.5:1–4.0:1. The frost line height is raised to 8–10 die diameters, and internal bubble cooling is used with a controlled exhaust volume to reduce bubble oscillation. Processing aid addition at 500–1,000 ppm is frequently required to prevent die-lip build-up and maintain a clean edge, but the exact amount must be optimised because excessive fluoropolymer can lower interlayer adhesion in coextrusions. Melt temperature should not exceed 240 °C, because the high surface-to-volume ratio of thin film accelerates oxidative gel formation. Published data for this specific configuration is limited because output, die diameter, and IBC design dominate the stability envelope; line trials are required to set repeatable limits. The terminal products are lightweight retail roll bags, produce film stock, and thin inner sleeves for small-gauge package inserts.

Refuse sacks and industrial can liners produced with HDPE 870F are normally formulated as blends rather than 100% HDPE, because the high-density fraction improves stiffness and gauge strength but reduces puncture and tear. A common starting point is 65–80 wt% HDPE 870F with 20–35 wt% LLDPE or mLLDPE having a melt index in the 0.5–1.0 g/10 min range, plus 2–4 wt% carbon black masterbatch where UV exposure or opacity is required. The blend is run on a grooved-feed blown film extruder with a die gap of 1.5–2.0 mm and a blow-up ratio of 4:1–5:1; the high-stalk bubble is retained, but the LLDPE fraction reduces stalk height by 10–20% and requires slightly lower melt temperature at the die, in the 200–215 °C range. Dart impact under ASTM D1709-16a Method A and Elmendorf tear under ASTM D1922-15 are measured on line samples rather than quoted from datasheet values because the LLDPE type and masterbatch carrier resin produce a wider batch-to-batch shift than the HDPE base resin. A 35 µm blend typically meets a dart impact of 120–180 g, but this range is indicative only and must be confirmed on the specific line. Slip and antiblock levels are reduced relative to grocery sack film because a high coefficient of friction is less critical in manual can-liner fitting. Terminal articles include industrial can liners, compactor bags, heavy-duty refuse sacks, and bundle wrap for construction materials.