PetroChina Fushun FHP5060 is converted industrially as a high-density polyethylene blown-film grade with nominal melt flow rate 0.50 g/10 min (ISO 1133-1:2022, 190 °C, 2.16 kg) and nominal density 0.950 g/cm³ (ISO 1183-1:2019). In thin-gauge carrier sack production, the resin is fed without predrying unless condensation from outdoor storage has wetted the pellet surface; in that case, a hot-air hopper at 55–60 °C for 2–3 h is applied before the extruder throat. Single-screw blown-film lines with grooved feed sections, barrier screws, and L/D ratios of 30:1 to 36:1 are used. The melt is discharged through a spiral mandrel die with diameter 100–250 mm and die gap 1.0–1.6 mm. High-stalk bubble geometry is maintained at blow-up ratio 3.0:1–4.5:1, with stalk height 6–9 die diameters and frost line height 8–12 die diameters for gauges from 12 µm to 25 µm. The frost-line window is narrow because quench at less than 6 die diameters freezes out machine-direction orientation and reduces dart impact, while a frost line above 12 die diameters induces bubble flutter that creates gauge banding of ±15% at the collapsing frame.

On high-output lines exceeding 1.5 kg/h per cm of die circumference, internal bubble cooling is required. Without IBC, the high-stalk bubble oscillates after the frost line, producing transverse-direction thickness variation that cannot be corrected by conventional air-ring adjustment. The resultant film is tested to ASTM D1709-22 Method B for dart drop, ASTM D1922-23 for Elmendorf tear, and ISO 527-3:2018 for tensile strength. At 20 µm, commercial carrier film produced from a 0.50 g/10 min HDPE grade typically shows dart impact above 150 g and Elmendorf tear above 2.0 N in the machine direction, but published data for FHP5060 in this exact configuration is limited. Heat-seal temperature for side welds is maintained at 135–155 °C with jaw pressure 0.30–0.50 MPa and dwell 0.5–1.0 s. Below 130 °C, seal strength measured to ASTM F88/F88M-21 falls below 8 N/15 mm; above 160 °C, molten film extrudes from the seal bead and produces leakers at the fold.

Why Does Die Melt Pressure Above 350 Bar Initiate Surface Melt Fracture in Heavy-Gauge HDPE Liners?

At 50–150 µm gauge, FHP5060 is extruded into industrial liners, construction debris sacks, and bulk packaging where puncture resistance and seam integrity determine acceptance. The die gap is widened to 1.4–2.0 mm to reduce die-lip shear stress, and the melt temperature is held at 195–230 °C at the adapter. On a 65 mm grooved-feed extruder with L/D 33:1, screw speed above 90 rpm can push die melt pressure beyond 350 bar. When this pressure is exceeded, the film surface develops a finely spaced roughness known as melt fracture, most visible at the outermost edges of the collapsed bubble and on the inside surface of the lay-flat. The defect is not eliminated by increasing air-ring cooling or drawdown ratio; the pressure must be reduced by lowering screw speed, raising the final die zone temperature, or adding an external fluoropolymer-based process aid masterbatch at 0.02–0.08 wt%.

Heavy-gauge liner production uses a high-stalk bubble with BUR 3.0:1–4.0:1 and stalk height 7–11 die diameters. Internal bubble cooling is commissioned when line output exceeds 80 kg/h on a 200 mm die; otherwise gauge uniformity at the collapsing frame exceeds ±10%. Film is qualified in the laboratory using ASTM D1709-22 Method B for dart impact, ASTM D1922-23 for Elmendorf tear, and ISO 527-3:2018 for tensile properties. For 70 µm industrial liner film, typical acceptance limits specify dart impact above 500 g and minimum tensile strength at break above 25 MPa in both directions. Heat sealing is conducted at 145–170 °C with jaw pressure 0.30–0.50 MPa and dwell 0.8–1.5 s. Seal peel strength measured to ASTM F88/F88M-21 is monitored; values below 10 N/15 mm indicate contamination or low seal temperature. The addition of slip and antiblock concentrates at 0.10–0.25 wt% reduces blocking during reel storage, but excess erucamide above 0.15 wt% migrates to the film surface and reduces ink adhesion after corona treatment.

In three-layer coextrusion for moisture-barrier industrial packaging, FHP5060 is placed as the outer layer to contribute stiffness and water-vapour resistance while an LLDPE sealant layer provides low-temperature sealing. The HDPE layer is processed on a separate extruder at 190–215 °C, while the LLDPE layer is run at 200–225 °C and the tie layer at 190–215 °C. Layer distribution is typically 25/35/40 or 20/40/40 by volume, with the HDPE outer layer kept below 40% of total thickness to avoid interfacial instability. When the HDPE layer exceeds 40% or the LLDPE layer thins below 10 µm, interfacial waves develop and appear as surface bands after printing. Die gap is set at 1.2–1.8 mm on a 250 mm spiral mandrel die, and total film gauge is maintained at 50–120 µm. The coextruded film is corona-treated to 40–44 mN/m wetting tension measured by ASTM D2578-23 before printing or lamination.

Moisture-vapour transmission is measured by ASTM F1249-20 at 38 °C and 90% relative humidity; HDPE decreases the transmission rate relative to a pure LLDPE structure of equal thickness, but the improvement is governed by layer thickness and orientation. The film is not an oxygen barrier; ethylene-vinyl alcohol or polyamide cores are required where modified-atmosphere performance is specified. For food-contact use, the converter must verify that all layer components meet FDA 21 CFR 177.1520 or regional migration requirements; the HDPE layer alone does not confer food-contact compliance to the finished structure.

Calcium Carbonate-Filled HDPE Films for Paper-Like Packaging Substrates

FHP5060 is blended with calcium carbonate masterbatch at 20–40 wt% total filler to produce paper-like carrier envelopes, food service wraps, and printable packaging substrates. The filler is introduced at the main feed throat or through a side feeder on a single-screw film extruder; separate twin-screw compounding is unnecessary unless filler content exceeds 40 wt%. A screen pack of 100/250/120 mesh is installed ahead of a spiral mandrel die with gap 1.8–2.2 mm to trap agglomerates. Back pressure increases by 25–50 bar when filler loading is raised from 20% to 40%, requiring the extruder drive to maintain at least 80% torque reserve. Melt temperature is held at 180–210 °C to limit degradation of the stearic acid coating on the carbonate filler. BUR is kept at 2.5:1–3.0:1 because higher bubble expansion around calcium carbonate particles creates pinholes and lowers burst strength. Final film gauge is 30–80 µm.

Bending stiffness and dead-fold character are the primary performance objectives. These properties improve with filler loading up to 35 wt%, after which dart drop and Elmendorf tear measured by ASTM D1709-22 and ASTM D1922-23 decline steeply. The surface energy is raised by corona discharge to 40–44 mN/m before flexographic printing; ink adhesion is checked by ISO 2409:2013 cross-cut tape removal. Calcium carbonate particle size should remain between 5 µm and 10 µm with a fatty-acid surface coating. Uncoated filler or coarse particles above 15 µm increase die-lip buildup and form visible white specks in printed areas. Published data for FHP5060 in this filled system is limited, particularly above 35 wt% filler, where elongation at break and pinhole resistance become batch-sensitive on single-screw lines.

When Temporary Containment Cover Film Requires UV-Stabilized HDPE Without Geomembrane Certification

Temporary landfill covers, pond liners, and construction enclosure membranes are produced from FHP5060 in thicknesses from 150 µm to 1.5 mm by thick-gauge blown film or flat-die sheet extrusion. For outdoor exposure, carbon black masterbatch is dosed at 2.0–3.0 wt% with carbon black primary particle size below 25 nm and dispersion assessed by microscopy or extrusion-screen tests. A UV stabilizer package based on hindered amine light stabilizers is added at the converter’s specified ratio; the resin itself does not carry a UV-resistant formulation. Die gap is widened to 2.0–2.8 mm and BUR is reduced to 2.0:1–3.0:1 to handle the thick melt web without collapsing the bubble. Melt temperature is held at 200–230 °C. The sheet is qualified for outdoor service using oxidative induction time to ISO 11357-6:2018 or ASTM D3895-19; OIT below 100 min at 200 °C indicates inadequate stabilizer dispersion or oxidation of the melt during conversion.

FHP5060 is not classified as a dedicated geomembrane resin. For permanent containment, GRI GM13 and ASTM D5397-20 requirements for stress crack resistance and long-term durability must be evaluated before specifying this grade. Published data for FHP5060 in this specific configuration is limited; the converter must perform notched constant tensile load testing and hydrostatic resistance trials on the finished sheet rather than relying on film-grade mechanical properties.

Agricultural silage covers and greenhouse side sheets are made from FHP5060 by blending white or black masterbatch and converting on high-stalk blown-film lines at 80–120 µm thickness. Die diameters from 300 mm to 600 mm produce lay-flat widths of 1.5–4.0 m at BUR 2.5:1–3.5:1. Ultraviolet stabilizer masterbatch is included at 0.5–1.5 wt% for films intended for seasonal exposure. The conversion window is less sensitive than thin-gauge bag film because the heavier gauge tolerates broader frost-line variation, but die-lip buildup from additives becomes the controlling defect when the line runs longer than 96 h.