SHARQ HDPE F1 in vest-style grocery carrier production operates as a high-molecular-weight blown-film resin with a nominal melt flow rate of 0.05 g/10 min at 190°C/2.16 kg (ISO 1133-1:2022) and density 0.948 g/cm³ (ISO 1183-1:2019). The grade is processed on high-stalk monolayer lines with die gap 1.2–1.4 mm, melt temperature 190–210°C, blow-up ratio 3.5:1–4.5:1, and frost-line height 8–10 die diameters. On a 65 mm grooved-feed extruder fitted with a 250 mm spiral-mandrel die, line speed for 12.5 µm vest carriers is typically 70–90 m/min. Dart impact release testing per ASTM D1709-22 Method A commonly uses a 120 g floor at 12.5 µm, though published data for this specific configuration is limited. Tensile yield stress in film is measured per ISO 527-3 and remains in the 20–24 MPa range for the neat grade. Edge trim and off-spec film are shredded and reintroduced at up to 20 wt% without destabilizing the high-stalk bubble. Corona treatment to 38–42 dyn/cm per ASTM D2578 is applied when flexographic printing is specified. Pre-drying is not required; however, when pellets are transferred from cold storage into a production hall above 60% relative humidity, surface condensation can cause feed-throat bridging. Terminal products include vest-style grocery carriers, produce roll bags, and small retail bags.

Why Does Frost-Line Air Geometry Set the Output Ceiling in Refuse-Sack Coextrusion?

Three-layer refuse sack lines running HDPE F1 in the core encounter an output limit set by frost-line air geometry rather than screw torque. In a representative 3-layer structure, the core contains 65–75 wt% SHARQ HDPE F1, one skin contains 10–15 wt% LLDPE C6 with density 0.918 g/cm³, and the other skin contains 10–15 wt% clean post-industrial HDPE regrind; the balance is additional HDPE F1 or a color masterbatch. The die gap is 1.6 mm; blow-up ratio is 3.8:1; melt temperature is 195–215°C. Production-scale 75 mm extruders with 30 L/D barrier screws and a 350 mm die sustain 280–320 kg/h when internal bubble cooling and a high-pressure dual-lip air ring hold the frost line at 8–11 die diameters. The HDPE F1 core contributes extensional viscosity and strain hardening; once the frost line rises above the cooling plenum, dart impact per ASTM D1709-22 Method B at 25 µm falls below the 250–350 g specification window used by municipal waste bag buyers. Elmendorf tear per ASTM D1922-23 shows machine-direction values 3.0–4.5 times the transverse-direction values; oscillating haul-off and die rotation are used to redistribute the orientation imbalance. Screen pack pressure increases with regrind gels; when pressure differential exceeds 0.4 MPa across a 200 mesh screen pack, the line is shut for screen changes. Terminal products are star-sealed refuse sacks, drawstring liners, and wheeled-bin liners.

Dry-food liner film production with HDPE F1 operates in a narrower compliance regime than consumer refuse sacks because the olefin polymer layer must satisfy 21 CFR 177.1520(c) and EU Regulation 10/2011 Annex I Table 1. For cereal liners and bakery insert films at 18–35 µm, converters run the grade as a monolayer at 100% or as the core layer in three-layer coextrusions where the skins may reduce seal initiation. In monolayer cereal liners, blow-up ratio is 4.0:1, die gap is 1.4 mm, melt temperature is held at 190–205°C, and output on a 65 mm extruder is deliberately limited to 200–230 kg/h to reduce gel formation. Seal initiation is the central conversion conflict: HDPE F1 seals 10–15°C higher than LLDPE sealants, so seal-bar setpoints must be mapped with heat seal strength per ASTM F88-21 over 120–170°C at 0.5 s dwell and 0.28 MPa jaw pressure. Hot tack per ASTM F1921-18 is not the primary strength of monolayer HDPE F1; for high-speed form-fill-seal operations, a coextruded LLDPE sealant skin is preferred. Food-contact validation is not inferred from a resin datasheet; converters validate the finished film by overall migration testing under EN 1186-1 and EN 1186-14 with the limit of 10 mg/dm² from EU Regulation 10/2011. Oxygen transmission rate at 25 µm is typically 1,500–2,200 cm³/m²·day·atm per ASTM D3985-24; water vapor transmission rate is in the range of 5–8 g/m²·day at 38°C and 90% RH per ASTM F1249-24. Terminal products include dry-cereal liners, cracker pouches, and bakery film inserts.

Heavy-Gauge Industrial Sacks and the 5.0:1 Blow-Up Ratio Ceiling

Heavy-duty industrial sacks made from HDPE F1 are produced at 50–100 µm to carry mineral wool, fertilizers, and polymer powders. The process uses a die gap of 1.8 mm and melt temperature of 200–220°C; blow-up ratio can be increased to 5.0:1, but above this ratio the high-density bubble becomes sensitive to ambient air drafts on non-enclosed film towers. On 90 mm extruders with 400 mm dies, output is typically 350–400 kg/h; internal bubble cooling is required to prevent a re-crystallization front that causes blocking and poor flatness. The film is evaluated for tear strength per ISO 6383-2 and dart impact per ISO 7765-1 or ASTM D1709-22 Method B, because terminal sacks must survive sharp edges from insulation batts and granular products. A critical conflict is additive carryover: clean indoor regrind may be added at 20–30 wt%, but when the regrind contains printing ink, gel counts increase and screen pressure rises above 0.35 MPa, reducing line uptime. The finished sacks are typically taped or stitched; heat sealing is less common at this gauge because HDPE F1 seal strength at thicknesses above 50 µm is more difficult to stabilize across the seal bar.

When 50% Post-Consumer Recyclate Is Blended with HDPE F1 for Municipal Liner Production

Municipal liner lines incorporating 50 wt% post-consumer HDPE recyclate use HDPE F1 as the melt-strength restorer and gel diluent. PCR from rigid containers typically has density 0.955–0.965 g/cm³ and melt flow rate 0.4–1.0 g/10 min (ISO 1133-1:2022). Blending at 50:50 narrows the processing window to melt temperature 185–205°C, blow-up ratio 3.0:1–3.5:1, and die gap 1.8–2.0 mm. Production records on 75 mm lines indicate that gel-related screen pack changes become necessary at pressure differentials above 0.45 MPa; line output is reduced by 20–30% relative to virgin HDPE F1. The resulting 18–25 µm film must still pass municipal refusal sack tests, including dart impact per ASTM D1709-22 Method B and tear per ASTM D1922-23, although the specification floor is frequently lowered to 180–220 g at 25 µm for PCR-rich products. Residual PP contamination from bottle caps forms unmelted inclusions that act as stress raisers; converters observe a sharp decline in tear resistance when PP content exceeds 3 wt% of the regrind fraction. Published data for this specific configuration is limited, so converters must verify gel level and bubble stability on their own equipment. Terminal products include low-carbon municipal bag programs and commercial waste liners.

Cast film and extrusion coating are outside the intended processing window for SHARQ HDPE F1; the high molecular weight produces head pressure above 0.4 MPa and melt fracture at die shear rates above 200 s⁻¹ on small-diameter dies, and published data for cast-film use is limited. Drawstring household refuse liners in non-PCR markets are a shallow process zone: 100% SHARQ HDPE F1 at a 1.5 mm die gap and 4.0:1 blow-up ratio requires no additional down-gauging limits beyond those already specified for retail carrier films.