On upward high-stalk blown film lines fitted with 45–65 mm grooved-feed extruders at L/D 28:1–30:1 and spiral mandrel dies of 150–250 mm, TPC KF052A is converted into vest-style carrier bag film at a nominal density of 0.952 g/cm³ under ISO 1183-1 and a nominal melt flow rate of 0.05 g/10 min under ISO 1133-1:2022 at 190°C and 2.16 kg. The feeding zone is held at 170–180°C, the compression zone at 185–195°C, the metering zone at 200–210°C, and the die at 200–210°C. Die gap is set between 1.4 mm and 2.0 mm. The high molecular weight of the grade produces a stable stalk at 6–9 die diameters above the die face with a blow-up ratio of 3.8:1 to 4.5:1; frost line height is controlled at 650–900 mm. When melt temperature drops below 190°C, gauge uniformity deteriorates and dart impact scatter under ASTM D1709 Method A increases; when die lip temperature exceeds 215°C, oxidation gel generation becomes visible as surface specks within 30 min. Typical monolayer formulation is 98.5–99.0 wt% KF052A with 1.0–1.5 wt% of a 40% silica antiblock masterbatch and, where colour is required, 2–4 wt% of a PE-based pigment masterbatch. The film is produced at 15–25 µm and is evaluated for tensile properties under ASTM D882, for Elmendorf tear under ASTM D1922, and for dart drop impact under ASTM D1709 Method A. The web is converted on bag-making machines in 2-up or 3-up configurations, with side-seal or bottom-seal tooling, perforation, and handle die-cutting. Finished articles are 15–30 L vest-style carrier bags, retail shipment sacks, and light merchandise bags with die-cut handles.

What Limits Reclaim Letdown in Three-Layer Refuse Sack Structures?

Coextrusion of refuse sacks with KF052A in the outer skin layers exposes throughput limits controlled by viscosity mismatch between virgin high-molecular-weight HDPE and post-consumer reclaim. The nominal melt flow rate of KF052A is 0.05 g/10 min under ISO 1133-1:2022, whereas sorted post-consumer HDPE crumb and agglomerate can range from 0.02 g/10 min to 0.25 g/10 min within a single lot. A 70 mm three-layer grooved-feed extrusion line with a 300 mm spiral mandrel die, die gap of 1.6 mm and blow-up ratio of 4.0:1 can run 20 µm film at 180–220 kg/h when reclaim is isolated in the core. At reclaim loadings above 50 wt% of the core layer, gels from PP labels, PET fragments and paper fibre ash nucleate micro-tears at the die lip. The resulting film loses 25–40% of its dart impact value under ASTM D1709 Method A relative to the virgin monolayer control. Screen packs are arranged as breaker plate, 40/60/100 mesh; upstream pressure rises from 220 bar to 310 bar over 48 h, and a slide-plate continuous melt filter is back-flushed once per shift. Seal jaw temperature is capped at 160°C for mixed PCR structures; above this temperature, char from residual paper labels migrates to the seal surface and reduces seal strength under ASTM F88. The layer distribution in Table 1 is used for 20 µm refuse sacks. Finished articles are 30 L, 60 L and 120 L refuse sacks and institution bin liners at 16–35 µm.

Embossing Drum Liners Without Sacrificing Machine-Direction Tear

Industrial drum liners are produced from KF052A at 14–18 µm on a 60 mm extruder with L/D 30:1 and a 200 mm spiral mandrel die; barrel temperatures are 180–215°C from feed throat to die, and melt temperature is maintained at 195–205°C. The bubble is run at BUR 3.5:1 and the die gap is set to 1.8 mm. Below BUR 3.0:1, the film loses transverse extensibility and splits during in-line embossing; above BUR 4.0:1, the stalk becomes unstable and gauge profile variation exceeds ±8%. In-line embossing uses a steel pattern roll and a rubber back-up roll at a surface temperature of 50–60°C and a nip load of 35–50 N/mm of face length. Embossing penetration is limited to less than one third of nominal gauge; deeper embossing reduces Elmendorf tear under ASTM D1922 and machine-direction tear under ASTM D1004 by more than 15%. Seal initiation temperature for KF052A in this configuration is measured at 125–130°C, and a continuous heat-seal tester per ASTM F88 records plateau seal strength between 140°C and 165°C. The film is converted into 55–120 L drum liners and heavy-duty refuse containers for non-hazardous solid production waste. The liners are not specified for hydrocarbon solvents or strong oxidizing acids; contact with such media produces swelling and oxidative embrittlement within 24 h at ambient temperature.

Food-contact produce roll bags are produced from KF052A on a 50 mm upward blown film line with a 250 mm die, die gap of 1.8 mm and BUR 4.0:1. Barrel temperatures are 170–210°C, and frost line height is held at 6–8 die diameters to keep haze low and gauge variation below ±6%. The film is corona treated to 40–44 mN/m surface tension at 45 m/min for water-based flexographic printability. In-line rotary pin perforation is applied at 300–500 mm intervals before the surface winder; the average bag length is 500–600 mm and film thickness is 10–15 µm. Because the application includes direct food contact, migration testing follows EU Regulation (EU) No 10/2011, Annex I and Annex V, with food simulants A, B and D2 assigned to aqueous, acidic and fatty produce. For the US market, olefin polymer compliance is established under FDA 21 CFR 177.1520. The relevant compliance matrix is listed in Table 2. Surface slip control for roll unwinding is achieved with 0.4–0.8 wt% silica antiblock masterbatch; excessive slip additive increases unwind telescoping at high line speeds. Finished roll bags are perforated HDPE produce packs typically 350–450 mm wide for in-store dispensers.

When HDPE Film Replaces Paper in Woven Bulk Sack Inner Liners

In animal feed and mineral bulk-pack operations, a blown HDPE inner liner of KF052A is inserted into woven PP or woven HDPE outer sacks to provide moisture protection and product containment. The liner film is produced at 20–25 µm on a 55 mm high-stalk line with BUR 3.8:1 and die gap 1.5 mm. The melt is extruded at 190–205°C into a cooling air stream at 18–25°C; lower air temperature stabilizes the stalk but increases retained stress, which can cause puckering when the liner is lap-sealed to the woven outer sack. The liner is heat-sealed at 145–155°C with dwell time of 0.8–1.2 s using serrated PTFE-coated sealing bars; seal strength is not less than 12 N/25 mm under ASTM F88. Fold-line flexing is evaluated with a Gelbo flex tester under ASTM F392, because the liner must withstand repeated handling after filling without pinhole development. Typical filled weights are 25 kg and 50 kg. The operational temperature limit is 70°C; seal strength declines more than 40% at 80°C, and the film begins to soften. KF052A liners are therefore not used for hot-filled compounds or autoclaved bulk products.