Monolayer bottom-seal T-shirt sack production with Sinopec Maoming HDPE HHM5202M2 places constraints on bubble stability that are not observed with fractional-melt LLDPE feedstocks. The resin is typically charged as received without predrying at ambient humidity below 50 % RH; above that threshold, hopper moisture condensation can produce surface defects on the film bubble. A common monolayer formulation for outlet-bound retail sacks is 96–98 wt% HHM5202M2, 1.0–2.0 wt% silica-based antiblock masterbatch, and 0.5–1.5 wt% erucamide slip masterbatch. The slip fraction is reduced to 0.5 wt% when the film is printed with water-based inks because bloom migration is accelerated at slit-seal temperatures above 120 °C. Extrusion is performed on a single-screw grooved-feed extruder with L/D 25:1–30:1 and a 100–160 mm dual-lip air ring die. Die gap is held at 0.9–1.1 mm, blow-up ratio at 3.5:1–4.5:1, and frost line height at 6–8 die diameters. Die temperature is controlled at 210 °C ± 5 °C. A high-stalk bubble configuration is preferred; the stalk diameter should remain below 80 % of die diameter to avoid helical instability. Downstream conversion uses bottom-seal machines with 500–650 mm film width and T-shirt bag punch units operating at 120–180 cycles/min. The film is tested according to ISO 1133-1:2022 for melt flow rate, ISO 1183-1:2019 for density, ASTM D1709-15ae1 for dart impact, ASTM D1922-23 for Elmendorf tear, and ISO 527-3:2018 for tensile properties. Finished sacks are evaluated for heavy metals under Directive 94/62/EC Annex II, with a total Cr VI, Pb, Cd, and Hg limit of 100 mg/kg. End-product forms include bottom-seal T-shirt bags, loop-handle retail sacks, and die-cut header sacks for non-food merchandise.

What Limits Drawdown Below 12 µm in High-Molecular-Weight HDPE Film Processes?

Sub-12 µm film from HHM5202M2 is governed by the melt strength of the bubble, not by the extruder plasticating capacity. The critical processing conflict is that increasing melt temperature to lower melt pressure promotes shear thinning and improves die flow, but reduces bubble load-bearing capacity and raises the probability of bubble rupture above 215 °C. Conversely, die temperatures below 200 °C produce shark-skin melt fracture on the outer bubble surface. The operational window is therefore 205 °C ± 5 °C at the die, and this must be maintained across the full die circumference within 3 °C. To reduce gauge to 12–15 µm, converters typically use 85–90 wt% HHM5202M2 and 10–15 wt% C4 or C6 LLDPE with a melt index of 0.8–1.0 g/10 min; if gauge falls to 10 µm, LLDPE addition is raised to 20 wt% and 0.5 wt% polymer processing aid masterbatch based on a fluoroelastomer is added. The bubble is run with a high-stalk configuration, blow-up ratio 3.0:1–3.8:1, frost line height 8–10 die diameters, and die gap 0.8–1.0 mm. A twin-lip air ring with lower lip flow at 60–70 % of total air volume stabilizes the stalk. Gauge variation across the web must remain below ±5 % at 12 µm; otherwise film thickness variations create weak points in perforation lines during roll-bag conversion. Tests are performed under ISO 7765-1:1988 or ASTM D1709-15ae1 Method A, with 66 cm dart height. Elmendorf tear values in MD and TD are obtained under ASTM D1922-23. Tear anisotropy above 1.5:1 MD/TD indicates excessive stalk elongation and is rejected because it causes bag splitting at cut-outs. End products include 10–12 µm perforated roll bags, star-sealed banana-liner sacks, and compactor bin liners.

Because the conversion window for industrial refuse sacks is narrower than for commodity film grades, the use of HHM5202M2 in this segment is concentrated in heavy-gauge sacks above 25 µm where high melt strength reduces sag and allows haul-off speeds above 40 m/min. A typical compound is 80–90 wt% HHM5202M2, 8–15 wt% post-industrial HDPE trim regrind, and 2–4 wt% carbon black masterbatch with 40–50 wt% pigment loading. The regrind fraction must be screened to remove particles above 250 µm, since high-molecular-weight tails in the regrind cause gel specks and dart impact variability. These sacks are classified under EN 13592:2017 for household waste collection and are also subjected to tensile seam strength evaluation under ISO 527-3:2018 at a jaw separation speed of 500 mm/min. Heavy metal restrictions follow Directive 94/62/EC Article 11, and the carbon black masterbatch must comply with its supplier REACH registration under Regulation (EC) No 1907/2006. Film is blown on a 65–90 mm extruder with L/D 28:1 and die diameter 200–300 mm. Die gap is set at 1.2–1.5 mm. The bubble is cooled with ambient or chilled air; frost line is maintained at 5–7 die diameters to produce balanced dart and tear. Blow-up ratio is 3.0:1–3.5:1. After slitting, tubing passes through a star-seal bottom former or a draw-tape insertion unit. Perforations are introduced by a rotary pin wheel. Winding tension is maintained at 4–6 N per 100 mm film width to prevent blocking. Finished types include star-sealed construction refuse sacks, draw-tape yard waste sacks, and perforated roll liners for 50–200 L containers.

When a High-Density Core Is Coextruded with Metallocene LLDPE Skins

Coextrusion of a HHM5202M2 core with metallocene LLDPE skins is used where stiffness from the HDPE core must be combined with lower seal initiation temperature and higher dart impact from the skins. The core layer contains 65–80 wt% HHM5202M2, with 10–20 wt% mLLDPE added to reduce bubble stress and 10–15 wt% regrind trim. Skin layers are each 10–15 wt% of total thickness, formulated from mLLDPE or a plastomer, with slip/antiblock masterbatch at 0.5–1.0 wt% in the skin only. Because all layers are polyethylene, no tie resin is required, but viscosity ratios must remain below 1.5:1 at 250 s⁻¹ to avoid interfacial instability. The structure is tested under ASTM D1894-14 for skin coefficient of friction, ASTM D1709-15ae1 for dart impact, and ASTM D1003-21 for haze if the application uses clear skins. If inks or adhesives are used, the converter should verify that ultraviolet-curing primers meet the specific migration limits of Regulation (EC) No 1935/2004 only when packaging contact is predicted; for industrial mailers, this is not a mandatory framework. Production uses a three-layer blown-film die with a spiral mandrel design. Die gap is 1.4–1.6 mm, die temperature 215 °C ± 5 °C, blow-up ratio 3.0:1–3.5:1, frost line 6–8 die diameters. The higher die gap is required because the core layer is highly viscous; below 1.2 mm, shear rates exceed 1500 s⁻¹ and trigger melt fracture at the skin/core interface. Bubble cage stabilization is employed to limit gauge bands. After treatment to 38–42 mN/m by corona discharge, the film is converted on a form-fill-seal line. End products include courier mailers, industrial wrap films, and heavy-duty appliance dust covers.

Refuse Sack Compression Stress Retention Under EN 13592 Loading

Household refuse sacks manufactured from HHM5202M2 are characterized less by tensile yield than by the ability of the bottom seal and side folds to retain contents under impact and compression. The governing test is EN 13592:2017, which specifies capacity, drop resistance, and seal integrity requirements for sacks intended for household waste collection. A typical formulation for 20–30 µm household sacks is 88–93 wt% HHM5202M2, 5–10 wt% LLDPE extrusion-grade modifier, and 1–2 wt% black or grey masterbatch. The LLDPE fraction is essential below 25 µm because it raises dart impact under ASTM D1709-15ae1 from below 80 g to above 100 g, a shift that determines whether sacks pass a 66 cm loaded drop test. Extrusion is performed on a single-layer blown-film line with L/D 25:1, die diameter 150–250 mm, die gap 1.0–1.2 mm, blow-up ratio 3.5:1, and frost line 6 die diameters. The bubble is collapsed through a V-guide after 5–8 m of haul-off height. The tube is slit, perforated, and formed into star-seal sacks at 120–160 cycles/min. Sealing temperature for star seals is 140–155 °C with dwell 0.35–0.60 s; above 160 °C, thin-gauge sections exhibit seal burn-through. Besides EN 13592:2017, the converter may apply ISO 527-3:2018 for tensile ultimate elongation, which typically must exceed 400 % in MD for draw-tape sack mouth retention. Heavy metal concentrations are controlled under Directive 94/62/EC Annex II to a total of 100 mg/kg. Product forms include star-sealed pedal bin liners, draw-tape refuse sacks, and grey kitchen waste bags with tie handles.

For temporary containment panels welded from 0.5 mm sheet, HHM5202M2 is used as the primary ply because the low melt flow range of 0.15–0.25 g/10 min under ISO 1133-1:2022 provides high zero-shear viscosity for extrusion stability at wide widths. The formulation is 100 wt% HHM5202M2 with 2.5–3.0 wt% carbon black UV stabilizer masterbatch; no mineral fillers are included because calcium carbonate loading above 5 wt% reduces hot-wedge weld peel strength. Panels are produced on a wide-width blown-film line with 600–1200 mm die diameter, die gap 1.5–1.8 mm, blow-up ratio 2.5:1–3.0:1, and die temperature 210 °C ± 5 °C. The lower blow-up ratio yields preferred MD tensile strength and limits web wander during panel assembly. Performance is evaluated under ISO 527-3:2018 for tensile yield and break, ASTM D882-18 for thin-sheet tensile, and ISO 12236:2006 for static puncture resistance. Welded seam peel is assessed under ASTM D6392-12. The carbon black masterbatch is selected with a UV rating for 12-month outdoor exposure; published data for this specific grade in multi-year weathering is limited. Hot-wedge welding is performed at 300–350 °C with seam overlap 40–60 mm and roller pressure 0.5–0.7 MPa. Ultrasonic thickness gauges check for thickness reduction below 10 % at the seam. Panels are joined by hot air welding if the onsite temperature is below 5 °C, with preheating of the weld track to 30 °C to prevent brittle fracture. End products are temporary construction containment curtains, dust-control partitions, and non-critical waste transfer pit liners.