On a three-layer blown-film line equipped with a 250 mm spiral mandrel die and external bubble stabilisation, Versalis Clearflex MDPE TF6 OKH is processed as the core layer of silage and agricultural covering films. Incoming resin MFR is verified under ISO 1133-1:2022 at 190 °C/2.16 kg; typical nominal MFR for this grade falls in the 0.5–0.7 g/10 min range, and density measured by ISO 1183-1:2019 method D is typically within 0.930–0.936 g/cm³. The core formulation comprises 60–80 wt% MDPE TF6 OKH, 15–25 wt% metallocene LLDPE for tear resistance, and 8–12 wt% white masterbatch; a hindered-amine UV stabiliser masterbatch is added at 0.3–0.6 wt% when the film is specified for 12–24 month outdoor exposure. Melt processing is carried out on a 90 mm grooved-feed extruder with L/D 30:1, a barrier screw, and a screen changer; barrel setpoints range from 180 °C near the feed throat to 230 °C at the adapter, while the die is held at 220–240 °C and melt pressure before the screen changer is typically 28–35 MPa. The bubble is run at BUR 2.5:1 with a frost line height of 600–900 mm above the die face, a configuration that balances layflat width stability with dart-drop energy absorption. Compliance for silage film is assessed under EN 13207:2018, tensile properties under ISO 527-3:2018, and dart impact under ISO 7765-1:2017; where the film is used for food-contact secondary packaging, EU 10/2011 Annex I overall migration of 10 mg/dm² must be confirmed against the OKH additive package. The extrusion window yields bale-wrap film at 25–30 µm, silage bags at 150–200 µm, bunker covers at 100–150 µm, and greenhouse side sheets at 180–220 µm. Resin should be pre-dried at 70–80 °C for 3–4 h if storage humidity exceeds 60% RH; melt temperatures above 250 °C are avoided because gel formation from the oxidised polyethylene fraction increases gel-count defects and reduces bubble stability.

What limits edge-bead formation in flat-die MDPE geomembrane extrusion?

Edge-bead formation in flat-die MDPE geomembrane extrusion is governed by die-lip temperature uniformity, polymer melt swell, and the air gap between the die and the three-roll calendering stack. When Versalis Clearflex MDPE TF6 OKH is used as the primary polyolefin layer, the formulation is set at 97.0–98.0 wt% resin with 2.0–2.5 wt% carbon black masterbatch and 0.1–0.3 wt% antioxidant package; for applications requiring higher modulus, the formulation may be modified with 20–40 wt% HDPE, but edge-bead control then requires a 5–10 °C reduction in die-lip temperature. The sheet line operates with a 120 mm single-screw extruder at L/D 30:1, melt temperature 200–230 °C, die width 2,200 mm, die gap 1.8–2.4 mm, and air gap 20–35 mm; the polished calendering rolls are held at 60–90 °C to stabilise gloss and thickness uniformity in the 0.5–3.0 mm sheet. For welding, hot-wedge fusion is run with wedge temperature 420–460 °C, seam speed 1.5–2.5 m/min, and roller pressure 0.4–0.6 MPa; seam integrity is verified under ASTM D4437-08 non-destructive evaluation and ASTM D6392-12 fusion-seam strength testing. Compliance for geomembrane applications is anchored to ASTM D6693-10 tensile properties, ASTM D5397-20 notched constant tensile load stress-crack resistance, and where landfill specifications apply, the property envelope described in GRI GM13 is used as the benchmark. Oxidative induction time is evaluated under ASTM D3895-19 and should remain at or above 100 min at 200 °C for long-term buried service. Terminal products include landfill basal liners at 1.5–2.0 mm, pond and canal liners at 0.75–1.5 mm, and secondary containment sheets at 1.5–2.5 mm. Wedge temperatures above 460 °C produce oxidative gel at the seam root, while air-gap distances above 35 mm increase edge-neck-in and bead irregularity; published data for TF6 OKH as a primary geomembrane resin is limited, so seam peel and shear trials are required before project qualification.

Stretch hood film extrusion: elastic recovery, puncture resistance, and pallet stabilisation

Stretch hood film based on Versalis Clearflex MDPE TF6 OKH is run as a three-layer blown film at 120–200 µm total thickness for pallet unitisation. The core layer comprises 60–80 wt% MDPE TF6 OKH, while the skin layers each contain 10–20 wt% metallocene LLDPE to raise puncture propagation resistance and elastic recovery; slip and antiblock masterbatch is added at 0.1–0.3 wt%. Processing uses a 350 mm die, die gap 1.8–2.2 mm, blow-up ratio 1.8–2.2:1, melt temperature 200–230 °C, and output 350–450 kg/h. The bubble is run with a high stalk and moderate frost line height 700–1,000 mm to preserve transverse-direction toughness while sufficient longitudinal elastic recovery is retained for corner-tear resistance during pallet wrapping. Compliance is evaluated under ISO 527-3:2018 for tensile properties, ISO 7765-1:2017 for dart drop, and ASTM D1922-15 for tear resistance; film thickness uniformity is monitored by an online capacitance gauge with tolerance ± 5%. Terminal products include stretch hood film at 120–200 µm for brick and bag pallet loads, household appliance overwrap, and greenhouse pallet covers. Pre-drying at 70 °C for 3–4 h is required at storage RH above 60%; melt temperatures below 200 °C create visible melt fracture and reduce puncture resistance.

Accumulator-head extrusion blow moulding of 20–220 L containers using Versalis Clearflex MDPE TF6 OKH requires parison swell control through die-lip geometry, melt-temperature profiling, and accumulator-fill pressure. The formulation is typically 100 wt% MDPE TF6 OKH; for containers demanding higher top-load strength, 10–20 wt% HDPE is compounded in, and colour concentrate is added at 1–3 wt%. Processing is conducted on an accumulator-head machine with a 110 mm extruder at L/D 24:1, shot capacity 2.5 kg, melt temperature 185–215 °C, parison die gap 1.8–2.5 mm, blow pressure 0.7–0.9 MPa, and mould temperature 15–30 °C. The pinch-off weld for a 220 L drum is cooled under pressure for 20–40 s; inadequate cooling at the pinch-off reduces ESCR and creates a leak path. Compliance for packaging is defined by UN 31H1 and ADR 6.1 where dangerous goods are transported, FDA 21 CFR 177.1520(c) for US food-contact containers, and EU 10/2011 Annex I for European food-contact migration with an overall migration limit of 10 mg/dm². Stress-crack resistance is assessed under ASTM D1693-15 condition B in 10% Igepal CO-630 at 50 °C. Terminal articles include 120 L open-top drums, 25 L jerrycans, 200 L UN-certified intermediate bulk container inner bottles, and 20 L automotive screenwash containers. Melt temperature above 215 °C produces parison sag variability greater than 15%, and sharp pinch-off geometries should be radiused to avoid stress concentration at the weld line.

When high-stalk blown-film extrusion displaces LDPE in heavy-duty sack manufacture

High-stalk blown-film extrusion of MDPE TF6 OKH is specified when the target sack film must combine increased modulus with low gel count and controlled film thickness in the 80–200 µm range. The formulation comprises 70–90 wt% MDPE TF6 OKH and 10–30 wt% LDPE or linear-low-density polyethylene; slip and antiblock masterbatch is added at 0.1–0.3 wt% to prevent blocking in wound rolls. The line uses a 90 mm grooved-feed extruder with L/D 30:1, die gap 1.8–2.2 mm, blow-up ratio 2.0–2.5:1, and stalk height of 6–8 die diameters; melt temperature is maintained at 200–230 °C with output typically in the range 250–350 kg/h on a 350 mm die. The high-stalk configuration delays crystallisation and improves bubble stability, but frost line height should remain below 1,200 mm to avoid excessive film blocking and weak transverse-direction tear properties. Compliance is evaluated under ISO 527-3:2018 for tensile properties, ISO 7765-1:2017 for dart drop, and ASTM D1922-15 for Elmendorf tear. Terminal films include 25 kg industrial sacks, 50 kg chemical powder sacks, collation shrink film at 50–80 µm, and freezer film at 40–70 µm. Pre-drying at 70 °C for 3–4 h is required if storage RH exceeds 60%; melt temperatures below 200 °C increase melt fracture at the die lip and generate visible shark-skin on the sack surface.

MDO-PE substrate drawing elevates modulus without compromising heat-seal initiation

MDO-PE lamination substrate production uses a cast or blown base film that is uniaxially stretched in the machine direction to raise modulus, reduce haze, and produce a heat-sealable PE surface for recyclable pouches. The MDPE TF6 OKH base film is extruded at 80–120 µm, then conditioned to 100–125 °C over heated rollers before stretching at a draw ratio of 4:1–6:1 in the machine direction. The formulation for the MDO substrate is 85–100 wt% MDPE TF6 OKH and 0–15 wt% LLDPE; processing aid masterbatch may be added at 0.1–0.5 wt% to suppress melt fracture at high shear. The oriented film is annealed at 112–125 °C on an annealing roll group to control shrinkage below 2% in the machine direction at 90 °C. Compliance for flexible food packaging is assessed under EU 10/2011 Annex I and FDA 21 CFR 177.1520(c); mechanical properties are evaluated under ISO 527-3:2018, and shrink characteristics are measured according to ASTM D2838-18. Terminal products include mono-material stand-up pouch laminates, recyclable PE barrier packaging, and print lamination film. Published data for TF6 OKH in MDO configurations is limited; pilot-line draw ratio mapping is required because excessive draw above 6:1 causes transverse-direction splitting at the film edge.