On a three-layer cast film extrusion line equipped with a 2,400 mm coat-hanger die, a 0.8 mm die slot, and vacuum box edge pinning, Braskem Green PE SLL218 is introduced as the core layer at 100 wt% with melt pump discharge pressures between 85 bar and 110 bar. The nominal melt flow rate of the grade is 1.0 g/10 min at 190 °C/2.16 kg per ISO 1133-1:2022, and nominal density is 0.918 g/cm³ per ISO 1183-1. The outer layers are metered at 10 wt% to 15 wt% of total structure; per 100 parts of SLL218 in each skin layer, 3–5 phr of polyisobutylene cling masterbatch and 5–8 phr of LDPE with a melt index of 1.8 g/10 min are added to stabilise the melt curtain and control cling force. Melt temperatures at each extruder adapter are held between 238 °C and 250 °C, while the polished chrome chill roll is maintained at 22 °C to 28 °C; chill roll temperatures below 18 °C induce differential surface crystallisation that manifests as machine-direction curl and gauge bands at line speeds above 350 m/min. Air gap between die lip and chill roll contact is set at 18 mm to 25 mm. Film thickness for machine wrap runs from 12 μm to 17 μm, while hand wrap runs from 18 μm to 23 μm. In-line edge trim is recycled into the core layer at 5 wt% to 8 wt% without measurable gel formation when extruder screw speed is held at or below 110 rpm. Cling force is measured according to ASTM D5458 and maintained at 80 g to 120 g for a 500 mm sample width; tensile elongation at break is evaluated per ISO 527-3 with specimens conditioned at 23 °C ± 2 °C and 50 % ± 5 % relative humidity. The terminal article is a pallet-stabilising stretch wrap for non-direct food contact logistics; where incidental food contact is declared, the cling masterbatch and skin layer must be validated under FDA 21 CFR 177.1520 and EU Regulation No 10/2011 for overall migration below 10 mg/dm². Thermal stability of the PIB cling additive in the skin layer becomes limiting above 260 °C, producing smoke and deposit on the casting roll; during short stops the melt temperature should therefore be reduced to 180 °C.

When Silage Film Oxygen Ingress Exceeds 1400 cm³/m²·day·atm at 25 °C

Blown silage wrap produced from SLL218 is typically extruded on a monolayer or three-layer blown film line with die diameter between 200 mm and 350 mm, die gap from 1.8 mm to 2.4 mm, and blow-up ratio set between 2.2 and 3.0. Melt temperature measured at the die head is held from 190 °C to 215 °C; frost line height is maintained at 4 to 6 die diameters to prevent excessive machine-direction orientation without sacrificing transverse-direction tensile. The formulation for a monolayer silage grade uses 100 parts SLL218, 10–15 phr LDPE, 4–6 phr carbon black masterbatch with aggregate particle size from 17 nm to 25 nm, 0.3–0.5 phr HALS UV stabiliser, and 0.1–0.2 phr polymer processing aid. Carbon black loading is determined by opacity and weathering requirements; below 4 phr, UV screening in 12-month outdoor exposure becomes insufficient, while above 6 phr the film surface roughness raises coefficient of friction above 0.45 by ISO 8295, causing baler tracking issues. Oxygen transmission rate is measured by ASTM D3985 at 23 °C and 0 % RH; converter specifications for silage barrier commonly require OTR below 1400 cm³/m²·day·atm for a 25 μm film. Thickness for silage wrap is typically 25 μm to 40 μm, and roll width is 750 mm or 1500 mm; the terminal article is a stretch wrap used around grass, maize, or whole-crop silage bales for anaerobic fermentation. Mechanical integrity is evaluated through puncture resistance per ASTM D5748 and dart impact per ASTM D1709 Method A. Compliance for the film falls under EU REACH and the absence of Substances of Very High Concern; where the film contacts wet acidic silage leachate, extraction of additives under EU Regulation No 10/2011 simulant B should be verified. Process limitation: at blow-up ratios below 2.0, transverse-direction tear strength declines to levels that allow splitting at baler friction points, and film yield stress in the machine direction increases sufficiently to cause irregular pre-stretch on bale wrappers.

Heavy-duty form-fill-seal sack lines running SLL218 in a three-layer blown configuration often demand a film thickness of 70 μm to 130 μm and a die gap of 2.0 mm to 2.5 mm to compensate for low melt strength. The layer ratio is maintained at 30/40/30, with the core containing 15–20 phr LDPE to increase bubble stability and the outer layers containing 0.2–0.4 phr slip/antiblock masterbatch. During extrusion, barrel temperatures are profiled from 170 °C at the feed throat to 210 °C at the die, and internal bubble cooling is used to raise output above 250 kg/h on lines with 85 mm extruder screw diameter and 30:1 L/D. The resultant film is converted into heavy-duty shipping sacks for resin granules, fertiliser, and construction powders on form-fill-seal equipment, where seal strength measured by ASTM F88 must remain above 22 N/15 mm after filling at 35 kg load. Dart impact resistance is specified between 800 g and 1000 g for 100 μm film per ASTM D1709 Method A. REACH compliance applies, and no direct food-contact claim is made unless the specific additive package is tested under EU Regulation No 10/2011. SLL218 is not optimal for sack constructions requiring stiffness; if the sack body exceeds 130 μm gauge, blend addition of high-density polyethylene at 10–20 phr improves crease resistance but reduces low-temperature impact.

What Limits Seal Strength After Ethylene Oxide Sterilisation in Laminated Sealant Webs?

Sealant webs laminated to biaxially oriented polypropylene or polyester in dry food and medical device packaging are produced from SLL218 on cast film lines with a die gap of 0.7 mm to 0.9 mm, melt temperature from 240 °C to 260 °C, and chill roll temperature between 20 °C and 25 °C. Film thickness for the sealant layer is typically 20 μm to 30 μm. Formulation uses 100 parts SLL218, 5–15 phr LDPE or metallocene LLDPE to lower heat seal initiation temperature to 85 °C–95 °C, 0.5–1.5 phr silica antiblock masterbatch, and 0.2–0.5 phr erucamide slip masterbatch. Heat seal strength is measured by ASTM F88 with a 25 mm wide seal prepared at 120 °C, 1.4 bar seal bar pressure, and 0.5 s dwell. After ethylene oxide sterilisation at 38 °C and 60 % relative humidity, seal strength loss exceeding 15 % has been recorded when slip additive loading exceeds 0.4 phr; migrated erucamide forms a weak boundary layer at the seal interface. Medical packaging structures using SLL218 sealant webs therefore restrict the combined slip and antiblock package below 1.0 phr. The terminal laminate pouch is used for dry foods, powders, and medical devices requiring microbial barrier. Compliance must include FDA 21 CFR 177.1520 for olefin polymers, EU Regulation No 10/2011 with overall migration below 10 mg/dm², and ISO 11607-1 for medical packaging validation. The bio-based carbon fraction of SLL218 is verified by ASTM D6866-22 Method B; this value is not a substitute for performance compliance in sterile barrier systems.

Tear Anisotropy Management in Freezer-Grade Blown Film

The anisotropy in dart impact and Elmendorf tear behaviour in SLL218 freezer film becomes significant when the bubble is collapsed at low frost line height or when blow-up ratio deviates from 2.5 to 3.0. On a three-layer blown line with die diameter 250 mm, die gap 1.8 mm, and melt temperature 195 °C to 220 °C, the layer distribution is set at 1/1/1 by output, with outer layers containing 0.3–0.6 phr of a low-temperature-stable slip/antiblock package. Formulation for the core layer is 90–95 wt% SLL218 plus 5–10 wt% LDPE; the LDPE component raises transverse-direction tear strength but reduces gloss. Film thickness for frozen vegetable and seafood bags is 40 μm to 70 μm, and the terminal pouch is run on vertical form-fill-seal machines at filling temperatures from -25 °C to -18 °C. Dart impact resistance measured at -20 °C according to ASTM D1709/A is used as a critical-to-quality value; a drop below 250 g at 50 μm thickness typically indicates excessive frost line height or insufficient LDPE. Elmendorf tear resistance per ASTM D1922 or ISO 6383-2 is used to quantify tear anisotropy; a machine-direction to transverse-direction ratio below 0.4 indicates excessive machine-direction orientation. The film is tested for low-temperature brittleness per ISO 974 or ASTM D746, and coefficient of friction is maintained between 0.15 and 0.30 per ASTM D1894 after 24 h conditioning at 23 °C. Direct food contact compliance is required; SLL218 must be used with an additive package and film structure meeting FDA 21 CFR 177.1520 and EU Regulation No 10/2011 overall migration below 10 mg/dm². Operational boundary: at chill roll or frost line conditions that produce excessive MD orientation, freezer bags exhibit zippered seal failure along the machine direction because oriented lamellae are susceptible to low-temperature crack propagation.

On High-Output Rotary Ring Lines, Stretch Hood Draw-Down Demands Controlled Melt Strength

Stretch hood lines operating at take-off speeds of 22 m/min to 28 m/min place a high draw demand on the film between the nip and the rotary ring. SLL218 is extruded on a three-layer blown line with die diameter 300 mm to 400 mm, die gap 2.0 mm to 2.5 mm, and blow-up ratio 3.0 to 3.5; melt temperature at the die is held at 190 °C to 215 °C. The structure uses 70–80 wt% SLL218 and 20–30 wt% LDPE to provide the necessary melt strength and transverse-direction elongation. Thickness is 50 μm to 150 μm, depending on pallet load weight and outdoor storage duration. The terminal film must stretch over 1200 mm by 1000 mm pallets and recover to secure the load. Published mechanical data for SLL218 in stretch hood constructions with specific rotary ring geometries is limited; converters typically set target values for dart impact at 600 g or above per ASTM D1709/A at 100 μm and tensile elongation at break above 500 % in both directions per ISO 527-3. Slippage of the film against the pallet cover is controlled by adding 0.3–0.6 phr of a high-molecular-weight silicone masterbatch to the inner layer, while the outer layer may contain 0.2–0.5 phr of a UV stabiliser for outdoor storage. Compliance is governed by the general industrial packaging requirements under REACH, and no direct food-contact claim is made for this construction unless the specific structure is brought into compliance with EU Regulation No 10/2011. A process failure mode observed on production equipment occurs when the blow-up ratio exceeds 3.5: the bubble becomes laterally unstable at high take-off speed and creates crescent-shaped thickness bands that reduce hoop recovery force.