On high-speed pre-stretch pallet-wrapping lines operating at 250–300 m/min with 100–200% pre-stretch, Braskem FL31 is processed as the primary core resin in a three-layer cast coextrusion. The material is dosed at 70–85 wt% in the core layer, with mLLDPE at 15–25 wt% to raise ASTM D5748-95 protrusion puncture resistance, while the outer skins carry a polyisobutylene cling concentrate at 0.8–2.0 wt% and a silica-based antiblock at 0.5–1.5 wt%; layer distribution is set at 10/80/10 for 17–23 µm machine-grade film. Under ASTM D5458-95 peel cling, removable cling force typically shifts from 0.8 N/cm to 1.4 N/cm as the cling concentrate moves from 1.0 wt% to 2.0 wt%. The downstream cast line uses a 35:1 L/D barrier screw, 0.7 mm die gap, 90–120 mm air gap, and a chrome chill roll held at 18–24°C; edge trim is recycled at 10–20%. Above 20% edge trim, screw torque fluctuation and gel formation in the melt curtain increase. The material is also tested in accordance with ISO 527-3:2018 tensile and ISO 7765-1:1988 free-falling dart. Terminal grades include machine-grade palletization rolls, coreless pre-stretched rolls, and hand-wrap tubes.

What Limits Chill-Roll Replication and Haze in Lamination-Grade Cast Polyethylene Webs?

The use of Braskem FL31 as a heat-seal web in adhesive lamination with 12 µm polyester or 20 µm biaxially oriented polypropylene places the cast layer in direct food-contact position. Compliance under FDA 21 CFR 177.1520(c) applies to the olefin polymer; for export to the EU, Regulation (EU) No 10/2011 requires overall migration below 10 mg/dm² under the assigned food simulant. In a cast coextrusion formulation, FL31 is run at 60–75 wt%, LDPE at 20–30 wt% to widen the processing window and suppress draw resonance, and an erucamide slip concentrate at 0.5–1.5 wt% to bring kinetic coefficient of friction to 0.10–0.20 when measured under ISO 8295:1995. The downstream process uses a 0.5–0.8 mm die gap, melt temperature 230–260°C, and an air knife at 4–6 bar pinning the web to a polished 15–25°C chill roll; corona treatment is set to 38–42 mN/m before lamination. Solventless adhesive coating at 1.5–3.0 g/m² or extrusion lamination with LDPE at 8–10 g/m² is used downstream. Pre-drying is not required below 60% relative humidity; in humid transfer conditions above 60% RH, a 60°C hopper dryer for 1 h prevents surface moisture defects. Terminal types include sealant webs for snack laminates, frozen food pouches, condiment sachets, and lidding films.

On bale-wrapping lines programmed for 32–36 wraps per bale and 50% pre-stretch, the cast web is converted from 22–25 µm three-layer silage film produced with Braskem FL31 at 75–85 wt% in the core. The outer layers contain LDPE at 10–20 wt%, a combined HALS/UV masterbatch at 4–6 wt%, and pigment masterbatch at 2–5 wt%; this loading is balanced because UV masterbatch above 6 wt% reduces ASTM D5748-95 puncture resistance and increases chill roll fouling. Compliance is anchored to EN 13207:2018 for thermoplastic stretch films used for ensiling, with tensile and tear properties verified under ISO 527-3:2018. The cast process runs through a 2200 mm die, a gear pump, 0.8 mm die gap, 120–160 mm air gap, and a matte-finish chill roll held at 18–22°C to create differential cling; edge trim at 8–12% is reintroduced to the core. Film is post-slit to 750 mm rolls and wrapped under high tension on bale wrappers. Terminal formats include white, black, and green bale wrap for grass haylage, maize silage, and whole-crop ensiling.

When a Hygiene Backsheet Web Moves from Blown to Cast Coextrusion

Conversion from blown-line to cast coextrusion for breathable or non-breathable backsheet webs places Braskem FL31 at 70–85 wt% of the film layer, with LDPE at 10–20 wt% to improve chill roll release, and titanium dioxide masterbatch at 5–10 wt% to achieve opacity for nonwoven lamination. A fluoropolymer processing aid at 0.2–0.5 wt% is added only when melt fracture appears above 260°C. Compliance records typically include Regulation (EC) No 1907/2006 REACH SVHC screening, OEKO-TEX Standard 100 product class I, and ISO 10993-5:2009 cytotoxicity when the converter is qualifying the finished absorbent article; published data for this specific configuration is limited at the raw-resin level, and end-use validation remains on the finished device. The cast process uses a 4.5 m die, 80–150 mm air gap, silicon rubber nip chill roll at 15–20°C, and a melt temperature window of 235–260°C. Corona treatment is set to 39–41 mN/m for adhesive lamination to spunbond polypropylene; above 42 mN/m, surface oxidation can weaken adhesive bond strength after 90 days. Terminal products are cast backsheet webs for infant diaper lamination, adult incontinence backsheet, and feminine hygiene outer layers.

For temporary surface protection, a 40–60 µm cast masking web is produced with Braskem FL31 at 80–90 wt% as the backing film, mLLDPE at 5–15 wt% for tear propagation control, an anti-static concentrate at 0.5–1.5 wt% to prevent dust attraction on flat glass, and UV stabilizer at 0.5–1.0 wt% when outdoor exposure exceeds 30 days. The web is tested under ASTM D882-18 tensile and ASTM D3330/D3330M-04(2018) peel adhesion to stainless steel, with typical film-to-substrate adhesion kept below 0.5 N/cm to avoid adhesive transfer after 90 days of weathering. The cast backing film is extruded through a 0.8 mm die gap, 150–180 mm air gap, and a matt steel chill roll at 20–25°C; one side is corona treated to 38–42 mN/m and then coated with water-based acrylic pressure-sensitive adhesive at 3–5 g/m² dry coat weight. Anchorage below 38 mN/m leads to adhesive pick-off during high-speed unwind. Terminal types include temporary masking for stainless steel sheet, anodized aluminium extrusions, PMMA sheet, and flat glass handling.

High-Clarity Overwrap for Bundled Paper Products and Tissue Packaging

At 25–35 µm gauge and 180–250 m/min overwrap line speed, Braskem FL31 is processed in mono-layer cast film with 80–95 wt% FL31, 5–15 wt% LDPE to reduce neck-in, and a slip/antiblock masterbatch at 1.0–2.0 wt%. Haze measured under ISO 14782:1999 is held below 6% using a polished chill roll with roughness below 0.3 µm Ra at 20–25°C; coefficient of friction under ISO 8295:1995 is maintained at 0.20–0.35 to avoid tray jams in overwrap machines. The film is corona treated to 38–40 mN/m before printing, but pot-life of the treated surface is 30–60 days; after that the roll must be retreated or rejected. Compliance includes FDA 21 CFR 177.1520(c) for indirect food contact in paper packaging, and Regulation (EU) No 10/2011 when the wrapped product is stored adjacent to food. Terminal types include clear overwrap for paper reams, tissue bundles, napkin sleeves, and sanitary protection bundles.