In high-output pallet-unitization converting, Braskem LL318 is fed as the core backing resin in monolayer and A/B/C coextruded machine stretch film. The formulation window in cast-film lines typically loads LL318 at 68–82 wt% in the core layer, with a metallocene-catalyzed LLDPE skin-layer plastomer at 10–20 wt%, a glycerol-mono-oleate or polyisobutylene cling agent masterbatch at 2–5 wt%, and a fluoropolymer processing aid at 0.5–1.5 wt% to suppress melt fracture at high line speeds. Compliance verification on the converted film follows ASTM D882 for machine-direction and transverse-direction tensile properties, ASTM D5458 for cling force between film layers, ASTM D5748 for protrusion puncture resistance, and ASTM D1894 for machine-side coefficient of friction. Downstream processing runs on cast-film lines with single-screw extruders at L/D 30:1, a coat-hanger flat die with 0.6 mm die gap, air gap in the 8–12 mm band, a polished chill roll held at 18–22 °C, electrostatic edge pinning, and line speeds from 450 m/min to 650 m/min; edge trim is reintroduced through a repropelletizing loop as a dry, contaminant-limited regrind stream. Terminal products are machine-grade pallet wrap rolls commonly at 500 mm web width, 20–25 µm thickness, and 1,500–2,400 m roll lengths, specified for A-type pre-stretch carriages and high-throughput logistics wrapping of glass containers, building materials, and corrugated unit loads.

Which Coextruded Sealant Web Formats Remain Within EU 10/2011 Migration Limits?

For direct-contact cast sealant webs used in fresh produce, bakery, and frozen food overwrap, LL318 is evaluated under FDA 21 CFR 177.1520 olefin polymer conditions of use B through D and under Regulation (EU) No 10/2011, with compliance verified by EN 1186-1 total migration and EN 13130-1 specific migration protocols. The resin is most often specified in the sealant skin layer at 72–85 wt%, combined with a low-vicat LDPE at 5–10 wt% to widen the hot-tack sealing window, a synthetic silica/amide slip-antiblock masterbatch at 2–4 wt%, and a polyolefin plastomer at 5–12 wt% for puncture resistance in tray overwrap. Coextrusion is performed with a three-layer feedblock and a 0.8 mm die gap, a chill roll set at 22–26 °C, and corona treatment at 38–42 mN/m for subsequent flexographic printing or adhesive lamination. Operational boundaries apply above 85 °C seal-bar temperatures; converter qualification does not extend to retort sterilization, hot-fill above 80 °C, or fatty-food simulant D2 contact without layer-specific migration testing. Terminal product types include vented berry clamshell overwrap, frozen vegetable polybag, barrier lamination sealant web, and bakery tray film.

Silage Bale Wrap: Oxygen Ingress, UV Quenching, and Cling Decay

Baled silage wrap made with LL318 carries the primary function of maintaining anaerobic fermentation through high pre-stretch cling and puncture survival. The application-specific compliance benchmark is EN 14932, with tensile properties measured by ISO 527-3, tear propagation by ISO 6383-1, and UV weathering by EN 13206 covering-film protocols where regional specifications require separate UV-stability documentation. Formulation typically places LL318 at 60–70 wt% in the outer and core layers, an octene-based metallocene LLDPE at 18–25 wt% for dart impact retention, a hindered-amine light stabilizer and carbon-black or titanium dioxide masterbatch at 3–5 wt%, and a cling agent masterbatch at 0.5–1.5 wt%. Production uses a 1.0 mm die gap with a matte-finished chill roll at 20–25 °C, line speed limited to 300–400 m/min to retain film flatness, and an in-line pre-stretch unit that simulates baler application at 55–70% elongation before winding into 25–35 µm, 750 mm wide rolls. LL318 is not an oxygen-barrier polymer; oxygen transmission through a 25 µm film is governed by ASTM D3985, but no barrier claim is made and the film is positioned strictly as a cling and mechanical protective layer. Terminal product types are round bale wrap for grass silage, haylage, maize silage, and bale stack covers in seasonal forage storage.

When Pre-Stretch Activation Approaches Yield Across 300% Draw Ratios

High-yield pre-stretch machine films represent the most technically demanding cast-film application for LL318. The converter operates two counter-rotating rollers that impose a draw ratio of 200–300% before the film contacts the pallet load; this places the film beyond the yield point but below the machine-direction break point. LL318 is formulated in the core at 65–80 wt%, with a metallocene-catalyzed LLDPE skin-layer resin at 12–20 wt%, a polyisobutylene cling masterbatch at 2–4 wt%, and a processing aid at 0.3–0.8 wt%. Elastic recovery and retained load-holding capacity are characterized by ASTM D5459 for machine-direction stretch cling film, ASTM D882 for tensile hysteresis, ASTM D5748 for puncture resistance after pre-stretch, and ASTM D5458 for cling. The critical processing conflict is neck-in after die exit; with LL318-rich formulations, a 0.6–0.8 mm die gap and an 8–12 mm air gap produce neck-in of 8–12% on the chill roll, which if not compensated by edge-trim and die-deckle tuning causes edge bead and uneven stretch activation. Melt-curtain instability appears at line speeds above 550 m/min when the process temperature at the die exit drops below 225 °C; the converter must therefore run flat temperature profiles of 220–245 °C across zones and limit chill roll water temperature drift to ±1.5 °C to avoid thermal striations. Published data for this specific configuration is limited, so the following table represents a conservative converter specification window rather than universal values.

Terminal products are pre-stretched machine film rolls for high-speed pallet wrappers certified for 300% pre-stretch carriages; any lot failing the retained puncture floor is diverted to lower-draw manual applications.

After a corona-treated low-slip skin layer is added to a cast coextrusion, LL318-based films are used as temporary surface-protection masking on flat metal, rigid polymer sheet, and pre-painted coil. The product is specified not by food-contact legislation but by ASTM D3330 for peel adhesion to stainless steel, ASTM D882 for tensile elongation, ASTM D2578 for wetting tension after corona treatment, and ISO 527-3 for film tensile properties. Typical converter formulation loads LL318 at 65–75 wt% in the bulk layer, low-density polyethylene at 10–20 wt% to adjust the peel plateau, an ethylene-vinyl acetate copolymer at 5–10 wt% for conformability, and an antistatic/anti-UV masterbatch at 1–3 wt% where masking periods exceed 30 days outdoors. Production is run on a cast line with a 0.8 mm die gap, a matte chill roll to prevent blocking, skip-plasma treatment on one face only, and slitting to custom widths between 50 mm and 1,500 mm. The most common failure is peel escalation after heat aging; converters therefore validate peel retention at 60 °C for 72 h and reject lots if stainless-steel peel exceeds 2.0 N/25 mm after aging, as measured by ASTM D3330. Terminal product formats include laser-protective masking for stainless steel architectural sheet, temporary film for PVC window profiles, and polycarbonate glazing protection during fabrication.

Wide-Die Stretch Hood Converting Constrains Melt Curtain Stability and Transverse Draw

Stretch hood converters use LL318 in the outer layers of coextruded cast film because the resin’s low gel count and draw-down stability reduce the incidence of melt-curtain sag on wide dies. The governing performance standards for the finished hood are ASTM D882 for tensile properties, ASTM D5748 for puncture resistance, ASTM D5458 for cling behavior, and EN 14932 where pallet hoods are compared with bale-wrap stretch films; warehouse logistics buyers additionally audit ASTM D5414 for load-containment film behavior under vibratory motion. Standard formulations allocate 55–65 wt% LL318, 15–25 wt% very-low-density polyethylene or plastomer for low-temperature impact strength, 5–12 wt% metallocene LLDPE for tear resistance, 2–4 wt% slip/antiblock masterbatch, and 0.5–1.0 wt% processing aid. The cast line is configured with a 1.2 mm die gap, a 1,200–1,800 mm die width, air gap below 10 mm, a 30–35 °C textured chill roll for matte outer surfaces, and downstream gusseting that forms 50–120 µm hoods. Neck-in on wide dies is managed by die-deckle adjustments and edge trim at 3–6% of web width; if the melt curtain enters the chill roll with variable velocity across the web, the resulting transverse thickness variation creates weak points during pallet hood application. Terminal products are stretch hoods for palletised building materials, chemical drums, bagged cement, and appliance loads, where the film is applied by stretch hood machines at 80–120% stretching in both machine and transverse directions.