In blown-film conversion of agricultural silage balewrap, LyondellBasell Icorene 3560 CM BWN 8429 linear low density polyethylene is introduced as the primary structural component at 70–90 wt%, with the balance selected from low density polyethylene to modify bubble stability and machine-direction tear resistance. The grade is positioned as a linear low density polyethylene film resin; for converter sizing purposes, typical linear low density polyethylene film grades of this class fall within 0.916–0.924 g/cm³ density and 1.0–3.5 g/10 min melt mass-flow rate measured under ISO 1183-1:2019 and ISO 1133-1:2022 at 190 °C/2.16 kg, while actual lot certificates control the exact values. The formulation typically includes 0.5–2.0 phr polyisobutylene tackifier to generate the self-adhesion required on the bale surface and 0.15–0.40 phr hindered amine light stabilizer for ultraviolet resistance during 6–12 month outdoor exposure. Compliance testing is conducted to EN 13207:2017 for thermoplastic silage films and tubes, tensile elongation is measured under ISO 527-3:2018 at 500 mm/min, and dart impact resistance is evaluated under EN ISO 7765-1:2004 Method A. On production-scale blown-film lines with 60–100 mm single-screw extruders at L/D 28:1–30:1, a 200–350 mm die is operated with a die gap of 1.8–2.4 mm and a blow-up ratio of 2.5:1–3.2:1. Melt temperature is maintained at 185–210 °C; a dual-lip air ring and internal bubble stabiliser are used because the relatively low melt strength of the linear low density polyethylene requires tighter bubble control than a branched LDPE-rich formulation. Field observations indicate that melt-pressure fluctuation exceeding ±10 bar at constant screw speed correlates with non-uniform feeding of post-industrial edge trim; reclaimed trim should therefore be limited to 5–10 wt% with particle size below 8 mm to reduce bubble breathing. Terminal product forms are 25 µm round bale wrap in 750 mm × 1500 m rolls, silage bale tubes of 300–500 mm layflat width, and wide films for clamp silage pits.

What Limits High Holding Force in Cast Pallet-Wrap Film Using This Linear Low Density Polyethylene Grade?

High holding force in cast pallet wrap is limited primarily by the short-chain branching distribution across the resin, the plastomer addition level, and the thermal quenching rate at the chill roll. A typical production formulation for 15–23 µm machine stretch wrap contains the LLDPE grade at 75–90 wt%, a metallocene plastomer or ultra-low density polyethylene at 5–15 wt%, and polyisobutylene cling additive at 1.5–3.0 wt%; slip and antiblock additives are omitted because they depress the film-to-film cling force needed for pallet stability. Films are qualified under ASTM D4649-20 for stretch wrap selection, tensile properties are measured under ASTM D882-22 on 25 mm strips at 50 mm/min, and cling force is measured under ASTM D5458-16 after 24 h roll ageing. On cast-film lines, a 65–120 mm single-screw extruder with L/D 30:1 feeds a 1500–2500 mm flat die with a 0.5–0.8 mm die gap. Melt temperature is held between 210 °C and 245 °C; the melt curtain is pinned to a chill roll controlled at 18–25 °C by vacuum box or air-knife assist. Line speeds for 15 µm film can reach 350–450 m/min, with edge trim recycled at 2–4 wt%. Pre-stretching on powered wrapping equipment is set to 200–300 %; above this range, published data for this specific grade under high-speed cast film conditions is limited, and converter trials should measure neck-in width, cling decay over 48 h, and puncture propagation. Terminal product types are 500 mm × 1500 m machine wrap rolls, 450 mm × 300 m hand wrap rolls, and pre-stretched rolls for high holding force bundling.

Because heavy-duty industrial liners and sacks are prone to impact failure at low temperatures, a three-layer coextruded structure is used in which the LLDPE grade forms the core layer at 55–70 wt% of the total film mass. The skin layers, each accounting for 15–25 wt%, are based on high density polyethylene to improve stiffness and abrasion resistance, with fractional incorporation of the LLDPE grade at 10–20 wt% in the skins to maintain interlayer adhesion. The formulation of the core may include a processing aid masterbatch at 0.5–1.5 wt% and a colour concentrate at 1.0–2.5 wt%; no volatile plasticiser is added because monolayer heavy-duty sack film must retain tensile strength during filled drop tests. Film properties are verified under ISO 527-3:2018, free-falling dart impact under ASTM D1709-22 Method A, and Elmendorf tear resistance under ISO 6383-2:1983. Where the liner is intended for dry food contact, the structure is additionally verified against FDA 21 CFR 177.1520(c) and EU Regulation (EU) No 10/2011, with overall migration below 10 mg/dm² in the appropriate food simulant. Three-layer blown-film coextrusion is performed with a core extruder of 70–90 mm and skin extruders of 50–65 mm, each at L/D 30:1, feeding a 250–400 mm die with a 2.0–2.5 mm die gap. A blow-up ratio of 2.8:1–3.5:1 and melt temperature of 200–230 °C are maintained, with internal bubble cooling used to reduce frost line height. Finished products include 50 kg heavy-duty shipping sacks, flexible intermediate bulk container liners in 80–150 µm thickness, and polywoven sack inner liners for hygroscopic powders.

Extrusion Coating of Woven Polypropylene Sacks for Moisture-Barrier Industrial Packaging

The coating window on woven polypropylene sack lamination remains stable when the LLDPE fraction is held at 60–80 wt% of the coating compound and the low density polyethylene balance is maintained at 20–40 wt% to reduce neck-in and improve melt curtain stability. A processing aid masterbatch may be used at 0.03–0.08 wt% to suppress sharkskin at high shear, but filler is excluded because die lip deposit and draw resonance become visible at filler levels above 0.5 wt%. The melt is applied at 275–315 °C through a 1200–2200 mm flat die with a 0.5–0.7 mm die gap onto woven polypropylene fabric or sack kraft paper running at 80–250 m/min. The extruder is typically 100–150 mm with L/D 33:1; before lamination the substrate is corona-treated to 42–46 dyn/cm to achieve acceptable adhesion at a nip roll pressure of 3–5 kg/cm². A coating weight of 15–30 g/m² is standard for woven sacks, providing a moisture barrier sufficient for cement, fertiliser, and resin powders. Compliance for the coated structure is verified under ASTM D1238-23a for melt flow rate consistency, ISO 527-3:2018 for tensile strength of the free film, and ISO 1133-1:2022 for melt mass-flow rate at 190 °C/2.16 kg. Food-contact versions are tested under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011. Terminal products are coated polypropylene cement sacks, fertilizer bags, flexible intermediate bulk container outer liners, and industrial paper shipping sacks with moisture-resistant outer plies.

Because surface protection film requires a backing layer with consistent unwind force and controlled elongation during application, the LLDPE grade is utilised at 60–80 wt% in the backing compound, with the balance selected from low density polyethylene to adjust stiffness and corona retention. The pressure-sensitive adhesive is not melt-blended into the backing resin; it is applied as a solvent-based, hot-melt, or UV-cured layer after the backing film has been produced and surface-treated. The backing film is extruded by cast film or blown film methods at 30–80 µm thickness, with chill roll temperature held at 16–25 °C for cast film to limit crystalline growth and maintain clarity. Corona treatment is set to 38–42 dyn/cm before adhesive coating; lower values produce adhesive delamination during application, while higher values can cause film blocking on the coated roll. The backing layer is evaluated under ISO 527-3:2018 for tensile properties and ISO 6383-2:1983 for tear resistance; peel adhesion of the finished protection film is measured under ASTM D3330/D3330M-23a Method A on stainless steel panels after 24 h dwell. Compliance for general industrial use includes REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU; construction films used in interior applications may also be assessed under EN 13501-1 fire classification where relevant. Terminal products are surface protection films for stainless steel, coated metal, glass, and high-gloss automotive interior panels in widths from 100 mm to 1500 mm.

When a Coextruded Frozen-Food Packaging Film Replaces an LDPE-Rich Sealant Structure

Coextruded frozen-food packaging film replaces an LDPE-rich sealant structure when low-temperature impact strength and seal-through-contamination performance are required at distribution temperatures of −25 °C to −40 °C. The LLDPE grade is used in the sealant and core layers at 65–80 wt% of the total multilayer film, with a metallocene plastomer at 10–20 wt% to lower seal initiation temperature and a tie resin at 5–10 wt% if the structure includes an ethylene vinyl alcohol barrier layer. The outer skin uses a higher density polyethylene or polyamide for abuse resistance. The film is produced on a three-layer or five-layer blown-film line with die diameters of 200–350 mm, die gaps of 1.8–2.2 mm, and a blow-up ratio of 2.2:1–3.0:1; melt temperature is maintained at 195–225 °C. Total film thickness ranges from 40 µm to 80 µm, with the LLDPE-containing layers representing 65–80 wt% of the total. Films are tested under ASTM D882-22 for tensile properties, ASTM D1709-22 for dart impact at −25 °C, and seal strength under ASTM F88/F88M-23 at 130–160 °C seal jaw temperature. Food-contact compliance requires FDA 21 CFR 177.1520(c) and EU Regulation (EU) No 10/2011 with migration testing in food simulants; for frozen fatty foods, simulant D2 or a substitute is selected based on the intended food type. Terminal products are form-fill-seal pouches for frozen vegetables, fish, poultry, and ready-meal components where puncture resistance and seal integrity at low temperature are controlling parameters.