Braskem LF0720/20AF blown-film extrusion grade is characterized as a butene-copolymer linear low density polyethylene with nominal density 0.920 g/cm³ (ISO 1183-1) and nominal melt flow rate 2.0 g/10 min at 190 °C/2.16 kg (ISO 1133-1). The application scope documented below covers six downstream converting environments: pallet unitization stretch hood, heavy-duty sack and bulk liner, agricultural silage wrap, frozen food packaging, collation shrink bundling, and lamination sealant web. All numerical ranges are nominal industrial starting values validated on production-scale blown-film equipment; plant-level optimization remains subordinate to screw geometry, air-ring configuration, die lip condition, and ambient dew point.

Stretch Hood Film and Pallet Unitization: What Processing Limits Govern Downgauging?

Processing LF0720/20AF in stretch hood applications on a mono-layer or three-layer blown film line requires a die gap between 2.0 mm and 2.5 mm, a blow-up ratio from 2.2:1 to 3.0:1, and a frost line height of 6 to 9 die diameters. The principal process conflict is bubble stability during downgauging: at a blow-up ratio above 3.0:1, frost line oscillation becomes the limiting defect, and gauge variance expands to more than ±8% on air-cooled lines without internal bubble cooling. The formulation addition ratio for a standard 70 µm hood is 100% LF0720/20AF; where converters downgauge below 55 µm, 10–20 wt% of a metallocene polyethylene plastomer with density 0.902–0.908 g/cm³ is added to raise dart impact and puncture resistance, while a slip/antiblock masterbatch is let down at 1.0–2.0 wt% to control roll-to-roll blocking before hood application. The downstream process consumes the film through an automated stretch hood machine operating with film extension ratios from 40% to 120% depending on pallet dimensions; the film is sealed by impulse welding at the hood cover perimeter. Terminal product types include 50–120 µm pallet hoods for chemical and polymer bag stacks, ventilated hoods with perforated zones, and anti-condensation hoods for cold-chain transport. Industry compliance anchors are FDA 21 CFR 177.1520(c) 3.1a for general indirect contact, EU Regulation (EU) No 10/2011 for migration control if palletized food packages are in direct contact, and EN 14932:2007 for stretch-wrap film requirements where applicable.

Production-scale failure modes observed on 250 mm and 350 mm dies include bubble flapping when the air-ring velocity exceeds 12 m/s and the frost line height is kept below 5 die diameters; the resulting transverse direction thickness variation transfers to hood sealing failures at the pallet corners. Increasing the blow-up ratio from 2.2:1 to 2.8:1 raises transverse direction Elmendorf tear while lowering machine direction tensile strength, so the bubble geometry must be matched to the hood machine extension ratio. Batch-to-batch melt flow rate variation of ±0.2 g/10 min produces a measurable frost line shift of 5–10% at constant output unless internal bubble cooling air volume is adjusted. These are operational boundaries rather than product defects; published data for this specific pallet hood configuration is limited to line trials under controlled ambient dew point below 10 °C.

Heavy-Duty Sack Extrusion, Melt Fracture Dynamics, and Seal Integrity

In heavy-duty sack production, the primary process conflict resides in the simultaneous demand for low melt temperature to control bubble stability and high melt temperature to eliminate sharkskin melt fracture at the die lip. Extruders with L/D 27:1–30:1 barrier screws and Maddock mixing elements are specified because lower L/D equipment produces pulsation and gel-related pinholes when running LLDPE at high back pressure. The formulation addition ratio for 50–80 µm heavy-duty shipping sacks is typically 80–100 wt% LF0720/20AF; for applications requiring stiffness and machinability, 0–20 wt% LDPE or HDPE is added to increase modulus and reduce transverse direction tear propagation. The downstream production process runs on monolayer or three-layer blown film lines at a die gap of 1.8–2.2 mm, a blow-up ratio from 1.8:1 to 2.5:1, and a frost line height from 5 to 8 die diameters; melt temperature is maintained between 190 °C and 220 °C, and screen packs of 60/100/60 mesh are installed to reduce gel count. Terminal finished product types include 50–70 µm form-fill-seal industrial sacks for polymer granules, 100–120 µm FIBC inner liners, and valved sacks for powdery chemical fillers. Industry compliance references for dangerous goods inner liners include UN Model Regulations 6.1.5 for compatibility testing and Directive 94/62/EC for heavy metal limits; mechanical acceptance testing follows ASTM D1709A for dart impact, ASTM D1922 for Elmendorf tear, and ASTM F88 for seal strength.

Die lip build-up becomes an operational boundary when non-polyolefin masterbatch carriers are introduced at let-down ratios above 4 wt%; this produces oxidative plate-out and pinhole defects after 6–8 h of continuous extrusion. Pre-drying is not required for the base polymer, but outdoor pellet storage with surface condensation at relative humidity above 60% may require hopper air at 40–50 °C to avoid surface moisture entrapment. Seal strength measured on 60 µm sacks at 150 °C seal bar temperature reaches a plateau between 15 N/25 mm and 25 N/25 mm; below 135 °C hot-tack drops sharply on high-speed form-fill-seal lines. The data are line-specific and should not be interpreted as guaranteed values without a statistically valid die trial.

Agricultural silage film conversion with LF0720/20AF positions the polymer as a monolayer base or as the seal and tie layer in three-layer blown structures, particularly in round bale wrap where the film must retain cling after 12 months of UV exposure. The formulation addition ratio for silage film is 90–97 wt% LF0720/20AF; a UV stabilizer masterbatch based on hindered amine light stabilizers is added at 3–6 wt%, white masterbatch for light reflection is let down at 6–10 wt%, and a polyisobutylene-based cling agent is incorporated at 0.5–1.5 wt% active content. Downstream production uses a blown film line with die gap 2.0 mm, blow-up ratio 2.0:1–2.5:1, and melt temperature 190–210 °C; bubble stability is maintained by reducing frost line height to 5–7 die diameters because high UV masterbatch levels increase melt viscosity and die pressure. Terminal products include 25–35 µm round bale wrap on 500 mm and 750 mm rolls, clamp silage sheets, and oxygen barrier coextruded silage covers. Industry compliance is anchored to EN 14932:2007 for thermoplastic stretch films for bale wrapping; REACH 1907/2006 applies to the stabilizer package, and the film is not classified as food-contact unless specifically tested under EU Regulation 10/2011.

Where frozen food packing requires low-temperature puncture resistance through distribution at −30 °C, LF0720/20AF is fabricated into coextruded three-layer webs with 5–15 wt% metallocene VLDPE in the core to maintain dart impact after freezer conditioning. The formulation addition ratio is 85–95 wt% LF0720/20AF, 0–10 wt% LDPE for surface optics, and 1–2 wt% slip/antiblock masterbatch. Extrusion parameters on a three-layer die are die gap 1.8–2.0 mm, blow-up ratio 1.8:1–2.2:1, and melt temperature 180–205 °C. The terminal web is converted into 40–80 µm side-sealed bags, block-bottom pouches, and vacuum pouches for frozen vegetables and seafood. Compliance is governed by FDA 21 CFR 177.1520(c) 3.2a and EU Regulation (EU) No 10/2011 with overall migration limit 10 mg/dm²; seal strength is validated to ASTM F88 and dart impact to ASTM D1709A after conditioning at −18 °C for 24 h.

When Collation Shrink Force Exceeds Film Blocking Thresholds in Beverage Multipack

Collation shrink lines operate with high-stalk bubble geometry because the final film must develop controlled machine-direction and transverse-direction shrink without excessive roll blocking during warehouse storage. The formulation addition ratio for collation shrink is 90–100 wt% LF0720/20AF; where shrink uniformity is insufficient, 0–10 wt% metallocene LLDPE is added, and a synthetic silica-based antiblock concentrate is let down at 1.0–1.5 wt% to maintain a coefficient of friction below 0.35 on the outer web. The blown film process uses a die gap of 2.0–2.4 mm, blow-up ratio 2.5:1–3.5:1, frost line height 8–11 die diameters, and melt temperature 190–215 °C; internal bubble cooling is mandatory on high-output lines to prevent bubble wander. Terminal product types include 30–60 µm printed multipack bundling film for beverage bottles, cans, and household goods. The applicable free-shrink test method is ASTM D2732 at 120 °C; food-contact compliance follows FDA 21 CFR 177.1520(c) 3.2a when the film contacts primary packs, and EU Regulation 10/2011 applies if the multipack contains food-contact articles. Published data for this specific grade in high-stalk collation shrink configurations is limited; the cited range is a starting specification, not an intrinsic film property guarantee.

On solventless lamination lines, LF0720/20AF functions as a sealant web because its seal initiation temperature in the 85–95 °C range and high hot-tack strength tolerate high-speed form-fill-seal abuse at packaging speeds above 30 m/min. The formulation addition ratio is 100% LF0720/20AF or 98–99 wt% with 1–2 wt% antiblock masterbatch when the sealant web is used as the outer reverse side after lamination. Blown film extrusion for lamination uses a die gap of 2.0 mm, blow-up ratio 2.0:1–2.5:1, and melt temperature 190–210 °C. The blown web is corona treated to a surface energy of 38–42 mN/m before adhesive coating. Terminal film structures include laminated bags for dry foods, stand-up pouches, and overwrap for consumer goods. Regulatory compliance for direct food-contact laminate webs includes FDA 21 CFR 177.1520(c) 3.1a and EU Regulation 10/2011; migration testing is performed on the finished laminate, not on the individual substrate, under an overall migration limit of 10 mg/dm².