On three-layer blown-film lines producing 100–150 µm heavy-duty sacks for polymer pellet and granular fertilizer filling, Braskem LL118 (nominal density 0.918 g/cm³, melt flow rate 1.0 g/10 min at 190 °C/2.16 kg per ASTM D1238-20) is typically positioned as the high-toughness core at 60–80 wt%, while a low-density polyethylene of similar melt index is dosed at 10–20 wt% to raise bubble stability and a high-density polyethylene blow-moulding scrap fraction is dosed at 10–20 wt% to lift machine-direction tear resistance. The die gap for this layer structure is held between 1.8 mm and 2.4 mm; narrower gaps cause melt fracture at the high shear rates required for 450–550 kg/h outputs on a 350 mm spiral mandrel die, while wider gaps reduce transverse orientation and depress dart impact below the 400 g threshold frequently specified for free-fall drop sacks in export resin distribution. A 75 mm grooved-feed single-screw extruder with a length-to-diameter ratio of 30:1 and a barrier screw fitted with a Maddock mixer is normally operated at 65–80 min⁻¹, producing a melt temperature of 195–215 °C at the die. At this temperature range, the lower melt strength of butene LLDPE compared with octene mLLDPE requires a frostline height of 600–900 mm and a blow-up ratio of 2.2:1–2.8:1; a frostline above 1000 mm raises machine-direction elongation but reduces transverse-direction tear in the finished sack. Film at 70 wt% LL118, 15 wt% LDPE and 15 wt% HDPE commonly exhibits dart impact by ASTM D1709-15a Method B in the range of 450–600 g, Elmendorf tear by ASTM D1922-09 of 25–35 N/mm machine direction and 30–40 N/mm transverse direction, and tensile strength by ISO 527-3:2018 of 20–25 MPa machine direction and 18–23 MPa transverse direction. In conversion, seam failures on form-fill-seal lines are more frequently caused by low seal-bar pressure or insufficient dwell than by film tear, provided the weld is made above 115 °C; seal strength is verified to ASTM F88/F88M-21 at not less than 8 N/15 mm. Regulatory documentation for chemical packaging typically references REACH 1907/2006 Annex XVII and, for export packaging, the EU Packaging and Packaging Waste Directive 94/62/EC. The grade should not be held above 220 °C for prolonged residence times, because butene-based LLDPE begins oxidative degradation near 240 °C, producing die-lip deposits and gel counts above 5 per 100 cm² as measured by an optical film scanner.

What Limits UV-Stabilized Agricultural Film Structures Built on Butene Linear Low-Density Polyethylene?

Greenhouse cover and mulch films in the 30–75 µm range are usually produced on 2.5:1–3.0:1 blow-up ratio lines with a die gap of 1.2–1.8 mm and a melt temperature of 190–205 °C. With 20–30 wt% of a 0.3–0.8 g/10 min LDPE present in the outer layers, LL118 provides acceptable bubble stability for low-gauge agricultural film, but it functions as the principal carrier for stabilizer masterbatches and anti-fog concentrates rather than as the primary UV-resistant layer. A HALS package is typically dosed at 0.3–0.8 wt% in the core, and a UV-absorber masterbatch at 0.2–0.5 wt% active ingredient in the outer layer. Ethylene-vinyl acetate or an ethylene-acrylate copolymer at 5–10 wt% is introduced when higher mid-infrared retention and broader light diffusion are required; higher EVA addition lowers melt viscosity and can create bubble sag at die temperatures above 190 °C. The film should be processed with a frostline height below 650 mm; a taller frostline raises transverse tear but produces a hazy film because the LDPE skin forms a surface-roughened texture under slow cooling. Mechanical properties are checked to ASTM D882-18 for tensile and ASTM D1709-15a Method A for dart impact. For a 50 µm monolayer based primarily on LL118, published industrial data indicates dart impact around 180–250 g, which is below the rough-service requirement of many exposed greenhouse covers unless a high-performance octene mLLDPE layer is coextruded. The practical boundary in this segment is that butene LLDPE lacks the hot-air burst resistance of linear low-density grades with 1-octene comonomer; therefore, LL118-based agricultural films are most commonly used as inner liners or as short-service mulch films limited to one or two growing seasons. For export to the EU, the film falls under EN 13206:2017 for covering films if used in direct agricultural service, and any incorporated UV stabilizers must satisfy REACH 1907/2006 Annex XVII and the positive-list requirements of EU Regulation (EC) No 1935/2004 only when the film contacts food at harvest.

High-speed rotary-arm pallet lines converting 55–70 µm stretch hood film require a non-tacky, high-elongation core layer that does not fracture at the gusset corners during cold stretching. Three-layer structures are typically arranged with LL118 in the core at 50–70 wt%, metallocene LLDPE skins at 30–50 wt%, and an erucamide slip package at 300–600 ppm in the outer skin only. The die gap is held between 2.0 mm and 2.6 mm, blow-up ratio between 2.4:1 and 3.0:1, and melt temperature between 190 °C and 210 °C. The lower melt strength of a 1.0 g/10 min butene LLDPE requires the spiral mandrel die temperature to be profiled with a maximum circumferential variation of ±3 °C; otherwise, gauge variation above ±6 % creates stretch pockets that fail at the cold-stretch stage. On a 250 mm die served by a 70 mm barrier-screw extruder, output is routinely maintained at 180–220 kg/h for this gauge band. Cold-stretch failure at the gusset corners normally occurs when machine-direction elongation is below 450 %, a value that depends on core thickness and cooling-air temperature. LL118 can maintain machine-direction elongation in the 500–650 % range when the core is not over-oxidized; processors using melt temperatures above 220 °C often record a 10–15 % drop in elongation and an increase in gel particles to 5–10 per 100 cm² after 8–12 h of continuous production. Puncture resistance is checked by ASTM D5748-95(2012) after conditioning for 40 h at 23 ± 2 °C and 50 ± 10 % RH. For construction-material pallet loads, a minimum puncture energy of 2.0–2.5 J is frequently specified for 60 µm film. If the palletized product is food-grade, the core layer falls under FDA 21 CFR 177.1520(c) as an olefin polymer, and the finished film must meet EU Regulation (EU) No 10/2011 overall migration limits when placed on the EU market as food-contact packaging.

Heavy-Duty Can Liners, Recyclate Blends, and Melt-Pressure Management

LL118 is used in can liners and industrial refuse sacks at 40–80 µm thickness, frequently in monolayer or two-layer structures containing 20–30 wt% post-industrial recyclate or well-characterized post-consumer LLDPE. The recyclate component raises the melt-filtration requirement; a screen pack of 20/40/60/20 mesh produces backpressure of 180–240 bar on a 75 mm grooved-feed extruder at 85–95 kg/h. Because target gauge is thinner than heavy-duty shipping sacks, die gap is set at 1.2–1.8 mm and blow-up ratio at 3.0:1–3.5:1 to raise transverse tear. Above 3.5:1 blow-up ratio, film from LL118 without added LDPE tends to develop frostline oscillation and visible bubble instability. Melt temperature is held between 190 °C and 205 °C. With 25 wt% recycled content, dart impact by ASTM D1709-15a Method A generally falls between 150 g and 200 g, and Elmendorf tear by ASTM D1922-09 tends to be 20–25 N/mm machine direction and 25–35 N/mm transverse direction. These values are adequate for medium-duty can liners but not for load retention in puncture-heavy construction waste. Melt flow stability after recyclate addition is verified by ASTM D1238-20 at 190 °C/2.16 kg; shifts above 0.5 g/10 min can indicate uncontrolled dilution with fractional-melt LDPE or downgauging scrap. Odor and organic residues from recycled content require supplier documentation under REACH 1907/2006 for articles. No direct food-contact statement is supported unless the recyclate source and cleaning process meet EU Regulation (EC) No 282/2008 for recycled plastic food-contact materials.

When Frozen Food Packaging Requires Deep-Freeze Sealing with Low-Temperature Dart Impact Resistance

Frozen-food packaging in the 40–90 µm range challenges the seal layer differently from dry goods: the hot-tack window shifts lower, and the film must withstand flex cracking at −25 °C to −40 °C distribution temperatures. LL118 is usually coextruded as the bulk layer behind an EVA or ULDPE sealant with 6–18 wt% vinyl acetate, rather than used as the sealant itself. The LL118 bulk layer is processed with a die gap of 1.4–2.0 mm and a blow-up ratio of 2.2:1–2.8:1; melt temperature is kept at 195–210 °C. The lower melting point of the sealant layer requires die-lip edge encapsulation, and the line should be purged with a 1.0 g/10 min LLDPE before shutdown to prevent interlayer mixing. A 60 µm three-layer film based on a 50–60 wt% LL118 core typically shows dart impact of 300–400 g at −18 °C when tested by ASTM D1709-15a Method B, but the value can drop to 150–200 g when the core contains more than 20 wt% recycled LLDPE. Seal strength after flat-jaw sealing at 115 °C for 0.5 s is commonly specified above 6 N/15 mm by ASTM F88/F88M-21. Flex-crack resistance is assessed by ASTM F392-93(2004) Gelbo flex testing, with fewer than 1 pinholing event per 300 cm² after 10 cycles at −23 °C as a common pass criterion.

Standard or regulation	Applicability to frozen-food LLDPE structure	Typical release condition
FDA 21 CFR 177.1520(c)	Olefin polymers for direct or indirect food contact; LL118 as bulk polymer behind functional barrier depending on end-use	Compliance with extractive limitations specified for the polymer class
EU Regulation (EU) No 10/2011 Annex I Table 1	Plastic materials and articles intended for food contact; covers monomers, additives, migration limits	Overall migration 10 mg/dm² for plastic films under simulant conditions
REACH 1907/2006 Annex XVII	Restrictions on specific substances in recycled feedstocks, including phthalates and heavy metals	Supplier declaration for each recyclate batch
ASTM F392-93(2004)	Gelbo flex durability of flexible barrier materials, frozen-film flex cracking	Fewer than 1 pinhole per 300 cm² after 10 cycles at −23 °C
ASTM F88/F88M-21	Seal strength of flexible barrier materials, flat-jaw test	Above 6 N/15 mm at 115 °C, 0.5 s dwell

Published data for LL118-specific frozen-food film configurations is limited; most commercial databases report performance for the final coextruded structure rather than the LL118 layer in isolation. Process qualification is therefore performed on the intended coextrusion line with the actual sealant and tie layers, because the dart impact value at −18 °C can shift by more than 20 % depending on tie-layer thickness and sealant hardness.

When post-consumer recyclate is added to 18–25 µm counter-bag film, the rheological curve shifts and the stable bubble window narrows. On high-stalk lines, LL118 is typically blended with 30–50 wt% HDPE homopolymer to raise stiffness and allow down-gauging without excessive blocking; tack is further controlled with a silica anti-block at 1500–3000 ppm and a slip additive at 500–1200 ppm in the outer layer. Die gap is maintained at 0.8–1.4 mm, blow-up ratio at 3.5:1–4.5:1, and melt temperature at 190–205 °C; a 60 mm grooved-feed extruder typically delivers 70–85 kg/h under these conditions. Crystalline orientation in the HDPE fraction is developed by the high stalk, while the LL118 fraction contributes tear resistance and dart impact; a 20 µm film at 50 wt% LL118 and 50 wt% HDPE shows dart impact by ASTM D1709-15a Method A of 120–180 g and Elmendorf tear by ASTM D1922-09 of 12–18 N/mm machine direction and 18–25 N/mm transverse direction. If HDPE content exceeds 50 wt%, dart impact drops below 100 g and bag failure occurs at the fold creases under sharp product corners. Retail-bag film produced with post-consumer recyclate can carry a recycled-content claim only when the recyclate stream is traceable and complies with REACH 1907/2006 Annex XVII, and it must not be used for direct food contact unless the specific recyclate approval under EU Regulation (EC) No 282/2008 is in place.