Braskem LH218 is a butene-based linear low density polyethylene supplied as pellet with nominal density of 0.918 g/cm³ and nominal melt flow index of 2.0 g/10 min when measured under ISO 1133-1:2022 at 190°C/2.16 kg. In monolayer blown film extrusion for high-toughness industrial liners and garment bags, the grade is processed on grooved-feed or smooth-bore extruders with screw length-to-diameter ratios between 30:1 and 32:1, a barrier section, and a Maddock mixing element. Melt temperatures are maintained between 190°C and 210°C; sustained operation above 220°C reduces bubble stability, oxidizes the polymer melt, and increases gel speck formation. Die gap is set at 2.0 mm to 2.5 mm, blow-up ratio is held between 2.3:1 and 3.0:1, and frost line height is positioned 5 to 8 die diameters above the air ring. On a 75 mm single-screw blown film line with dual-lip air ring and internal bubble cooling, output commonly ranges from 120 kg/h to 180 kg/h at film thicknesses of 15 µm to 100 µm. Industrial liner acceptance criteria typically require tensile elongation at break of at least 500% in both machine and transverse directions per ISO 527-3:2018, and dart drop impact of not less than 80 g at 25 µm gauge per ASTM D1709 Method A. Film haze measured per ASTM D1003-21 is usually between 10% and 18% for a 25 µm film. The base olefin polymer falls within the scope of FDA 21 CFR 177.1520 and Regulation (EU) No 10/2011 for food-contact applications only when the finished film is tested for overall migration under EN 1186-1:2002; industrial non-food liners are specified against REACH Regulation (EC) No 1907/2006 and EU Directive 2011/65/EU. The main processing limitation is bubble instability when frost line height drops below 4 die diameters at high take-off speed, which creates transverse gauge bands and increases blocking tendency in collapsed film.

What Limits Seal Strength in PE/PE Laminate Sealant Webs During Step-Down Gauge Transitions?

In recyclable PE/PE flexible packaging, Braskem LH218 is used as the sealant web in gauges of 20 µm to 30 µm, laminated against a printed MDPE or HDPE outer web. The controlling variable is not ultimate heat seal force but the thickness tolerance of the sealant layer under transverse gauge transition. Seal initiation temperature for a butene LLDPE of 0.918 g/cm³ density typically sits between 95°C and 105°C, while the DSC peak melting point is near 122°C per ASTM D3418-21. A sealant formulation of 80 wt% LH218, 15 wt% LDPE with density 0.923 g/cm³, and 5 wt% anti-block masterbatch containing 5% synthetic silica reduces seal initiation temperature by 5°C to 8°C compared with neat LLDPE. The anti-block masterbatch is dosed to produce 2500 ppm silica in the final sealant layer. Hot-tack strength is measured per ASTM F1921 and seal strength per ASTM F88/F88M-21; typical seal strength for a 25 µm sealant web sealed at 130°C and 0.3 MPa for 0.5 s is expected to exceed 10 N/15 mm. Processing on a three-layer blown film line uses a die gap of 1.8 mm to 2.2 mm, blow-up ratio of 2.0:1 to 2.5:1, and melt temperature of 185°C to 205°C. The main limitation is that at 15 µm target gauge, a thickness variation of ±2 µm in the transverse direction can produce a 15% to 25% loss in hot-tack force due to reduced thermal mass under the seal bar. Recycled content in the sealant web should remain below 30 wt%; each 10 wt% addition of post-industrial LLDPE regrind tends to increase gel counts and reduce seal strength by 3% to 5%. Amine-based slip concentrates should be avoided in high-temperature lamination because their migration can produce seal contamination and variable coefficient of friction during pouch converting.

Three-layer cast stretch film lines running at linear speeds of 400 m/min to 700 m/min require a core resin with controlled melt viscosity to prevent draw resonance and edge weave. LH218 is added into the core layer at 55 wt% to 70 wt% of total throughput, while the cling layer and release layer are formulated with metallocene polyethylene or polyisobutylene cling agents. Total film gauge is typically 12 µm to 23 µm, with cling layer thickness allocation of 8% to 12% of total gauge. Extruder barrel temperatures are set between 220°C and 260°C, the slot die gap is 0.5 mm to 0.8 mm, and the chill roll temperature is maintained at 15°C to 25°C. Corona treatment is applied at 1.0 kW/m² to 2.0 kW/m² to raise surface tension above 38 mN/m per ASTM D2578-23. Cling force measured by ASTM D5458 is usually controlled between 200 g and 450 g for a 20 µm film, and machine-direction elongation at break should exceed 400% per ASTM D882. The main failure mode on high-speed cast lines is melt resonance when the draw ratio exceeds 60:1 or when the melt temperature drops below 215°C, causing film thickness oscillation and inconsistent pre-stretch performance on pallet unitization equipment.

Agricultural Silage Film: UV Stabilizer Loading and Film Ductility Retention

Agricultural silage and bale-wrap films formulated with Braskem LH218 are produced in thicknesses from 150 µm to 200 µm, usually as three-layer blown films with white outer and black inner layers. The outer white layer receives 8 wt% to 12 wt% of a masterbatch containing 10% hindered amine light stabilizer and 5% UV absorber in a PE carrier, yielding a total HALS concentration of 0.4 wt% to 0.6 wt% and titanium dioxide concentration of 0.8 wt% to 1.2 wt%. The black inner layer is compounded with 3 wt% to 5 wt% of a 40% carbon black masterbatch. Processing on a three-layer blown film line with internal bubble cooling uses melt temperatures of 195°C to 215°C, blow-up ratio of 2.0:1 to 2.5:1, and frost line height of 7 to 10 die diameters. Weathering resistance is evaluated under ISO 4892-2:2013 or ASTM G154-23; films are typically required to retain at least 50% of initial tensile elongation after 2000 h of accelerated weathering. Terminal products include silage bales, agricultural stretch hoods, and greenhouse side curtains. Published data for this specific grade in long-term field exposure is limited; end users should validate UV stabilization in the target geography because additive depletion rates depend on thermal history, surface-to-volume ratio, and pesticide contact. The film should not be stored in contact with halogenated disinfectants or solvents because stress cracking can develop in stressed film folds under partial wetting.

When FFS Lines Demand Bag Drop Impact Above 120 cm at −30°C

On form-fill-seal lines for heavy-duty shipping sacks used in fertilizer, polymer pellet, and industrial chemical packaging, Braskem LH218 is employed as the impact-absorbing core layer in three-layer films with total thickness of 160 µm to 200 µm. The outer skin is an HDPE or MDPE layer at 15% to 20% of total gauge, the core is LH218 at 55% to 60% of total gauge, and the inner seal skin is an HDPE/MDPE layer at 20% to 25% of total gauge containing 2% to 3% slip and anti-block masterbatch. Extrusion is performed on a three-layer blown film line with a 200 mm to 300 mm die, internal bubble cooling, blow-up ratio of 2.0:1 to 2.5:1, and melt temperatures of 190°C to 210°C. Dart drop impact measured per ASTM D1709 Method B on a 180 µm film is commonly specified above 700 g, and tensile elongation at break should exceed 700% per ISO 527-3. Bag drop impact at −30°C is controlled by film ductility and seal geometry; side seal strength on FFS lines is measured after sealing at 150°C to 180°C using ASTM F88. The main bottleneck is that excessive melt temperature above 215°C reduces the molecular entanglement required for low-temperature impact retention, while too low a blow-up ratio below 1.8:1 increases machine-direction orientation and lowers transverse tear resistance. The table below gives a typical three-layer heavy-duty sack structure using LH218 as the core.

Frozen food packaging lines that run at −25°C storage and −40°C blast freezing require films with low-temperature seal integrity and resistance to stress cracking at fold lines. LH218 is converted into monolayer or three-layer frozen food pouches with total gauge from 40 µm to 80 µm. The seal layer should not be down-gauged below 20 µm, because below this thickness the failure mode shifts from peel to delamination under frozen compression loads. Seal strength is measured after conditioning at −20°C per ASTM F88; a 50 µm film sealed at 140°C and 0.35 MPa for 0.5 s typically retains at least 8 N/15 mm. Blown film processing uses a blow-up ratio of 2.2:1 to 2.8:1, melt temperature of 190°C to 205°C, and die gap of 1.8 mm to 2.2 mm. For direct food contact, the finished pouch must comply with FDA 21 CFR 177.1520 or Regulation (EU) No 10/2011, and extractives testing should be carried out under the intended frozen and reheating conditions because additive migration is temperature-dependent.

On three-layer cast film lines producing liquid pouch films and overwrap, edge trim and roll start-up scrap containing Braskem LH218 are re-introduced in the core layer at 10 wt% to 20 wt% of total throughput. A continuous melt filter with 100 µm or 125 µm screens is installed upstream of the feedblock to limit gel seeds. Regrind addition above 30 wt% tends to raise visible gel counts above 5 defects per m² in thin-gauge film and reduces clarity. Extruder temperature profiles are kept between 220°C and 250°C, and the cast roll temperature is maintained at 18°C to 25°C. The main operational constraint is that inconsistent regrind particle size below 2 mm can create feeding surging and output variation of ±3% on a 300 kg/h cast line, which is visible as transverse gauge bands after stretching. The compliance matrix below summarizes regulatory anchors for typical downstream packaging applications.