SK LLDPE FN812 is supplied as a butene-based linear low-density polyethylene film grade for blown and cast film structures. The following application blocks are limited to downstream film sectors where butene-copolymer LLDPE is in routine industrial use. Each block identifies compliance frameworks, formulation ratios, conversion conditions, and finished article categories. Processing ranges are design references, not product specifications. Final compliance must be confirmed on the converted article under intended conditions of use.

Why Does FFS Sack Puncture Resistance Require a Butene-Backbone LLDPE?

Blown film extrusion of heavy-duty shipping sacks for granular polymer, fertilizer, and dry chemical packaging is governed by the relationship among dart impact, machine-direction tear, gusset weld integrity, and gauge uniformity. In conversion of SK LLDPE FN812 on high-throughput form-fill-seal lines, the resin is generally run in a blend rather than as a single-component film to balance melt strength and extensibility. A production-scale FFS film line with a grooved-feed extruder at L/D 30:1 and screw diameter 75 mm can sustain 190–210°C melt temperature when the die gap is kept at 1.8–2.2 mm and blow-up ratio does not exceed 2.5:1. At higher BUR, bubble instability appears as cyclic pumping in the frost line and produces gauge-band variation that interferes with automatic sack feeding and bottom-weld consistency. The compliance framework for such sacks typically references ASTM D1709-16a for dart impact, ASTM D882-18 for tensile properties, ASTM D1922-15 for Elmendorf tear, and ASTM F88/F88M-21 for seal strength. When dry food contact is required, the base resin is assessed under FDA 21 CFR 177.1520(c) and Commission Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm². For sacks intended to contain dangerous goods by road or rail, drop and stacking provisions under UN Model Regulations Chapter 6.1 may also apply to the filled package.

Formulation addition ratios in heavy-duty sack film are set by the need to retain dart impact while maintaining bubble stability. A common structure contains FN812 at 65–80 wt%, a high-pressure LDPE film resin at 18–33 wt%, a silica-based antiblock masterbatch at 0.5–1.5 wt%, and a migratory slip additive at 300–800 ppm based on total polymer mass. The LDPE component reduces bubble flutter and improves machine-direction tensile strength, but LDPE content above 35 wt% lowers dart impact and increases creep under stacked loads. Conversely, FN812 above 85 wt% raises ductile failure resistance but reduces melt strength on narrow die lines when film thickness drops below 80 µm. The downstream process is blown film extrusion followed by flexographic surface printing, slitting, gusseting, and conversion on an FFS machine where the web is folded, bottom-sealed, filled, and sealed in sequence. Heat seal temperatures are generally 125–150°C with dwell times of 0.5–1.0 s; excessive slip concentration above 1,000 ppm can create interfacial release layers that degrade seal strength. Terminal product types include valve sacks, open-mouth gusseted sacks, and FFS bags for polymer resin, mineral fillers, dry chemical powders, and granular fertilizers. Published data for FN812 at filler loading above 12 wt% in heavy-duty sack structures is limited; such formulations should not be extrapolated without plant trials.

In high-humidity cultivation zones, blown film bubble stability at night is governed by the interaction between low ambient temperature and radiative cooling of the film surface. Agricultural covering film based on butene LLDPE is selected where the target property set includes tear propagation resistance, hail impact resistance, infrared retention, and compatibility with mineral-based anti-dust additives. The relevant product standard for these films is EN 13206:2017 for thermoplastic covering films for agricultural and horticultural use. Accelerated weathering is assessed with ISO 4892-2 using xenon-arc or UVA-340 exposure, and tensile retention after weathering is verified by ISO 527-3:2018. A typical three-layer greenhouse film formulation includes an outer layer containing hindered amine light stabilizer masterbatch at 2–5 wt%, a core layer with FN812 at 45–65 wt%, LDPE at 15–30 wt%, and EVA with vinyl acetate content of 12–18 wt% at 10–25 wt%; an inner layer may contain antifog masterbatch at 0.5–1.5 wt% and an IR-absorbing mineral masterbatch at 1–3 wt%. The inclusion of FN812 in the core is driven by puncture resistance against hail and mechanical contact with crop support structures. The production process is three-layer coextruded blown film extrusion with die diameter 1,200–2,200 mm, die gap 1.6–2.0 mm, blow-up ratio 2.0–3.0:1, and internal bubble cooling for frost line control. Melt temperature is maintained at 180–200°C; sustained melt temperature above 220°C degrades the EVA layer, producing acetic acid odor and die lip deposit. Terminal product types include greenhouse cover films, low tunnels, and direct-cover floating films with thickness from 80–200 µm. An operational boundary is that certain sulfur-containing pesticide deposits inside the film can reduce UV stabilizer effectiveness; film should be tested for pesticide compatibility in high-sulfur crop protection programs.

Cast-Line Neck-In, Cling Layer Saturation, and Stretch Film Edge Tear

Machine-grade cast stretch film production at 350–600 m/min is a high-deformation-rate process in which melt extensional behavior at the die lip determines film gauge uniformity and edge trim loss. FN812 is incorporated in stretch film structures where a butene LLDPE modifier is required for economics or where a blown stretch line is used. In cast pallet wrap, FN812 is commonly blended with a metallocene LLDPE to raise dart impact and machine-direction tensile strength while accepting some reduction in ultimate stretch. The principal standards used for control are ASTM D4649-20 for selection and use of stretch wrap materials, ASTM D5748-19 for puncture resistance, and ASTM D882-18 for tensile properties. EN 14477:2004 is referenced when the film is used for protective wrapping of sharp-edged loads. A cast-film formulation typically consists of metallocene LLDPE at 55–75 wt%, FN812 at 20–40 wt%, polyisobutylene cling additive at 0.5–1.5 wt%, and antiblock masterbatch at 0.3–1.0 wt%. The cling additive concentration must be controlled within ±0.2 wt%; excessive cling agent migrates to the chill roll and forms a visible white deposit after 8–12 hours of continuous running. Production is carried out on a cast film line with slot die gap 0.4–0.8 mm, air gap 20–60 mm, chill roll temperature 20–30°C, and line speed 350–600 m/min. Neck-in distance from die edge to final film edge is measured with an optical gauge; for a butene LLDPE-rich layer, neck-in is higher than for LDPE-rich blends, and 10–20 wt% LDPE is normally added to stabilize edges. Terminal product types include pre-stretched hand pallet wrap at 12–20 µm, machine wrap at 17–30 µm, and blown stretch films for irregular loads. The operational boundary is that high line-speed oscillation in the air gap can induce draw resonance when FN812 content exceeds 50 wt% and melt strength is insufficient to dampen periodic thinning.

Production-scale observations on cast-film lines using comparable butene LLDPE-rich formulations show that neck-in is a nonlinear function of FN812 content. At 20 wt% FN812, edge trim may remain below 15%, but at 45 wt% FN812, edge trim can exceed 25% if the die lip to chill roll gap is not reduced. The practical processing window for a stable cast web is therefore defined by a melt curtain length of 20–40 mm and a chill roll surface roughness of 0.2–0.4 µm Ra. No external pre-drying is required when pellets are stored under dry ambient conditions, but surface moisture from condensation at relative humidity above 80% can generate curtain defects. Additives that interfere with cling performance include erucamide above 800 ppm and certain migratory antistats; these should not be used in the cling layer if the unwind-side coefficient of friction is specified below 0.3.

A frozen food packaging film must retain dart impact at sub-zero storage temperatures while maintaining controlled haze and reliable heat-seal strength after frost exposure. The primary compliance framework is food contact: the base resin is assessed under FDA 21 CFR 177.1520(c) and Commission Regulation (EU) No 10/2011, with overall migration below 10 mg/dm² under the intended time-temperature conditions. Mechanical performance is evaluated by ASTM D1709-16a for dart impact, ASTM D882-18 for tensile properties, ASTM F88/F88M-21 for seal strength, and ASTM D1003-21 for haze. In a three-layer coextruded frozen food film, FN812 is typically used in the core layer at 50–70 wt%, with LDPE at 10–25 wt%, a metallocene LLDPE skin layer at 5–15 wt% for sealing, silica antiblock masterbatch at 0.5–1.0 wt%, and erucamide slip additive at 300–700 ppm. The outer layer may contain synthetic silica-based antiblock at 1,000–2,500 ppm to lower film-to-film friction during freezing-tunnel contact. The film is produced on a coextruded blown film line with die gap 1.4–1.8 mm, blow-up ratio 2.2–2.8:1, melt temperature 185–205°C, and frost line height controlled by chilled air ring and internal bubble cooling. The web is printed, slit, and converted into bags with heat seal bars set to 120–150°C and dwell 0.4–0.8 s; seal strength is measured after conditioning at -20°C because frozen storage can reduce seal elongation. Terminal product types include frozen vegetable bags, ice cube bags, prepared frozen meal pouches, and retail frozen seafood bags. A known production-scale failure is seal contamination by erucamide bloom when slip concentration exceeds 800 ppm; this widens the seal initiation window unpredictably during high-speed bagging and should be avoided in films sealed within 48 hours of extrusion.

When Extrusion Lamination Uses FN812 as Sealant Web Against Aluminum Foil

Extrusion lamination of LLDPE onto aluminum foil is controlled by oxidation-induced adhesion at the melt curtain impingement point. The sealant web must combine low gel count, sufficient melt flow to wet the foil surface, and a seal initiation temperature low enough for high-speed vertical form-fill-seal packaging. The relevant adhesion standard is ISO 11339:2010 for T-peel strength of flexible laminates; seal performance is measured by ASTM F88/F88M-21; and food contact is assessed under FDA 21 CFR 177.1520(c) or Commission Regulation (EU) No 10/2011 as applicable to the finished laminate. In the sealant layer, FN812 is generally used at 80–100 wt%, with an optional LDPE component at 0–20 wt% for edge stability and a slip/antiblock masterbatch at 0.3–1.0 wt%. If direct adhesion to aluminum foil is insufficient, an anhydride-modified polyolefin tie resin is added at 5–15 wt% in a coextruded structure, or an adhesion-promoting surface treatment is applied to the foil. The process is extrusion lamination through a slot die with die gap 0.4–0.6 mm, air gap 100–200 mm, melt temperature 280–320°C, and nip roll pressure 40–80 N/cm. The high melt temperature is required to generate polar carbonyl species at the LLDPE-foil interface, but it narrows the thermal degradation window; holding the melt above 320°C for more than 10 min produces gel particles that appear as undispersed specks in the sealant layer. Terminal product types include aluminum foil lidding films, snack packaging laminates, wet wipe sachets, and medical device pouches. The operational boundary is that siliconized film or high-slip masterbatch in the sealant layer can create an adhesion failure mode during T-peel testing if the masterbatch is not predispersed under high shear.

A practical conflict in extrusion lamination is the simultaneous demand for high melt temperature for adhesion and low seal initiation temperature for downstream packaging. FN812 is selected because the butene branch structure lowers seal initiation compared with HDPE sealant webs, but sealant surface energy can shift during storage if slip additives migrate. On a laminator with 1,200 mm web width and 200 m/min line speed, melt curtain tension must be stabilized with an edge pinning system; otherwise edge curl and fold-over defects occur at the nip. Target coating thickness is usually 15–25 µm, with coat weight checked by difference weighing at ±0.5 g/m². Edge trim regrind above 20 wt% in the sealant layer increases gel formation and should be avoided in foil lidding applications where optical clarity of the sealant is specified.

Refuse sack conversion at a bottom-weld bag machine is sensitive to melt fracture, tear propagation, and recycled-content batch-to-batch viscosity shift. The mechanical performance baseline for consumer and institutional refuse sacks uses ASTM D1709-16a for dart impact, ASTM D882-18 for tensile properties, ASTM D1922-15 for Elmendorf tear, and EN 13592 for household refuse sack requirements. Where post-consumer recyclate is included, the key processing risk is a shift in melt mass-flow rate from contaminants such as polypropylene or high-density polyethylene. The PCR fraction is therefore normally restricted to 10–30 wt% and must be melt-filtered to 80–120 mesh. A representative formulation contains FN812 at 70–90 wt%, recycled LDPE/LLDPE at 10–30 wt%, carbon black masterbatch at 2–4 wt%, and optionally calcium carbonate masterbatch at 0–10 wt%. Calcium carbonate above 10 wt% reduces tear resistance and can increase pinhole formation at fold edges. The process is a single-layer or two-layer blown film extrusion line with die gap 1.4–2.0 mm, blow-up ratio 2.0–3.0:1, melt temperature 180–210°C, and internal bubble cooling for gauge uniformity. Bottom-weld conversion is performed in-line or from pre-slit rolls; the bag mouth is folded and welded with a thermal impulse sealer or continuous hot-knife sealer at 140–170°C. Terminal product types include household drawstring refuse sacks, janitorial bags, heavy-duty contractor sacks, and lightly pigmented clinical waste bags. The operational boundary is that recycled-content lots with polyethylene wax contamination can lower melt viscosity and cause bubble sag; such lots require incoming melt index testing by ASTM D1238-20 at 190°C/2.16 kg and may need down-blending with FN812 to restore bubble stability.