On high-throughput tubular film lines producing heavy-duty shipping sacks and industrial liners, Braskem FC31D is processed as the primary sealable core resin or as a 15–25 wt% let-down component in blends with high-pressure LDPE. The base resin has a density of 0.918 g/cm³ by ASTM D1505 and a melt flow rate of 1.0 g/10 min at 190 °C/2.16 kg by ASTM D1238. Annular dies for this segment use a die gap of 1.8–2.4 mm. The blow-up ratio is held between 2.0:1 and 2.8:1. Adapter melt temperature is limited to 190–220 °C.

The controlling process conflict in heavy-duty sack production is frost-line height selection. A frost-line height of 6–8 die diameters increases quench rate and improves bubble stability on grooved-feed extruders with 24:1–30:1 L/D. It also preserves transverse-direction orientation but can reduce machine-direction tear resistance. A frost-line height of 10–12 die diameters lowers orientation and improves machine-direction tear but increases bubble flutter on wide-gusseted films above 600 mm flat width. Dual-lip air rings with internal bubble cooling are specified when lay-flat width exceeds 800 mm. Dart impact is measured by ASTM D1709 Method A. Elmendorf tear is measured by ASTM D1922. Film thickness ranges from 80 µm to 180 µm. Gusseted tubes are converted on bottom-seal or side-gusset bag machines. Finished articles include FIBC liners, fertilizer sacks, resin pellet sacks, and construction aggregate bags. Published data for this specific configuration is limited; converters generally validate dart impact and tear on a 350 mm pilot die before full-width production.

What Melt Processing Limits Govern Silage and Greenhouse Film Production with FC31D?

In silage and greenhouse cover film, the lower melt temperature is set by melt pressure at the die lip. FC31D is extruded at adapter temperatures of 195–210 °C. Bubble stability is maintained at a blow-up ratio of 2.2:1–2.6:1. The frost-line height is positioned at 8–10 die diameters to balance optics and retained tear strength. Die gap is 1.8–2.2 mm. Silage films are generally three-layer structures. The outer layers contain carbon black masterbatch or titanium dioxide concentrates. The centre layer receives hindered amine light stabilisers at 0.2–0.6 wt% and slip/antiblock concentrates at 0.1–0.3 wt%. A LLDPE-carrier masterbatch rather than an LDPE carrier reduces viscosity mismatch in the screw mixing zone. The terminal products include bale wrap at 150–200 µm, silage trench covers at 100–150 µm, and greenhouse side or roof films at 150–200 µm. Weathering performance is evaluated by ASTM G155 or EN 13206 depending on the end-use specification. Acidic silage leachate resistance is not governed by the base polyolefin but by the stabiliser package; converter validation is required for ammonia-rich environments. Published data for this specific configuration is limited.

Placed in the sealant layer of three-layer or five-layer coextruded barrier films, FC31D provides the low seal-initiation temperature required on vertical form-fill-seal machines. Seal initiation is observed in the range of 95–110 °C for LLDPE blown film grades of this density and melt-index class. Hot-tack strength is measured by ASTM F1921. Seal strength after cooling is measured by ASTM F88. Frozen-food formats use 40–90 µm gauge. Dry-goods pouches commonly use 50–70 µm. Melt temperature in coextrusion is set between 205 °C and 225 °C. Die gap is 1.5–2.0 mm. Blow-up ratio is 2.0:1–2.5:1.

Food-contact compliance is determined by the full formulation, not by the base resin alone. The olefin polymer is evaluated under 21 CFR 177.1520(c). European converters validate overall and specific migration against EU 10/2011 as amended. Migration testing is conducted by EN 1186-1 and EN 13130-1. Low-temperature toughness for frozen-food packs is assessed by dart impact on ASTM D1709 with films conditioned at -18 °C for 24 h. The conditioning is outside the standard ambient procedure but is common converter practice. Published data for this specific configuration is limited; end-use validation is required because coextrusion quench rates alter sealant-layer crystallinity and additive distribution.

Pallet Containment Film Blends and Cling Layer Structuring

On a three-layer blown film line dedicated to stretch hood film, FC31D is used in the core and machine-direction load-bearing layers. Film gauge is between 80 µm and 120 µm. A blow-up ratio of 2.0:1–2.4:1 is set to preserve machine-direction elongation. Die gap is held at 2.0–2.4 mm to avoid melt fracture at high output. Melt temperature is maintained between 190 °C and 220 °C. Stretch hood film requires a balance of stiffness, tear resistance, and puncture resistance. The slip additive system controls cling and release. Erucamide slip at 500–1500 ppm is used for pallet containment films. Coefficient of friction is measured by ISO 8295 or ASTM D1894. Puncture resistance is measured by ASTM D5748. The terminal products are pallet hoods, agricultural wrap, and top sheets. Slip levels above 1500 ppm can produce surface bloom that reduces sealability in folded hood corners. Die-lip deposit formation occurs when low melt temperature is combined with high slip additive concentration. A fluoropolymer processing aid at 400–1000 ppm is used to delay deposit formation. Published industrial data for this specific grade in pallet containment is limited; converters validate on 400 mm dies with three-layer heads.

When FC31D Is Specified as the Sealable Core Layer in Laminated Bulk Packaging

Operators specifying FC31D in laminated PP woven bulk bags generally use a blown film of 20–40 µm bonded to the woven substrate. The film is corona-treated inline to 38–42 mN/m. Wetting tension is measured with ISO 8296. Bond strength after lamination is evaluated by ASTM D1876 or by the converting line peel test. The sealant layer forms the inner surface of the bag. Sealing is performed on heat impulse or hot-bar closing systems at 140–180 °C. The low melt viscosity of FC31D relative to LDPE reduces channeling in the seal area but increases the risk of web stretching on adhesive laminators. Tension control is set below 0.2 N/mm per film width for 30 µm gauge. The finished articles include dry bulk FIBC liners, mineral export bags, and chemical cargo sacks. Data for chemical permeation with specific cargoes is limited; converters test with the relevant cargo or simulant according to the transport specification.

Die Lip Deposits Are Managed by PPA and Reverse Barrel Profiles

Masking films for stainless steel sheet, PVC profiles, and automotive transit require low gel counts and low visual defect levels. FC31D is run with a fluoropolymer processing aid at 400–1200 ppm to delay die lip deposit formation. The die gap is narrowed to 1.2–1.8 mm for film gauges of 30–60 µm. Blow-up ratio is set at 2.0:1–2.5:1. Melt temperature is held between 190 °C and 215 °C. The low upper limit is selected to reduce gel formation. The penalty is reduced die lip purge interval. A lower melt temperature increases shear stress at the die lip and accelerates deposit formation with some slip and antiblock packages. Barrel temperature profiles are set with a reverse profile: 180 °C in the feed section and 205 °C at the metering section. The raw film is corona-treated to 40–44 mN/m for adhesive coating. Peel adhesion of the finished protective film is measured by ASTM D3330 or FINAT FTM 1. The base resin does not contribute tack; adhesion derives from the coextruded or coated adhesive layer. Incompatibility with solvent-borne adhesives should be tested because low-molecular-weight fractions may migrate and alter peel adhesion over time. Published data for this specific configuration is limited; converters usually approve batches by gel count on a 250 mm blown film pilot line and by 1000 kg extrusion scale-up.