Why Does FM31D Maintain Dart Impact Resistance in Heavy-Duty Sack Blown Film?

In heavy-duty sack and liner extrusion, Braskem FM31D—a linear low-density polyethylene copolymer with nominal density 0.918 g/cm³ per ASTM D792-20 and melt flow rate 1.0 g/10 min per ASTM D1238-20—is blended with high-pressure low-density polyethylene at addition levels of 70–85 wt% FM31D and 15–30 wt% LDPE. A slip/antiblock masterbatch is added at 1–4 wt%, and a polymer processing aid concentrate is introduced at 0.5–1.5 wt% to suppress melt fracture on air-cooled blown film lines. The downstream process is a single-screw extruder with a barrier screw design, L/D ratio 30:1–36:1, die diameter 200–400 mm, die gap 1.8–2.5 mm, blow-up ratio 2.0:1–3.0:1, melt temperature 190–230°C, and frost line height held within 4–6 die diameters. On production lines converted from high-pressure LDPE, bubble sway and edge flutter are observed when the frost line is pushed above 6 die diameters or when the melt temperature exceeds 230°C at the die head; the instability is attributable to limited melt strength of linear polyethylene and requires lower specific output than comparable LDPE campaigns. Resin temperature above 240°C is not recommended because oxidative gel formation increases and may produce film defects at the die lips. Compliance for non-food heavy-duty sacks and FIBC liners is assessed against ASTM D1709-16a for dart drop, ASTM D1922-15 for Elmendorf tear, ASTM D882-18 for tensile properties, ISO 21898:2004 for FIBC non-dangerous goods packaging, and the registration and downstream communication obligations of EU REACH. Terminal product types include FIBC internal liners, heavy-duty shipping sacks for polymer resin, granular fertilizer, petrochemical additive bags, and construction material sacks.

Frozen vegetable, seafood, and ice cream packaging operations introduce FM31D as the primary blown film resin at 60–80 wt%, with high-pressure low-density polyethylene at 10–25 wt%, a metallocene plastomer at 5–15 wt% to depress low-temperature brittle point, and a slip/antiblock concentrate at 1–3 wt%. The extruded web is a three-layer coextruded blown film structure, with die gap 1.5–2.0 mm, blow-up ratio 1.8:1–2.5:1, melt temperature 175–210°C, and corona-treating set to a target wetting tension of 38–42 dyn/cm prior to lamination or surface print. The die gap is narrower than in sack film to maintain gauge uniformity in low-thickness webs of 40–80 μm, and the low-temperature impact response is monitored by ASTM D1790 or ASTM D1709 with specimens conditioned at −18°C to −25°C. Compliance for frozen food contact uses FDA 21 CFR 177.1520 for olefin polymers, EU Regulation (EU) No 10/2011 Annex I with overall migration testing per EN 1186-1, and food contact GMP under 2023/2006/EC. Published data for this specific FM31D frozen food configuration is limited; therefore, migration testing is executed on the finished laminate rather than extrapolated from resin TDS values. Terminal product types include frozen vegetable pouches, frozen seafood bags, ice cream overwrap, and barrier laminate sealant webs used in vertical form-fill-seal lines.

When UV Stabilizers Are Melt-Compounded into FM31D for Multi-Season Greenhouse Cover

The selection of a three-layer coextruded cover structure begins with additive partitioning and surface bloom behavior, not short-term tensile strength. In this application, FM31D is melt-compounded at 72–88 wt% with a UV-stabilizer masterbatch at 8–18 wt%, an anti-fog/anti-dust concentrate at 1–3 wt%, and an IR-blocking thermal additive system at 2–5 wt% where night-time heat retention is specified. The downstream production process is three-layer coextruded blown film with die gap 1.8–2.4 mm, blow-up ratio 2.5:1–4.0:1, melt temperature 190–230°C, and separation of the UV-stabilizer-rich outer layer from the anti-fog-rich inner layer to prevent interlayer additive migration and surface bloom defects. Industrial line observation indicates that UV masterbatch let-down below 8 wt% at the specified carrier concentration produces uneven surface distribution in the outer layer, with localized haze bands and premature film cracking after 12–18 months of continuous exposure; this is a processing limitation rather than a resin limitation. Compliance is evaluated under EN 13206 for agricultural covering films, ISO 4892-2 accelerated weathering, ASTM D1003 for haze, ASTM D624 for tear resistance, and ISO 527-3 for tensile properties of films. Terminal product types include multi-season greenhouse covers, low-tunnel covers, silage bunker covers, and nursery overwintering films.

E-Commerce Mailer Film Converts Best When FM31D Is Used as a Post-Consumer Recyclate Dilution Resin

E-commerce mailer and carrier bag film produced with post-consumer recyclate relies on virgin LLDPE dilution to restore impact and tear strength after the recycled melt fraction introduces gel particles, residual unsaturation, and variable melt flow. In this configuration, FM31D is added at 50–75 wt%, post-consumer recycled LDPE/LLDPE at 20–40 wt%, a processing aid masterbatch at 1–3 wt%, and an antioxidant concentrate at 0.5–1.5 wt%. The extruder requires a grooved-feed or barrier screw with length-to-diameter 30:1–36:1, a screen changer fitted with 80–120 μm mesh packs, a vacuum vent configured to reduce residual moisture below 0.1 wt%, and die gap 1.8–2.8 mm because the recycled melt fraction lowers bubble stability. Blow-up ratio is held at 2.0:1–3.0:1, melt temperature at 185–225°C, and line speed is adjusted to prevent draw resonance at the lower melt strength of recyclate-containing blends. Compliance for the finished mailer includes EU Packaging and Packaging Waste Directive 94/62/EC with aggregate heavy metals not exceeding 100 mg/kg for lead, cadmium, mercury, and hexavalent chromium, EU REACH registration and SVHC disclosure, and ISO 14021 for recycled content claims if verified through controlled blending batch records. Terminal product types include e-commerce shipping mailers, parcel bags, industrial donation sacks, and retail carry-out bags with post-consumer recycled content targets.

Operationally, pallet unitization with stretch hood film requires a tubular film that survives downward stretching over palletized freight without puncturing at sharp corners, and FM31D is used in this application as the dominant layer resin at 65–80 wt%, with high-pressure LDPE at 20–35 wt% and a processing aid concentrate at 0.5–1.5 wt%; no cling additive is incorporated because the holding force is generated by elastic recovery rather than tack adhesion. The film is produced on three-layer coextruded blown film lines with die gap 1.6–2.4 mm, blow-up ratio 2.5:1–4.0:1, melt temperature 190–225°C, and film thickness 60–150 μm, followed by gusseting, layflat winding, and perforation on the converting line. Excessive blow-up ratio above 4.0:1 or melt temperature above 225°C leads to bubble instability and inconsistent TD stretch distribution during hood application, a production-scale failure mode reported on hood lines running at high output. Compliance is verified by ASTM D882 for tensile elongation at break, ASTM D1922 for Elmendorf tear, ASTM D1709 for dart impact, and REACH communication obligations; the product is not intended for direct food contact unless the structure includes a separately compliant food-contact layer. Terminal product types include stretch hood film for palletized freight, building material transit wraps, white goods protective covers, and industrial furniture stretch covers.

Direct Food-Contact Overwrap Haze, Blocking, and Coefficient of Friction

For thin-gauge produce, bakery, and garment bag films produced from FM31D, the formulation space is deliberately narrow because the resin is operated at 85–100 wt%, with slip/antiblock concentrate at 0.5–2.5 wt% and processing aid at 0.3–1.0 wt%, and all additive concentrates must be selected from food-contact-compliant masterbatch systems under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011. The process uses a monolayer or two-layer blown film line with die gap 1.2–2.0 mm, blow-up ratio 1.5:1–2.5:1, melt temperature 170–200°C, and a reduced frost line height to control haze via rapid quenching. Unlike heavy-duty sack or hood film, the operating window is narrower at the lower end because the thin web is sensitive to melt fracture and gauge bands when the die gap is below 1.2 mm or when the processing aid let-down is below 0.3 wt%. Compliance testing for the finished film uses ASTM D1003 for luminous transmittance and haze, ASTM D1894 for coefficient of friction, ASTM D2457 for gloss, and ASTM D882 for tensile properties, with food-contact migration testing per EN 1186-1 where applicable. Terminal product types include fresh produce bags, bakery overwrap, dry goods bags, and garment bags used in retail and distribution. Published data for this specific FM31D direct-food overwrap configuration is limited, so the resin supplier's food-contact statement should be confirmed for each converter-specific formulation.