At cast film line speeds above 300 m/min on a three-layer A/B/A line equipped with a 250 mm slot die, the core layer carries the tensile load while the skin layers control cling and release. FLEXOMER VLDPE 1137 is metered from a separate gravimetric hopper into the core layer at 10–20 wt%, blended with a linear low-density polyethylene having a melt index of 2.0 g/10 min. The nominal density of the grade, 0.902 g/cm³ per ISO 1183-1, depresses the overall film density and permits down-gauging from 20 μm to 15 μm only after puncture testing according to ASTM D5748. The melt index of 0.8 g/10 min at 190 °C/2.16 kg per ISO 1133-1:2022 is lower than that of the skin-layer LLDPE; screw speed differentials are therefore set to maintain a viscosity-matched interface. Extruder barrel zones are kept at 185–210 °C, the die at 230–245 °C, and the chill roll at 18–22 °C. The air gap between die exit and chill roll is held at 100–150 mm to stabilize the melt curtain without overdamping edge bead. Cling force is adjusted with polyisobutylene or sorbitan monostearate additive systems; migration of these to the film surface is temperature-dependent and is measured by ASTM D5458 peel cling. The terminal product is a 15–23 μm machine pallet wrap requiring pre-stretch levels of 180–250% on turntable wrappers. A processing constraint arises when the VLDPE fraction exceeds 25 wt% in the core: melt curtain resonance appears as periodic thickness bands and is corrected by reducing line speed or increasing melt temperature 5–8 °C. Indirect food contact follows European Regulation (EC) No 1935/2004; direct food packaging requires FDA 21 CFR 177.1520(c) olefin polymer provisions. Additives must be screened for REACH and RoHS Directive 2011/65/EU where applicable. Granules should remain free of surface condensation at ambient relative humidity below 60%; pre-drying is not required for moisture removal but prevents hopper bridging.

What Governs Puncture and Sealing in Coextruded High-Barrier Films?

Unless the frost line is kept below 9 die diameters on a seven-layer blown film line, a coextruded bubble containing FLEXOMER VLDPE 1137 in the sealant layer becomes increasingly sensitive to gauge-banded instability. The grade is compounded as a skin or sub-skin sealant at 15–30 wt% of the food-contact layer, with the balance comprised of metallocene LLDPE and an antifog masterbatch at 2–4 wt%. A die gap of 1.4–1.8 mm, blow-up ratio of 2.2–2.8, and melt temperature of 210–225 °C produce a quenched crystalline morphology that retains low-temperature ductility. Melt pressure upstream of the die is maintained below 320 bar to limit shear-induced degradation of octene short-chain branches. Puncture resistance is tested according to ASTM D5748; tear propagation is evaluated by Elmendorf method ASTM D1922 or ISO 6383-2. For frozen-food packaging, toughness at −30 °C is confirmed by low-temperature dart impact per ASTM D1709 method A. Heat seal strength is normally specified above 8 N/15 mm after sealing at 115–125 °C for 0.5 s at 2 bar jaw pressure, but converter-specific seal curves govern because molecular-weight distribution and antiblock additives shift the seal plateau; published data for this exact film structure is limited. Compliance with EU Regulation (EU) No 10/2011 requires overall migration below 10 mg/dm² and specific migration limits for additives used in the sealant layer. FDA 21 CFR 177.1520(c) supports direct food contact for this polyolefin class. The terminal structure is a 40–90 μm barrier film containing EVOH or polyamide, printed and converted into stand-up pouches, vacuum bags, or frozen food overwrap. Process limitations include a narrow stable window when EVOH is the core barrier: resin temperature at the interfacial ties must remain between 205 °C and 230 °C to avoid EVOH gel formation against the tie layer. If excess antiblock or slip is present in the VLDPE layer, seal initiation shifts upward by 3–5 °C; this effect is quantifiable on a production heat sealer such as a Sentinel or J.A. King unit.

Sealant Web Formulation on High-Speed Laminating Lines

On tandem lamination lines with a 300 mm slot die and motor-driven chill stack, FLEXOMER VLDPE 1137 is blended with LDPE of melt index 4.0 g/10 min at 20–40 wt% to produce a low-sealing-temperature web. Coating weight is maintained at 12–20 g/m² on substrates such as biaxially oriented polypropylene film, metallized PET, or kraft paper. The melt temperature at the die is held between 280 °C and 320 °C; above 320 °C, low molar-mass fractions generate visible fuming and deposit wax-like degradation products on the cold roll. Neck-in is measured at each edge and should remain below 25 mm per side at 250 m/min; edge bead trim is recycled into the coating feed if permitted by the laminator’s rollstock procedure. Adhesion to non-porous substrates is promoted by an in-line corona treater operating at 2–4 kW and by ozone dosing at 1–2 g/h; for aluminum foil, a solventless polyurethane primer may be applied before the polymer web. Seal strength is tested by ASTM F88 and seal initiation by ASTM F2029. The VLDPE-containing sealant reduces seal initiation by approximately 8–12 °C compared with an LDPE-only sealant of density 0.918 g/cm³; the exact shift depends on coating weight and substrate heat sink effects. The terminal product is a flexible lamination for pre-made pouch stock, confectionery wraps, or retort lidding. A key limitation is that VLDPE 1137 is not used as the sole food-contact layer in retort applications above 121 °C unless the complete laminate is validated under the intended retort schedule. Polyisobutylene-based cling additives from adjacent cast film campaigns must not contaminate the coating feedstock because they lower seal plateau and create pinholing at low coating weights.

Heavy-duty tubular film used for FIBC liners and shipping sacks imposes simultaneous demands on dart impact, tear propagation, and pinhole resistance after filled-drop cycles. FLEXOMER VLDPE 1137 is incorporated into the middle layer of a three-layer blown structure at 20–30 wt% blended with high-strength LLDPE and a minor LDPE component. The selected bubble geometry uses a die diameter of 350 mm, blow-up ratio of 2.0–2.5, and frost line height of 700–900 mm. Melt temperature is controlled at 195–215 °C to preserve octene branch integrity and minimize gel formation in sustained production runs. Slow crack growth resistance is assessed on compression-molded sheet according to ASTM F1473; film tear is measured by ISO 6383-2. Filled-drop performance is validated under ISO 21898 for FIBCs, where the liner must withstand cyclic drop testing without pinhole formation. Typical liner thickness is 80–120 μm, depending on fill weight and hazard class. The outer woven polypropylene bag provides mechanical restraint, while the liner supplies barrier and contamination control. Compliance for dangerous goods packaging may require UN certification under ADR/RID/IMDG and the applicable test program in Chapter 6.5 of the UN Recommendations on the Transport of Dangerous Goods, depending on the product filled. A processing constraint emerges in sustained campaigns: back pressure from a grooved feed section can exceed 350 bar if screw speed is pushed above 90 rpm on a 60 mm extruder, causing melt-temperature overshoot. This is corrected by reducing screw speed or using a barrier screw with an L/D of 30:1. The terminal product includes FIBC liners for hygroscopic chemicals, carbon black masterbatch bags, and heavy-duty layflat tube packaging.

When VLDPE 1137 Enters a Recycled PP Impact-Modification Stream

FLEXOMER VLDPE 1137 can be metered at 5–15 wt% into a recycled polypropylene homopolymer crumb stream to improve low-temperature impact performance for injection-molded crates and pallets. The compounding operation is run on a corotating twin-screw extruder with 40:1 L/D and 75 mm screw diameter. The VLDPE pellets are fed downstream of the PP melt zone via side feeder to minimize thermal exposure and to preserve elastomeric phase particle size. Barrel temperatures from the feed section to the die are set from 180 °C to 230 °C; the melt temperature at the die should not exceed 240 °C. Screw speed in the dispersion zone is maintained between 400 rpm and 600 rpm to generate elongational and shear stress sufficient to distribute the octene-rich domains without destroying them. Impact resistance is measured by notched Izod at −20 °C and 23 °C according to ASTM D256; flexural modulus is measured by ASTM D790. Inclusion of 10 wt% VLDPE reduces flexural modulus relative to neat recycled PP, and this trade-off must be evaluated against the required stacking strength of the molded crate. Xylene-soluble content according to ISO 16152 is used to monitor the dispersed elastomeric fraction. Compliance for industrial packaging does not require food-contact clearance; however, REACH Annex XVII and RoHS Directive 2011/65/EU apply to electrical and electronic applications if the crates are used in controlled environments. The terminal product is a low-temperature-resistant reusable pallet collar or logistics crate. A known failure mode is phase inversion when VLDPE exceeds 20 wt%; gloss and surface hardness decline, and gate blush appears on injection-molded parts. The melt-flow mismatch between recycled PP and VLDPE also means that mold fill pressure must be lowered by reducing injection velocity from 80 mm/s to 50 mm/s to avoid jetting.

Collation shrink bundling for multi-pack bottles is run on single-layer and three-layer blown lines where push-through damage from bottle caps is the primary failure mode. FLEXOMER VLDPE 1137 is blended at 10–20 wt% with LLDPE in the core layer to increase puncture resistance while retaining shrink tension. Blow-up ratio is set at 2.5–3.2, frost line at 5–8 die diameters, and die gap at 1.0–1.4 mm. Shrinkage is produced by orientation during bubble drawing; transverse-direction free shrink is measured by ASTM D2732 after immersion in 120 °C oil. The film is slit into bands and sealed on continuous-motion shrink tunnels operating at 160–180 °C. The terminal product is a 35–60 μm collation film for beverage can bundles. A process limitation is that VLDPE in the skin layers increases blocking on the film roll; therefore the grade is placed only in the core or sub-skin layers. Published data for this specific collation-shrink configuration is limited, so each line must validate tunnel temperature profile against final package bundle tightness.