Sealant Layer Design for Vertical Form-Fill-Seal Lines Operating Above 60 Cycles/min

SABIC COHERE VLDPE 8170 is specified for the sealant web of coextruded films in high-speed vertical form-fill-seal and horizontal form-fill-seal operations. The resin has a density of 0.912 g/cm³ measured under ISO 1183-1:2019 and a melt flow rate of 1.0 g/10 min at 190°C/2.16 kg under ISO 1133-1:2022. In a three-layer blown film coextrusion configuration, the sealant layer is typically formulated with 70–90 wt% VLDPE 8170, 10–30 wt% C4 or C6 LLDPE for modulus adjustment, 2–4 wt% silica-based antiblock masterbatch, and 0.5–1.5 wt% erucamide slip masterbatch. The use level above 90 wt% VLDPE 8170 in a 12 µm sealant layer can reduce coefficient of friction below 0.35 measured under ASTM D1894-14, but may increase blocking tendency on the film roll; antiblock is therefore held at 2–4 wt% with median particle size 5–8 µm. On a production-scale three-layer line with a 60 mm grooved-feed barrier screw and 30:1 L/D ratio, melt temperature is controlled between 190°C and 210°C, die gap is maintained at 1.8–2.4 mm, and blow-up ratio is set at 2.5:1 to avoid unbalanced MD/TD tear orientation. Frost line height is held between 600 mm and 900 mm to minimize seal-initiation variability. High-speed jaw sealing on VFFS lines uses jaw temperatures of 120–135°C, dwell times of 0.2–0.4 s, and seal bar pressure of 0.4–0.7 MPa. The critical process conflict is between seal initiation and seal strength: higher VLDPE concentration in the sealant layer reduces seal initiation temperature but can lower ultimate seal strength at elevated die gap if the layer is below 8 µm. Seal strength after 24 h ageing is tested under ASTM F88/F88M-21; hot tack is measured under ASTM F1921/F1921M-20 at 0.2 s dwell and 0.5 MPa seal bar pressure. The sealant web complies with FDA 21 CFR 177.1520(c) for olefin polymers and with EU Regulation (EU) No 10/2011 overall migration requirements for food contact, provided the coextruded structure is not subjected to exposure conditions exceeding those in 21 CFR 176.170(c). Terminal film products include stand-up pouches with zipper closures, gusseted dry-food bags, frozen vegetable sacks, and HFFS pillow packs for granular or powdered goods. On high-output lines, bubble instability is the primary production bottleneck; at die gaps below 1.5 mm, melt fracture can appear on the sealant layer at screw speeds above 90 rpm.

What Constrains Gauge Variation in Pre-Stretched Pallet Hood Film?

Pre-stretched pallet hood and stretch hood film production requires low modulus and high puncture resistance, both influenced by VLDPE 8170 concentration. In this cast film application, the formulation is based on 70–85 wt% VLDPE 8170 blended with 15–30 wt% C8 LLDPE to improve tear propagation resistance and limit machine-direction split. A polyisobutylene or low-molecular-weight polyethylene tackifier is added at 0.5–2.0 wt% to set cling force between 2.0 N and 4.0 N per 25 mm, measured under ASTM D5458-95(2020). The cast line is configured with a 120 mm barrier screw extruder having 30:1 L/D, melt temperature 220–240°C, die gap 0.5–0.8 mm, air gap 150–200 mm, and chill roll temperature 15–25°C. Line speed is normally set between 120 m/min and 250 m/min, with pre-stretch ratios between 70% and 90% applied at the wrapper. The limiting process variable is transverse-direction gauge uniformity; at chill roll temperatures above 25°C, the VLDPE-rich layer can become tacky and cause blocking during pre-stretch, while below 12°C the film may develop internal stress bands that appear as alternating thick-thin gauge bands on the pallet. Puncture resistance is tested under ASTM D5748-19, dart impact under ISO 7765-1:1988, tensile elongation under ISO 527-3:2018, and tear propagation under ISO 6383-2:1983. The film must also comply with REACH Regulation (EC) No 1907/2006 Article 33 communication obligations and with EU Directive 94/62/EC packaging and packaging waste requirements where the pallet hood is used as transport packaging. Terminal applications include pallet unitization for beverage crates, insulation boards, gypsum board stacks, and bagged chemicals. Production-scale failure modes include cling-force drift when tackifier masterbatch is added after the feed throat; metering of liquid tackifier through a side injector at the melt zone is specified at 0.5–2.0 wt% to maintain batch-to-batch cling within ±0.5 N/25 mm.

Heavy-duty industrial liners and internal liners for flexible intermediate bulk containers are produced from blown film in the 100–250 µm thickness range, where the compound formulation commonly contains 60–80 wt% SABIC COHERE VLDPE 8170, 20–40 wt% high-stiffness butene LLDPE, 1–3 wt% processing aid masterbatch, and 2–4 wt% carbon black masterbatch when UV exposure is specified. The VLDPE component lowers the low-temperature brittleness threshold and increases puncture propagation resistance compared with a pure LLDPE structure. Production is performed on a high-stalk blown film line with a 350 mm die, 2.0:1 to 2.5:1 blow-up ratio, die gap 2.0–2.8 mm, melt temperature 190–210°C, and internal bubble cooling to stabilize frost line height between 800 mm and 1200 mm. The manufacturing bottleneck is roll blocking at the core, especially above 200 µm film thickness; to reduce blocking, slip masterbatch dosage is maintained at 800–1200 ppm erucamide and the film is wound with decreasing tension from 120 N/mm at the core to 60 N/mm at the outer diameter. Puncture resistance is measured under ASTM D5748-19, tear resistance under ISO 6383-2:1983, and low-temperature impact under ASTM D1790-21. The structure is qualified for industrial packaging using ASTM D4169-22 distribution cycle simulation and ISTA 3B for packaged-product performance. Regulatory compliance is limited to general chemical safety obligations under REACH and CLP Regulation (EC) No 1272/2008; for liners used with dangerous goods, the complete UN packaging certification is determined by the outer FIBC construction rather than the PE film alone. Terminal product forms include drum liners for viscous resins, FIBC inner liners for hygroscopic powders, construction rubble bags, and agricultural silage covers. Published data for the exact low-temperature sealing strength of this specific filled compound configuration is limited; end users perform drop-test validation at -20°C when the liner is to be used in cold-chain transport.

Compounding PCR-Rich Blown Film with Metallocene VLDPE 8170

Post-consumer recycled LDPE and LLDPE film feedstocks exhibit batch-to-batch melt flow index drift and gel-particle variability, which degrade blown film bubble stability and dart impact in refuse bags and construction film. Compounding with 15–25 wt% SABIC COHERE VLDPE 8170 is specified to restore extensional flow and low-temperature dart impact in non-food PCR-rich film. The formulation consists of 70–80 wt% washed PCR film granulate, 15–25 wt% VLDPE 8170, 2–5 wt% carbon black masterbatch, and 0.5–1.0 wt% stabilizer masterbatch. Typical PCR feed has an apparent melt flow rate of 0.7–1.5 g/10 min at 190°C/2.16 kg under ISO 1133-1:2022; the target compound MFR is held between 0.8 g/10 min and 1.2 g/10 min by adjusting the VLDPE fraction. The compounding step uses a co-rotating twin-screw extruder with 40:1 L/D and 75 mm screw diameter, with PCR introduced at the main feed throat and VLDPE pellets introduced through a side feeder at barrel section 6 to minimize thermal history. Melt temperature is controlled at 180–200°C, screw speed between 300 rpm and 400 rpm, and vacuum degassing at -0.08 MPa absolute to reduce volatiles. The primary processing conflict is gel-particle accumulation on the screen changer; a continuous melt filter with 200 µm mesh and backflush interval of 120–180 s is used to maintain die pressure below 18 MPa. The compound is then extruded on a blown film line with a 2.5:1 blow-up ratio and melt temperature 190–205°C into film thicknesses of 30–80 µm. Film property validation includes dart impact under ISO 7765-1:1988, tear resistance under ISO 6383-2:1983, and tensile properties under ISO 527-3:2018. The compound is intended for non-food packaging and waste bags; compliance is limited to REACH SVHC communication and EU Directive 94/62/EC packaging requirements. For recycled content claims, mass balance is verified under ISO 22095:2020. Flame-retardant or crosslinked PCR grades should not be used without additional stabilizer screening because residues may cause gel agglomerates at processing temperatures above 200°C. Terminal products include refuse sacks, construction film, industrial liner bags, and carrier bags with recycled content. Published data for this specific configuration is limited; the 15–25 wt% addition range is an industrial starting point based on MFR normalization in PCR streams with melt flow values below 1.5 g/10 min.

Extrusion coating and lamination of lightweight packaging papers, aluminium foil, and biaxially oriented polypropylene requires a polymer layer that balances low seal initiation, adhesion to the substrate, and neck-in control at high line speed. In this application, SABIC COHERE VLDPE 8170 is used in the sealant coating layer at 50–70 wt%, blended with 30–50 wt% LDPE to increase melt strength and reduce edge neck-in. The coating is processed on a tandem extrusion line with a 90 mm screw extruder, 28:1 L/D, die gap 0.5 mm, air gap 200–250 mm, and melt temperature 240–260°C at the die. Line speed ranges from 150 m/min to 300 m/min, with the chill roll at 15–20°C and corona treatment set to 42–46 dyn/cm for lamination strength. The main processing defect is draw resonance at low melt strength; the LDPE content above 30 wt% is specified to suppress edge weave and maintain coating thickness tolerance within ±2 µm. Substrate adhesion is tested under ASTM D1876-08 for peel strength, seal strength under ASTM F88/F88M-21, and coating weight is controlled by beta gauge to 10–20 g/m². Compliance for food-contact applications is established under FDA 21 CFR 177.1520(c) for the olefin polymer and EU Regulation (EU) No 10/2011 for overall migration. For paper-based laminates, the applicable regulatory framework also includes FDA 21 CFR 176.170(c) for paper and paperboard in contact with aqueous and fatty foods. Terminal products include sachet laminates for dry beverage powders, lidding films for dairy cups, and aluminium foil-based pharmaceutical strip packs where the sealant layer is the heat-seal medium. Films coated with VLDPE 8170 are not suited to retort or steam sterilization above 121°C; for those conditions a higher-density sealant grade is specified.

When Low Modulus Governs Clean Peel in Polycarbonate and PMMA Protection Films

Surface protection films for polycarbonate sheets, PMMA panels, aluminium composite panels, and polished stainless steel require a low-modulus cast film that conforms to surface roughness without leaving adhesive residue after removal. The film is produced from a blend of 80–95 wt% SABIC COHERE VLDPE 8170 and 5–20 wt% ethylene vinyl acetate or styrenic block copolymer to adjust peel adhesion to the substrate. Peel adhesion is typically set between 0.05 N/25 mm and 0.40 N/25 mm depending on surface polarity, measured under ASTM D3330/D3330M-04 method A after conditioning at 23°C and 50% RH for 24 h. The cast film line uses a 75 mm extruder with 30:1 L/D, melt temperature 180–230°C, die gap 0.5–0.8 mm, air gap 120–180 mm, and a matte chill roll at 12–18°C. The matte roll is laser-engraved with Ra 0.8–1.6 µm roughness to control unwind noise and blocking. The film is corona-treated on the reverse side to 38–42 dyn/cm for subsequent adhesive coating. The production bottleneck is chill roll release: at chill roll temperatures below 10°C, the VLDPE-rich film sticks to the matte roll and develops surface pinholes during stripping; at temperatures above 22°C, the matte texture transfers poorly and blocking increases on the roll. Tensile modulus is measured under ISO 527-3:2018, tear strength under ISO 6383-2:1983, and optical haze under ASTM D1003-13. Regulatory compliance in electronics and automotive glazing supply chains includes REACH SVHC screening, RoHS Directive 2011/65/EU for substances in electrical and electronic equipment, and DIN 53363 for tear propagation in film. Terminal products include protection film for polycarbonate machine guards, PMMA advertising panels, aluminium composite façade sheets, and pre-coated metal for elevator interiors. Published data for the adhesion modulation of VLDPE 8170 with EVA in this specific configuration is limited; peel force is therefore validated on the actual substrate with 48 h ageing at 60°C before full production runs.