In a five-layer coextruded blown film line configured with a 250 mm spiral mandrel die and 2.0–2.4 mm die gap, Braskem FLEXUS VLDPE 9200 is fed to the sealant skin extruder at 15–35 wt% of the skin layer, usually alongside a linear ethylene/α-olefin carrier resin. The low nominal density of approximately 0.905 g/cm³ under ASTM D792-20 and the melt index of approximately 1.0 g/10 min under ASTM D1238-20 (190°C/2.16 kg) allow the sealant layer to be extruded at melt temperatures between 190°C and 215°C. Operating the sealant extruder barrel above 230°C produces measurable chain scission, which degrades hot-tack strength and can raise gel counts in the film. Blow-up ratios from 2.2:1 to 3.0:1 and frost line heights in the 600–800 mm range are used to balance optical haze against bubble stability; higher frost line heights on this grade tend to increase haze in 25 µm monolayer films. The sealant layer is usually specified at 15–25 µm within a total film thickness of 70–110 µm, either as the inner layer of a triplex laminate or as the sealant component of a five-layer barrier structure containing an EVOH core and nylon or polyolefin outer webs. The heat-seal behaviour measured under ASTM F88/F88M-21 is characterized by seal initiation in the 90–100°C range at 0.5 N/mm² jaw pressure and 0.5 s dwell, a property that supports packaging machinery running above 50 cycles/min on frozen vegetable and snack packages. Under ASTM F1921-18, the hot-tack window remains useful for caulking seal-bar contamination in longitudinal fin-seal areas, although the upper limit narrows when the sealant skin contains more than 20% post-industrial regrind. Compliance for food-contact use rests on FDA 21 CFR 177.1520 for olefin polymers and EU 10/2011 with an overall migration limit of 10 mg/dm²; the converter must still conduct end-test verification on the finished laminate because coating weights and barrier layers affect the migration extraction profile. Terminal structures include printed BOPP/adhesive/barrier/PE laminates for frozen meat, seafood and snack pouches, where the VLDPE layer supplies low-temperature toughness and reliable seal integrity through fold edges.

What Limits Pre-Stretch Ratio in Machine Film Containing VLDPE 9200?

In cast stretch film production, pre-stretch ratios above 250% are governed less by the base resin’s ultimate elongation than by the film’s resistance to tear propagation and thickness variations in the pre-stretched web. A typical machine film formulation dry-blends 30–50 wt% FLEXUS VLDPE 9200 with a 1.0–2.0 g/10 min metallocene C8 LLDPE and a cling masterbatch at 1–3 wt% polyisobutylene. Extruder runs on a 120 mm single-screw with 30:1 L/D and a barrier screw are set from 180°C in the feed throat to 250°C at the die, while the cast roll is maintained between 18°C and 25°C. At line speeds of 600–900 m/min, draw resonance becomes visible when the melt strength is insufficient; the VLDPE’s low density reduces melt tension compared with high-pressure LDPE, but the blending approach with an LLDPE carrier controls edge weave and neck-in. Dart impact resistance evaluated under ASTM D1709-16a and Elmendorf tear resistance under ASTM D1922-15 improve as VLDPE content increases, but addition above 50 wt% can reduce the cling layer’s cohesive strength and cause blocking if the finished reel is wound above 0.55 N/mm web tension. The terminal pallet-wrap film is routinely pre-stretched on powered turntable wrappers at 200–300%; the film can accommodate this because elongation at break under ASTM D882-18 remains above 700% in machine direction for typical formulations. The processing window, however, narrows at chill-roll temperatures above 28°C, at which point migration of the cling additive is too rapid and reel-blocking defects appear within 24 h of winding.

Extrusion coating and lamination with FLEXUS VLDPE 9200 requires a different thermal profile from blown film because oxidative bonding to the substrate is part of the process mechanism. Melt temperatures at the die are held between 280°C and 320°C, and the air gap between the die and the laminator nip is commonly set at 100–200 mm to allow controlled oxidation of the molten web. When coating paperboard, aluminum foil or polypropylene substrates, the coating weight is rarely below 12 g/m² for a pure VLDPE layer; below that level, draw resonance and pinhole formation become difficult because the melt curtain has low extension stiffness. Practical coating weights for heat-seal layers in lidding and sachet structures range from 15 g/m² to 30 g/m², and a coextruded layer of high-pressure LDPE or an anhydride-modified tie polymer is used when adhesion to aluminium foil must exceed 3 N/15 mm in peel testing under ASTM F88/F88M-21. The lower Vicat softening point of VLDPE 9200, typically in the 88–95°C range under ASTM D1525-17e1, enables heat-seal responses at temperatures 10–20°C lower than conventional LDPE coatings, which is an advantage for heat-sensitive contents in pharmaceutical or aseptic packs. The converter must predry paperboard substrates above 6–8% moisture content only to the board manufacturer’s specification; excess moisture flashes off at the nip and produces pinholes. In foil-based structures, a minimum coating weight of 18 g/m² is usually specified to maintain hermetic seal integrity after flexural cracking. Compliance is governed by EU 10/2011 for food contact, FDA 21 CFR 177.1520 for olefin polymer coatings, and ISO 11607-1:2019 when the laminate is converted into pouches for terminally sterilized medical devices.

The terminal formats cover lidding stock for dairy cups, aseptic sachets, pharmaceutical strip packs and paperboard trays where the VLDPE layer is the heat-seal interface. Extrusion lamination is preferred over adhesive lamination for these structures because the molten VLDPE layer performs both substrate bonding and heat-seal functions in a single pass, eliminating a secondary coating operation. The limiting constraint is the narrow oxidation window: insufficient melt oxidation produces poor foil adhesion, while excessive oxidation at the die lip creates carbon specks and pinholes that compromise seal integrity.

When Seal Bars Are Run Below 0.4 MPa on Horizontal FFS Lines

Horizontal form-fill-seal lines running liquid concentrate sachets of 50–500 mL demand a sealant layer that can flow around product residue at low jaw pressure. In this application, FLEXUS VLDPE 9200 is converted into a 60–90 µm monolayer or two-layer film at melt temperatures of 190–215°C. Jaw temperatures on the FFS machine are set between 105°C and 120°C, while dwell time is maintained at 0.2–0.6 s. At jaw pressures below 0.4 MPa, seal strength measured under ASTM F88/F88M-21 can fall below 2.5 N/15 mm, particularly when the sachet fill contains surfactants or low-viscosity hydrocarbons that leave a contaminating film on the seal area. The low seal-initiation temperature of the VLDPE layer reduces the heat load on the filled package, which is important for thermally sensitive liquid formulations such as enzyme detergents, agricultural adjuvants and automotive additives. The grade is not suitable for retort or hot-fill processes above 90°C because the seal layer softens close to its Vicat point, and the resulting creep can produce seal failure during prolonged holding. The terminal products are pre-measured industrial liquid sachets and household detergent pouches, where seal integrity under drop and leak testing is the critical specification rather than optical appearance.

Post-consumer LLDPE recyclate with a melt index of 3.5–6.0 g/10 min can be compounded with FLEXUS VLDPE 9200 at 20–40 wt% to recover dart impact and machine-direction tear resistance in thick gauge liners. On a corotating twin-screw extruder with 40:1 L/D and a temperature profile from 180°C to 230°C, the VLDPE component must be metered into the downstream side feed rather than the main hopper to limit shear heating and preserve its low-crystallinity structure. The compounded pellets show improved dart impact under ASTM D1709-16a when the VLDPE addition reaches 30 wt%, but the effect plateaus because the recycled matrix increasingly dominates the fracture mode. Above 230°C, oxidative degradation of the recyclate is accelerated, and the VLDPE no longer compensates for gel formation; an antioxidant masterbatch is required if the recyclate carries transition-metal residues from mixed-film waste. The finished blown-film process for refuse sacks and industrial liners typically uses a 2.0:1 blow-up ratio and 25–40 µm gauge. Terminal articles include heavy-duty refuse sacks, e-commerce mailers and protective over-wrap for industrial rolls, where the performance requirement is puncture resistance rather than food-contact compliance.

Low-Migration Backing Film for Acrylic Pressure-Sensitive Adhesive Coating

Surface protection film backing produced from VLDPE 9200 is converted on a cast-film line equipped with a 1.8 m die, 0.5 mm die gap and 15–25°C polished chill roll. The backing gauge is usually 25–60 µm, and the film is corona-treated to 40–46 mN/m before solventless or waterborne acrylic adhesive coating. The low-crystallinity ethylene copolymer structure gives a conformable backing that follows curved sheet metal and injection-moulded polycarbonate parts, but it also increases the solubility of low-molecular-weight additives if the film is not synthesized with low catalyst residues and low antioxidant loading. For temporary protection of painted metal or display glass, the backing is required to leave no residue after 7–30 days of UV exposure; conversion tests for adhesive anchorage and residue are often conducted by an in-house peel method aligned with ASTM D3330/D3330M. Published data for this specific film/adhesive/weathering configuration is limited, so validation on the target substrate is mandatory. RoHS compliance is checked under IEC 62321-5:2013 when the final article is used in electronics packaging or point-of-sale transport; REACH SVHC screening is necessary for export into the European Union. The terminal formats include protective masking for polished stainless steel sheet, pre-coated aluminium panels and injection-moulded PC display parts.