Braskem FLEXUS VLDPE 8020 is a very-low-density ethylene copolymer with nominal density 0.902 g/cm³ and melt flow rate 2.0 g/10 min at 190°C/2.16 kg. The downstream applications below are limited to converting sectors where the grade functions as a sealant web, toughness modifier, cling layer, or low-temperature flexibiliser. Process parameters are reported from production-scale extrusion and film converting environments and are referenced to standard test designations rather than laboratory-scale inference.

In blown-film coextrusion producing three-layer barrier food packaging, Braskem FLEXUS VLDPE 8020 is used as the heat-seal layer at 80 wt% to 100 wt% concentration, with the balance typically a 0.923 g/cm³ LDPE or butene-LLDPE. The resin’s density of 0.902 g/cm³ permits seal initiation at lower seal-bar temperatures than conventional LLDPE; on a 30 µm monolayer cast film, seal initiation is observed in the 82°C to 90°C range under 300 N seal-bar force and 0.5 s dwell. In production, a 70 mm 30:1 L/D single-screw extruder with a barrier screw running at 90 rpm to 110 rpm feeds the sealant layer of a three-layer blown-film line with die temperature 215°C to 230°C, blow-up ratio 2.0:1 to 2.5:1, and frost line height maintained between 4 and 7 die diameters. Compliance for direct food contact is assessed under FDA 21 CFR 177.1520(c) for olefin polymers and EU Commission Regulation (EU) No 10/2011 overall migration limit of 10 mg/dm² under test condition OM2; REACH Article 33 communication obligations apply to downstream deliveries. The converted reel stock terminates in form-fill-seal pouches for frozen vegetables, snack dry mixes, processed cheese, and fresh-cut produce, where seal-through-contamination performance and low-temperature puncture resistance determine line efficiency.

Reduction of VLDPE 8020 content to 80 wt% in the sealant layer is common when line output exceeds 220 m/min, because the lower melt strength of the neat resin can induce bubble instability on high-stalk configurations. At 20 wt% LDPE addition, the seal initiation temperature increases by approximately 3°C to 5°C, while dart drop impact on 40 µm film tested under ASTM D1709-22 increases from 650 g to 780 g. Frost-line oscillation greater than ±2 cm produces gauge bands of 3% to 5% deviation in the sealant layer, which translates to intermittent weak seals on horizontal form-fill-seal machines. The formulation limit is set by hot tack: above 30 wt% LDPE, hot tack force under ASTM F1921-18 at 110°C seal-bar temperature declines below 2.5 N/25 mm in some production runs; trials indicate that 15 wt% LDPE is preferred for high-speed vertical form-fill-seal packaging of powders.

Why Does Pallet Unitisation Require Low-Temperature Stretch Retention?

Pallet unitisation films processed on high-output cast lines at draw ratios between 2.0:1 and 3.5:1 incorporate 15 wt% to 40 wt% Braskem FLEXUS VLDPE 8020 in the core and cling outer layers to maintain elongation after cold outdoor storage. At -18°C, a 70 µm three-layer stretch hood film containing 30 wt% VLDPE 8020 and 70 wt% LDPE falls within EUMOS 40509 load-unit rigidity limits for A7 pallets, with puncture resistance measured under ASTM D5748-19 at 4.5 J/mm and dart drop impact under ASTM D1709-22 at 850 g. The low crystallinity allows the film to be drawn over a 1,200 mm × 1,000 mm pallet hood at 55% to 65% pre-stretch without stress whitening, whereas conventional butene-LLDPE grades in the same recipe show visible necking at 45% pre-stretch. Processing on a three-layer cast line with 2,500 mm die width and 0.8 mm die gap uses melt temperatures of 210°C to 230°C and chill roll temperature 18°C to 24°C; edge trim is recycled at 10 wt% to 15 wt% back into the core layer, with reclaimed material kept below 20 wt% because transverse-direction tear anisotropy increases. Terminal products include pallet hoods for glass containers, cement bags, beverage bottles, and insulation panels, where load stability, water resistance, and dust protection are specified in factory acceptance tests. REACH registration and the absence of intentionally added perfluorinated slip agents are required under downstream EU packaging supply contracts; certificate of analysis traceability should include melt flow rate per ISO 1133-1:2022 and density per ISO 1183-1:2019.

Production-scale failure modes observed on hood application lines include edge-fold splitting when the VLDPE content exceeds 40 wt%, because the coefficient of friction against steel rollers falls below 0.15 and web tracking becomes unstable. On a three-layer stretch hood line running at 350 m/min, reducing VLDPE 8020 in the outer layer from 35 wt% to 25 wt% stabilised web tension at 85 N/m and eliminated periodic 2 mm to 3 mm edge defects. Melt temperature should not exceed 235°C, since odour and gel formation above 240°C can create film inclusions that reduce elongation at break below the 300% internal specification. Pre-drying is not required at ambient RH below 60%; above 60% RH, surface moisture on pellets can produce splay in the outer layer and is controlled by hopper drying at 60°C to 70°C for 2 h.

Across a cast surface-protection line configured with a 2,400 mm die and a 45°C matte chill roll, an adhesive-free protective web is produced from Braskem FLEXUS VLDPE 8020 blended with 8 wt% to 15 wt% LDPE for controlled self-adhesion to stainless steel and glass. The cast film at 20 µm to 50 µm thickness is embossed on a rubber pressure roll at 0.4 MPa nip pressure to create microvoids that reduce peel adhesion to the target surface; unwind peel adhesion measured after 30 days on mirror-finish stainless steel under ASTM D3330-23 Method A ranges from 0.10 N/25 mm to 0.40 N/25 mm depending on chill roll temperature and embossing depth. The 100 wt% VLDPE 8020 formulation is often applied to glossy acrylic and painted metal because plasticiser migration into the protected surface is lower than with EVA-based cling formulations; however, it should not be used in contact with high-plasticiser PVC sheets without preliminary migration testing, because low molecular weight species can transfer and alter surface gloss at 50°C. Compliance in automotive and building-material applications is derived from REACH Annex XVII restrictions and EU RoHS Directive 2011/65/EU for lead, cadmium, mercury, and hexavalent chromium below 100 ppm each; for indirect food-contact use in protective sheets that are later removed from food equipment, EU 10/2011 migration testing may be required depending on the final plant audit. Terminal products are reel-form temporary protective films for automotive painted bumper covers, architectural aluminium extrusions, stainless steel appliances, and coated glass sheets.

Peel adhesion drift is the dominant quality defect in this application. When chill roll temperature fluctuates by ±3°C, film crystallinity changes and peel force can shift by 0.05 N/25 mm to 0.10 N/25 mm within a single mill roll. To maintain adhesion below the customer’s 0.25 N/25 mm threshold for painted polycarbonate, production uses an oscillating nip speed differential of 1.2:1 to align surface microtexture. Addition of more than 15 wt% LDPE increases the elastic modulus and reduces conformability by 20% to 30%, producing bridging and air entrapment on curved bumper surfaces. A 30 µm gauge with a 25 µm cling-functional surface layer is the usual specification; below 15 µm, pinholing under 50× optical inspection occurs at 0.8 m² per 10,000 m² when the chilled roll is not freshly polished.

Sealing Through Tyvek and Clear Lidding Without Coating Interruption

Medical device pouches that seal through uncoated Tyvek 1073B use Braskem FLEXUS VLDPE 8020 as a continuous sealant web extrusion-laminated onto aluminium foil, PET, or nylon lidding substrates at coating thicknesses between 25 µm and 40 µm. In a 100 wt% VLDPE 8020 sealant layer, seal initiation against uncoated Tyvek begins at 78°C to 85°C on a 300 mm rotary sealer with 0.5 s dwell and 400 N force, allowing pouch sealing below the distortion temperature of PET lidding. This configuration meets the seal strength requirement of ISO 11607-1:2019 clause 5.3.1, with burst and dye penetration tested according to ASTM F1140-22 and ASTM F1929-15; a 32 µm coating on 12 µm PET and 40 g/m² Tyvek routinely exceeds 1.0 N/15 mm seal strength under ASTM F88/F88M-21 before ethylene oxide sterilisation. The addition level of VLDPE 8020 in lidding sealant layers is typically 90 wt% to 100 wt%; if flowability for thin coating below 25 µm is required, 10 wt% LDPE with melt flow rate 4.0 g/10 min is added, which raises seal initiation by 4°C to 6°C but eliminates edge beading. Processing uses a 90 mm 30:1 L/D extruder feeding a 1,200 mm slot die at 250°C to 280°C melt temperature; screw speed is adjusted to maintain 20 m/min to 40 m/min line speed, and the web is quenched on a 20°C chill roll before primerless lamination. Terminal products include peelable pouches for syringes, lidding for thermoformed trays used in surgical kits, and vented pouches for catheters. Compliance under EU MDR requires ISO 10993-5:2009 cytotoxicity testing of the final device package if the sealant is reported as a patient-contacting material, and sterilisation compatibility is validated under ISO 11137-1:2006/Amd 1:2013 for gamma doses up to 50 kGy; yellowing of the VLDPE layer after 50 kGy can occur and should be evaluated for peel and burst acceptance.

Production failure modes in medical lidding converting include sealant layer thinning at the die edge caused by neck-in exceeding 12% at 30 µm thickness. Line operators compensate by increasing edge bead thickness to 40 µm, but this creates uneven sealing during tray lidding. On a narrow-web line running at 80 m/min, switching from 100 wt% VLDPE 8020 to a 90/10 blend with LDPE reduced neck-in from 15% to 8% and stabilised coating basis weight within ±2 g/m²; however, the hot tack plateau narrowed from 75°C to 100°C to 80°C to 95°C. This is acceptable for Tyvek but may limit sealing through wet or contaminated regions. Pre-drying is not required at RH below 50%, but if stored above 60% RH, a 2 h hopper drying at 65°C prevents surface moisture from causing foam in the molten web. Under ISO 13485:2016, lot-level testing of density and melt flow rate per ISO 1133-1:2022 is retained for 7 years in the device master record.

When Low-Temperature Flexibility Outweighs Density in Containment Liners

Containment geomembrane sheet produced by flat-die cast extrusion at thicknesses from 0.75 mm to 2.00 mm incorporates 20 wt% to 50 wt% Braskem FLEXUS VLDPE 8020 in a VLDPE/LLDPE blend to maintain stress crack resistance after installation in cold climates. The low density of 0.902 g/cm³ reduces secant flexural modulus and imparts elongation at break above 800% when tested under ASTM D638-14 Type IV at 23°C. In a 1.50 mm sheet containing 30 wt% VLDPE 8020, 2.5 wt% carbon black masterbatch, and 67.5 wt% LLDPE, low-temperature brittleness under ASTM D746-20 passes at -70°C, while puncture resistance under ASTM D4833-07 exceeds 350 N. This formulation is deployed in pond liners, temporary landfill caps, canal liners, and secondary containment basins where sheet installation occurs below 5°C and welded seams must retain elongation at -20°C. Process conditions use a 120 mm 32:1 L/D single-screw extruder with melt temperature 200°C to 230°C, die gap 1.8 mm, and a three-roll calendering stack with a top roll at 55°C and a bottom roll at 70°C; bubble extraction by vacuum slot is essential because entrapped air causes voids that initiate environmental stress cracking at carbon black-rich regions. Compliance is evaluated under GRI-GM13 for VLDPE geomembrane properties and ISO 13438:2019 for chemical resistance; ultraviolet resistance is tested by ASTM D7238-20 for 10,000 h xenon-arc exposure with retained tensile strength of at least 80%. Terminal products are fabricated by wedge welding and extrusion fillet welding into large-area panels for water containment and waste cover systems.

Weldability of the 30 wt% VLDPE 8020 formulation differs from standard HDPE because the lower sintering plateau extends the wedge-welding window to 380°C to 420°C and increases the risk of squeeze-out in thickness below 1.00 mm. At 50 wt% VLDPE 8020, shear strength of wedge welds according to ASTM D6392-12 procedure declines to 85% of the parent sheet; at 20 wt%, low-temperature ductility improves but melt homogenisation with LLDPE becomes poorer. Field reports from containment installers indicate that seam failure in freezing conditions originates from incomplete fusion at the sheet edge due to thickness variation above 5%, so on-line thickness scanning with 2 mm resolution is specified. Use of more than 2.5 wt% carbon black masterbatch raises melt pressure by 15% and reduces MFR to 1.5 g/10 min; this can be managed by raising barrel zone 5 temperature to 215°C but not beyond 225°C to avoid excessive oxidised gel.

Collation Shrink Puncture Thresholds and Double-Bubble Process Limits

Above 140 m/min, double-bubble lines exhibit edge-localised seal and puncture failures in low-gauge multipack shrink film; 10 wt% to 25 wt% Braskem FLEXUS VLDPE 8020 is added to the middle layer of a three-layer shrink film to raise edge toughness without sacrificing free shrink. In a 45 µm film produced from 75 wt% LLDPE and 25 wt% VLDPE 8020 in the core, puncture resistance under ASTM D5748-19 increases from 2.8 J/mm to 4.1 J/mm, while free shrink at 120°C under ASTM D2732-14 remains above 20% in the transverse direction. The core formulation is extrusion-blended in the main extruder of a three-layer double-bubble line with die temperature 205°C to 220°C, first bubble BUR 1.8:1 to 2.2:1, and second bubble transverse stretch ratio 4.5:1 to 5.0:1; the addition of VLDPE 8020 reduces crystalline orientation and prevents the film from splitting at the seal edges when shrinking around sharp bottle caps. Terminal products are printed and clear collation shrink sleeves for 250 mL to 2.0 L beverage bottles, canned food multipacks, and household chemical bundles, where the packaging is regulated by EU 94/62/EC and must not exceed the sum concentration of lead, cadmium, mercury, and chromium(VI) of 100 mg/kg under the same directive. FDA 21 CFR 177.1520(c) applies when the shrink film is used for indirect contact with bottled water; direct fatty-food contact is not claimed for the printed finished film because the printing system governs final status.

Process limits on double-bubble lines include a narrower air pressure tolerance in the second bubble when VLDPE content exceeds 25 wt%. The lower melt strength of the VLDPE core causes bubble diameter oscillation of ±3% and corresponding transverse gauge variation above 8%, which creates loose bands on bottle shoulders. To compensate, the second bubble is run with internal air pressure 0.4 kPa to 0.6 kPa lower than for butene-LLDPE controls, and the water ring is moved 20 mm to 30 mm closer to the second nip to stabilise the bubble neck. At 15 wt% VLDPE 8020, the film retains 80% of its transverse shrink at 110°C, and production records show that reel hardness measured by a Schmidt hammer remains at 55 to 60 units after 48 h ageing. Use of more than 25 wt% VLDPE 8020 in the core leads to blocking on the winder because the surface coefficient of friction exceeds 0.45 at 35°C; where blocking is observed, 1,000 ppm of a migratory slip additive is introduced, but that can raise seal initiation by 6°C and must be validated for downstream shrink tunnels.