Industrial cast stretch film lines running Braskem FLEXUS VLDPE 7020 at nominal density 0.902 g/cm³ (ASTM D792) and melt flow rate 2.0 g/10 min (ASTM D1238, 190°C/2.16 kg) position the material in the cling skin or core sublayers of three-layer pallet-wrapping structures rather than in heavy-duty puncture-critical monolayers. The compliance basis for the finished film is governed by ASTM D5458 for cling, ASTM D5748 for protrusion puncture resistance, and EN 14932 for stretch wrap designation in logistics applications. In a three-layer A/B/C cast formulation, the two cling skins contain 70–85 wt% FLEXUS VLDPE 7020 with 15–30 wt% of an mLLDPE or LLDPE of melt index 3.5–4.5 g/10 min, while the core layer may contain 0–40 wt% FLEXUS VLDPE 7020 blended with LLDPE or LDPE to maintain dart impact. Monolayer cast film can be produced at 100 wt% addition, but high unwind noise and neck-in on wider lines limit practical use beyond 1,500 mm die width. Production on a 30:1 L/D single-screw cast line with barrel profile 180–260°C and die temperature 250–265°C requires an air gap of 10–20 mm, a chill roll set point of 18–25°C, and a vacuum box or air knife to lock the web to the forming roll. Terminal article types are machine pallet stretch films of 12–23 µm nominal gauge and hand pallet wraps of 10–15 µm. Additive packages for cling include polyisobutylene at 0.5–1.2 wt% in the skin only; higher levels raise cling force above 2.5 N/cm and produce blocking on wound film rolls, while lower levels fail to meet minimum cling for high-speed pallet wrapping. The operational boundary is set by melt temperature: sustained operation above 290°C initiates oxidative degradation, reduces dart impact, and creates gel formation on the chill roll. Chill roll temperatures below 15°C are also not recommended because condensation on the forming roll creates surface haze and inconsistent cling distribution across the web.

What Limits Seal Initiation Temperature in Low-Density Food Packaging Sealant Layers?

Blown film coextrusion of lamination-grade sealant webs uses FLEXUS VLDPE 7020 at addition levels of 20–40 wt% in the sealant skin of asymmetrical five-layer barrier films, where the opposing layer is a nylon or EVOH barrier. The sealant blend typically contains 60–80 wt% of a linear low-density polyethylene with melt index 1.0–2.0 g/10 min; adding VLDPE below 20 wt% fails to lower seal initiation temperature below 95°C, while exceeding 40 wt% risks blocking of the collapsed bubble during windup. Compliance for direct food contact follows FDA 21 CFR 177.1520 for olefin polymers and EU Regulation 10/2011 with overall migration limit 10 mg/dm² under aqueous and fatty food simulants. The production process uses a multi-layer blown film line equipped with internal bubble cooling and die gap 1.8–2.5 mm, blow-up ratio 2.0:1–2.8:1, melt temperature 195–215°C at the die, and frost line height 300–500 mm above the die. Terminal products include ≤35 µm lamination films for flow-wrapped confectionery, fresh pasta pouches, and pre-made vertical form-fill-seal bags. The critical processing limit is condensation on pellets: if storage occurs at relative humidity above 85%, surface moisture must be removed by a 60–70°C desiccant hopper dryer at 2 h residence; otherwise bubble instability and dart impact loss are observed. The material should not be combined with high levels of behenamide or erucamide in the sealant layer, as migration above 1,000 ppm total amide may reduce seal strength and interfere with ink adhesion in downstream printing.

Extrusion Coating of Kraft and Paperboard Without Tie-Layer Adhesives

Extrusion coating and laminating lines apply FLEXUS VLDPE 7020 as a heat-seal layer on paperboard for dry food sachets and pharmaceutical strip packaging. The addition ratio in the coating blend is 30–50 wt% FLEXUS VLDPE 7020 with 50–70 wt% LDPE of melt index 7–8 g/10 min; the LDPE is required to keep neck-in within 3–5 cm at line speeds above 150 m/min. Lower VLDPE content below 30 wt% increases seal initiation temperature, while higher content above 50 wt% reduces melt strength and causes edge weave on wide coaters. The process uses a 90–120 mm single-screw extruder with 28:1–33:1 L/D, die temperature 290–310°C, air gap 150–250 mm, and corona treatment at 42–46 dyn/cm for adhesion to paperboard. Finished product types are sachet stock and lidding membranes with coat weights 12–20 g/m². The compliance route is indirect food contact under FDA 21 CFR 176.170(c) for paper and paperboard components and EU 10/2011 where the coating is the food-contact side. Published data for this specific configuration is limited; start-up losses on older coating lines are typically higher than on cast film lines because the oxidation-promoted adhesion to paperboard depends on melt temperature and air gap residence time. Processing above 320°C produces excessive low-molecular-weight aldehydes and should be avoided.

When Stretch Hood Layflat Exceeds 1,800 mm and Warehouse Storage Drops Below −20°C

Blown film conversion of heavy-duty stretch hoods and pallet covers uses FLEXUS VLDPE 7020 as an impact-modifying and puncture-resistant component in LLDPE-rich formulations. The addition level is 25–35 wt% in the outer layers of a three-layer blown structure, with 65–75 wt% C8-LLDPE of density 0.918–0.920 g/cm³ and melt index 0.9–1.2 g/10 min. Blends below 25 wt% show brittle puncture failure in ASTM D5748 at −20°C, while blends above 35 wt% reduce modulus below 180 MPa in ISO 527-3 and cause unstable bubble geometry at layflat widths above 1,800 mm. The process is performed on a high-stalk blown film line with maximum die diameter 400–500 mm, die gap 2.0–2.5 mm, blow-up ratio 2.5:1–3.2:1, and melt temperature 185–200°C; internal bubble cooling is mandatory to maintain bubble symmetry. The terminal articles are stretch hoods of 120–180 µm thickness for palletized construction goods, appliance shipping, and cold-storage pallet wrapping. Compliance for industrial packaging is generally verified through ASTM D1709 dart drop impact, ASTM D5748 puncture resistance, and EUMOS 40509 load stability for palletized freight. At sub-zero storage, the seal area and gusset fold are the primary failure zones; the addition of VLDPE shifts the ductile-to-brittle transition below −25°C, but if the grade is blended above 40 wt%, the film loses tensile modulus and the gusseted folds show stress whitening after repeated flexing. The grade should not be blended with high-pressure LDPE above 20 wt% in this application because melt strength becomes excessive and the film tends to tear at the perforation line.

Compounding of heterophasic polypropylene impact copolymers with 10–25 wt% FLEXUS VLDPE 7020 reduces low-temperature notched impact failure without requiring an additional PP-g-MAH compatibilizer at the lower addition range. The blend is prepared on a 40:1 L/D co-rotating twin-screw extruder with zone temperatures from 190°C to 230°C, screw speed 400–600 rpm, and vacuum devolatilization at −0.07 MPa absolute. The VLDPE is fed downstream after the PP melting section to limit shear heating; adding it above 25 wt% reduces flexural modulus below 900 MPa and creates surface tackiness on injection molded parts. The terminal component types are automotive interior trim retainers, appliance housings, and caps where low-temperature impact is specified. Mechanical compliance is verified under ISO 180 notched Izod at −20°C, ISO 178 flexural modulus, and ISO 527-2 tensile yield. The grade is not intended for use in compounds that will be sterilized with ethylene oxide at temperatures above 55°C because residual peroxide from the PP matrix can induce chain scission of the VLDPE fraction, and the material is not suitable for direct food contact in this application unless the final compounded formulation is re-qualified under FDA 21 CFR 177.1520. Batch-to-batch variance in VLDPE melt index should be controlled within ±0.3 g/10 min to maintain consistent phase morphology.