What Limits Load Retention in Cast Pallet Unitization Film?

Cast pallet stretch film production with Marlex® 7120X is run on high-speed cast lines where chill roll temperature and melt profile govern gauge uniformity and cling stability. On a five-layer cast coextrusion line with die width of 2,400–2,800 mm and chill roll setpoint of 18–24°C, the skin layers are formulated with 85–100 wt% Marlex® 7120X, 0–10 wt% LDPE, and 0.5–2.5 wt% polyisobutylene-based cling additive masterbatch. If cling additive concentration exceeds 2.5 wt%, unwind force under ASTM D5458-18 rises above 3.0 N/cm and roll blocking increases in warehouse storage at ambient temperatures above 30°C; below 0.5 wt%, load shift during transit exceeds the retention window required by automated palletization. Melt temperatures are held at 210–245°C on cast lines running at 300–600 m/min; excursions above 250°C degrade the polyisobutylene cling species and reduce cling force by more than 15% after 48 h of roll aging. Chill roll temperature below 12°C raises quench-related surface haze under ASTM D1003-13, while temperature above 30°C slows crystallization and increases blocking. Puncture resistance under ASTM D5748-19 and tensile properties under ISO 527-3:2018 are used for incoming film qualification, while edge trim at 8–12% of web width is reintroduced into the core layer at 0–15 wt% without measurable puncture loss. Terminal product types include hand wrap film, machine stretch wrap, and pre-stretched pallet wrap used in logistics and distribution.

On blown film lines equipped with oscillating haul-off units and internal bubble cooling, hexene LLDPE silage wrap is processed at blow-up ratios of 2.2–2.8:1, die diameters of 250–400 mm, and melt temperatures of 195–225°C. Multilayer structures containing 96–99 wt% Marlex® 7120X with 0.3–0.8 wt% hindered amine light stabilizer masterbatch and 0.2–0.5 wt% polymer processing aid are used for round bale wrap. Film thickness commonly ranges from 25–40 µm; tear propagation resistance measured according to ISO 6383-2:1983 is required to remain above the minimum values set in EN 13206:2017 for thermoplastic films used in agriculture. The processing aid loading above 0.5 wt% reduces die lip deposit on the 300 mm die but can lower cling in a coextruded tack layer, which is limited to 5–10 wt% of total thickness. UV stabilization packages are validated by ISO 4892-2:2021 accelerated weathering followed by residual elongation at break under ISO 527-3:2018. Field failure modes such as punctures at bale corners and splitting along the machine direction are monitored because they are more sensitive to film orientation than to thickness alone. Terminal product types include round bale silage film, pit sealing sheets, and greenhouse tunnel films where tear resistance and UV retention are specified for seasonal exposure.

Form-Fill-Seal Food Contact Compliance and Seal Integrity

For high-speed form-fill-seal converters, Marlex® 7120X is configured as three-layer blown film or five-layer cast film with sealant webs comprising 70–100 wt% Marlex® 7120X, 0–20 wt% LDPE to modify seal initiation, and 0.5–2.0 wt% slip/antiblock masterbatch. Seal strength is measured under ASTM F88/F88M-21; hot tack performance is measured under ASTM F1921-18 to avoid seal pop-open at high fill speeds. The film surface is corona-treated to 38–42 mN/m inline before lamination or printing. Food contact compliance is maintained under FDA 21 CFR 177.1520(c) for olefin polymers and Commission Regulation (EU) No 10/2011 for plastic materials intended to contact food, with overall migration below 10 mg/dm². Frozen food packaging qualification adds dart impact testing under ASTM D1709-16a Method B at -18°C; films that develop microcracking at this temperature are rejected because seal and barrier continuity fail after transportation vibration testing. Terminal product types include frozen vegetable bags, cereal liner films, snack packaging, and liquid pouch stock.

Where high bubble stability and dart impact above 1,000 g at 200 µm gauge are required, industrial sack liners and FIBC films use monolayer or coextruded blown film formulations based on 65–90 wt% Marlex® 7120X, 10–30 wt% LDPE or mLLDPE, and 0–5 wt% carbon black or antistatic masterbatch. The compounds are extruded through die gaps of 1.8–2.5 mm at BUR of 3.0–4.0:1 and melt temperatures of 180–220°C. Dart impact is measured under ASTM D1709-16a, Elmendorf tear under ASTM D1922-15, and secant modulus under ISO 527-3:2018 for converter specifications. Carbon black masterbatch addition above 5 wt% reduces bubble stability and can produce melt fracture on single-screw lines with L/D 24:1; lines with L/D 30:1 or barrier screws are used to maintain output without adding processing aids. Reclaimed edge trim is maintained below 10 wt% because reclaim streams with higher gel formation reduce dart impact at welded seams. Terminal product types include flexible intermediate bulk container liners, chemical sack liners, and industrial inner liners for bulk packaging.

When 7120X Replaces LDPE in Coextruded Surface Protection Film

In applications requiring controlled peel adhesion from polished metal and rigid polymer panels, Marlex® 7120X is used in the carrier layer of coextruded cast surface protection film. The carrier formulation contains 90–100 wt% Marlex® 7120X, while the coextruded or coated pressure-sensitive adhesive layer contains an ethylene-vinyl acetate or thermoplastic elastomer component at 2–10 wt% of total film weight. Peel adhesion is measured under ASTM D3330/D3330M-04 Method A and is typically maintained between 0.5–1.5 N/cm for non-marring removal from polished aluminum and acrylic. The cast line includes a 2,000 mm die, polished chill roll at 20–25°C, and line speed of 80–180 m/min. Capacitance-based thickness scanning is used to maintain gauge uniformity at ±1 µm; deviations beyond this range produce adhesive transfer and inconsistent unwind tension. Industrial assembly film compliance references REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU; food contact is not claimed for this construction. Terminal product types include protective masking for stainless steel panels, pre-coated aluminum building sheets, and rigid PVC profiles.

After incorporation of calcium carbonate masterbatch to yield 40–60 wt% filler loading in the final compound, the hexene LLDPE substrate is cast and subsequently stretched in the machine direction at draw ratios of 2.0–3.5:1 and oven temperatures of 60–80°C on a cast film line fitted with an in-line machine-direction orientation unit. Water vapour transmission rate is measured under ASTM E96/E96M-22; tensile properties are measured under ISO 527-3:2018. For hygiene backsheet laminates, calcium carbonate dispersion below 8 µm top-cut and average particle diameter of 1.5–2.0 µm are required to prevent pinhole formation at 25 g/m² basis weight. Screen pack blockage occurs when dispersion quality degrades or when reclaim containing gel is added above 10 wt%. Cytotoxicity testing under ISO 10993-5:2009 is applied when the laminate is intended for medical drapes, although published data for this specific resin in medical laminates is limited. Terminal product types include diaper backsheets, breathable laminate films for underpads, and personal protective garment films.