Cast Film Optical Haze and Pre-Stretch Retention in High-Speed Pallet Wrapping

Cast film converted from MarFlex® 7105FL is typically produced on lines equipped with a 90 mm barrier screw, L/D 30:1, compression ratio 3.0:1, and a die width of 2.0–3.0 m. For down-gauged wrap below 12 µm, the resin is melt-blended with a single-site polyethylene plastomer at 10–20 wt%, the plastomer having a density below 0.902 g/cm³. Melt temperature is held between 210 °C and 245 °C, the die gap is set at 0.6–1.0 mm, and the polished chill roll is maintained at 18–25 °C. On a 2.5 m line running at 350 m/min, screen-pack pressure above 35 MPa at constant throughput indicates gel accumulation, poor mixing, or metal fatigue in the screen changer. Machine-direction tensile elongation is measured under ASTM D882 as an indirect check on pre-stretch uniformity, while cling is tested under ASTM D5458 and puncture resistance under ASTM D5748. Turntable wrappers commonly apply 200–250% pre-stretch; at the upper limit, edge tear propagation initiates if web thickness variation exceeds ±5%. Haze values below 2.0% measured per ASTM D1003 require a clean chill roll and controlled wax pickup. Melt flow rate is verified at 190 °C/2.16 kg under ASTM D1238 or ISO 1133-1. If the grade is combined with chlorinated wax or an incompatible processing aid, cling uniformity shifts, so only saturated masterbatches are used.

Silage wrap and greenhouse cover webs are produced on three-layer blown-film lines with die diameters of 250–350 mm, die gaps of 1.6–2.2 mm, and layflat widths of 1,500–2,500 mm. The core layer contains MarFlex® 7105FL with 0.3–0.6 wt% hindered amine light stabilizer and 0.1–0.3 wt% UV absorber concentrates; outer layers incorporate slip and antiblock concentrates at 0.5–1.5 wt%. Blow-up ratios between 2.0:1 and 2.6:1 are used to balance dart impact and tear, with frost line height kept at 8–12 die diameters. Melt temperatures above 220 °C increase gel formation from high-molecular-weight stabilizer by-products, while temperatures below 185 °C produce visible melt fracture at high output. Field failures in silage wrap below 25 µm most often appear as crease splitting after 12–18 months of UV exposure and silage acid contact; tensile elongation is checked under ISO 527-3 and dart drop under ASTM D1709. Roll geometry must maintain web thickness variation below ±5% because stacked rolls in storage develop permanent deformation at the core. Batch-to-batch variation in stabilizer dispersion can be detected as a screen pack pressure increase of 1.5–3.0 MPa over an 8 h run.

What Seal Initiation and Hot Tack Window Are Achievable in Coextruded Food Packaging?

The sealant webs in three-layer food packaging are usually run as a coextruded skin layer at 15–25% of total structure, paired with a polyamide or EVOH barrier core and tie layers. In such structures, the linear low-density polyethylene provides seal initiation near 100–115 °C; published data for this specific converted configuration is limited, so converters generate a seal-force curve per ASTM F88 and hot-tack values per ASTM F1921 across a 10 °C gradient before setting packaging line dwell times. On high-speed flow wrappers, a hot-tack window of 0.2–0.5 s at 0.3–0.5 N/mm seal force is common for polyethylene-based sealant webs, though actual values depend on web thickness, die-gap orientation, and additive package. Slip and antiblock additives must be selected from compliant masterbatches because overall migration above <10 mg/dm² under EU No 10/2011 can affect organoleptic testing. Pre-drying is not required unless ambient humidity exceeds 60%, at which point additive concentrates may agglomerate and create visible gels.

Form-fill-seal lines converting heavy-duty sacks run 80–150 µm webs at fill rates of 25–35 cycles/min. On three-layer blown-film extruders, the core layer of MarFlex® 7105FL is blended with 10–20 wt% high-pressure LDPE to improve bubble stability at blow-up ratios of 1.8:1–2.0:1. Dart impact is measured per ASTM D1709, Elmendorf tear per ASTM D1922, and coefficient of friction per ASTM D1894. Web thickness variation above ±6% causes intermittent seal-bar leaks at lap seals.

When Extrusion Lamination Lines Run Above 300 m/min on Foil and Paperboard

At line speeds above 300 m/min, extrusion lamination of MarFlex® 7105FL onto paperboard and aluminium foil requires blending with 20–30 wt% LDPE or a low-melt-index extrusion-coating grade to control neck-in and draw resonance. Melt temperature is set between 285 °C and 315 °C; below 280 °C, adhesion to foil falls below practical peel values, while above 320 °C, smoke generation and oxidative gel formation increase. Die gaps of 0.6–1.0 mm and air gaps of 200–250 mm are employed, with internal deckles adjusted to keep edge bead below 2 mm. T-peel adhesion is measured under ASTM D1876; acceptable values are often specified between 1.5 N/15 mm and 4.0 N/15 mm depending on foil thickness and corona treatment level. When a coextruded tie layer of ethylene-acrylic acid or ethylene-methacrylic acid is required, the supplier’s recommended melt temperature and backpressure limits must be observed; published data for this specific configuration is limited. Longer air gaps above 250 mm reduce peel strength because the oxidised film surface cools below the necessary level for carboxylic acid bonding.

Surface protection films for stainless steel sheet, painted aluminium profiles and glass are extruded at 40–80 µm using MarFlex® 7105FL blended with 5–15 wt% LDPE and a pressure-sensitive adhesive concentrate. Peel strength is adjusted between 0.5 N/25 mm and 2.0 N/25 mm per ASTM D3330. Blow-up ratios of 2.0:1–2.5:1 reduce visible gel defects that would mark polished metal surfaces.