On a three-layer cast stretch-film line, ExxonMobil mLLDPE C4LL 5036.UV is specified in the outer layers of agricultural bale-wrap film at 25 µm total thickness. The C4 butene backbone and the incorporated UV package are used as a surface layer rather than as the sole film component; a representative A/B/A weight distribution is 30/40/30 or 25/50/25, with the core containing a broader-molecular-weight LDPE or a lower melt-index butene LLDPE. When the grade is used at 100 % in monolayer cast film, the extrusion line is run with a 0.6–0.9 mm die gap and a 15–25 °C polished chill roll; temperatures above 28 °C reduce chill-roll adhesion and produce gauge bands from air entrapment. A 90 mm single-screw extruder with an L/D of 30:1 and a barrier screw is typically set to a 190–210 °C flat-zone profile; the melt temperature at the die is not allowed to exceed 220 °C because the HALS component in the UV package undergoes volatile loss at prolonged high-temperature residence. Automatic beta-gauge scanning at 50–100 mm intervals maintains transverse gauge variation within ±1.5 µm; gauge outliers above ±2.5 µm cause neck-in and local pre-stretch failure on bale wrappers operating at 50–70 % pre-stretch. Tensile behaviour is tested according to ASTM D882; elongation at break in the transverse direction is the primary degradation indicator because UV microcracking is detected earlier in transverse film specimens. Stalk puncture is measured with ASTM D5748, and cling force after outdoor storage is measured with ASTM D5458. Accelerated weathering follows ASTM G154-23 Cycle 1 with UVA-340 lamps at 0.76 W/m²·nm irradiance and 60 °C black-panel temperature. Agricultural bale-wrap films are assessed under EN 14932, which specifies mechanical and UV-durability requirements for wrap used in forage conservation. End products are 500 mm and 750 mm wide rolls with 25 µm film; failure on farm wrappers appears most often as machine-direction splitting when the film has been stored in UV light before application or when edge trim was re-introduced at high levels into the UV-stabilised skin.

Why Is Chill-Roll Surface Roughness Critical in UV-Stabilised Cast Pallet Wrap?

Cast pallet wrap made from C4LL 5036.UV is run at 12–23 µm on high-speed three-layer cast lines with polished or matte chill rolls. The UV-stabilised resin is placed in the two outer layers at 20–30 wt% of total film, while the core contains a butene LLDPE or LDPE with a lower melt-flow index. Target melt temperature is 200–215 °C on a 120 mm barrier screw with L/D 30:1; die pressure at the coat-hanger die remains between 80–140 bar for a 2.2–2.5 m die width. Cling is generated in one outer layer by adding 1.0–3.0 wt% polyisobutylene or a proprietary cling masterbatch; the opposite outer layer is modified with a release additive. Chill-roll surface roughness is controlled to 0.02–0.10 µm Ra. Polished rolls below 0.02 µm Ra increase unwind cling to levels that can stall power pre-stretch rollers, particularly in 20 µm film at 250–300 % pre-stretch. Conversely, roughened rolls above 0.12 µm Ra raise haze above the typical 3.0 % measured by ASTM D1003. Puncture resistance is measured by ASTM D5748; tear resistance is measured by ASTM D1922 but is a secondary specification for cast wrap. Outdoor yard storage is simulated with ASTM G154-23 Cycle 1 for 500–1000 h; elongation retention after weathering is measured by ASTM D882. The end products are machine pallet-wrap rolls for outdoor storage of bagged cement, polymer resin sacks and industrial components. Edge trim is typically re-introduced into the core layer at 5–10 wt%; trim is excluded from the UV-stabilised outer layer because dilution of the HALS package accelerates surface embrittlement. Batch-to-batch melt-index variation is checked by ISO 1133-1:2022 at 190 °C/2.16 kg; a shift of more than ±0.3 g/10 min from the supplier certificate requires adjustment of die gap and chill-roll speed to maintain the target gauge and pre-stretch behaviour.

Where short-cycle greenhouse and low-tunnel cladding is required, C4LL 5036.UV is coextruded as the outer skin layer in three-layer blown film at 150–200 µm total thickness. A three-layer die with a 1.8–2.2 mm die gap and 200–400 mm die diameter is operated with a blow-up ratio of 2.2:1–2.8:1; the frost line is held at 700–1000 mm above the die using an internal bubble cooling air flow of 20–35 m/s and an external cooling ring with 70–90 % air-ring opening. The outer skins contain C4LL 5036.UV at 60–100 wt%; the core contains EVA with 12–18 wt% vinyl acetate or an LDPE designed for high melt strength. The EVA-containing core must be pre-dried at 65 °C for 4 h when ambient relative humidity exceeds 60 %; C4LL 5036.UV itself is not hygroscopic and is not routinely pre-dried. Melt temperatures are kept at 190–210 °C at the die; higher temperatures increase EVA volatiles and can reduce bubble stability. UV durability of the outer skin is tested under ISO 4892-2 Method A with xenon-arc exposure at 0.51 W/m²·nm at 340 nm and a black-standard temperature of 65 °C. The film is considered acceptable for short-cycle outdoor use when elongation at break measured by ISO 527-3 retains at least 50 % of the original value after 3000 h exposure. Haze and total light transmittance are measured by ASTM D1003; 150 µm greenhouse film requires total transmittance above 80 % in the 400–700 nm photosynthetically active radiation band. Elmendorf tear is measured by ASTM D1922, and puncture at low temperature is checked by ASTM D5748. European compliance for covering films is evaluated under EN 13206, which includes durability classifications for agricultural and horticultural use. End products are greenhouse roofs, low-tunnel hoops and soil-warming covers in folded widths from 2 m to 12 m. The C4 butene comonomer provides lower puncture toughness than C6 metallocene grades, so the grade is positioned for short-cycle tunnel applications rather than multi-year hard-cover greenhouses where EVA/C6 systems are preferred.

Tubular Blown Film for Heavy-Duty Sacks and FIBC Liners

In tubular blown film for heavy-duty sacks, FIBC liners and outdoor construction-material packaging, C4LL 5036.UV is processed at 80–150 µm in mono-layer or three-layer coextruded tubes. A three-layer structure uses the UV-stabilised resin in the surface layers at 20–25 wt% each, with a fractional-melt LDPE or HDPE core at 50–60 wt%. The die diameter is typically 200–400 mm, die gap 1.4–2.0 mm, and blow-up ratio 2.5:1–3.0:1. Internal bubble cooling is required above 80 µm to maintain output; line speed is limited by bubble instability and melt fracture rather than extruder throughput. A 90 mm grooved-feed single-screw extruder with L/D 30:1 is run at 190–215 °C; screen-changer melt pressure is kept below 350 bar to avoid shear-induced degradation of the UV stabilizer. Dart impact is measured by ASTM D1709 Method A on 100 µm film; industrial sack acceptance is often 400–600 g, but published data for C4LL 5036.UV in this specific structure is limited. Elmendorf tear is measured by ASTM D1922; transverse-direction tear is the weaker direction in butene comonomer blown film and is monitored at 20–60 N/mm depending on thickness. Heat-seal profiles are generated by ASTM F88; seal initiation for metallocene C4 LLDPE is typically 105–115 °C, and side-seal or bottom-seal converters use 180–220 °C seal-bar temperatures. Outdoor UV resistance is specified by ASTM G154-23 Cycle 1 for 1000 h or ISO 4892-2 for 2000 h; the film is expected to retain 70 % of original elongation at break. End products include woven outer-bag liners, FIBC liners for mineral powders, and heavy-duty bags for fertilizers, salts and construction chemicals stored outdoors. Converters avoid dry blending UV masterbatch into the skin layers because re-letdown above 10 wt% of edge trim in the skin depresses weathering resistance and broadens the seal-initiation window.

Because temporary roof covers, masonry curing films, and scaffold sheeting are subjected to wind flutter and UV exposure, C4LL 5036.UV is extruded on flat-die cast film and sheet lines at 100–250 µm. The resin is blended with 10–25 wt% LDPE or a rheology modifier masterbatch to increase melt strength; the UV-stabilised resin is not used as a monolayer if flame retardant additives are required, because brominated and antimony-containing systems interfere with the HALS package. The flat-die body is set at 220–240 °C, and the polishing stack temperature is held at 40–70 °C to limit warpage in 4 m wide sheets. Tensile properties are measured by ISO 527-3; tensile strength at break for 150 µm sheet is typically 25–35 MPa in the machine direction. Tear resistance is measured by ASTM D1004, and low-temperature flexibility is checked at -20 °C using a bending test based on ISO 8570. Weathering colour change and chalking are assessed by ISO 2810 with natural outdoor exposure in Florida or Arizona; artificial weathering follows ISO 4892-2 with 2000 h exposure, after which the sheet is required to retain 50 % of the original elongation at break. The product is fixed to scaffolding or roof substructures with eyelet-reinforced edges; failure in service occurs predominantly by flutter-induced tearing around the eyelets rather than by UV embrittlement when the sheet thickness is above 150 µm. Below 100 µm, wind flapping and abrasion remove degraded surface layers quickly, so the UV package alone does not determine service lifetime. Converters producing temporary weather barriers must document that the final sheet meets fire-class requirements under EN 13501-1 where applicable; this often requires a flame-retardant core layer, with C4LL 5036.UV used only in the outer UV-protective skins. On a 120 mm single-screw extruder with L/D 33:1, melt-pressure variation should remain within ±10 bar to avoid sheet-thickness fluctuation beyond ±5 % of nominal gauge.

When Lamination Skin Films Are Exposed to UV-Cured Inkjet Inks and Outdoor Weathering

Cast lamination films based on C4LL 5036.UV are produced at 25–75 µm and are used as weather-resistant protective skins over PVC banner substrates or woven polyethylene scrim. The mLLDPE resin is coextruded with a tie layer of maleic anhydride-grafted polyolefin at 10–15 wt%; the outer surface is corona-treated to 42–48 mN/m dyne level immediately before in-line lamination. The cast line uses a 0.5–0.8 mm die gap, a 20–30 °C chill roll, and a vacuum box or air knife for pinning. The film is laminated to PVC-coated scrim by thermal lamination at 120–140 °C or by solventless polyurethane adhesive at 2.0–3.5 g/m² coat weight. The UV package in C4LL 5036.UV resists yellowing during outdoor exposure; colour shift is measured according to ISO 4892-2 with 1000 h exposure and should be below 3.0 ΔE as determined by spectrophotometer and CIELAB calculation. Gloss retention is measured by ASTM D2457 at 60°; laminated outdoor media typically specify retention of at least 70 % gloss after 1000 h xenon-arc exposure. Direct adhesion to PVC is limited because non-polar mLLDPE does not adhere without corona or tie resin; delamination is evaluated by ASTM D1876 T-peel on 25 mm strips. The end product appears as outdoor banners, building wraps, vehicle-side printed media, and trade-show graphics, where the mLLDPE skin protects water-based and UV-cured inkjet inks from abrasion and rainfall. For flame-retardant banner applications, the lamination film must meet DIN 4102-1 B2 or NFPA 701 depending on jurisdiction; C4LL 5036.UV as the outer layer is typically paired with an FR-treated scrim or PVC core because the polyolefin skin alone fails the relevant vertical burn test. Edge curl in large-format lamination is controlled by keeping the film below 0.8 % shrinkage after 90 °C for 10 min; shrinkage is measured by ASTM D1204. A 65 mm main extruder with L/D 30:1 is used for the skin layer; die-pressure fluctuation above ±5 bar produces visible kiss-lamination defects and adhesive strike-through on wide-format laminators running at 30–80 m/min.