On high-speed five-layer cast film lines producing machine pallet wrap, the outer cling skin is a discrete coextruded layer whose low crystalline fraction and surface tack determine the peel force against the opposite film face. Braskem FLEXUS VLDPE Cling is introduced in the outer skin at 8–12 % of total film thickness; the core and sub-skin layers are typically LLDPE, with an additional outer layer designed for controlled unwind. Melt temperature at the feedblock is maintained between 220 °C and 250 °C because thermal exposure above 260 °C accelerates oxidative chain scission in the low-density branches, reducing cling after 30 days of roll storage. On production-scale cast film lines equipped with 90 mm barrier screws and 30:1 L/D barrels, throughputs between 300 kg/h and 600 kg/h are common depending on die width and chill roll width. The chill roll surface is controlled at 18–24 °C and the air gap is kept between 0.5 mm and 2.0 mm to suppress crystalline haze without inducing blocking in the finished roll. Melt flow rate for typical VLDPE cling resins, determined by ISO 1133-1:2022 at 190 °C and 2.16 kg, ranges from 1.0 g/10 min to 4.0 g/10 min; this viscosity window controls feedblock pressure and the ability to maintain a uniform skin thickness at line speeds above 350 m/min. Peel cling measured by ASTM D5458 at 23 ± 2 °C and 50 ± 5 % relative humidity is generally specified between 70 g/in and 150 g/in for automated palletizers. Puncture propagation resistance measured by ASTM D5748 on 17–23 μm film is normally maintained above 2.0 J. Tensile elongation at break by ASTM D882 regularly exceeds 400 % in the machine direction when edge pinning and vacuum box settings are stable. Migratory slip and antiblock packages should be excluded from the cling skin; erucamide bloom at levels above 500 ppm can suppress the surface tack interface and reduce measured peel cling.

The central process conflict appears when the cling skin is thinned below 6 % of total thickness to reduce raw-material cost. At that point, normal die-bolt and thermal non-uniformities become large relative to the skin, and cross-web cling variability can exceed ±15 g/in. This variability causes tail adhesion failures on automatic stretch wrappers when the finished roll is used at speeds above 28 wraps/min. Conversely, increasing the cling skin above 12 % elevates roll blocking tendency, especially when warehouse storage temperature exceeds 30 °C for prolonged periods. The operational boundary therefore lies in a narrow thickness band; published data for this specific configuration is limited, and production trials generally require in-line cling force monitoring at the rewinder rather than reliance on laboratory sampling alone.

Does UV-Stabilizer Loading in the Skin Layer Interfere with Bale Wrap Cling Retention?

When round bale silage wrap is converted on three-layer blown-film lines, the outer cling skin must retain low-temperature tack after prolonged warehouse storage and resist the puncture demands of rough bale surfaces. Braskem FLEXUS VLDPE Cling is coextruded at 10–15 % of a 25 μm finished film, with a core of LLDPE and a second skin of metallocene LLDPE. The extrusion profile uses melt temperatures of 190–220 °C, a blow-up ratio of 2.5:1 to 3.0:1, and a frost line height below 800 mm from the die. Raising the frost line above 800 mm increases crystalline orientation in the cling skin and reduces peel cling below the 60 g/in threshold commonly demanded by agricultural contractors. ASTM D5748 puncture propagation resistance is generally specified at 2.5 J or more on 25 μm film, and ASTM D1922 Elmendorf tear values fall between 300 gf and 600 gf in the machine direction. Oxygen transmission is dominated by the core layer and must be verified on the finished film by ASTM D3985 at 23 °C and 0 % relative humidity, because the thin cling skin contributes only marginally to the total barrier. The primary compatibility constraint in this segment is UV stabilization: when hindered amine light stabilizer loading exceeds 0.5 wt% in the skin layer, low-molecular-weight amine species can migrate to the surface and disrupt the paraffinic tack interface. Some field reports also document cling retention losses after 6 months of storage at warehouse temperatures above 30 °C, but published data for this specific Braskem grade in UV-stabilized agricultural film is limited. Amide-based antiblock systems in the cling skin should be avoided unless validated by ASTM D5458 after 24 h conditioning.

Where refrigerated protein trays are overwrapped at 28–40 cycles/min on semi-automatic stretch-wrapping stations, the film must combine controlled cling force with low extractable content and no detectable odour transfer into high-moisture foods. Braskem FLEXUS VLDPE Cling is used in cast food overwrap at thicknesses of 8–12 μm, often as the inner cling skin in a two- or three-layer structure. Cling force measured by ASTM D5458 is maintained in the lower portion of the range, typically 40–80 g/in, because excessively high tack causes dispenser drag and film breakage on high-speed overwrap equipment. Corona treatment is usually applied only to the outer printable surface or omitted entirely from the cling surface; surface oxidation can raise surface energy and create a brittle skin that lowers peel cling. The base polymer falls within the olefin polymer class evaluated under FDA 21 CFR 177.1520, and the finished film must also satisfy EU Regulation 10/2011 Annex I if sold into European food packaging. Overall migration testing is conducted under ASTM D4754-14 or the applicable food simulant protocol; the standard EU overall migration limit is 10 mg/dm² for the finished article. Organoleptic evaluation is commonly performed by ASTM E1870 panel testing to detect odor or taste transfer into dry and fatty simulants. The processing limitation in this food segment is additive selection: antifog masterbatches, antistatic systems, and release agents must be evaluated for bloom because migratory species compete with cling and can also raise extractable levels. When a high-cling overwrap is used on fresh-cut produce, the oxygen and carbon dioxide transmission rates of the finished film govern condensation management and must be checked by ASTM D3985 and ASTM F2476, respectively.

Protective Masking Peel Adhesion Limits on PMMA and Powder-Coated Aluminium

FLEXUS VLDPE Cling is coextruded as a 15–20 μm cling skin on a 50–70 μm LDPE backing for temporary surface protection of PMMA sheet and powder-coated aluminium profiles. Peel adhesion to the substrate, measured by ASTM D3330/D3330M at 180° peel angle and 300 mm/min withdrawal speed, remains below 0.5 N/25 mm, eliminating residue from acrylic adhesive systems. Storage above 35 °C should be avoided because thermal relaxation in the VLDPE skin increases contact area and can raise unmask peel force beyond the acceptable threshold.

Contrasting with machine-wrap cast film, stretch hood logistics demand a much higher thickness and a different balance of cling because the film is stretched vertically and transversely over a palletized load in a single forming operation. Braskem FLEXUS VLDPE Cling is used as the inner or outer skin of a 50–150 μm three-layer blown stretch hood film, with LLDPE in the core and a slip-modified outer surface where differential cling is required. The blown-film line runs a high-stalk bubble at a blow-up ratio of 3.0:1 to 3.5:1, with internal bubble cooling and melt temperatures of 190–220 °C. The cling skin is normally placed only on the inside of the bag so that the exterior slides over the load during application. Cling force is evaluated by ASTM D5458, and the target is typically 80–150 g/in after stretching, while the non-cling side coefficient of friction is controlled below 0.40 by ASTM D1894. Puncture resistance by ASTM D5748 is specified above 4.0 J for 100 μm film because the load corners and sharp edges of appliance cartons or construction panels concentrate stress during the horizontal and vertical stretching sequence. Tensile elongation by ASTM D882 is generally maintained above 500 % in both machine and transverse directions. The main process conflict is gusseting: if a cling skin is present on both surfaces, the film blocks inside the gusset folds and the bag fails to open on the stretch hood machine. Single-sided cling is therefore the default, and coextruded structures using an outer slip layer are preferred when line speeds exceed 40 loads/h.

When Roll Diameter Exceeds 350 mm in Manual Dispenser Cling Film

Manual dispenser rolls above 350 mm diameter impose a different failure mechanism than pallet stretch film: the roll weight compresses the inner wraps and can cause blocking at the core if the cling skin is too aggressive. Braskem FLEXUS VLDPE Cling is formulated into 6–10 μm cast film for foodservice and cold-chain manual overwrap, with the cling layer thickness reduced to 5–8 % of the total film structure. Unwind force is controlled by balancing the cling layer against a back side that carries a controlled slip package; peel cling by ASTM D5458 is commonly held between 35 g/in and 60 g/in for manual dispensers. The film is converted on cast lines without corona treatment on the cling side, and the rewinder tension is maintained below 12 N/25 mm to prevent roll hardness from inducing blocking. In bakery rack covers and cold-chain pallet consolidation, the terminal product must retain cling at refrigerator temperatures near 4 °C, but the same film should not thermally anneal during ambient storage above 30 °C because increased contact area raises unwind noise and web breakage. This segment is more sensitive to surface migration than thick stretch hoods because the film thickness is low; additives that bloom at 500 ppm or above can dominate the surface within days and reduce tack uniformity.