On cast coextrusion lines producing 60–90 µm high-barrier pouches, SABIC COHERE VLDPE 8102 is incorporated as the sealant web against EVOH or polyamide barrier cores. The base resin is characterised by a density of 0.902 g/cm³ under ASTM D1505 and a melt index of 1.0 g/10 min at 190 °C/2.16 kg under ASTM D1238. The sealant layer, typically 15–30 µm of the total gauge, is coextruded with tie layers derived from maleic anhydride-grafted polyethylene. Seal initiation is evaluated by heat-seal strength per ASTM F88/F88M using a 25 mm flat jaw, 0.5 s dwell, and 0.28 MPa pressure; hot tack is measured per ASTM F1921 on a J&B Hot Tack Tester at 0.20 MPa sealing pressure. The reduced crystallinity of the VLDPE lowers the onset of molecular interdiffusion across the seal interface relative to 0.918 g/cm³ LLDPE, permitting converting lines to reduce sealing temperature or increase cycle speed without changing the barrier structure. Slip and antiblock masterbatches, usually let down at 2–4 wt% of the sealant layer, are required to avoid blocking on rewind; kinetic coefficient of friction is then specified below 0.35 under ISO 8295. Food contact compliance rests on FDA 21 CFR 177.1520(c) olefin polymer provisions and on Commission Regulation (EU) No 10/2011 Annex I authorised substance constraints. After corona treatment at 38–42 mN/m, the sealant surface is suitable for lamination or printing in the converting step. The weak boundary layer risk associated with additive bloom should be checked by wetting tension measurement per ASTM D2578 before adhesive lamination.

How Does BUR Influence Energy-to-Break in Three-Layer Agricultural Silage Film?

Because the quench rate in thick coextruded blown film is governed by bubble diameter and frost-line height, the use of COHERE 8102 as a core layer changes tear and puncture response at blow-up ratios from 2.0:1 to 3.0:1. On heavy-duty sack and silage lines running 80–120 µm film, the grade is blended with LLDPE or HDPE at core-layer loadings of 20–40 wt% to improve low-temperature dart impact without sacrificing bubble stability. Dart impact is measured by ISO 7765-1 Method A or ASTM D1709 Method B; Elmendorf tear is measured in machine and transverse directions per ISO 6383-2. At BUR below 2.0:1, the orientation balance shifts toward the machine direction, producing elongated tear propagation and lower transverse-direction tear resistance; above 2.8:1, the low modulus of the VLDPE phase may destabilise the bubble if the external cooling air ring is not equipped with dual-lip or iris adjustment. The film is processed at melt discharge temperatures of 185–210 °C through a die gap of 1.8–2.2 mm; higher melt temperatures lead to surface tack and blocking at the collapsing frame. Additives for slip and antiblock are required in the skin layers, while the VLDPE core is generally left unmodified to preserve interlayer adhesion. Puncture resistance after film conditioning at 23 ± 2 °C and 50 ± 10 % RH is evaluated with a hemispherical probe under ASTM D5748. Published data for the specific BUR-to-energy-to-break response of this grade in aged silage film is limited; industrial practice relies on dart impact and tear retention after UV exposure rather than isolated tensile yield.

Extrusion Coating Sealant Webs on Foil-Based Laminates

In tandem extrusion coating of 6–12 µm aluminium foil for retort and lidding applications, COHERE 8102 is applied as a 15–25 µm sealable layer. Melt temperature at the die lip is maintained between 280 °C and 310 °C, with air gap 150–250 mm to accelerate oxidative polarisation and adhesion to the aluminium oxide surface. The MFR of 1.0 g/10 min permits drawdown without web neck-in beyond 5 % at line speeds up to 250 m/min when the die-to-roll geometry is optimised. Adhesion to unprimed foil is inspected by peel testing per ASTM F904 on the laminate after two-week storage; cohesive failure in the polymer rather than interfacial delamination confirms adequate anchorage. Sustained melt temperatures above 320 °C should be avoided because gel particles formed by thermo-oxidative crosslinking increase die lip build-up and disrupt coating uniformity. The sealant layer can be formulated with a heat-seal promoter of 5–10 wt% lower-density polyolefin or an ionomer replacement if the laminate must seal through contamination. Retort pouch articles made with this web are tested for seal integrity after thermal processing at 121 °C for 30 min under ASTM F88/F88M. Compliance is supported by FDA 21 CFR 177.1520 and EU Regulation 10/2011 overall migration limits of 10 mg/dm² when tested with simulant D2 for olive oil and retort conditions. In chilled or frozen packaging, the low-temperature flexibility of the VLDPE reduces flex-crack formation at −20 °C, a property monitored by pinholing after Gelbo flex testing per ASTM F392.

When a processor lowers the gauge of cast surface protection film below 30 µm, the deformation resistance of the adhesive-bearing web becomes the limiting factor in high-strain application of the film to brushed stainless steel and anodised aluminium profiles. COHERE 8102 is used as the carrier layer at 80–95 wt% of the coextruded structure, with the remaining balance being a skin of ethylene-vinyl acetate or maleic anhydride-grafted polyethylene for pressure-sensitive adhesive anchorage. The low density of 0.902 g/cm³ reduces tensile stress at yield, allowing the film to conform to embossed surfaces without lifting at radii below 2 mm. Elongation at break is measured on conditioned specimens by ISO 527-3, and the film is typically run at 15–35 m/min on cast film lines with chill roll temperatures of 18–22 °C. Corona treatment of the outer surface to 36–40 mN/m is necessary if the protective film is laminated to a printed carrier or if the film is to be re-reeled after slitting. Blocking is assessed by ISO 11501 for film-to-film friction. Where the film is delivered as a temporary surface protection product, the peel adhesion from SUS304 stainless steel is specified between 1.5 N/25 mm and 5.0 N/25 mm after ageing 24 h at 60 °C, measured by FINAT Test Method FTM 1. A process conflict arises when outer-surface corona treatment exceeds 42 mN/m; excessive oxidation lowers interfacial bonding to the PSA layer during coextrusion and can produce transfer of low-molecular-weight species to the protected substrate after outdoor exposure. In coil-coating applications, the film is removed after 6–12 months; ageing tests therefore include UV exposure per ISO 4892-3 cycle 1 to check that the polymer does not leave haze or residue on the metal surface.

High-Speed Wrapper Throughput Depends on Cast Stretch Film Puncture Resistance

For pallet wrapping at pre-stretch ratios of 200–300 %, the core layer of a three-layer cast stretch film may contain COHERE 8102 at 30–50 wt% blended with LLDPE of 0.918 g/cm³ density to balance holding force and puncture resistance. The low crystallinity of VLDPE increases puncture energy absorption under the corner stress of rectangular loads, as measured by ASTM D5748 probe puncture after stretching to 250 %. Machine-direction force at break is tested per ISO 527-3 on film samples cut at 15 mm width; cling is evaluated on the unwind roll by ASTM D5458. The molten web is chilled on a matte steel roll at 20–25 °C with air gap 10–20 mm from the die. Because the grade has MFR 1.0 g/10 min, it is not used as the cling layer; cling layers are compounded with tackifier and lower molecular weight polyolefins. Potential edge tear on high-speed wrappers is mitigated by blending 10–20 wt% of a higher-density LLDPE or by using a coextruded skin with higher modulus. The process window narrows when core-layer VLDPE content exceeds 60 wt%; the film may develop roll blocking under high winding tension, and blocking is tested with a two-platen method under ISO 11501. Silage wrapping requires a separate film structure with higher opacity and UV stabilisation; in that application, the VLDPE-containing core is loaded with hindered amine light stabilizers and a black masterbatch to maintain tear resistance after field exposure.

When MDO-PE Recyclable Pouches Require a Low-Seal-Initiation VLDPE Web

Mono-material pouch conversion imposes a seal-temperature ceiling below the shrinkage threshold of the oriented polyethylene outer layer. A biaxially oriented MDO-PE outer layer is combined with an inner sealant web of COHERE 8102 to retain film integrity through the sealing step without exceeding that damage threshold. The sealant web, extruded at 20–30 µm, is laminated or adhesive-laminated to the MDO-PE substrate, forming a structure that remains above 90 wt% polyethylene. Seal initiation at the inner web is evaluated by heat-sealing across a range of 90–150 °C on a rotary jaw sealer with 0.5 s dwell; the low seal initiation avoids shrinkage wrinkles in the MDO-PE outer ply during pouch conversion. Tear propagation along the machine direction is assessed by ISO 6383-2; the low-density VLDPE phase arrests tear propagation through the oriented outer layer. Blocking is controlled by adding 3–5 wt% of a slip/antiblock masterbatch to the sealant layer, while keeping the coefficient of friction below 0.30 per ISO 8295 to preserve machinability on vertical form-fill-seal equipment. The use of a low-seal-initiation polymer permits the pouch to enter polyethylene recycling streams when a suitable mono-material barrier coating such as SiOx on the outer layer is present. Published data for the specific recyclability assessment of this grade in CEFLEX-referenced sorting streams is limited beyond laboratory-scale studies. In dry food and frozen food packaging, seal strength after frozen storage at −18 °C for 72 h is verified by ASTM F88/F88M; the sealant web is also checked for flex-crack resistance using ASTM F392 Gelbo cycles to ensure barrier retention through distribution.