Metallocene linear low density polyethylene grade SABIC SUPEER mLLDPE 8115 is converted primarily on blown film and cast film lines where seal initiation temperature, hot tack strength, and dart impact resistance are economically decisive. The resin is typically characterised by a nominal density of 0.915 g/cm³ per ISO 1183-1 and a melt flow rate of 1.0 g/10 min per ISO 1133-1 at 190°C/2.16 kg. The octene comonomer distribution produces a lower seal initiation temperature than C4-LLDPE of similar density, but the same distribution reduces melt strength and requires bubble stabilisation on conventional blown film lines. At ambient relative humidity below 60%, no pre-drying is needed; if pellets are stored in unheated silos and condensation forms on the pellet surface, a hopper dryer at 60°C for 4 h should be used before film extrusion to prevent pinholes. The application scenarios below are separated by converting line configuration and end-use mechanical demand; no single processing window applies across all downstream uses.

Coextruded Produce Flow-Pack Sealant Web and Gas Transmission Control

The sealant layer in a three-layer blown film for modified atmosphere produce packaging is commonly a 70/30 wt% blend of SABIC SUPEER mLLDPE 8115 and a low density polyethylene with melt flow rate between 0.7 g/10 min and 1.2 g/10 min at 190°C/2.16 kg. The structure is distributed as 15 µm outer layer, 20 µm core, and 15 µm inner sealant layer, giving a total thickness of 50 µm. The sealant layer is usually extruded on a single screw with 25:1 L/D, a Maddock mixing section, and a screen pack of 20/40/60 mesh. The die gap is set at 2.0 mm, the blow-up ratio is 2.5:1, and the frost line height is kept at 6 to 8 die diameters. Melt temperature at the die is maintained between 190°C and 210°C to avoid thermal degradation of the anti-fog additive while still eliminating gel formation in the melt.

Label claims for oxygen and water vapour transmission are verified under ASTM D3985 at 23°C and 0% RH and under ASTM F1249 at 38°C and 90% RH. The anti-fog agent is a food-grade sorbitan ester or glycerol monooleate compounded into the sealant layer at 0.5–1.5 wt%. Overdosing above 1.5 wt% can create plate-out on the die lip and reduce surface tension below 36 dyn/cm, which leads to printing ink adhesion loss on the outer web. Anti-fog performance is evaluated by a cold-fog test at 4°C for 24 h and by contact angle measurement per ASTM D5946; the target contact angle after ageing is below 20° on the internal surface. The film must also pass an organoleptic panel for smell and taste because aldehydes and ketones from overheated additive packages can migrate into leafy produce at detectable thresholds below 1 ppb. Coefficient of friction is measured per ISO 8295; the outer layer is controlled to 0.35 or below to maintain horizontal form-fill-seal web tracking. Seal initiation is measured per ASTM F2029 and seal strength per ASTM F88. The terminal package is a flow-wrapped leafy green, prepared salad, or fresh-cut vegetable pack with print on the outer reverse-printed OPP or PET web. Compliance is established under EU 10/2011 with overall migration below 10 mg/dm² per EN 1186-1 and under FDA 21 CFR 177.1520 for olefin polymers. Edge trim reclaim should be limited to 20 wt% because repeated heat history in the sealant layer increases gel particles and reduces seal integrity.

In deep-freeze packaging for IQF vegetables and seafood, the primary mechanical requirement is dart drop impact measured at -18°C per ASTM D1709 Method A. Films that pass ambient dart impact often lose between 40% and 60% of their impact strength when frozen; therefore the frozen-state test is specified before qualification. A typical monofilm or three-layer structure uses 60–70 wt% SABIC SUPEER mLLDPE 8115 and 30–40 wt% LDPE with density 0.918–0.924 g/cm³. The LDPE fraction stabilises the bubble because the mLLDPE melt strength is insufficient to maintain a stable frost line above 8 die diameters without assistance. Conversion conditions include a die gap of 2.3 mm, blow-up ratio 2.8:1, melt temperature 195–215°C, and in-line corona treatment to 38–40 dyn/cm. The heat seal curve at freezer filling temperatures is less relevant than the seal strength after film surface condensation. Condensation can occur when the film moves from a cold storage area to a warmer packaging hall; therefore sealing bars are set to maintain dwell 0.5 s and pressure 2.5 N/mm² to displace moisture at the seal interface. The film’s surface treatment should be applied as a post-cooling treatment rather than pre-cooling to avoid decay below 36 dyn/cm before lamination or printing. Terminal products are frozen vegetable pillow packs, seafood bags, and freezer-ready retail pouches. For fatty food contact, the film is tested with food simulant D2 under EU 10/2011 and FDA 21 CFR 177.1520 condition of use E. Slip agent dosage is deliberately reduced because erucamide bloom is retarded at freezer storage temperatures; surface slip is achieved by the base resin’s low coefficient of friction after corona treatment and by the line’s web path design rather than by post-crystallisation additive migration.

When Low Seal Initiation Replaces C4-LLDPE in Retort-Sensitive Laminates

In adhesive laminates for dry food and liquid detergent stand-up pouches, the sealant web is a 20–30 µm blown or cast film produced from 70–80 wt% SABIC SUPEER mLLDPE 8115 and 20–30 wt% LDPE or ethylene-vinyl acetate with vinyl acetate content below 9 wt%. The web is laminated to PET or metallised PET with a solventless adhesive applied at 1.5–2.0 g/m². Corona treatment at 40 dyn/cm is applied in line before lamination to achieve stable adhesive anchorage. Lamination is performed on a solventless laminator with nip temperature 50°C and secondary curing at 40°C for 24 h. The sealant web should be produced without primary amide slip in the seal layer if the laminate is used for liquid detergent pouches because primary amides can migrate to the PET side and reduce adhesive bond strength. Low seal initiation is critical because high-speed pouch lines operate with seal dwell times below 0.4 s. The seal window is generated per ASTM F2029 with a flat-plate sealer at 300 N pressure and 0.5 s dwell. Seal strength is measured per ASTM F88 on 25 mm strips; hot tack is measured per ASTM F1921. Comparative C8-mLLDPE and C4-LLDPE seal initiation data are available from resin suppliers; the difference is typically 5–10°C. The mLLDPE 8115 layer permits lower jaw temperature and reduces odour formation from adhesive degradation. The terminal structure is not suitable for retort above 121°C; steam pressure at retort temperatures softens the sealant layer and creates delamination at the adhesive interface. Compliance includes EU 10/2011, FDA 21 CFR 177.1520, and REACH SVHC disclosure under Article 33. For food contact, the final laminate must pass EN 1186-1 overall migration and specific migration for primary aromatic amines if a polyurethane adhesive is used. Residual isocyanate in solventless adhesive must stay below 0.5% by mass before lamination; otherwise the free isocyanate can migrate into the sealant layer and reduce sealability after one week of aged roll stock.

What Limits Dart Impact and Tear Propagation in Heavy-Duty Sack Lines?

Heavy-duty sacks for resin pellets, pet food, and construction materials are converted from a three-layer blown film with a core layer of 40 wt% HDPE and 60 wt% SABIC SUPEER mLLDPE 8115. The HDPE raises modulus and reduces creep under stacked load; the mLLDPE contributes dart drop impact per ASTM D1709 Method A and Elmendorf tear propagation resistance per ASTM D1922. Conversion uses a die gap of 2.5 mm, a blow-up ratio of 3.0:1, and melt temperature 200–230°C. Internal bubble cooling is required because the film gauge and low melt strength of the metallocene component produce bubble instability with ambient air cooling alone. A PPA processing aid is dosed at 200–400 ppm to suppress sharkskin on the inner die wall. Melt pressure at the die is held below 350 bar; higher pressure triggers melt fracture and can damage the die gap adjusters. The bubble cooling air temperature is set to 8–12°C with an IBC exhaust volume adjusted to hold frost line height at 4–5 die diameters. Adding HDPE above 50 wt% reduces dart impact below specification; adding mLLDPE above 70 wt% creates sack sidewall creep at warehouse stack temperatures above 40°C. At output rates above 250 kg/h on a 400 mm die, shear-induced melt fracture appears first at the die lip because the metallocene grade has a high shear sensitivity. The terminal sack is slit and bottom-welded, with puncture resistance measured per ASTM D5748 and drop test at 1.2 m for a 25 kg fill at 23°C. Export to the EU requires REACH registration and, if the sack is used to ship recycled electronic components, RoHS Directive 2011/65/EU documentation for lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE. The structure is not intended for direct food contact unless a separate food-grade inner liner is used, because the HDPE core can contain recycled content.

Pallet stretch film lines running at 600–900 m/min require a polyolefin with controlled neck-in and high puncture resistance after pre-stretch. A cast film formulation for machine wrap contains 55–70 wt% SABIC SUPEER mLLDPE 8115, 20–30 wt% C6 LLDPE, and 5–10 wt% LDPE; cling is provided by polyisobutylene at 1–3 wt% in the outer layer. The film is extruded through a flat die with 0.5–0.8 mm die gap, an air gap of 40–60 mm, and a chill roll set at 20–25°C. Edge trim levels remain below 5% because high edge trim re-feed introduces oxidised gel particles that create holes during pre-stretch. Neck-in is measured from deckle to final film width; acceptable neck-in is set by the line’s trim reclaim system, typically below 50 mm per side. The film is produced on a cast line with 7-layer capability but the formulation is usually confined to three functional layers: an outer cling layer, a core for puncture resistance, and an inner release layer. Pre-stretch ratio on machine wrap is normally 200–250%; films that cannot survive this elongation exhibit transverse tears at the pallet corners. The core layer is formulated with 1–2 wt% hydrocarbon resin to increase elastic recovery, but hydrocarbon resin addition above 2 wt% can reduce tear resistance per ASTM D1922 and make edge trim more brittle. Machine-direction elongation is evaluated per ASTM D882, peel cling per ASTM D5458, and puncture resistance per ASTM D5748. The terminal product is a 20–23 µm hand wrap or 25–30 µm machine wrap for pallet stabilisation. Roll blocking can occur if the cling layer exceeds 3 wt% polyisobutylene or if the stored roll temperature exceeds 35°C. The film is not intended for food contact unless the specific formulation is tested under EU 10/2011 because cling agents can raise overall migration in fatty food contact.

Ageing Resistance and Infrared Retention in Multi-Season Greenhouse Covers

Greenhouse and low tunnel covers are manufactured from a three-layer blown film with a total thickness of 150–200 µm. The outer layer contains 70 wt% SABIC SUPEER mLLDPE 8115 and 30 wt% LDPE; the core may include EVA for infrared barrier properties. The metallocene resin improves dart impact and Elmendorf tear strength per ASTM D1709 and ASTM D1922, which reduces splitting during tunnel installation. UV stabilisation uses a hindered amine light stabiliser and a benzophenone UV absorber at combined loading 0.3–0.6 wt%. The HALS and UV absorber are added as a masterbatch at 3–6 wt% depending on carrier resin. If the masterbatch carrier is LDPE, the total LDPE fraction rises and reduces the dart impact contribution of the mLLDPE. Weatherability is evaluated per ISO 4892-2 with xenon arc exposure to 3000 h; the film is then inspected for light transmission per ASTM D1003 and tear propagation after weathering per EN 13206. The film is sampled every 8 h during production for gel count per ASTM D7310; gel particles above 200 µm in the outer layer can nucleate weathering cracks after 1500 h of xenon exposure. Anti-blocking is managed with synthetic silica at 1000–2000 ppm; higher loadings reduce light transmission below the greenhouse requirement of 85% total PAR. Processing uses a die gap of 2.0 mm, blow-up ratio 2.4:1, and melt temperature 190–210°C. The line must be equipped with internal bubble cooling because the high film thickness slows bubble cooling and increases blocking risk. The terminal product is a multi-season greenhouse cover or low tunnel film. Service life is not assessed solely by tensile elongation; the practical limit is film rupture under wind load after 2–3 seasons. The film is not food-contact rated unless separate migration testing is performed.