Relene LLDPE F18010 is a butene-1-based linear low-density polyethylene resin produced by Reliance Industries Limited for primary use in blown film extrusion. The grade is specified with a nominal melt flow index of 1.0 g/10 min measured under 2.16 kg load at 190 °C by ASTM D1238 or ISO 1133-1, and a nominal density of 0.918 g/cm³ determined by ASTM D1505 or ISO 1183-1. The polymer chain incorporates butene-1 as the short-chain branching comonomer, distinguishing it from hexene- and octene-based linear polyethylene grades. As a conventional Ziegler-Natta resin, F18010 presents a broader molecular weight and comonomer distribution than metallocene-catalyzed linear low-density polyethylene, a feature that affects seal performance, optical haze, and extrusion pressure. Typical applications include heavy-duty sacks, industrial liners, carrier bag film, agricultural silage wrap, and coextruded sealant layers. The material is supplied as stabilized pellets and is not designed for injection molding or rotational molding service.

What Limits Stable Bubble Geometry in High-BUR Butene LLDPE Extrusion?

Stable bubble geometry on conventional blown film lines is governed by the interaction of melt temperature, die gap, blow-up ratio, and frost-line position. In production runs on a 75 mm single-screw extruder with 30:1 L/D and a 200 mm die, the recommended melt temperature for Relene LLDPE F18010 is held between 190 °C and 220 °C. At setpoints below 185 °C, viscosity rise increases melt pressure at the die and can produce sharkskin on the outer film surface; the onset is visible as fine transverse ridges under 20× surface microscopy. At setpoints above 230 °C, bubble sag and adhesion become measurable in runs exceeding 2 h, while the retained dart impact under ASTM D1709 may decline because of oxidative chain scission. The die gap is typically set at 0.8 mm to 1.5 mm; a wider gap lowers shear rate and melt fracture tendency but reduces the machine-direction tear resistance as measured by ASTM D1922. Blow-up ratios between 2.0:1 and 2.8:1 are commonly used. Above 3.0:1, the lower melt strength of butene LLDPE relative to LDPE allows oscillation, especially when the frost-line height is raised above 8 die diameters without changing air ring volume. Internal bubble cooling stabilizes the bubble if frost-line height is lowered rather than compensating with extra melt temperature. These boundaries are narrow; a setpoint change of ±5 °C at 200 °C can shift the bubble diameter and produce gauge bands in the collapsed film.

Against an autoclave LDPE of 0.923 g/cm³ density and equivalent melt flow index, Relene LLDPE F18010 shows higher tensile yield stress and higher dart impact strength at equal thickness when tested under ASTM D882 and ASTM D1709, respectively. The same comparison also shows lower draw-down and lower bubble stability because long-chain branching in LDPE contributes strain hardening. Against a high-density polyethylene of 0.950 g/cm³ density, F18010 provides lower secant modulus and higher elongation at break under ASTM D882. Converters selecting it for industrial liners accept the stiffness reduction to obtain puncture resistance and fold-crack resistance under ASTM D1709 and ASTM F1306. Differences from a hexene-based LLDPE with 0.920 g/cm³ density and 0.5 g/10 min MFI are concentrated in dart impact and hot-tack; the hexene grade can retain higher toughness after downgauging, while F18010 operates at lower head pressure and permits faster start-up on lines with modest drive capacity.

When F18010 Replaces a Fractional-Melt Hexene Grade in Stretch Film Structures

Replacement of a fractional-melt hexene LLDPE in stretch film or heavy-duty sack layers with Relene LLDPE F18010 is evaluated through film tear, dart impact, and stretch force measurements rather than resin density alone. In cast stretch film, F18010 is not the primary resin because its 1.0 g/10 min MFI is high for cling performance; in blown stretch film, it can serve as a core layer. The higher MFI lowers viscosity and reduces extruder motor load on a 65 mm extruder at 180–200 °C compared with a 0.5 g/10 min hexene resin. However, the butene comonomer reduces the homogeneous tie-chain population relative to hexene or octene, so film elongation at break under ASTM D882 may be lower when the film is drawn beyond 400 %. Seal initiation temperature, measured by ASTM F2029, is typically higher than a metallocene linear low-density polyethylene but lower than an HDPE sealant layer. The practical boundary for substitution is determined by the film’s required dart impact under ASTM D1709; if the target exceeds the value attainable with F18010 at a given gauge, a hexene or octene linear resin is retained. Published comparative data for F18010 in stretch film structures is limited, so field evaluation on the converter’s line is required before substitution.

In heavy-duty sack sealant layers, F18010 is used at thicknesses from 10 µm to 40 µm with a total sack structure typically between 80 µm and 150 µm. Seal strength is evaluated according to ASTM F88 after sealing at 115 °C to 145 °C bar temperature; the exact plateau depends on dwell time and jaw pressure. Hot-tack tests under ASTM F1921 are used to verify that the seal can hold the weight of filled product before the weld has cooled. On a three-layer line, placing F18010 in the inner layer and HDPE in the outer layers provides creep resistance from the HDPE and toughness from the LLDPE core. The selection of F18010 over a hexene LLDPE in this structure is generally based on cost per kilogram and acceptable downgauging, not on maximum toughness. Slip and antiblock additives, when required, are added through masterbatch at 1–2 wt%; the coefficient of friction is measured under ISO 8295.

Melt Pressure Instability Appears Outside the 190–220 °C Setpoint Band

Extruder records from blown film lines indicate that melt pressure fluctuation for Relene LLDPE F18010 becomes measurable when barrel setpoints fall below 190 °C or when screw speed exceeds 90 rpm on a 75 mm extruder with 30:1 L/D. A pressure transducer positioned before the screen changer shows amplitude of 5–15 bar under such conditions, linked to solids-bed breakup in the compression zone. Raising the feedthroat temperature from 30 °C to 45 °C and increasing the first barrel zone to 190 °C reduces the fluctuation amplitude to below 5 bar. At the upper boundary, maintaining die zones at 220 °C or lower limits gel generation; teardown after 24 h continuous operation at 230 °C has shown oxidised deposits at the die lip. Batch-to-batch variation in melt flow index of ±0.1 g/10 min around nominal 1.0 g/10 min is typically within standard buying specification, but it can shift the ideal temperature setpoint by 3–5 °C when gauge uniformity below 5 % is required. Because the resin’s melt tension is lower than LDPE, the bubble cannot support large frost-line height changes; frost-line position should be controlled within ±1 die diameter for consistent transverse direction gauge.

Relene LLDPE F18010 appears in three-layer agricultural film structures at total gauges from 30 µm to 80 µm. In silage wrap and mulch films, the resin is used as a core layer or as a blend partner with LDPE to improve puncture resistance under ASTM F1306. For UV-stabilized exposed film, carbon black masterbatch is added at 2–4 wt% or a hindered amine light stabilizer system is compounded as a single-layer concentrate; the resulting film retention of tensile elongation after accelerated weathering under ISO 4892-2 is controlled mainly by the stabilizer package, not by the base resin. Published data for F18010 specifically in carbon-black-loaded or UV-stabilized agricultural film is limited, so target lifetimes require outdoor and accelerated testing on the converter’s final film formulation. In non-exposed layers, the resin’s low density of 0.918 g/cm³ provides conformability around stored fodder without excessive stiffness.

Regulatory Documentation and Food-Contact Verification

Polyethylene film converters are responsible for validating that the finished package, including any masterbatch, ink, or adhesive, complies with the relevant food-contact and chemical regulations. For Relene LLDPE F18010, supplier documentation should confirm that the base resin is manufactured to permit compliance with FDA 21 CFR 177.1520 for olefin polymers, and that supporting documentation under Commission Regulation (EU) 10/2011 is available for European food-contact use. The table below identifies the primary verification areas and the associated standards or regulations. No single certificate covers the converted film because lamination, solvent residues, and migration from additives require separate assessment.

Coextruded lamination and barrier film structures use F18010 as a low-density toughness layer beneath a barrier layer of ethylene vinyl alcohol or polyamide. The adhesive layers are typically maleic anhydride-grafted polyolefins; F18010 is placed in the sealant or outer abuse layer. The film’s contribution to total structure tear strength is measured under ASTM D1922, and the lamination bond strength is measured under ASTM F88 or ASTM F904. Because F18010 contains only standard stabilization and no reactive adhesion promoter, it cannot replace tie resins; direct contact between F18010 and EVOH without an adhesive layer results in delamination under ASTM F904 below typical target values. In this end use, the selection criterion is the balance between the low density of 0.918 g/cm³ and the melt flow index of 1.0 g/10 min, which supports the required sealant flow during high-speed pouch converting. No further processing recommendation is required beyond confirming adhesion after lamination.