SCLAIR LLDPE FP120-A is a linear low-density polyethylene film resin produced by a solution polymerization process with a 1-octene comonomer. The material is supplied as a pellet with a nominal density of 0.920 g/cm³ when determined according to ASTM D792 and a nominal melt index of 1.0 g/10 min when measured at 190°C under a 2.16 kg load per ASTM D1238. The resin is intended for blown-film extrusion and is used in monolayer and coextruded structures for heavy-duty packaging, industrial liners, agricultural film, and collation shrink. The stated melt index and density are nominal values; lot-specific certificate-of-analysis data should be obtained before production planning.

SCLAIR is a registered trademark of Nova Chemicals Corporation. The alphanumeric designation FP120-A identifies the film-extrusion series and the additive package; the full comonomer content is a production-controlled parameter that is not typically disclosed in public datasheets. The 1-octene short-chain branches result in a narrower short-chain-branch distribution than many conventional Ziegler-Natta butene-based LLDPE grades. The molecular architecture is substantially linear, although the solution process may introduce a low level of long-chain branching, but not enough to match the melt tension of a high-pressure LDPE. This structural difference has practical consequences in extrusion: the melt is less shear-thinning than an LDPE of similar melt index, and the processing window is governed by melt pressure, melt temperature, and die-lip shear stress rather than by melt fracture limits alone.

In comparison with a butene-based LLDPE of equal density and melt index, SCLAIR LLDPE FP120-A generally provides higher dart impact when measured under ASTM D1709 and higher Elmendorf tear resistance when measured under ASTM D1922. The absolute improvement is not a fixed ratio; it depends on film gauge, blow-up ratio, frost line height, and the amount of high-pressure LDPE present. The product is therefore not a direct drop-in where the process was optimized around the brittleness or tear pattern of a butene grade. Published data for the exact property increment in a specific multi-layer structure is limited, and line trials remain the reliable method for confirming a replacement.

Compared with a linear-medium-density polyethylene, FP120-A has a lower density and therefore lower modulus and lower yield stress under ASTM D882. Compared with a high-pressure LDPE, it has higher elongation at break and higher puncture resistance. Compared with a propylene-based film resin, the polyethylene has a lower melting point and better low-temperature impact toughness, which is suitable for packaging stored below 0°C. A butene grade may remain preferable when very high machine-direction tear strength is critical and gauge reduction is not required. Material selection must be based on testing, not on general family-level comparisons.

Does a narrow molecular-weight distribution reduce the extrusion melt-pressure ceiling in FP120-A?

It reduces shear thinning, which raises the melt-pressure sensitivity to screw speed. On a 75 mm single-screw blown-film extruder with an L/D of 24:1 to 30:1, the material typically reaches the pressure limit of the downstream screen pack and spiral mandrel die earlier than an LDPE of comparable melt index. The melt pressure should be measured at the breaker plate and maintained below the equipment manufacturer’s maximum rating, commonly 35 MPa to 45 MPa depending on the die body and clamp design. If a grooved-feed bushing is used, the feed-section temperature must be held between 50°C and 70°C; higher feed-zone temperatures can cause premature melting, which reduces the friction-induced conveying capacity of the grooves and destabilizes hopper feed.

Barrel temperatures should be profiled from 160°C in the feed zone to 210°C in the metering zone. Adapter and die zones are typically set at 210°C to 230°C. The melt temperature measured directly at the die should remain between 215°C and 240°C for a residence time of 2 min to 4 min. If the melt temperature exceeds 250°C, oxidative chain scission and crosslinking can generate gels that appear as pinhole-sized defects in film below 50 µm. The upper temperature boundary is therefore defined not only by the polymer melting point but also by the stabiliser package and the available oxygen in the screw and die zones.

The die gap should normally be set between 1.5 mm and 2.5 mm. Reducing the die gap below 1.0 mm can increase die-lip shear stress beyond the critical level for sharkskin melt fracture. On a typical spiral mandrel die, sharkskin onset is observed at linear output rates above approximately 1.8 kg/h per millimetre of die circumference, but this value is a starting-point estimate that must be verified for the specific die geometry, die temperature, and screen-pack condition. A fluoropolymer processing aid masterbatch may be used to delay melt fracture, but it can also affect surface energy and seal performance if over-dosed.

Bubble stability is usually optimized when the frost line height is maintained between 6 and 10 die diameters and the blow-up ratio is kept between 2.0:1 and 3.0:1. Orientation-induced property imbalances are evaluated from Elmendorf tear ratios under ASTM D1922. A blow-up ratio near 2.5:1 often produces a more balanced machine-direction and transverse-direction tear profile for industrial sack film, but the actual optimum depends on die diameter, air-ring design, and ambient air temperature.

For larger lines with die diameters from 250 mm to 400 mm, the same melt-pressure and melt-temperature constraints apply, but the specific output per die circumference may be lower because of differences in bubble cooling capacity and heat removal. A high-output line with internal bubble cooling may require a lower blow-up ratio or a higher frost line to avoid bubble sag. The grade can be run on high-output lines, but the screw must deliver sufficient dispersive mixing; if the screw is worn, pressure fluctuations and melt-temperature variation increase. Pressure fluctuation at the breaker plate should remain below ±0.5 MPa; larger fluctuations indicate irregular feed, worn flights, or screen-pack blinding.

In coextruded films, SCLAIR LLDPE FP120-A can be used in the core or sealant layer. In a three-layer sack structure with an outer layer of high-pressure LDPE, the core layer contributes toughness and puncture resistance. The layer distribution should be determined by the end-use requirement; a common starting point is an outer LDPE layer of 15% to 20% of the total thickness, a core layer of 50% to 60%, and a sealant layer composed of the same LLDPE or a lower-density metallocene polyethylene. Interface stability in coextrusion depends on the viscosity ratio of the layers; at die-lip shear rates, the viscosity of SCLAIR LLDPE FP120-A is lower than some high-molecular-weight HDPE layers but higher than many LDPE materials. This viscosity balance can be adjusted by changing the melt temperature of the individual extruders. Interfacial adhesion is then evaluated with a peel test under ASTM F88 after film production.

When replacing a butene-grade LLDPE in heavy-duty liner specifications

Replacement should begin with a seal-curve evaluation rather than a simple melt-index comparison. SCLAIR LLDPE FP120-A contains a higher alpha-olefin comonomer, which broadens the melting endotherm on a differential scanning calorimetry trace run under ASTM D3418. The heat-seal initiation temperature is generally lower than that of a butene-based LLDPE of identical density, but the magnitude of the shift is affected by film cooling rate, thickness, and the presence of surface antiblock and slip additives. A heat-seal map should be generated on the actual production film; seal strength is measured under ASTM F88 using jaw pressure of 0.2 MPa and dwell time of 0.5 s over a temperature range of 115°C to 140°C.

In heavy-duty liners, the higher dart impact under ASTM D1709 can support a gauge reduction from 100 µm to 80 µm in some monolayer structures, but the revised structure must also pass tear-propagation resistance under ASTM D1922 and puncture resistance under ASTM D5748 or the specific end-user protocol. Gauge reduction should not be implemented from data-sheet values alone because the service failure mode includes folding, filling, and drop loading. When a converter adds reprocessed edge trim, the addition level should be limited; a typical maximum is 20% by weight for heavy-duty film, but higher levels may be acceptable if the trim is clean, dry, and not degraded. The physical properties of the final blend should be retested at each trim addition level.

If the existing extruder runs near maximum motor amperage, the narrow-molecular-weight-distribution resin may require a reduction in screw speed of 5% to 10% relative to a broad-MWD butene grade at the same die size. In some cases, changing the screen pack from a 100-mesh to an 80-mesh pack lowers backpressure and offsets motor load, but filtration efficiency is reduced. The decision should be based on the acceptable gel level in the final film and the historical contamination level of the regrind stream.

Blown Film Surface Quality and Screw Design Considerations

Die-lip build-up is the primary surface-defect generator in long-run production of SCLAIR LLDPE FP120-A. The standard stabiliser package does not eliminate die-lip deposition when melt temperature is excessive or when the die lip is worn. A chrome-plated spiral mandrel die with a fixed or rotating die assembly is typical. Surface defects are evaluated visually and, when quantitative data are required, by film haze measurements under ASTM D1003 and gloss measurements under ASTM D2457. A sudden increase in haze or a decline in gloss often precedes visible die-lip deposits on the heater bands.

The screw should provide both dispersive and distributive mixing for masterbatch incorporation. A barrier screw with a Maddock mixer section or a comparable dispersive element is common on extruders with diameters from 75 mm to 120 mm. The screw should be checked for wear at the flight land and the mixing section; a worn screw can produce high-temperature shear zones and increase the melt-temperature variation. The melt-temperature variation measured at the die should remain within ±2°C on a stable production line. Larger variation indicates poor mixing or non-uniform temperature control.

Surface friction is not an inherent fixed property of the resin. If the application requires a low coefficient of friction, the converter should add a slip or antiblock masterbatch and verify the coefficient of friction under ASTM D1894. Over-dosing of slip additives can cause seal contamination and reduce seal strength; the effect should be checked on the heat-seal curve. Oil-based processing aids and certain antistatic agents can migrate to the film surface and interfere with lamination adhesion. When such additives are required, adhesion should be evaluated with a peel test under ASTM F88 or the applicable laminating protocol.

Melt temperature and residence time define the upper oxidative boundary.

Thermal degradation in the extruder is primarily oxidative at normal processing temperatures. The stabiliser package is designed for conventional extrusion, but the resin should not be held at melt temperature for prolonged shutdown periods. If a line stops while filled, the melt should not remain above 200°C for more than 10 min; longer hold times increase the risk of gel formation and discoloration. Purging with a lower-melt-temperature polyethylene is required when the machine is shut down or when transitioning to a different polymer. For frequent product changes, the resin can be purged with high-pressure LDPE, but the purging material should be compatible with the subsequent film product.

Repeated extrusion of the same film edge trim should be controlled to limit the buildup of oxidized material. In film production, edge trim is often ground and returned to the extruder at a ratio of 5% to 20%. Each heat history consumes some of the antioxidant; at high trim levels, the final film may show lower dart impact or more gels. The level of regrind should be validated by testing the final film under ASTM D1709 and ASTM D1922. If the process uses a high level of regrind, additional antioxidant masterbatch may be necessary, but the addition must be evaluated for migration and food-contact compliance.

The product is evaluated for food-contact use within the olefin polymer category. For the United States, FDA 21 CFR §177.1520 applies to olefin polymers used in food contact, provided the final article meets the specified extractives and end-use limitations. For European Union applications, the final article must comply with Commission Regulation EU No 10/2011; the overall migration limit and specific migration limits depend on the complete formulation, including the base resin, masterbatches, and processing aids. The supplier can provide a compliance certificate for the base resin, but the converter is responsible for final-article compliance.

Storage should be in a dry indoor area at temperatures below 50°C and away from direct sunlight. Although polyethylene is not hygroscopic, condensation can occur when cold pellets are moved into a warm humidity-controlled building; surface moisture then produces streaks and bubbles in thin-gauge film. If condensation is suspected, the pellets can be dried with hot air at 70°C to 80°C for 1 h to 2 h. The resin should not be exposed to strong oxidizing agents, chlorinated solvents, or prolonged high-temperature storage, as these conditions can consume the stabiliser package or extract polymers and additives. No additional pre-drying is required for normal indoor storage; the use of a desiccant is not required for a polyolefin.

The product has operational boundaries in extrusion and conversion. It is not recommended for injection molding or rotational molding because the molecular architecture and stabiliser package are designed for film-grade shear and thermal history. For blown-film applications requiring very high melt strength, blending with LDPE or selecting a higher-melt-strength resin is preferred. Published data for the exact performance of SCLAIR LLDPE FP120-A in every coextruded structure is limited; therefore, validation on the intended line remains necessary before commercial specifications are fixed.