Japan Polyethylene Corporation supplies HARMOREX mLLDPE NF384A as a metallocene-catalyzed ethylene-α-olefin copolymer intended for film extrusion, particularly sealant webs and lamination films. The grade is classified under ISO 17855-1:2016 as linear low-density polyethylene, and its manufacturer-published typical melt mass-flow rate is 1.0 g/10 min at 190°C/2.16 kg according to ISO 1133-1:2022. Density is reported as 0.920 g/cm³ at 23°C under ISO 1183-1:2019. Those two parameters place NF384A in the low-flow segment of metallocene LLDPE film resins, where melt strength and solid-state toughness are typically favored over low-viscosity draw. The metallocene catalyst architecture yields a narrower molecular weight distribution and more uniform short-chain branching than conventional Ziegler-Natta C4-LLDPE, but the resin remains chemically distinct from ethylene-vinyl acetate copolymers and from plastomers with density below 0.910 g/cm³.

The model designation NF384A should be read as a supplier-specific grade code rather than a standardization committee designation. Procurement specifications should therefore reference both the grade name and the relevant test method designations because the certificate of analysis may list additional lot-specific values such as ash content, gel rating, and additive package level. The product is supplied in pellet form; pellet geometry and bulk density are controlled within supplier internal limits and are not normally specified by converters.

The values in Table 1 are typical values, not batch-certified limits. Film property values are dependent on specimen thickness, cooling rate, and orientation. For example, the dart drop impact value is measured on a 40 µm cast film unless otherwise stated; changing thickness to 25 µm reduces the measured value in a non-linear manner due to thickness-dependent energy absorption. Similarly, tensile properties follow ISO 527-3:2018 for films and are sensitive to draw ratio and test speed. Converters should not use Table 1 as a substitute for a customer-specific specification sheet. Lot-to-lot variability in melt mass-flow rate is commonly held within ±0.2 g/10 min for film grades; converters should verify that the certificate of analysis reports the same test condition and specimen preparation.

Rheological fingerprinting of NF384A can be performed under ISO 11443:2021 with a capillary die of 1 mm diameter and 20 mm length across an apparent shear rate range of 100 s⁻¹ to 10,000 s⁻¹. Because the molecular weight distribution is narrow, the shear-thinning slope is lower than for conventional LLDPE; apparent viscosity remains higher at high shear rates and head pressure does not decrease as rapidly with increasing screw speed. This feature influences screw selection: barrier screws with aggressive Maddock mixers may generate excessive shear heating, and constant-depth metering sections are often preferred.

What Limits Heat-Seal Response in Multi-Layer Lamination Structures?

Seal initiation temperature governs whether a film can maintain cycle speed on vertical form-fill-seal equipment, horizontal flow-wrapping machines, and lamination converters. For NF384A, the narrow melting distribution provided by metallocene catalysis generally produces a lower seal initiation temperature than C4-LLDPE of equivalent density when tested under ASTM F1921-12. The exact setpoint is laminate-specific because printed polyester, oriented nylon, or aluminum foil layers act as thermal resistances between the seal jaw and the sealant layer. A converter may set the seal-bar temperature 10 °C to 15 °C lower than a conventional LLDPE sealant, but the final setting must be established on the target line and validated with peel-strength data under ASTM D1876-08 for laminated films or ISO 527-3:2018 for unsupported film.

Hot-tack strength is the limiting property when film travels through a collapsing chute or gusset former before the seal has cooled. NF384A is evaluated for hot-tack under ASTM F1921-12. The grade is used in liquid detergent refill pouches, heavy-duty food pouches, and medical device overwrap where the seal must support product weight immediately after jaw opening. A documented process failure is intermittent seal creep at the gusset fold when seal-bar temperature is reduced below the onset of crystalline melting or when jaw temperature ripple exceeds ±2 °C. Servo-driven seal jaws with closed-loop proportional-integral-derivative temperature control reduce the occurrence of partial fusion at the seal perimeter.

Published data for this specific configuration is limited; for qualification, a three-factor design of experiments is generally needed because seal initiation temperature, dwell time, and interfacial contamination from lamination primers interact. The recommended starting dwell time for 20 µm sealant layers is 0.3 s to 0.5 s, but dwell must be adjusted for thicker laminates. No single hot-tack value can be extrapolated across all jaw geometries.

On single-screw cast-film lines with 25:1 to 30:1 L/D barrier screws, NF384A is generally processed at melt temperatures between 240 °C and 280 °C. Lower melt temperatures reduce thermal degradation, odor, and extractables, while higher temperatures improve melt homogeneity and reduce un-melted gel propagation. Because the grade has a relatively low melt flow rate, extruder head pressure and drive torque are typically higher than for an equivalent 1.0 g/10 min Ziegler-Natta C4-LLDPE. The observed torque increase on a 90 mm extruder at 250 kg/h is often 5 % to 15 % depending on screw design and temperature profile; this is not a defect but must be accounted for in drive sizing. Fluoropolymer process aid is added at 200 ppm to 500 ppm to postpone sharkskin melt fracture in thin-gauge cast film above 100 m/min line speed.

On blown-film lines, bubble stability is governed by the frost-line height, blow-up ratio, and melt viscosity. NF384A’s low melt flow rate supports higher bubble stability than high-flow mLLDPE grades but increases die pressure. Starting conditions on a 100 mm extruder with a 250 mm die typically include melt temperature above 220 °C, die gap 1.2 mm to 2.0 mm, and blow-up ratio 2.0 to 3.0. The specific frost-line height must be adjusted to avoid crystalline orientation that reduces dart impact and tear propagation resistance. Blown film gauge variation is controlled with automatic air ring systems using non-contact capacitance sensors; manual adjustment is insufficient for thickness tolerance below ±5 % in high-speed production.

Chill-roll temperature on cast film lines should be kept below 30 °C for consistent optical properties, but roll condensation must be avoided. Edge pinning with electrostatic edge pins or air knives is standard for thin-gauge webs to prevent neck-in and preserve flatness. If edge trim is recycled, the addition rate should not exceed 20 % of the virgin feed unless the film’s optical quality and gel rating are revalidated.

When Coextrusion Replaces Monolayer Cast Film at Equivalent Throughput

Coextrusion places NF384A in the sealant layer of three-layer or five-layer films where the core layer is high-density polyethylene or polypropylene. The thermal gap between NF384A and HDPE or PP must be managed in the feedblock and die. If the die temperature is set for the high-melting core, the sealant layer may overheat, increasing odor and extractables; if the die temperature is set for the sealant layer, the core may not melt. A common profile uses a feedblock temperature in the range of 220 °C to 250 °C and a die temperature near 230 °C, but these values depend on the core resin. Mixing of layers at the interface is controlled by matching viscosities at the processing temperature; NF384A’s low melt flow rate is more compatible with high-viscosity HDPE core grades than with high-flow PP grades, so layer viscosity ratios should be checked using capillary rheometry data under ISO 11443:2021.

Layer ratio is commonly 10 % to 20 % sealant by mass, but the optimum depends on heat-seal strength, stiffness, and total film cost. In liquid packaging where the sealant layer is in contact with the product, the layer must be continuous and free of interfacial gels. Coextruded film can be tested for seal strength under ASTM F88/F88M-21 for flexible barrier materials. The sealant layer must also be corona-treated if lamination to polyester or metallized film is required after coextrusion; surface tension is specified in accordance with ISO 8296:2003 or ASTM D2578-17.

Relative property differences between NF384A, conventional C4-LLDPE, and EVA are summarized in Table 2. The table is intended for qualitative orientation only; each comparison is method-dependent and should be verified with the actual films at target thickness.

The comparison with EVA is included because converters often replace EVA sealant layers to improve organoleptics and reduce acetic acid corrosion. NF384A is not a direct drop-in for EVA in low-temperature sealing applications; its seal initiation temperature may be higher than EVA in some configurations, and seal-bar settings must be adjusted. Differences within the HARMOREX family are also method-dependent: higher-flow metallocene grades such as NF484A are generally selected for thin-gauge film at high line speed, while NF384A is preferred for thicker lamination webs and higher hot-tack demands. Published data for this specific configuration is limited, so substitution trials should use side-by-side seal curves and film physicals rather than single-point datasheet values.

Regulatory, Organoleptic, and Storage Considerations

Food-contact compliance for NF384A must be established from the supplier’s lot-specific declaration and the finished packaging migration test. The grade is generally positioned for food contact under FDA 21 CFR 177.1520(c) as an olefin polymer, and under EU Regulation No 10/2011 Annex I when the final article meets overall and specific migration limits. Those statements do not automatically cover all food simulants or conditions of use; for fatty foods, migration testing must be performed on the final laminate, not the resin alone. Organoleptic performance is evaluated under ISO 6658:2017 sensory testing protocols or equivalent user-specific methods, but no universal value exists because odor and taint are matrix-specific.

Storage of the resin should be in dry, shaded conditions at ambient temperature below 50 °C. Prolonged exposure to ultraviolet light accelerates oxidation and gel formation. Polyolefins do not require drying under normal humidity, but condensation from cold storage must be avoided because surface moisture on pellets can create film defects. Injected or extruded film scrap should not be blended at high percentages without checking gel rating and color.

In cast-film production, process deviations are often observed as melt fracture at high shear rates, dimpling on chill rolls, or gauge bands in the machine direction. Melt fracture is controlled by increasing die gap or adding fluoropolymer process aid; dimpling is addressed by raising melt temperature or reducing line speed. In blown-film lines, low bubble stability may appear as oscillating frost line or irregular layflat width; remedies include reducing blow-up ratio or increasing melt temperature. Because NF384A has low melt flow, purging after coextrusion should use a high-flow LLDPE or a commercial purging compound to remove degraded resin from screw flights and die lips. The grade should not be processed at melt temperatures above 300 °C for extended periods, as this promotes oxidation and impairs film appearance. Avoid combination with amine-based additives that can generate color bodies at high processing temperatures; if such additives are required, their use must be verified in a controlled compounding trial.