ExxonMobil Exceed mLLDPE 2018MA is a metallocene-catalysed linear low-density polyethylene resin supplied in pellet form for blown film extrusion. The grade designation identifies a nominal density of 0.918 g/cm³ when measured under ASTM D1505 or ISO 1183-1:2019, and a nominal melt index of 1.0 g/10 min when measured under ASTM D1238 or ISO 1133-1:2022 at 190°C under a 2.16 kg load. The “MA” suffix refers to a medium-antiblock additive package; exact slip and antiblock loadings are stated on the certificate of analysis. The metallocene catalyst architecture produces a narrower molecular weight distribution and more uniform short-chain branching distribution than conventional Ziegler-Natta products at equivalent density and melt index. These structural features affect film toughness, optics, seal response and extrusion rheology. The grade is normally considered for monolayer and coextruded packaging films in which low seal initiation and high dart impact are required at thicknesses from 20 µm to 80 µm.

What Distinguishes 2018MA from Conventional Ziegler-Natta Butene-Based Film Resins?

At equal density, conventional butene-based Ziegler-Natta LLDPE concentrates comonomer in the lower-molecular-weight fraction, creating a broad composition distribution and a tendency toward higher extractables, higher haze and higher seal initiation. The metallocene architecture of Exceed 2018MA narrows the comonomer distribution; the resulting film property profile is reflected in standard tests. Dart drop impact under ASTM D1709 is typically higher for the metallocene resin at 25 µm thickness; Elmendorf tear under ASTM D1922 shows a more balanced machine-direction/transverse-direction relationship; and heat-seal initiation measured under ASTM F88 shifts to lower platen temperature for a defined seal strength. Haze measured under ASTM D1003 is generally lower because the uniform short-chain branching distribution reduces crystal-boundary light scattering. The same narrow distribution, however, reduces melt elasticity and increases high-shear viscosity relative to a broad-distribution Ziegler-Natta grade; this combination alters die pressure and bubble stability. Converters cannot assume identical extrusion settings when switching from a conventional butene-based LLDPE to 2018MA. Within the Exceed family, the base resin properties remain tied to the 0.918 g/cm³ density and 1.0 g/10 min melt index class, but suffix changes such as HA or CA represent different surface-additive packages rather than changes in the base polymer architecture. Compared with high-pressure LDPE, 2018MA has lower melt strength; compared with high-melt-index Exceed grades, it has greater melt viscosity and generates higher extruder head pressure at a given screw speed.

A qualitative comparison of film attributes is summarised below.

In blown film processing on a single-screw extruder with a 24:1–30:1 L/D barrier screw and a 150 mm–400 mm die, the melt temperature is usually maintained between 180°C and 220°C. The upper boundary is based on oxidative stability over residence time; prolonged operation above 220°C can increase gel formation, while operation below 180°C can elevate melt pressure and motor load. Die-gap selection is a critical process variable for this mLLDPE. A gap in the range 1.5 mm–2.5 mm is commonly used to reduce die land shear stress and avoid sharkskin. Die gaps of 0.8 mm–1.0 mm may be acceptable for low-output pilot lines but can initiate surface melt fracture at commercial outputs. Because the resin has a narrower molecular weight distribution than LDPE, the shear viscosity at high die-land shear rates is relatively high, and head pressure rises more steeply with screw speed. A melt pressure transducer located before the screen pack is recommended; the maximum allowable pressure is specified by the extruder manufacturer and must not be exceeded. Bubble stabilisation usually requires a dual-lip air ring and internal bubble cooling once output exceeds about 0.8 kg/h per cm of die circumference; below this output a single-lip air ring may be adequate. The frost line height should be increased moderately compared with LDPE to compensate for lower melt strength, but excessive frost line height can reduce film clarity and increase blocking tendency. Pre-drying is not required if the pellet surface is dry. If condensation has formed during storage above 60% relative humidity, drying at 70°C for 2 h in a desiccant hopper dryer prevents bubble surface defects. Edge trim reclaim can be added at levels up to 30% if the reclaim has not undergone excessive heat history; any change in reclaim ratio requires retesting of dart impact under ASTM D1709 and tear under ASTM D1922.

When 2018MA Is Selected for Low-Temperature Sealant Layers in Coextruded Film

Low seal initiation is a primary technical driver for using mLLDPE in coextruded sealant layers. In a three-layer polyethylene film, the sealant layer is often specified at 10 µm–20 µm within a total thickness of 50 µm–100 µm. The density of 0.918 g/cm³ reduces the melting peak relative to medium-density sealants, while the comonomer uniformity of the metallocene resin narrows the melting range and can lower the seal temperature required to reach 2.0 N/25 mm seal strength under ASTM F88. Hot tack performance is not an automatic consequence of low seal initiation; hot tack must be measured under ASTM F1921 on the specific packaging structure. The melt index of 1.0 g/10 min provides sufficient flow to wet the seal bar without the excessive melt flow that can cause seal thinning at high temperatures. For vertical form-fill-seal applications, jaw release and package surface slip depend on the additive package in the sealant skin and the overall film formula; the medium-antiblock package in 2018MA is designed to address blocking but may require additional slip for high-speed packaging. Published data for this specific configuration are limited, so seal initiation and hot tack should be confirmed on the target coextrusion line. If the sealant layer is intended for direct food contact, the final film must meet the end-use conditions of FDA 21 CFR 177.1520(c) and the migration limits of Commission Regulation (EU) No 10/2011, including any applicable simulant and time/temperature condition. Use of flame treatment or corona treatment on the sealant layer is not recommended unless the treatment is applied to an outer layer and the sealant surface is protected, because oxidation of the sealant reduces seal strength.

Compared with enhanced melt strength Enable mLLDPE resins, 2018MA is not specifically designed for high-stalk bubble geometry. High-stalk extrusion of mLLDPE with conventional narrow molecular weight distribution can create bubble instability and high gauge variation; Enable grades use a modified macromolecular architecture to increase extensional hardening. If a processor requires a high-stalk film line for high stiffness or high throughput, a direct evaluation of 2018MA against an Enable grade should be made under the same die, blow-up ratio, frost line height and output. No single data sheet value can substitute for this comparison because bubble stability is influenced by melt elongation behaviour that is not captured by melt index or density alone.

The “MA” additive package includes an inorganic antiblock that increases surface roughness at the film face, reducing blocking. Because antiblock concentrates in the film surface layers after extrusion, its efficiency depends on melt temperature and die gap; at melt temperatures below 180°C, dispersion may be incomplete on single-screw lines without mixing elements. Slip additives, if used, migrate to the surface gradually over 24 h–72 h after extrusion; coefficient of friction measured under ASTM D1894 should be evaluated after storage under controlled temperature and humidity. Pellet storage should be in a dry area below 50°C to prevent additive bloom and pellet agglomeration. The resin is not hygroscopic, but surface condensation on cold pellets introduced to a warm processing area can create voids in the film; pellets should be allowed to reach ambient temperature before hopper loading or be dried as described.

Blown Film Melt Fracture Thresholds and Die Gap Adjustments

Melt fracture in metallocene LLDPE initially appears as small-scale surface roughness, often called sharkskin, perpendicular to the machine direction on the bubble surface. In 2018MA the onset is governed by die land shear stress rather than total extruder throughput. If sharkskin occurs, the first correction is to increase the die gap from 0.8 mm or 1.0 mm to 1.5 mm or above; this reduces apparent shear rate at constant output. A second correction is to raise the die lip temperature by 5°C–10°C on both lips simultaneously to reduce wall viscosity. Heating only the outer lip can create asymmetric surface stresses and lower film impact performance. The use of a fluorine-containing polymer processing aid is a further alternative; processing aids coat the die lip and reduce melt fracture, but their use must remain within food-contact restrictions under FDA 21 CFR 177.1520 and EU 10/2011. Published melt fracture curves for this specific grade are limited, so the safe maximum output for a given die gap must be established on the production line. If bubble instability occurs after widening the die gap, the appropriate adjustment is not to reverse the die gap change but to modify the internal bubble cooling airflow, the lower nip speed, or the blow-up ratio. A blow-up ratio between 2.0 and 2.5 is commonly used for polyethylene film, but the exact ratio is dependent on final film tear balance under ASTM D1922. At high back pressures, screen pack and breaker plate design should be examined; a continuous screen changer reduces pressure excursions during screen changes.

In extrusion coating or cast film, the melt index of 1.0 g/10 min is lower than typical extrusion-coating resins; therefore 2018MA is not generally selected as the sole extrusion-coating grade. In cast film, a melt index above 3.0 g/10 min is often preferred for drawdown and motor load reduction. When 2018MA is used in a cast film blend, the blend must be tested for neck-in under a defined coat-polymer line speed; neck-in is higher for narrow molecular weight distribution resins than for LDPE. For lamination films, adhesion to substrates is system-dependent; corona treatment of the polyethylene surface to a dyne level between 38 dyn/cm and 42 dyn/cm measured under ASTM D2578 is typical, but storage time and slip migration reduce surface energy. Published data for this specific configuration are limited.

Routine characterisation of 2018MA includes melt flow rate under ASTM D1238 or ISO 1133-1:2022, density under ASTM D1505 or ISO 1183-1:2019, and film tests including dart drop under ASTM D1709, Elmendorf tear under ASTM D1922, tensile properties under ASTM D882, haze under ASTM D1003, and coefficient of friction under ASTM D1894. The regulatory boundary is defined by the final packaging article rather than the resin alone. For food-contact use, US requirements reference FDA 21 CFR 177.1520(c) and the associated conditions of use; European requirements reference Commission Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm² and specific migration limits for listed substances. REACH registration under Regulation (EC) No 1907/2006 is documented in the safety data sheet. RoHS compliance under Directive 2011/65/EU applies only to electrical and electronic equipment packaging; the resin is not classified as containing restricted substances above applicable thresholds. For outdoor film, the grade requires an additional UV stabiliser package; exposure life must be tested under ASTM D3826 or ISO 4892-2. The resin is not formulated as a flame-retardant material and should not be used where fire safety standards require a specified oxygen index or low smoke performance.

A compliance checklist is provided below.