For blown-film converters specifying a metallocene-catalysed linear low-density polyethylene with a density of 0.912 g/cm³ and a melt index of 0.85 g/10 min, Dow ELITE AT mLLDPE AT 6410 is supplied as an ethylene-octene copolymer produced by a solution process. The base resin specification is measured under ASTM D792 and ASTM D1238, the latter using a 2.16 kg load at 190°C. The product belongs to the manufacturer’s advanced-technology metallocene family and is configured primarily for air-cooled and internal-bubble-cooled blown-film lines rather than cast-film or injection-moulding equipment. Converters select this grade where film structures require a dart drop impact of ≥850 g at 25 µm following ASTM D1709A, low seal-initiation temperature, and a balance of longitudinal and transverse tear properties. The octene comonomer and narrow molecular weight distribution distinguish the material from conventional Ziegler-Natta butene LLDPE grades of similar density.

What Resin Properties Define the AT 6410 Specification?

The manufacturer’s published technical data list the following resin properties.

The density of 0.912 g/cm³ is lower than the 0.916 g/cm³ to 0.922 g/cm³ range common for general-purpose LLDPE film grades. The melt index of 0.85 g/10 min is lower than the 1.0 g/10 min typical of many commodity film grades, which increases shear viscosity and bubble stability but raises extruder motor load at fixed screw speed. The melting point near 122°C and Vicat softening point near 98°C indicate a narrow comonomer distribution rather than the broader melting range of heterogeneous Ziegler-Natta copolymers. This narrow distribution contributes to lower seal initiation and lower haze, but the exact values are film-structure dependent and should be measured using ASTM F88/F88M and ASTM D1003 on the finished blown film.

Because the octene comonomer introduces C6 short-chain branches, the resin creates a more uniform short-chain branching distribution than butene-based LLDPE. In conventional butene LLDPE, the C2 branches of butene are less effective at forming tie molecules at equivalent crystallinity; this is one reason the metallocene octene resin delivers higher dart impact at equal density and film thickness. The narrow molecular weight distribution from metallocene catalysis narrows the melting range and reduces the level of high-molecular-weight gel-like species. Haze values below 8% at 25 µm are achievable under ASTM D1003 when the die build-up and frost-line height are controlled. The trade-off is a lower melt strength than high-pressure LDPE and a smaller stable processing window in high-stalk bubble operations.

Processing Window on Grooved-Feed Blown-Film Lines

On a 55 mm grooved-feed single-screw extruder with a 30:1 L/D barrier screw and a 150 mm spiral mandrel die, the resin is processed with a flat or reverse temperature profile from 180°C to 220°C at the die exit. The recommended die gap is 1.5 mm to 2.5 mm, and the blow-up ratio is maintained between 2.0:1 and 3.0:1. A frost-line height of 6 to 8 die diameters is typically used. Above 8 die diameters, the bubble becomes laterally unstable because the metallocene resin has a lower melt strength than high-pressure LDPE; below 5 die diameters, the film surface becomes sticky and the transverse-direction tear balance shifts. For thicknesses below 15 µm, internal bubble cooling or a dual-lip venturi air ring is required to hold gauge variation within ±8%. Melt temperature excursions above 240°C increase gel formation and lot-to-lot viscosity variation; excursions below 180°C raise motor load and may exceed the screw’s maximum torque on high-output extensions.

Incoming resin lot testing for film lines typically includes density by ASTM D792, melt index by ASTM D1238, and melting temperature by ASTM D3418. Lot-to-lot variation in melt index should be monitored to ±5% of the certificate of analysis value when the resin is used on high-speed lines, because viscosity changes alter screw torque and die pressure. Off-line rheometry using a capillary rheometer at 190°C and shear rates from 100 s⁻¹ to 1000 s⁻¹ can segregate lots for problematic film lines. The melt index ratio between 10 kg and 2.16 kg loads is typically used as a relative indicator of molecular weight distribution.

For heavy-duty sacks, the resin is compounded with slip and antiblock additives at the converter, typically 500 ppm to 1500 ppm erucamide and 1000 ppm to 3000 ppm silica. These additive loadings are influenced by the low starting coefficient of friction of the metallocene resin and must not exceed the level that causes plate-out on the collapsing frame. Antiblocking performance is assessed by blocking force under ASTM D3354. In five-layer coextrusion lines, AT 6410 is placed in the core or tie layers to contribute dart impact while maintaining drawdown. The skins are typically high-density polyethylene or LDPE. Layer distribution is maintained using gravimetric hopper feeders with ±0.2% mass accuracy to reduce lot-to-lot variation. Package testing then includes heat-seal strength by ASTM F88/F88M, hot-tack by ASTM F1921, and drop impact by ASTM D5276 on the converted sack.

When AT 6410 Replaces High-Pressure LDPE in Heavy-Duty Sack Lines

Replacement of high-pressure LDPE with AT 6410 changes bubble dynamics and property balance. The metallocene resin’s narrow molecular-weight distribution and absence of long-chain branching reduce melt strength and make high-stalk bubble operating conditions unstable; therefore, the line is operated at a lower frost-line height and a wider die gap than would be used for LDPE. The replacement table below summarises the principal differentiating factors. The values for conventional Ziegler-Natta butene LLDPE and high-pressure LDPE are typical ranges from commercial literature and are not part of the AT 6410 specification. Published data for direct comparative studies on identical film lines are limited, so converter-specific trials remain necessary.

A conventional butene LLDPE at the same density and melt index would be expected to exhibit lower dart impact and higher haze because butene branches produce fewer effective tie molecules at a given crystallinity. A high-pressure LDPE at similar density has long-chain branching and higher melt strength, but does not typically achieve the same dart impact at 25 µm as AT 6410. Within the metallocene LLDPE category, AT 6410 is distinguished by its density of 0.912 g/cm³ and melt index of 0.85 g/10 min. Lower-density plastomers with densities below 0.905 g/cm³ provide better clarity and seal properties but lower modulus and melt point. Higher-density mLLDPE grades above 0.918 g/cm³ provide greater stiffness and temperature resistance but sacrifice dart impact and tear.

For food-contact applications, the resin may be used as a component of a finished article; the relevant U.S. regulation is 21 CFR 177.1520, paragraph (c), for olefin polymers. The manufacturer’s compliance letter specifies the allowed food types and conditions of use for the base resin; it does not cover printing inks, adhesives, recycled content, or processing aids introduced downstream. Under EU Regulation 10/2011, the finished film is subject to an overall migration limit of 10 mg/dm² for food contact, and specific migration limits for additives must be verified. REACH compliance is documented in the supplier safety data sheet, and the product is not expected to contain Substances of Very High Concern above 0.1% w/w. These statements do not constitute a legal compliance declaration for a converted package. The resin is not hygroscopic, so drying is not generally required for moisture; however, condensation on cold pellets stored above 60% RH should be removed before processing. Avoid melt temperatures above 240°C and avoid blending with high levels of recycled LDPE that may contain oxidatively degraded gel or unknown amine-based processing aids, because these can introduce film defects and reduce tear consistency.

In collation shrink film lines where longitudinal shrink is controlled by film tension and frost-line geometry, AT 6410 is typically incorporated at 20 wt% to 40 wt% with high-pressure LDPE or linear-low-density polyethylene to increase puncture resistance while maintaining shrink tension. Films are measured for puncture resistance under ASTM D5748, tensile modulus under ASTM D882, and free shrink under ASTM D2732. Published data for this specific blend configuration are limited; converters determine final blend ratios by running a designed experiment on their own blown-film line, as the balance between shrink tension and dart impact shifts with die gap, blow-up ratio, and frost-line height.