Luban LLDPE DFDA-7047 is a butene linear low-density polyethylene resin supplied as free-flowing pellets for blown film extrusion. The nominal density is 0.918 g/cm³ when tested in accordance with ISO 1183-1:2019, and the nominal melt mass-flow rate is 1.0 g/10 min at 190 °C under a 2.16 kg load per ISO 1133-1:2022. The grade is produced in a low-pressure gas-phase polymerization process using a Ziegler-Natta catalyst and butene as the short-chain branching comonomer. The resulting molecular architecture combines density-controlled crystallinity with a broad short-chain branching distribution, establishing the balance between film collapse resistance and melt extensibility required in monolayer and coextruded blown film structures. Typical conversion targets include heavy-duty shipping sacks, agricultural greenhouse covers, consumer carrier bags, frozen food packaging, liners, and lamination film substrates. The resin is intended for processing without predrying when freshly opened; however, condensation on cold pellet surfaces in humid environments above 60 % relative humidity can introduce moisture that produces bubble defects and surface specks.

Because the base resin is formulated without slip or antiblock additives, converters must dose surface-tension modifiers as masterbatch when coefficient of friction below 0.20 is required. This additive-free base allows the same resin to be used in food-contact, printing, and lamination structures without interference from migratory additives. The grade is not intended for long-term outdoor exposure unless a UV stabilizer package is incorporated at the converter or compounder.

What Limits Melt Processing Window on Monolayer Blown Film Lines?

On a 45 mm to 65 mm single-screw blown film line with a 24:1 to 30:1 L/D ratio and a spiral die gap between 1.2 mm and 2.0 mm, DFDA-7047 has a practical melt temperature set point of 190 °C to 220 °C. The lower boundary is not fixed by melting alone but by melt fracture and bubble-instability onset; the higher boundary is set by oxidative chain scission and crosslinking leading to gel deposition on the die lip. On five-zone extruders, the barrel profile is typically set from 160 °C at the feed throat to 200 °C at the metering zone, with screen pack filtration at 60 mesh or finer to remove carbonized particles. The recommended blow-up ratio is 2.0:1 to 2.5:1, with a frost line height of 1.5 to 2.0 die diameters for balanced machine-direction and transverse-direction orientation. At blow-up ratios above 3.0:1, the low melt flow rate produces high bubble tension; bubble sway and weld-line instability have been observed in field reports on unsupported collapsing frames.

Throughput response is backpressure-limited rather than melt-temperature-limited. Because the melt mass-flow rate is 1.0 g/10 min, screw speed increase beyond the die restriction creates a steep melt-pressure increase. On a 60 mm extruder with a 200 mm die, melt pressure at the breaker plate can approach 35 MPa before melt temperature exceeds 215 °C; however, published data for this specific configuration is limited, and the pressure depends on screw geometry, screen pack condition, and die lip wear. Operators should avoid abrupt screw-speed changes because the residence time distribution in a barrier screw can produce unmelted resin at the die lips when screw speed is increased by more than 15 % per minute. A temperature profile with too low a feed-zone temperature can cause solid-bed breakdown failure, while too high a feed-zone temperature reduces the frictional work needed for melting and feeds partially molten resin into the compression zone.

Rheologically, the resin behaves as a shear-thinning pseudoplastic melt. The melt flow rate ratio between 21.6 kg and 2.16 kg loads, I21/I2, is commonly reported in the range 25 to 30 for conventional butene LLDPE film grades. This shear-thinning response permits stable screw pumping in barrier screws with compression ratios between 2.5:1 and 3.0:1. Screws with compression ratios above 3.5:1 can generate excessive shear heating, causing local melt temperatures above 230 °C and gel formation even when the barrel set points remain at 200 °C.

Changeover from a metallocene LLDPE or plastomer requires purging because the catalyst residues and narrow molecular weight distribution materials can interact with the antioxidant package and form interfacial gels. A 0.5 g/10 min LDPE purge at 180 °C for 20 min followed by DFDA-7047 has been used to remove residues on 25:1 L/D general-purpose screw designs. The resin should not be purged with polypropylene, PET, PVC, or EVOH without complete removal; these materials can form incompatible gels and die lip deposits that require shutdown and abrasive cleaning.

Bubble cooling limits dominate at film gauges below 25 µm. The low melt index provides higher melt tension and greater resistance to distortion, but the frost line must be raised when the gauge drops below 15 µm to prevent wrinkles that originate from too-rapid quenching. On air-cooled lines, an air ring with dual-lip flow control and a blow-up ratio limited to 2.0:1 is preferred for thin film; otherwise, edge flutter can generate gauge variation that exceeds ±5 % of target. In-line process monitoring on production-scale lines shows that the melt pressure before the screen pack rises nonlinearly with screw speed. As the screen pack blinds with gel and contamination, a pressure increase of 20 % above the startup pressure is used as a change criterion. Running beyond this pressure rise can trigger screen pack collapse and metal contamination in the die. Screen pack configuration typically includes a 20/40/60 mesh stack or a 100 mesh candle filter.

Tensile, Tear, and Optical Property Benchmarks at 40 µm Film

The data in Table 1 are compiled from publicly available supplier datasheets and represent typical values for blown film produced at 40 µm gauge, using a blow-up ratio of 2.5:1, a die gap of 1.5 mm, and a melt temperature of 210 °C. Values are not sales specifications; lot-to-lot variation and converter conditions alter results, particularly for tear and impact.

The dart impact value of 95 g at 40 µm places the grade in the intermediate toughness range for butene LLDPE. The Elmendorf tear balance is anisotropic: TD tear is approximately 2.3 times MD tear, a common consequence of crystalline orientation induced by the bubble. If a converter seeks improved MD tear, raising the frost line height and reducing the blow-up ratio to 1.8:1 shifts orientation toward the machine direction, but at the cost of TD tear and dart impact. The optical values of 13 % haze and 60 GU gloss are acceptable for industrial sacks, liners, and agricultural films; they are not appropriate for high-clarity retail packaging where LDPE or metallocene grades with haze below 8 % are selected.

When a Higher Melt Index Grade Beats DFDA-7047 in Converter Economics

The principal differentiation from DFDA-7042, a 2.0 g/10 min butene LLDPE of the same 0.918 g/cm³ density, appears in extruder throughput and film toughness. In a backpressure-limited line, the higher MFR grade can be run at a higher screw speed before die pressure reaches the extruder limit; this increases mass throughput at equal melt temperature. The penalty is typically lower dart impact and tear strength because the lower molecular weight resin has less tie-molecule connectivity. In applications where film gauge is above 80 µm and extrusion output dominates conversion cost, DFDA-7042 is often chosen. In thin film below 30 µm, DFDA-7047 is preferred because its higher melt elasticity stabilizes the bubble and preserves mechanical properties.

Relative to a hexene LLDPE of equivalent density and melt mass-flow rate, DFDA-7047 generally shows lower dart impact and transverse-direction tear because butene-derived ethyl branches are less effective at connecting adjacent crystalline lamellae than hexene-derived butyl branches. In converter comparisons at 25 µm film, the hexene grade may show 20 % to 40 % higher dart impact, but the butene grade often exhibits lower melt pressure and lower cost per ton due to comonomer and licensing economics. This tradeoff is acceptable for non-demanding liners where the main failure mode is tensile overload rather than puncture.

Compared with a branched autoclave LDPE of the same melt index, DFDA-7047 has higher tensile yield and dart impact at equal film gauge, but worse optical clarity and higher screw torque. LDPE retains an advantage in extrusion coating and high-speed cap liners where neck-in and edge tear resistance are controlled by long-chain branching; DFDA-7047 is not recommended for extrusion coating onto paper because the low melt strength causes edge instability and draw resonance.

Metallocene LLDPE grades of the same density and melt index offer narrower molecular weight distribution, lower extractables, and better organoleptics, but they typically generate higher melt pressure and require blending with LDPE for bubble stability. DFDA-7047, with a broader molecular weight distribution, generally processes on standard single-screw lines without LDPE addition. The broad distribution also reduces melt fracture at high shear rates but may lower ultimate puncture resistance relative to a well-chosen metallocene grade.

Differences from high-density polyethylene are more severe. At equal film gauge, DFDA-7047 has lower modulus and tensile yield stress than an HDPE film grade of 0.945 g/cm³ to 0.955 g/cm³ density, but it exhibits higher dart impact and lower haze due to lower crystallinity. HDPE grades are selected when high stiffness and moisture barrier are required; DFDA-7047 is selected when puncture resistance and sealing performance dominate.

For high-speed bag conversion and form-fill-seal applications, the base resin is typically not supplied with slip or antiblock additives. To obtain a kinetic coefficient of friction below 0.20 under ASTM D1894-14 testing, erucamide slip masterbatch is let down at 2 wt% to 5 wt% using a gravimetric feeder. Plate-out on collapsing frames and nip rolls occurs when the erucamide concentration in the film exceeds 0.1 wt%; cleaning intervals may shorten from 72 h to 24 h in warm ambient conditions above 30 °C. The resin also accepts silica antiblock masterbatches at 5 wt% to 10 wt% for film-to-film separation.

Table 2 summarizes compliance positions for the resin as sold. Compliance of the finished article must be verified individually because processing aids, inks, adhesives, and laminating layers affect the final migration and heavy-metal profile.

The product should be stored in a clean, covered area below 50 °C and away from direct ultraviolet exposure. Prolonged storage beyond 12 months may cause additive bloom and surface oxidation; such material should be purged or evaluated for melt mass-flow rate and gel count before use. The grade is not intended for applications requiring long-term outdoor weathering without a UV stabilizer package, nor for direct contact with strong oxidizing agents, aromatic hydrocarbons, or chlorinated solvents at elevated temperature.

In coextruded structures, DFDA-7047 is typically placed in the core layer or skin layer of laminated films where its tear and sealing performance contribute to the final film. The sealing initiation temperature measured on heat-seal equipment at 0.5 s dwell and 2 bar pressure typically falls between 100 °C and 110 °C; however, actual heat-seal curves depend on gauge and skin-layer composition. For sterile packaging, irradiation doses up to 25 kGy are generally tolerated by the neat resin, but peroxide formation and color shift should be monitored when slip additives are present.

Typical blown film defects observed on production lines include die-lip deposit, bubble instability, film wrinkling, and poor gauge uniformity. Die-lip deposits from oxidized material are minimized by maintaining melt temperature below 220 °C and avoiding prolonged residence time above 15 min. Bubble instability can be corrected by lowering blow-up ratio or increasing frost line height, not by increasing melt temperature beyond the oxidative boundary. Poor gauge uniformity at thin gauges is often caused by uneven air ring flow or die gap misalignment; the die gap should be checked with a feeler gauge to within ±0.05 mm.