Linear low density polyethylene LLDPE DFDA-9047H is a film-grade ethylene/1-butene copolymer produced via gas-phase polymerisation using a Ziegler-Natta catalyst. The product is supplied as pellets and is specified with a nominal density of 0.920 g/cm³ measured in accordance with ASTM D1505-18 and a nominal melt flow rate of 1.0 g/10 min measured at 190 °C under 2.16 kg load in accordance with ASTM D1238-20. The principal release specifications on producer certificates are typically melt flow rate 1.0 ± 0.2 g/10 min, density 0.920 ± 0.002 g/cm³, tensile stress at break ≥12 MPa, elongation at break ≥500%, dart drop impact on 25 µm film ≥100 g, and Vicat softening point ≥95 °C. The H suffix may indicate a narrow specification window or a modified additive package; suffix conventions are not harmonized across producers, so the batch certificate remains the controlling document. The grade is intended for blown film extrusion in heavy-duty sacks, agricultural greenhouse and mulch films, frozen food packaging, lamination films, and industrial liners. Its molecular weight and comonomer distribution are controlled to provide a balance between bubble stability, dart impact resistance, and seal initiation temperature relative to lower-molecular-weight butene LLDPE grades. Lot-specific certificates should be reviewed before compounding or film conversion because typical values may vary across production sites.

What Distinguishes DFDA-9047H from Conventional Butene LLDPE Film Grades?

Compared with the widely available DFDA-7042 grade, which is usually specified at a melt flow rate of 2.0 g/10 min and density 0.918 g/cm³, DFDA-9047H has a lower melt index and a slightly higher nominal density. The lower melt index corresponds to a higher average molecular weight and a longer stress-relaxation time, which raises extensional viscosity under blown-film deformation. Measured on 40 µm film, the dart impact value of DFDA-9047H typically falls in the range of 120 g to 150 g under ASTM D1709-16a Method A, whereas DFDA-7042 film of comparable thickness typically falls between 90 g and 110 g. The higher melt strength permits a larger blow-up ratio and a taller frost line without bubble flutter, but extruder back pressure at constant screw speed is typically higher by 5% to 12%, and motor load increases accordingly.

In contrast to metallocene-catalysed LLDPE of similar density, DFDA-9047H has a broader molecular weight distribution and a more heterogeneous short-chain branching distribution. This reduces shear thinning, improves bubble stability and gauge uniformity on single-screw film lines with relatively short L/D ratios, but produces higher haze and lower dart impact at equivalent melt index than a typical metallocene LLDPE. For blown film converters, the practical distinction is that DFDA-9047H tolerates wide processing windows while retaining tear and puncture properties.

These are typical directional values, not release limits. The higher dart and tear values are accompanied by slightly higher haze and a moderate increase in extruder pressure compared with the lower-molecular-weight grade.

Melt Rheology and Extrusion Behaviour on Single-Screw Film Lines

The melt flow rate of 1.0 g/10 min under ASTM D1238-20 places DFDA-9047H in the low-flow film extrusion class. Processing on a single-screw extruder with a grooved feed section and an L/D ratio of at least 24:1 is recommended. A barrier screw with a Maddock mixing section gives satisfactory melt temperature uniformity; screen packs of 60/80/100 mesh are typically mounted upstream of the adapter. Recommended barrel temperatures range from 180 °C at the feed throat to 210 °C at the metering section, with die temperature held at 210 °C to 230 °C. Melt pressure should be kept below 35 MPa to avoid excessive shear heating. For film thicknesses below 60 µm, a die gap of 1.2 mm to 1.5 mm is common; thicker films may require 1.8 mm to 2.0 mm. Blow-up ratio is usually maintained between 2.0:1 and 3.0:1, and the frost line is set at 6 to 10 die diameters above the die face.

If the resin has been stored under high humidity and surface moisture is visible, drying at 60 °C to 70 °C for 1 h is sufficient; long residence above 80 °C risks pellet agglomeration. Cast film processing is possible but less common for this flow class. On chill-roll lines, the melt temperature may need to be raised toward 230 °C to reduce extrusion pressure, and the air gap should be kept short to limit draw resonance. Published data for this specific configuration is limited; processors should verify process parameters on production-scale equipment because the lower melt index can increase motor load and residence time compared with 2.0 g/10 min grades.

When the Blow-Up Ratio Shifts from 2.0:1 to 3.0:1

The table below lists typical property values obtained on 40 µm blown film produced at a blow-up ratio of 2.5:1 and a die gap of 1.5 mm. Values should be read as typical lot data, not as guaranteed release limits.

Haze and gloss are sensitive to frost line height and die-to-frost-line cooling rate. A shorter frost line increases quench rate and generally reduces haze, but it also raises film blocking tendency when slip agent concentration is low. A taller frost line increases crystallinity development before the bubble collapses, which can improve dart impact but raise haze. The lower melt index of DFDA-9047H permits a more extended bubble without losing stability, but film converters should map the specific die and air ring because local cooling rates differ between air-ring geometries.

Dart Impact, Tear Resistance, and Optical Quality Are Directly Affected by Frost Line Height

For agricultural greenhouse and mulch film, puncture resistance during wind load and hail exposure is a controlling design requirement. DFDA-9047H is selected over general-purpose LLDPE when the film must survive repeated stress after puncture. The combination of 1.0 g/10 min melt flow rate and 0.920 g/cm³ density shifts failure mode from brittle tear to ductile yield in slow puncture events. The higher molecular weight increases the energy required to propagate tears in the transverse direction, which is often the limiting direction in field installations. Converters running 40 µm film at a blow-up ratio of 3.0:1 report better bubble stability with DFDA-9047H than with 2.0 g/10 min LLDPE grades under the same cooling air velocity. If gauge variation exceeds ±7%, the bubble temperature profile and die gap should be checked before adjusting resin.

Heat sealing of DFDA-9047H film requires lower temperatures than HDPE and higher temperatures than metallocene LLDPE of similar density. On a laboratory heat sealer with 0.5 MPa jaw pressure and 1 s dwell, the seal initiation temperature is typically observed between 105 °C and 115 °C; seal strength is measured according to ASTM F88/F88M-21. Hot tack force is evaluated under ASTM F1921-18 and becomes a limiting parameter in vertical form-fill-seal machines running above 40 cycles/min. The plateau seal strength on 40 µm film commonly reaches 12 N/15 mm to 16 N/15 mm. These values shift with film gauge, seal jaw dwell time, and cooling rate.

For high-speed packaging lines, the coefficient of friction is controlled by erucamide or behenamide slip agents migrating to the film surface. Kinetic coefficient of friction measured according to ASTM D1894-14 usually falls to 0.10 to 0.20 after 24 h aging at 23 °C. Blocking force under ASTM D3354-15 is used as a release criterion, but target values must be set for the specific antiblock loading because migration kinetics depend on film crystallinity and storage temperature.

Food-contact compliance for DFDA-9047H is not established by the resin designation alone; the supplier batch certificate and lot-specific migration testing remain controlling. When certified, the base olefin polymer falls within the scope of FDA 21 CFR 177.1520(c) for polyolefin food-contact uses. Under European legislation, compliance with Regulation (EU) No 10/2011 requires verification of the overall migration limit of 10 mg/dm² under the simulants assigned to the intended food type. The grade is typically supported for RoHS 2011/65/EU and REACH SVHC restrictions by a supplier declaration, but these documents must be obtained for the specific production lot. Medical implant and parenteral fluid-contact applications are outside the intended use window; additional USP Class VI or ISO 10993 testing would be required.

Relative to high-pressure LDPE, DFDA-9047H has lower long-chain branching, higher dart impact, and better environmental stress crack resistance; however, it has lower melt elasticity and may require a higher melt temperature for stable bubble formation at very high frost lines. Relative to HDPE blown film grades, it has lower flexural modulus and lower continuous-use temperature. Continuous service above 80 °C is not recommended, and oxidative stability depends on the antioxidant package remaining intact during processing. Melt temperatures above 260 °C should be avoided to prevent thermal degradation. Avoid blending with polyamide or ionomer resins without checking for acid or amine interactions that can destabilize the antioxidant system.