SABIC LDPE 4024WN and 7019EC: Film Grades Compared

Industrial conversion of low-density polyethylene into film and coated substrates requires grade selection based on melt flow rate, density, and molecular weight distribution. SABIC LDPE 4024WN and SABIC LDPE 7019EC occupy adjacent positions in the SABIC LDPE portfolio but are assigned to different conversion routes. Published technical data sheets identify SABIC LDPE 4024WN as a blown-film grade with a typical melt flow rate of 4.0 g/10 min at 190 °C/2.16 kg under ISO 1133-1:2022 and a nominal density of 0.924 g/cm³ under ISO 1183-1:2019. SABIC LDPE 7019EC is assigned to extrusion coating and high-speed film conversion, with a typical melt flow rate of 7.0 g/10 min and a nominal density of 0.919 g/cm³ under the same methods. The 0.005 g/cm³ density differential shifts crystalline fraction, seal initiation behavior, permeability, and blocking tendency. The comparison is therefore carried out through process equipment behavior rather than nominal datasheet substitution because blown film, cast film, and extrusion coating lines impose different shear histories and cooling rates on the melt.

Rheological and thermal fields governing the SABIC LDPE pair

Single-point melt flow rate values under ISO 1133-1:2022 do not fully predict die pressure or melt fracture because LDPE exhibits non-Newtonian shear thinning. Capillary rheometry under ISO 11443 over shear rates from 10 s⁻¹ to 10⁴ s⁻¹ shows that SABIC LDPE 7019EC has lower apparent viscosity across the entire shear range. In an L/D 30 single-screw extruder with a 90 mm screw and a flat die having a 0.8 mm lip gap, the higher melt flow rate of 7019EC reduces specific energy consumption and melt temperature rise, but the associated molecular weight reduction lowers extensional viscosity. Extensional viscosity is the dominant rheological parameter controlling draw resonance in extrusion coating and bubble stability in blown film. Consequently, 4024WN is preferred where bubble stability at blow-up ratios between 2.2:1 and 3.0:1 is required, while 7019EC is preferred where a low-viscosity melt must wet a moving paper or aluminium substrate at line speeds exceeding 100 m/min.

On production-scale blown film lines equipped with Ø60 mm grooved feed extruders and 250 mm annular dies, SABIC LDPE 4024WN is typically processed at barrel temperatures from 150 °C to 180 °C and die temperatures from 170 °C to 185 °C. Frost line height, usually set 6–8 die diameters above the air ring, controls crystallite orientation and governs tensile anisotropy measured by ISO 527-3. Bubble instability on such lines is observed as a low-frequency oscillation of the frost line when the air ring velocity exceeds 25 m/s or when internal bubble cooling pressure fluctuates by more than 0.5 mbar. Under those conditions, film gauge variation measured by scanning capacitance sensors can increase from a baseline of ±4% to ±8%, and dart impact values under ASTM D1709A drop accordingly. Published data for this specific configuration is limited, but the failure mode is consistent with reduced melt strength and accelerated cooling of the outer bubble surface.

What limits seal initiation temperature in 4024WN compared with 7019EC?

Seal initiation temperature in LDPE films is governed by crystalline melting onset, molecular weight, and surface contact. The lower density of SABIC LDPE 7019EC, 0.919 g/cm³, reduces the crystalline fraction and shifts the onset of melting to a lower temperature relative to the 0.924 g/cm³ grade 4024WN. This difference is measurable by differential scanning calorimetry under ISO 11357-3. Using a laboratory heat sealer with 0.5 MPa dwell pressure and 1 s dwell time, the lower melting onset of 7019EC typically permits a seal initiation temperature 3–6 °C lower than that of 4024WN, although lot-specific seal initiation curves are required for specification. Hot tack, the ability of a molten seal to resist opening forces before crystallization, is also influenced by molecular weight. When hot tack is measured under ASTM F1921, the higher molecular weight of 4024WN generally provides a broader hot-tack plateau at seal temperatures between 110 °C and 140 °C, but restricts low-temperature sealability. Conversely, 7019EC may exhibit lower hot tack at elevated seal temperatures if the melt thins excessively.

SABIC LDPE 7019EC is specified for extrusion coating lines that operate at melt temperatures between 280 °C and 320 °C, measured by an infrared melt probe at the die exit. In these lines, the polymer melt exits a coat-hanger die with a die gap between 0.5 mm and 0.8 mm and is drawn in air over a distance of 100–250 mm before contacting a chill roll at 15–20 °C. Neck-in, the reduction in coating width from die width to final laminate width, is a critical production variable. Lower melt tension in 7019EC increases neck-in relative to higher-molecular-weight LDPE grades; converters compensate by reducing die-to-chill-roll distance or increasing line speed. At line speeds above 150 m/min, draw resonance may appear as regular thickness bands across the web, measured by beta gauge at ±2 µm variation. The lower density of 7019EC also improves anchorage to paper and aluminium under ASTM F904 peel testing because oxidative species generated at high melt temperature react with the substrate surface. Published data for this specific configuration is limited.

When extrusion coating replaces blown film in flexible packaging laminates

Film performance in flexible packaging is commonly benchmarked by water vapor transmission rate under ISO 15106-2 and oxygen transmission rate under ASTM D3985. The density differential between the two grades affects permeability because transport through polyethylene films occurs primarily through the amorphous phase. At 50 µm thickness and 23 °C, 0% relative humidity, an LDPE film with density 0.919 g/cm³ typically exhibits a water vapor transmission rate roughly 10–15% higher than a film with density 0.924 g/cm³. Published data for these specific SABIC grades may differ after accounting for orientation and additive packages. Tensile properties must be measured with ISO 527-3 on specimens conditioned at 23 ± 2 °C and 50 ± 10% relative humidity for 88 h per ISO 291. For blown films of 4024WN, the higher density contributes to higher modulus and yield stress, while 7019EC delivers greater low-temperature impact flexibility due to lower crystallinity. When a laminate structure replaces blown film with extrusion-coated 7019EC, the final puncture resistance under ASTM F1306 is governed as much by the substrate and coating weight as by the LDPE grade.

Surface and additive interactions differ by conversion route. In blown film, slip and antiblock concentrates are compounded at 0.5–1.5 wt% to reduce coefficient of friction measured under ISO 8295. For SABIC LDPE 4024WN, film coefficient of friction targets below 0.20 are achieved with erucamide-based slip additives; migration kinetics in the polymer matrix depend on crystallinity. The lower crystalline fraction of 7019EC accelerates additive bloom after extrusion coating, which can reduce coefficient of friction more rapidly but may also create haze development within 24 h on the reel. In extrusion coating lamination, the high melt temperature degrades some antioxidants and consumes slip additives, requiring higher initial concentrations than blown film. Additive interaction failures observed on production lines include plate-out on the die lip when slip concentration exceeds 1000 ppm at 300 °C, and blocking of finished reels when storage temperatures exceed 40 °C.

Global food-contact standards and the test methods that anchor 4024WN and 7019EC

Both SABIC LDPE grades are expected to be evaluated under FDA 21 CFR 177.1520(c)(2.2) for olefin polymers used in food-contact articles, and under EU Regulation 10/2011 for plastic materials and articles intended to come into contact with food. The relevant European overall migration limit is 10 mg/dm², tested by EN 1186-1. Compliance is also routinely verified against REACH Article 33 for substances of very high concern at the 0.1% w/w threshold. Neither grade contains intentionally added phthalates or heavy metals. However, food-contact compliance must be confirmed for the finished laminate or film because printing inks, adhesives, and coating primers contribute their own migration species. The lower sealing temperature of 7019EC can reduce thermally generated off-taste compounds that form above 150 °C; organoleptic testing under EN 1622 or ISO 13302:2003 is often required for taste-sensitive applications.

Specification engineers should request lot-specific certificates because SABIC LDPE 4024WN and SABIC LDPE 7019EC may be produced across multiple reactors; melt flow rate and density are controlled within narrow limits, but additive type and concentration may vary by regional production. Pre-drying is not normally required for either grade when stored under 23 °C and 50% relative humidity; however, resins stored at relative humidity above 60% can carry surface moisture that generates bubbles in extrusion coating at melt temperatures above 280 °C. The lower density of 7019EC produces a softer film after cooling, which raises the risk of roll blocking if rewind tension exceeds 250 N/m on cast film lines. Conversely, 4024WN in thick blown film sections above 200 µm may show higher modulus but lower tear propagation resistance when embossed to high draw ratios.