SABIC LDPE 2023JN and HP2023JN: Specs, MFI and Applications

Low-density polyethylene grades SABIC LDPE 2023JN and SABIC LDPE HP2023JN are high-pressure free-radical polymerisation products supplied as pelletised extrusion resins for blown film, extrusion coating, lamination, and selected blow-moulding applications. The nominal melt flow index for both grades is 4.0 g/10 min when measured at 190°C with a 2.16 kg load according to ISO 1133-1:2022; the equivalent ASTM D1238-20 value is also 4.0 g/10 min. Density measured on compression-moulded plaques at 23°C is 0.923 g/cm³ per ISO 1183-1:2019. The distinction between 2023JN and HP2023JN is not found in these two headline values but in the high-purity additive and gel-control package of the HP variant. 2023JN is selected for standard film and coating webs; HP2023JN is selected where optical defects, extractables, and organoleptic carryover must be minimised.

The high-pressure polymerisation route introduces short-chain and long-chain branching. These branches give LDPE its characteristic strain hardening and melt tension, which are not captured by density or MFI alone. A converter specifying 2023JN for a 40 µm heavy-duty sack film obtains bubble stability because the polymer melt elongates without localised necking. In extrusion coating, the same branching slows draw resonance and neck-in on high-speed lines. The 0.923 g/cm³ density is a compromise between low stiffness and adequate dart impact at ambient temperature; higher-density LDPE grades reduce gas permeability and raise modulus but sacrifice sealability. The 4.0 g/10 min MFI provides lower melt viscosity than fractional-MFI blown film grades and higher viscosity than 7–8 g/10 min coating grades, placing 2023JN in a general-purpose conversion window.

What Does Melt Flow Index Alone Predict in a Long-Chain Branched LDPE?

MFI is a single-point, low-shear stress measurement. ISO 1133-1:2022 defines the die as 2.095 mm in diameter and 8.000 mm in length, with the polymer melt held at 190°C and forced through the die by a 2.16 kg piston load. The measured 4.0 g/10 min therefore describes the inverse of apparent viscosity only near the low-shear plateau. It does not measure extensional viscosity, strain hardening, melt tension, or shear-thinning slope in a high-rate die. For LDPE, two resins with the same 4.0 g/10 min MFI and 0.923 g/cm³ density can differ in molecular weight distribution and long-chain branching frequency. This is why a capillary rheometer with a 30:1 L/D die is used to generate a shear-viscosity curve from 50 s⁻¹ to 5,000 s⁻¹ at 190°C before a grade is transferred to a 90 mm extruder. Published shear-thinning data for SABIC LDPE 2023JN specifically are not included in every product data sheet; the converter must obtain a certificate of analysis or run a rheology check on the production lot.

On an extruder, the 4.0 g/10 min MFI translates into moderate backpressure and specific energy consumption. A 90 mm single-screw extruder with a 30:1 L/D and a Maddock barrier section will typically deliver 200–250 kg/h of 2023JN at 80–100 rpm with a melt temperature of 190–210°C, although actual output depends on die restriction and head pressure. In blown film, the die pressure is commonly 200–350 bar; in extrusion coating, head pressure may exceed 300 bar because of narrow 0.5–0.8 mm die gaps. The 2023JN grade is not suitable for extremely thin 8 g/m² coating because the viscosity would force high melt temperature and accelerate oxidation. HP2023JN has the same rheological profile but fewer gel nuclei, which reduces the formation of oxidation-induced pinholes at high temperature.

Processors should not use MFI as the sole incoming quality check. A lot with 4.0 g/10 min MFI but elevated low-molecular-weight fraction can generate lower melt tension, causing bubble flutter. Conversely, a slight reduction to 3.6 g/10 min may increase backpressure and melt temperature due to shear heating. Certificate-of-analysis trends for 2023JN commonly show lot-to-lot MFI variation within ±0.2 g/10 min; when the value drifts outside this range, die pressure and film gauge profiles require compensation. If the melt temperature exceeds 230°C in blown film for more than 30 minutes, oxidative degradation generates carbonyl species that reduce heat-seal strength and increase visible gel count. This is a critical boundary. The HP2023JN grade does not remove the boundary; it only delays the onset of visible defects through lower initial gel concentration.

Blown film lines running 2023JN or HP2023JN typically use a 1.6–2.0 mm die gap and a dual-lip air ring. Barrel set points range from 160°C in the feed throat to 190–200°C at the die, with die temperature held slightly above barrel exit to reduce melt fracture on the outer bubble surface. The blow-up ratio is maintained between 2.0:1 and 3.0:1 to balance machine-direction and transverse-direction tensile properties. At a BUR of 2.5:1, a 40 µm monolayer film shows acceptable dart impact for heavy-duty sacks; the exact dart impact is governed by film gauge, frost line height, and draw. A frost line height of 6 to 10 die diameters is typical for air-cooled lines; a shorter frost line quenches the bubble faster, reduces crystallinity, and improves gloss in HP2023JN film. However, quenching too rapidly can create a wide orientation gradient and reduce tear propagation resistance. The density of 0.923 g/cm³ sets the crystalline fraction after cooling; lower-density LDPE would provide better impact at freezer temperatures, while higher-density LDPE improves stiffness and barrier.

Seal initiation is typically observed near 105°C on laboratory heat-seal equipment using 0.5 N/mm² pressure and 0.5 s dwell. The exact value for each lot depends on film thickness and coextruded layer construction. Because 2023JN and HP2023JN are used as heat-seal layers in lamination, seal-through-contamination performance depends on the high-purity additive package in HP2023JN, which lowers low-molecular-weight migratables. In monolayer or coextruded sealant webs, the film should not be held above 230°C for extended periods, and excessive corona treatment should be avoided if organoleptic performance is critical.

Film Opticals, Gel Count, and Food-Contact Compliance Matrix

High-clarity film and food-contact laminates require more than melt strength. The HP2023JN variant is produced under tighter filtration and dryer purge conditions. Gel count is evaluated by film surface inspection according to ISO 18553 or internal camera systems; the HP grade is specified to reduce visible gel bodies in a 25 µm sealant web. Haze and clarity are measured according to ISO 14782 and ASTM D1003; gloss at 60° is measured according to ISO 2813. In a 40 µm blown film, the actual haze depends on die gap, melt temperature, frost line height, and air-ring flow. The high-purity package alone does not guarantee optical performance if the line is run with a frost line below 5 die diameters or with excessive die lip oxidation. A standard 2023JN film may have acceptable opticals but can show visible gel defects at coating weights below 15 g/m², where a single 50–100 µm gel can create a pinhole.

The conversion of these resins into food-contact packaging is not defined solely by the resin certificate. The converter must validate migration under the intended contact conditions. For fatty foods or hot-fill, specific migration of antioxidants and slip agents from the final laminate must be below the limits in Regulation (EU) No 10/2011; HP2023JN is formulated to reduce low-molecular-weight species, but the final value depends on coating weight, extrusion temperature, and downstream corona treatment. The same principle applies under FDA 21 CFR 177.1520(c)2.1, where the olefin polymer must meet extractables limits for the intended temperature of use. If the film is used outside these limits, compliance cannot be assumed from the resin data sheet.

When Extrusion Coating Weight Drops Below 15 g/m², Die Gap and Air Gap Must Be Tightened

Extrusion coating uses the 2023JN and HP2023JN grades at much higher melt temperatures than blown film because adhesion to paperboard, aluminum foil, or oriented PET requires oxidative surface functionalisation. The melt temperature is set between 300°C and 325°C, depending on screw design and residence time. At these temperatures, the polymer melt oxidizes at the free surface; carbonyl and carboxyl species then bond to polar substrates during the nip. If the melt temperature drops below 290°C, adhesion falls and peel strength measured by TAPPI T 540 or ISO 11339 decreases. If the melt temperature exceeds 330°C, the polymer undergoes chain scission, visible fuming, and gel formation. The process window is therefore narrow. On a 120 mm extrusion coating line, the die gap is reduced from 0.8 mm to 0.5 mm when coating weight drops below 15 g/m²; this maintains a sufficiently high shear rate at the die lip to reduce draw resonance.

Air gap is the distance between the die exit and the nip. For thin coating, a shorter air gap of 100–150 mm is used to limit neck-in and preserve melt temperature. Neck-in is the reduction in web width caused by elastic recovery and surface tension after the melt exits the die. At 10–20 g/m² coating weights, neck-in of 20–40 mm per edge is common on lines running 4.0 g/10 min LDPE; the exact value depends on die width, air gap, and melt temperature. HP2023JN does not significantly alter neck-in because the rheology is unchanged, but it reduces edge instability defects associated with gel particles. Draw ratio, the ratio of line speed to melt velocity at the die, is commonly between 10:1 and 30:1. When draw ratio exceeds 30:1, draw resonance can appear as periodic gauge bands; increasing melt temperature or reducing line speed suppresses the instability.

Coating weight is measured by inline beta gauge or gravimetric per ISO 4591. In flexible packaging, 2023JN is used as a sealant layer on aluminum foil or metallised films at 12–25 g/m². HP2023JN is specified for low-odor and low-extractable laminates where the sealant layer contacts food. Adhesion values above 200 N/m on paperboard are achievable after oxidation, but the actual value is substrate-dependent and must be validated with the specific board grade and flame or corona pre-treatment. Startup and shutdown procedures are also critical. At 300–325°C, a stagnant melt can degrade within minutes. Before a line stops, the extruder and die should be purged with a lower-MFI LDPE or a purging compound that is stable at 300°C. Failure to purge creates black specks and gel tails that contaminate the coating for hours after restart. On a 120 mm screw, the residence time distribution is broad; the tail of the distribution can be 10–15 minutes, so temperature reductions must be initiated early. HP2023JN reduces the concentration of pre-existing gel nuclei, but it does not protect against new gels generated by thermal oxidation during startup.

For lamination film and blow-moulding applications, the 4.0 g/10 min MFI is low enough to retain melt strength but high enough to allow screw plastification at moderate temperatures. In small blow-moulded containers, a melt temperature of 160°C to 190°C is used; published data for the exact blowing pressure and cycle time for these specific grades is limited because the grade family is primarily sold as an extrusion resin. When higher drawdown is required in cast lamination, converters may blend 10–20 wt% of an 8.0 g/10 min LDPE with 2023JN; this reduces die pressure and permits thinner gauge with only a minor loss in melt tension. The density of 0.923 g/cm³ remains the controlling factor for water vapor transmission rate, which is higher than that of HDPE or BOPP. This property is relevant in overwrap and breathable packaging, where the LDPE layer contributes toughness and sealability rather than barrier.

The heat-seal performance of these grades is evaluated on laboratory sealers at 0.5 N/mm² dwell pressure and 0.5 s dwell time; the seal initiation temperature is typically observed between 105°C and 115°C. However, the actual hot-tack window on a vertical form-fill-seal machine running 60–80 packages/min depends on film thickness, cooling rate, and contamination resistance. 2023JN provides a broad hot-tack window due to its long-chain branching; HP2023JN extends this into high-clarity, low-gel laminates. No single laboratory value substitutes for packaging line validation.