Comparison of Korean LDPE grades from LOTTE Chemical, LG Chem, and Hanwha TotalEnergies is most meaningful when melt flow rate (MFR), density, and long-chain branching (LCB) distribution are evaluated under identical test protocols. Low-density polyethylene is classified by ISO 1183-1 with density 0.915–0.932 g/cm³; film-grade MFR is routinely reported at 190 °C/2.16 kg per ISO 1133-1:2022. The three suppliers operate high-pressure free-radical processes in which reactor configuration—autoclave or tubular—controls branching topology. Publicly available technical bulletins for individual grades often omit molecular weight distribution parameters; therefore, comparative ranking should be based on rheological response, film properties, and conversion behavior rather than nominal density alone. Test protocols referenced in the following comparison include ISO 527-3 for tensile film properties, ASTM D1003 for haze, ASTM D2457 for 60° gloss, ASTM D1709A for dart impact, and ASTM D1922 for Elmendorf tear.

How Does Long-Chain Branching Distribution Shape Melt Elasticity and Extensional Flow?

Long-chain branching in LDPE is generated by backbiting and intermolecular hydrogen abstraction during free-radical polymerization. Autoclave reactors produce a broader branching distribution and higher melt elasticity; tubular reactors yield more uniform short-chain branching but retain LCB. Korean suppliers have historically allocated different grade families to different reactor platforms. LOTTE Chemical film grades generally emphasize balanced drawdown and bubble stability; LG Chem grades frequently target optical clarity and dart impact; Hanwha TotalEnergies grades include high-melt-strength resins designed for thick film and foam. These differences are not absolute across the catalog, and published data for the exact reactor assignment of individual grades is limited.

Shear-thinning behavior is measured by parallel-plate rotational rheometry per ISO 6721-10 at 190 °C under nitrogen. A conventional LDPE film grade typically shows a viscosity ratio η*(0.1 rad/s)/η*(100 rad/s) between 8 and 18; higher ratios correlate with greater melt elasticity. Capillary rheometry per ISO 11443 with a 1 mm die and 20:1 L/D provides apparent viscosity data for process modeling. In a 65 mm grooved-barrel blown-film extruder with L/D 30:1 and 300 mm spiral die, grade-to-grade differences in shear melt pressure among resins of equivalent MFR remained below ±10 bar at screw speed 75 min⁻¹. The observed range is smaller than typical barrel pressure control tolerance; extrusion throughput is therefore not the primary discriminator among the three suppliers.

Extensional rheology via a Rheotens melt elongation tester is the more sensitive differentiator. Melt tension values for LDPE film grades at 190 °C and draw acceleration 2.4 mm/s² generally range from 0.5 to 2.5 cN across MFR classes 0.3–4.0 g/10 min. Higher melt tension grades resist draw resonance in extrusion coating and permit higher frost line heights in blown film. Within the same MFR class, high-melt-strength Hanwha grades have shown less bubble flutter at frost line height 600–700 mm, whereas higher-clarity LG Chem grades may require frost line height below 550 mm to avoid excessive haze development. Published data for the specific LOTTE grade configuration is limited; LOTTE technical recommendations for film extrusion tend to use narrower air gaps for neck-in control.

On a 90 mm single-screw blown-film line with L/D 30:1, 250 mm spiral die, 1.8 mm die gap, and dual-lip air ring, bubble stability is governed by frost line height, blow-up ratio (BUR), and melt temperature. A grade with MFR 2.0 g/10 min can be run at BUR 2.5:1 and frost line height 650 mm; reducing frost line below 400 mm increases haze because the crystalline morphology is quenched too rapidly. Higher-melt-strength Hanwha grades maintain bubble diameter within ±2 mm at frost line height 700 mm, while a lower-melt-strength LG Chem grade may exhibit long-period diameter oscillation unless melt temperature is raised to 190 °C. LOTTE general-purpose film grades typically accept frost line heights between 500 mm and 650 mm without excessive bubble flutter.

Frost line height also controls tear balance. In LDPE blown film, MD tear and TD tear respond in opposite directions to BUR and frost line height. A BUR increase from 2.0:1 to 3.0:1 raises TD orientation and lowers tear strength in MD while improving TD tear. Korean grade comparisons must therefore be run at identical BUR and frost line; otherwise, apparent supplier differences are an artifact of the processing window. Gel content and fisheye contamination are also monitored for high-clarity film. Camera-based gel counters with detection threshold 50–100 µm are used; for optical grades, gel counts above 10 particles/m² at 100 µm threshold are typically cause for rejection. Published lot-to-lot variance data for all three suppliers is limited, but pellet handling and conveying cleanliness often dominate gel count variability.

Antiblock, slip, and antioxidant formulations are grade-specific and are not interchangeable across the three suppliers. Slip agents reduce coefficient of friction to 0.08–0.25 per ISO 8295; typical antiblock masterbatch additions are 2,000–5,000 ppm of calcined silica or diatomaceous earth. Overdosing above 8,000 ppm can lower dart impact and raise haze. Slip agent migration kinetics are temperature dependent; erucamide-based slip systems do not reach equilibrium coefficient of friction for 24–48 h after film winding. Rapid testing after 2 h can misrank two suppliers because nucleation and migration distance differ by surface crystallinity. Oleamide systems bloom faster but increase blocking and screw slip. Antioxidant packages influence color and organoleptic migration; food-contact film grades should be verified against EU (EU) No 10/2011 overall migration limit of 10 mg/dm² and FDA 21 CFR §177.1520. Grade-specific compliance statements differ, especially for grades containing EVA comonomer; EVA-containing resins are outside the strict polyethylene classification and require separate migration evaluation.

Optical and Mechanical Benchmarks for Korean LDPE Film Grades

Table 1 consolidates representative property ranges for general-purpose film grades across the three suppliers. Ranges are drawn from supplier technical bulletins where available; when individual grade data are not published, the range is assigned to the broad LDPE envelope and marked as typical. The values are not intended for specification without lot-specific certificates of analysis.

These ranges overlap heavily; the practical selection criterion is often not mean tensile strength but lot-to-lot additive consistency and film gauge variation. Hanwha high-melt-strength grades tend to shift the dart impact and tear envelope upward at equivalent MFR, while LG Chem high-clarity grades shift haze and gloss toward the optical end. LOTTE film grades typically occupy the middle band, which can be advantageous when a single resin is used across multiple packaging lines.

Table 2 summarizes compliance documentation typically available from the three suppliers for LDPE film grades. Food-contact statements are grade-specific and are not a substitute for lot-specific certificates of analysis.

When Neck-In and Drawdown Become Critical in Extrusion Coating

Extrusion coating and lamination are the most demanding conversion modes for LDPE melt elasticity. On a 120 mm single-screw extruder feeding a 1,200 mm slot die with 0.6 mm die gap, 200 mm air gap, and 150 m/min line speed, neck-in is measured as the width reduction between die exit and coating edge. Korean LDPE coating grades typically target neck-in below 8–12 % of die width. High melt strength from LCB suppresses draw resonance and edge instability. Among the three suppliers, lower-MFR high-melt-strength Hanwha grades tend to exhibit the lowest neck-in at equivalent coating weight; LG Chem coating grades may require smaller air gaps to maintain edge stability at 200 m/min. LOTTE technical bulletins for extrusion coating grades emphasize drawdown ratio, with maximum line speed before edge tear typically limited by melt elasticity rather than extruder output.

Adhesion to paperboard and aluminum foil is influenced by oxidation at the air gap. Melt temperature at the die exit is typically set to 310–330 °C for LDPE extrusion coating; higher melt temperature increases carbonyl formation and improves adhesion but raises odor and gel formation. Processors report that optimal adhesion with paperboard at 15 g/m² coating weight is obtained when the melt film is exposed to an air gap residence time of 0.1–0.2 s. All three Korean suppliers provide grades with antioxidant packages that maintain thermal stability at 320 °C; grades designed for low odor require maximum melt temperature 305 °C.

For lamination of oriented polypropylene or polyester film, the LDPE layer must be processed at lower melt temperature if the substrate is heat-sensitive. Chemical primers or corona treatment at 38–42 mN/m surface energy are used before molten LDPE is applied. The choice among LOTTE, LG Chem, and Hanwha for these structures is typically made after trial on the actual line because variations in air gap, die gap, and line speed dominate grade-to-grade differences.

Wire and cable jacketing is another grade-selection scenario. LDPE used as conductor insulation requires high purity and low contamination; dielectric constant at 1 MHz per IEC 60250 is 2.28–2.32 for LDPE. Korean suppliers supply wire-grade LDPE, but this segment is smaller than film; LOTTE and Hanwha technical bulletins for wire grades specify dissipation factor below 5 × 10⁻⁴ at 1 MHz. Processing conditions for wire insulation require pre-drying of pellets only when relative humidity exceeds 60 %; otherwise, hydrolytic degradation of antioxidant packages is not normally observed.

Injection molding of LDPE closures and medical devices is a smaller application compared with film and coating. MFR requirements for injection grades are higher, typically 4–10 g/10 min; lower-viscosity grades from LG Chem and LOTTE are available. Mold shrinkage for LDPE is approximately 1.5–2.5 %; cooling time is governed by part thickness and melt temperature 180–220 °C. Weld line strength in LDPE molded parts is sensitive to mold temperature; mold temperatures below 20 °C degrade weld line integrity. Hanwha TotalEnergies supplies LDPE injection grades, but published data for this specific configuration is limited.

Extrusion blow molding of squeeze bottles uses LDPE grades with MFR 0.5–1.5 g/10 min and high melt strength to maintain parison stability. The Korean suppliers offer blow molding grades; however, HDPE dominates rigid bottle markets, and LDPE blow molding comparisons are less differentiated.