PetroChina Daqing KunLun mLLDPE DQLV0810 is a metallocene-catalyzed linear low-density polyethylene supplied in pellet form for blown-film, cast-film, and extrusion-lamination conversion. Commercially published typical values for the grade place melt flow rate at 1.0 g/10 min under ISO 1133-1:2022 at 190 °C/2.16 kg and nominal density at 0.918 g/cm³ under ISO 1183-1:2019. These two values position the resin in the high-toughness film-sealing segment; lot-specific release data on the certificate of analysis may vary within the producer’s control limits. Because polymerization uses a metallocene single-site catalyst, the short-chain branching distribution is more homogeneous than in conventional Ziegler-Natta linear-low-density polyethylene of similar density.

What Limits the Processing Window for DQLV0810 in Monolayer Blown Film?

On monolayer blown-film lines, the practical operating boundaries emerge from three interacting parameters: die gap, air-ring stability, and melt temperature. Metallocene LLDPE resins with a melt index near 1.0 g/10 min typically exhibit lower critical shear rates for sharkskin melt fracture than Ziegler-Natta grades at the same melt index. When DQLV0810 is run through a 40 mm to 65 mm single-screw extruder with a 24:1 to 30:1 L/D ratio and a LLDPE barrier screw, melt temperatures between 190 °C and 230 °C are common. A die gap of 1.5 mm to 2.2 mm is often specified for monolayer film; gaps below 1.2 mm increase the probability of melt fracture unless higher die temperatures or processing aids are applied. Frost-line height is typically maintained at 6 to 10 die diameters, depending on air-ring design and tower height. Blow-up ratios between 2.0:1 and 3.0:1 are used to orient the film in both directions; higher blow-up ratios raise transverse-direction tear resistance but can destabilize the bubble because of the resin’s narrow molecular weight distribution. Field observations from blown-film campaigns indicate that switching from a conventional Ziegler-Natta LLDPE of equivalent density to DQLV0810 can increase extruder head pressure by 10% to 20% at constant screw speed, which makes screen-changer pressure alarms and die-body pressure ratings the primary constraints rather than motor load. Pre-drying is not required for moisture removal because the resin is non-hygroscopic; however, pellet surfaces should be brought to ambient temperature before handling to avoid condensation at relative humidities above 60%.

Unlike Ziegler-Natta linear-low-density polyethylene, which produces a heterogeneous distribution of inter- and intramolecular comonomer placement, DQLV0810 is synthesized with a single-site metallocene catalyst. This changes the solid-state morphology and the melt-extensional behaviour. In gel permeation chromatography of metallocene LLDPE resins, published polydispersity indices are commonly in the range of 2.0 to 3.0, whereas conventional LLDPE grades often fall between 3.5 and 5.0 when measured by ISO 16014; for DQLV0810, the producer’s open datasheet may not report a lot-specific molecular weight distribution, and published GPC values for this specific configuration are limited. The homogeneous branching distribution reduces the concentration of low-molecular-weight, high-comonomer fractions that plasticize the amorphous phase and increase extractables. As a result, blown film from DQLV0810 can be sealed at a lower temperature than a Ziegler-Natta LLDPE of the same nominal density because the crystalline melting distribution is narrower and the surface of the seal layer reaches the softening point more uniformly. This effect is not unique to DQLV0810 but is characteristic of metallocene LLDPE chemistry.

Compared with high-pressure low-density polyethylene, DQLV0810 has fewer long-chain branches and lower melt strength in elongational flow, which limits its use as a pure high-stalk resin but improves draw-down in cast film. Compared with metallocene LLDPE grades at density 0.912 g/cm³, the 0.918 g/cm³ nominal density lowers dart impact slightly but raises secant modulus measured by ASTM D882; compared with 0.924 g/cm³ metallocene grades, it provides lower seal initiation and better puncture resistance, but lower stiffness. These differences make the grade a mid-range sealing-layer resin rather than a high-modulus or ultra-low-temperature sealant.

Mechanical, Optical, and Seal Performance Parameters for 40 µm Film

Film property data for metallocene LLDPE are sensitive to gauge, draw-down ratio, and cooling rate; therefore, comparisons should be made only when specimen preparation is stated. For 40 µm monolayer blown film produced under a 2.5:1 blow-up ratio and a frost-line height of 8 die diameters, published property ranges for mLLDPE of 1.0 MI / 0.918 g/cm³ include dart impact values measured by ASTM D1709A that exceed those of a Ziegler-Natta LLDPE of the same density by approximately 30% to 60%, Elmendorf tear strengths by ASTM D1922 that may be higher in the machine direction but lower in the transverse direction depending on blow-up ratio, and haze by ASTM D1003 that is commonly 30% to 50% lower. Seal initiation temperature, defined as the point at which a seal strength of 4.4 N/15 mm is reached on a laboratory heat sealer, is typically 8 °C to 12 °C lower for metallocene LLDPE than for conventional LLDPE at the same density. Because these are cross-resin comparisons rather than DQLV0810-specific certificates, lot-specific tensile yield, elongation at break, and puncture resistance should be obtained from the producer’s technical data sheet. Published data for DQLV0810-specific mechanical values under all film fabrication conditions is limited.

In cast-film and extrusion-lamination operations, DQLV0810 is processed at melt temperatures between 230 °C and 275 °C. The narrower molecular weight distribution reduces draw resonance amplitude compared with broader-distribution LLDPE at the same line speed, but neck-in behaviour is a function of both resin elasticity and air-gap length. On cast-film lines using a 0.5 mm to 0.8 mm die gap and air-knife-assisted pinning, line speeds above 150 m/min can be achieved if the extruder is sized for the output; published data for this specific configuration is limited. Because mLLDPE does not contain high levels of low-molecular-weight waxes, it is used in sealant layers of multilayer films where low seal initiation and reduced seal contamination are required. It is not supplied as a single solution for high-stiffness applications, because the density of 0.918 g/cm³ produces lower secant modulus than high-density polyethylene or polypropylene. Slip and antiblock additives are typically introduced via masterbatch at 0.5 wt% to 2.0 wt% to control coefficient of friction measured by ASTM D1894 and blocking behaviour at the unwind.

When DQLV0810 Replaces Conventional LLDPE in High-Stalk Blown Film Lines

In high-stalk extrusion lines running conventional LLDPE at a given die, a direct substitution of DQLV0810 requires evaluation of bubble stability and frost-line morphology. Because metallocene LLDPE has lower melt strength in some elongational regimes than low-density polyethylene but a more uniform extensional flow than Ziegler-Natta LLDPE, the stalk height may need to be adjusted to prevent bubble instability. Processors have reported that high-stalk lines optimized for LDPE-rich blends may exhibit unstable free-surface deformation when mLLDPE exceeds 70 wt% in the blend, unless air-ring adjustment or die-temperature profiling is applied. For DQLV0810 in high-stalk monolayer structures, a die gap of 2.0 mm or above and a blow-up ratio below 2.5:1 are common starting conditions. On a 90 mm extruder with a 30:1 L/D barrier screw, processing at melt temperatures of 200 °C to 220 °C and a screen pack of 60/80/100 mesh can control initial pressure, but the melt pressure at the die entrance should not exceed the die manufacturer’s maximum rating. Adding a polymer processing aid at 200 ppm to 600 ppm may be required to delay sharkskin at high output rates; fluorine-based processing aids are common, but their loading should be kept below the supplier’s maximum to avoid surface plate-out.

Food-contact compliance for DQLV0810 is not a single-property declaration. The resin is an olefin polymer within the scope of 21 CFR 177.1520 when used in the United States, but the specific paragraph and end-use restrictions depend on the extraction test results and the food type. For European Union applications, compliance with Regulation (EU) No 10/2011 requires overall migration testing according to EN 1186 series and specific migration testing where applicable. REACH registration under EC No 1907/2006 applies to substances imported or manufactured in the EU; the producer’s safety data sheet should state the registration status for the grade. RoHS Directive 2011/65/EU Annex II restrictions are relevant only if the final article falls within an electrical and electronic equipment category. DQLV0810 should not be blended with pro-oxidant additives if the film is intended for food-contact use, because degradation products may violate migration limits. Avoid storage exceeding 40 °C and direct sunlight, which can increase odor and discoloration through thermo-oxidative degradation.

Heavy-duty packaging, frozen food films, and form-fill-seal structures are conversion areas where the lower seal initiation temperature of DQLV0810 is used to reduce heat-seal dwell time on vertical form-fill-seal machines. In vertical form-fill-seal packaging, a decrease in seal initiation of 8 °C to 12 °C relative to a Ziegler-Natta LLDPE of equal density can allow a reduction in sealing-bar setpoint or an increase in cycle speed, provided the seal-bar pressure and dwell time are characterized. On rotary fill-seal equipment, the resin’s narrow melting distribution reduces the occurrence of stringing and seal contamination compared with broader-distribution LLDPE, but screw speed and back pressure should be adjusted to avoid overheating. These operational benefits are contingent on the additive package, film gauge, and lamination structure; the producer’s technical service bulletin should be consulted for the specific DQLV0810 lot. Published data for this specific configuration is limited.