PetroChina Dushanzi KunLun mLLDPE EZP2703HH is a 1-hexene-based metallocene linear low density polyethylene produced at the Dushanzi Petrochemical complex. The resin is synthesized in a gas-phase polymerization train using a single-site metallocene catalyst system, which yields a narrow molecular weight distribution and a controlled short-chain branching distribution relative to conventional Ziegler-Natta copolymers. The nominal melt flow rate is 2.7 g/10 min when determined at 190°C under a 2.16 kg load in accordance with ISO 1133-1:2022, and the nominal density is 0.927 g/cm³ when tested by ISO 1183-1:2019. These values position EZP2703HH as a stiff, medium-melt-viscosity film grade; the 1-hexene comonomer provides a different balance of toughness, seal initiation, and optics than 1-butene-based linear low density polyethylene of comparable density. The grade is supplied as natural pellets and is used in heavy-duty sacks, agricultural silage wrap, high-clarity packaging, and laminating film where puncture resistance and seal integrity are critical.

Specification Envelope and Routine Certification Data

The certificate of analysis for EZP2703HH normally reports melt flow rate and density as specification properties. Other properties in the following table are representative values obtained from blown-film evaluations at 25 µm gauge, 2.5 blow-up ratio, and 1.5 mm die gap; they are thickness-dependent and are not contractual release limits. Lot-to-lot melt flow rate control is commonly maintained within ±0.3 g/10 min, and density control is commonly maintained within ±0.003 g/cm³, though written purchase specifications should be confirmed with the producer.

Published film data for this specific grade across all commercial die configurations are limited; the values above should be used for grade selection rather than incoming material acceptance. Film test results change with gauge, draw, frost-line conditions, and additive package. The reported density of 0.927 g/cm³ yields a crystalline fraction higher than typical 0.918 g/cm³ C4-LLDPE film grades, which increases secant modulus and reduces oxygen and moisture vapor transmission rates at equal thickness. The hexene branch length, however, avoids the severe toughness loss that would accompany a butene copolymer at the same density.

In parallel-plate rheometry at 190°C and 1 rad/s, metallocene grades of this melt-index class typically show a narrower shear-thinning transition than conventional broad-molecular-weight LLDPE. The melt-phase rheology of EZP2703HH is characteristic of single-site linear low density polyethylene: lower plateau modulus and less shear thinning than broad-MW Ziegler-Natta resins. In practice, this translates to lower die-head pressure at equivalent output but higher sensitivity to melt-temperature gradients across the die lip. Multi-zone die temperature control with ±1°C band accuracy is recommended because the narrow molecular weight distribution provides less shear heating to mask local cold spots. Additive packages may include antioxidants, neutralizers, and processing aids; type and level must be verified on the certificate of analysis because some surface-migrating additives alter coefficient of friction and seal behavior. Coefficient of friction is tested according to ASTM D1894, and blocking force is tested according to ASTM D3354; these values are modified by additive concentration and film aging.

When 1-Hexene-Metallocene Chemistry Replaces Butene in Film Structures

The performance difference between EZP2703HH and a conventional Ziegler-Natta C4-LLDPE is most evident in dart impact, tear balance, and seal initiation. In Ziegler-Natta copolymers, the active sites are heterogeneous, producing a broad molecular weight distribution and a comonomer distribution skewed toward low-molecular-weight chains. High-molecular-weight chains contain fewer short-chain branches, forming larger crystallites that increase haze and decrease low-temperature toughness. In a metallocene 1-hexene grade, the single-site catalyst places comonomer more uniformly across molecular weight fractions; the longer C6 branch reduces crystallite size and tie-chain disruption. Film evaluations at 25 µm with 2.5 blow-up ratio and 1.5 mm die gap typically show EZP2703HH with lower haze and higher dart impact than a C4-LLDPE of similar melt index and density. The heat-seal initiation temperature shifts downward because the narrow composition distribution produces a narrower melting endpoint; less energy is required to achieve interfacial chain interdiffusion at seal-bar interfaces.

The comparative values are typical blown-film results and do not represent contractual specifications. Compared with lower-density mLLDPE grades in the same product family, EZP2703HH provides higher tensile yield and lower moisture vapor transmission at equivalent gauge, but the higher density reduces low-temperature impact relative to 0.918 g/cm³ metallocene products. Selection therefore depends on the target balance between stiffness and cold-temperature fracture resistance. Published data for this specific configuration are limited for sub-zero impact; if applications require performance below -10°C, the converter should evaluate dynamic puncture under ISO 6603-2 or comparable instrumented impact testing rather than relying on room-temperature dart impact alone.

Film converters running EZP2703HH on monolayer blown-film lines typically select extruders with 25:1 to 30:1 L/D ratios and grooved feed sections. Melt temperatures between 185°C and 215°C are used; lower temperatures reduce oxidative gel formation but increase die-head pressure, while higher temperatures raise internal bubble pressure stability but may lower melt extensibility. Because the metallocene resin has a narrow molecular weight distribution, die-head pressure at the same screw speed is generally lower than with a broad-MW Ziegler-Natta C4-LLDPE, but bubble stability is also lower than LDPE. Die gaps of 1.2 mm to 2.0 mm are recommended for 100% mLLDPE structures, compared with 0.8 mm to 1.2 mm for LDPE-rich structures. A blow-up ratio of 2.0 to 3.0 and a frost-line height held within ±10% of setpoint are typical; excessive frost-line fluctuation increases gauge variation and reduces dart impact on the final film. Converters using older single-lip air-ring equipment may need to blend 10% to 20% LDPE to restore bubble stability, though this blend raises haze and increases seal initiation temperature. Drying is not routinely required unless the pellets are stored under conditions that cause surface condensation; if wet pellets are introduced, surface moisture can produce blowholes and reduce film quality.

What Limits the Downgauging Window in Heavy-Duty Sack and Agricultural Films?

In heavy-duty sack and agricultural film structures, downgauging from 45 µm to 30 µm reduces mass per package but increases the required puncture energy per unit thickness. EZP2703HH is specified where the converter must maintain dart impact above 800 g at 25 µm and Elmendorf tear in machine direction above 2.0 N after slit-seal conversion. The grade is used in liquid-packaging bags, freezer film, and high-strength agricultural wraps. Heat-seal response is evaluated with ASTM F2029 for seal initiation and ASTM F1921 for hot-tack strength. The narrow melting distribution allows seal initiation around 103°C; however, the same narrow distribution reduces the temperature window for hot-tack strength. On vertical form-fill-seal lines running above 40 m/min, seal-bar temperature fluctuation of ±5°C can shift peel strength outside the target window. Processors therefore maintain seal-bar temperatures within ±3°C and verify seal strength with ASTM F88.

Regulatory compliance for food-contact uses is limited to national and regional approvals that apply to polyolefins derived from authorized monomers. In the United States, polyethylene resins may qualify under 21 CFR 177.1520 when the final article meets migration and end-use requirements. In the European Union, compliance is assessed under Regulation (EU) No 10/2011 with specified migration limits. Converters must verify that additives, printing inks, and lamination layers meet applicable food-contact obligations; the resin supplier’s certificate of analysis does not replace finished-article compliance testing.

Shipping and storage conditions are 25 kg net polyethylene bags on oil-free pallets. Storage should be in a dry, ventilated area below 40°C and away from direct sunlight; exposure to aromatic hydrocarbons, chlorinated solvents, or strong oxidizing acids should be avoided because these agents can induce environmental stress cracking or oxidative degradation. Before running, each hopper load should be checked for melt flow rate and density against the certificate of analysis using ISO 1133-1:2022 and ISO 1183-1:2019; lot-to-lot deviations outside normal ranges should be corrected by adjustments to die gap, melt temperature, and haul-off speed rather than by simple screw-speed compensation.