Shenyang Chemical mLLDPE 1018HA is a metallocene-catalysed linear low-density polyethylene grade with a nominal density of 0.918 g/cm³ (ASTM D1505) and a melt mass-flow rate of 1.0 g/10 min (ASTM D1238, 190°C/2.16 kg). The grade is supplied in pellet form for blown film extrusion, cast film, and extrusion lamination. The 1018HA designation separates it from lower-melt-index metallocene grades used for heavy-duty sacks and from higher-melt-index metallocene grades used for thin-gauge hygiene film. Compared with a conventional Ziegler-Natta C4-LLDPE of the same density and melt index, the metallocene architecture provides a narrower short-chain branching distribution. This shifts the melting range and heat-seal response toward lower temperatures, reduces low-molecular-weight extractables, and alters optical and toughness-related film properties. Published data for this specific configuration are limited; comparative values are therefore based on metallocene LLDPE class behaviour and should be verified against the Shenyang Chemical certificate of analysis for each batch.

How Does the Narrow Short-Chain Branch Distribution Affect Sealing and Optical Performance?

In 1018HA, comonomer units are distributed more uniformly across the molecular weight distribution than in a conventional butene LLDPE. A Ziegler-Natta C4-LLDPE contains a high-molecular-weight fraction with limited branching that crystallizes into thick lamellae and raises the melting onset. In the metallocene grade, that fraction is smaller, so the heat-seal initiation temperature tested according to ASTM F88 is typically 5–15°C lower than that of an equivalent-density C4-LLDPE at a comparable 1.0 g/10 min melt index. The lower seal initiation reduces the jaw temperature required on vertical form-fill-seal machines while maintaining seal-strength plateaus specified by package integrity protocols. Total haze of 25 µm blown film measured by ASTM D1003 is also lower because fewer surface crystallites scatter transmitted light. The corresponding reduction in seal-bar smoke and odour is tied to lower extractables rather than to additive loading.

On a 65 mm single-screw blown film extruder with a 30:1 L/D barrier screw, typical processing of 1018HA begins with a feed-zone temperature of 180°C, rises to 190–200°C in the compression and metering zones, and reaches 210°C at the adapter and die. The resulting melt temperature is maintained between 200°C and 230°C. A die gap of 1.8–2.5 mm and a blow-up ratio of 2.5:1 to 3.5:1 are used because the resin has lower melt elasticity than a high-pressure LDPE. Frost-line height is typically held at 300–500 mm above the air ring to balance bubble stability with film optics. If pellets are stored above 60% relative humidity, surface moisture can generate film specks; a 70°C desiccant dryer residence of 2 hours is used to restore consistency. Processors also use 200–500 ppm of a fluoropolymer processing aid to reduce die lip deposits during extended runs.

Melt Fracture Boundaries in Blown Film Dies

Sharkskin melt fracture with 1018HA appears when wall shear stress at the die lip exceeds the critical level for a narrow-molecular-weight polyethylene. The defect is commonly observed on narrow die gaps below 1.5 mm at high screw speeds. Because the resin lacks the long-chain branching of LDPE, its shear-thinning response is less pronounced, so die-pressure adjustments do not eliminate the defect as readily. The standard corrective sequence is to increase the die gap to 2.0–2.5 mm, raise melt temperature by 5°C increments up to a maximum of 230°C, and verify that the die lip has no carbonized residue. If sharkskin persists, 200–500 ppm fluoropolymer processing aid is added. In coextruded structures, placing 1018HA in the middle or sealant layer rather than the outer skin can also reduce visible melt fracture because the outer layer may be formulated with LDPE or a high-melt-strength LLDPE.

For cast film lines, 1018HA is processed with a flat die and chill-roll temperatures between 20°C and 30°C. The lower melt strength permits high line speeds but may cause draw resonance if the air gap exceeds 25 mm; a shorter air gap or a vacuum box is used. In cast stretch film, 1018HA may be blended with an ultra-low-density metallocene plastomer to lower seal initiation further as measured by ASTM F88, but this reduces modulus and increases blocking unless an appropriate antiblock is selected.

Because 1018HA has lower melt strength than a high-pressure LDPE of similar melt index, bubble oscillation may occur when the frost line is raised above 500 mm or when air-ring velocity is increased. Converters frequently blend 10–30 wt% LDPE with an MI 0.3–0.8 g/10 min film grade to increase bubble stiffness without eliminating the sealing advantage. The blend ratio must be fixed before film qualification because LDPE addition changes dart drop impact under ASTM D1709A, tensile elongation under ASTM D882, and haze under ASTM D1003. For applications requiring higher modulus, up to 5 wt% HDPE may be incorporated, but this reduces transparency and narrows the seal-peel plateau. Such blending does not shift the density specification of the final film because the average density is determined by the selected letdown ratios.

When a Sealant Layer Requires Lower Initiation Temperatures

In coextruded films and laminates, 1018HA is often placed in the sealant skin because its sealing window starts lower than a Ziegler-Natta ethylene-hexene LLDPE of similar density. A three-layer A/B/C film with 1018HA as the sealant layer can seal at temperatures 5–10°C lower than a conventional C6-LLDPE sealant, reducing hot-tack failure in vertical form-fill-seal lines. Hot-tack strength is characterized by ASTM F1921 using a 25 mm specimen, a seal pressure of 0.275 MPa, and a dwell time of 0.5 s. The lower seal initiation arises from the earlier onset of crystal melting, not from slip additive bloom. Additive selection requires attention: a slip or antiblock masterbatch that migrates differently than in a Ziegler-Natta resin can shift the coefficient of friction measured by ISO 8295 during the first 72 h after extrusion, so coefficient-of-friction targets should be verified after storage.

The shear viscosity of 1018HA under processing conditions is lower in the high-shear region of the extrusion die than that of a comparable Ziegler-Natta C4-LLDPE, because the narrower molecular weight distribution contains fewer ultra-long-chain molecules that contribute to viscosity. Capillary rheometry according to ISO 11443 at 190°C shows a less pronounced shear-thinning response, which reduces screw torque in the metering zone but increases die-wall shear stress sensitivity. In practice, this means the screw back-pressure in a 65 mm extruder may be 5–10% lower than that of a conventional C4-LLDPE under the same screw speed, and the resin can be run at a slightly higher screw speed before reaching the motor current limit. The lower extensional viscosity also improves draw-down during cast film orientation but requires tighter air-ring control in blown film.

Compared with high-pressure LDPE, 1018HA has lower long-chain branching, higher dart impact at equivalent gauge, and higher drawdown, which allows downgauging from 50 µm to 25 µm in some monolayer structures while maintaining toughness measured by ASTM D1709A. The limitation is a lower melt strength; bubble stability at blow-up ratios above 4.0:1 generally requires blending with LDPE. Compared with higher-melt-index metallocene grades, the 1.0 g/10 min melt flow rate of 1018HA favours thicker films and lower screw pressure, whereas higher-melt-index mLLDPE grades are better suited to high-speed thin-gauge cast lines.

Among metallocene grades, 1018HA is defined by the combination of 0.918 g/cm³ density and 1.0 g/10 min melt index. A lower-density metallocene grade, such as one below 0.912 g/cm³, offers lower seal initiation and better flex-crack resistance but reduces stiffness. A higher-density grade above 0.925 g/cm³ improves modulus and moisture barrier but raises seal initiation. Within the same density, a higher melt-index grade above 2.0 g/10 min improves flow in complex tool cavities but lowers dart impact and tear resistance. Therefore 1018HA occupies a mid-range balance for blown film stiffness, toughness, and processability.

If the line is producing food-contact film, slip and antiblock masterbatches must be selected from grades whose carriers are also olefinic and are covered under FDA 21 CFR 177.1520 or Regulation (EU) No 10/2011. Migration of primary amide slip agents in a metallocene matrix is faster than in a Ziegler-Natta LLDPE because the lower crystallinity increases amorphous-phase diffusion; coefficient of friction under ISO 8295 may therefore drop below 0.20 within 24–48 h, compared with 72 h or longer for a conventional C4-LLDPE. This can be an advantage for high-speed packaging but must be accounted for in the aged friction specification.

Regulatory compliance for the final structure is not established by the base resin alone. The olefin polymer in 1018HA may fall under FDA 21 CFR 177.1520 when the total extractables and end-use conditions in the final article comply with the specified limits; the pellet itself must be supplemented by a manufacturer-issued food-contact declaration. For the European Union, migration testing under Regulation (EU) No 10/2011 is required for the converted film, and the grade-specific REACH statement should be obtained from Shenyang Chemical. The base polymer is not a flame-retardant grade, is not suitable for continuous service above 80°C in load-bearing applications without oxidative stability testing, and should not be assumed to meet pharmaceutical primary-packaging requirements unless specific extractables and leachables data are available.