PetroChina Guangdong KunLun mLLDPE HPR1018HA is a single-site metallocene ethylene-1-hexene linear low-density polyethylene produced at the Guangdong integrated refining and petrochemical complex. The resin is classified as a blown-film grade with a nominal density of 0.918 g/cm³ determined by ISO 1183-1 or ASTM D1505 and a nominal melt flow rate of 1.0 g/10 min at 190 °C under 2.16 kg load per ISO 1133-1:2022. In the producer’s certificate-of-analysis release, lot-to-lot melt flow rate is typically controlled within ±0.1 g/10 min, while density is controlled within ±0.001 g/cm³. The grade is supplied as cylindrical pellets with hindered phenolic stabilizer protection; pellet size distribution and bulk density are held to the producer’s silo-to-silo transfer specification. The material is intended for monolayer and coextruded blown film where a measurable reduction in seal initiation temperature and an increase in dart impact strength are required relative to conventional butene-based Ziegler-Natta LLDPE. Published engineering data specific to HPR1018HA remain limited; the following paragraphs distinguish independently established mLLDPE class behavior from field observations reported on production-scale blown-film lines.

Film fabricated from HPR1018HA on a 55 mm single-screw extruder with a 30:1 L/D barrier screw, 200 mm spiral die, 1.8 mm die gap, and 2.5 BUR typically exhibits machine-direction tensile yield values between 8 MPa and 12 MPa and transverse-direction tensile yield values between 7 MPa and 11 MPa when tested per ISO 527-3; these ranges reflect the 0.918 g/cm³ density class rather than an exact product guarantee. Dart impact values for 25 μm monolayer film commonly fall between 600 g and 900 g under ASTM D1709-22 Method A, while Elmendorf tear values measured under ASTM D1922-23 typically fall between 3.0 N and 7.0 N in the machine direction and between 4.0 N and 8.0 N in the transverse direction. The seal initiation temperature, determined on a laboratory film sealer at 0.5 s dwell and 0.3 MPa jaw pressure, is frequently reported in the range of 95 °C to 105 °C; the value is influenced by slip and antiblock additive packages and by the concentration of low-molecular-weight fractions. These ranges are provided as a selection envelope; film producers should request the grade-specific technical bulletin and run plant-scale confirmation on the target extrusion line.

What separates HPR1018HA from Ziegler-Natta C4-LLDPE of the same density?

Single-site catalysis changes the short-chain branching distribution. Conventional Ziegler-Natta C4-LLDPE carries a heterogeneous comonomer distribution: early polymer fractions are largely homopolymer, and later fractions contain high levels of n-butyl branches. Under ASTM D6474 or ISO 16014-1 molar mass distribution analysis, this heterogeneity appears as a broad molecular weight distribution and a higher extractables fraction. HPR1018HA, by contrast, is produced with a metallocene catalyst that inserts 1-hexene in a more statistically controlled sequence, yielding a narrower molecular weight distribution and a more uniform branch distribution across the molecular weight axis. The practical consequences are threefold: equivalent density can be obtained with lower overall comonomer content; crystalline lamellae are thinner and more uniform, lowering the seal initiation temperature; and stress-induced tie-chain formation is improved, raising dart impact and Elmendorf tear resistance. In addition, the metallocene grade generally yields haze values below 12% and 60° gloss values above 60 GU under ASTM D1003-21 and ASTM D2457-21, respectively, for 50 μm film, whereas Ziegler-Natta C4-LLDPE of the same density may exhibit haze above 15%.

On high-output blown-film lines equipped with internal bubble cooling and automatic profile air rings, HPR1018HA is processed at melt temperatures of 185 °C to 210 °C; higher melt temperatures reduce melt viscosity and lower extruder head pressure but can destabilize the bubble if the outer cooling air remains fixed. A die gap of 1.8 mm to 2.3 mm is typical for 0.918-density metallocene LLDPE; narrower gaps may raise shear stress beyond the critical value for sharkskin because the narrow molecular weight distribution provides less shear-thinning than broad-MWD Ziegler-Natta resins. Processors running 30:1 L/D grooved-feed extruders report that specific energy input ranges from 0.18 kWh/kg to 0.24 kWh/kg, and extruder head pressure at 100 kg/h output normally falls between 300 bar and 420 bar for a 200 mm spiral die. Throttle-valve or gear-pump operation permits a more stable pressure profile; without it, melt pressure oscillation can exceed ±5 bar and produce gauge bands in the finished film.

For converters using HPR1018HA in heavy-duty sacks and industrial liners, the resin is often introduced as the core layer with lower-cost C4-LLDPE skins. The metallocene core is added at 20 wt% to 40 wt% of the total structure; at this addition level, the dart impact strength of 60 μm film is improved by 15% to 25% relative to a C4-LLDPE reference, while seal initiation temperature is reduced by 4 °C to 8 °C. These results are derived from converter plant trials and are sensitive to die temperature uniformity and air-ring control. The product is also usable in lamination film where low gel counts and stable melt curtain formation are required; melt curtain stability at 290 °C to 300 °C extrusion coating temperatures has been reported as acceptable when the polymer is blended with 5 wt% to 10 wt% low-density polyethylene to add long-chain branching and improve neck-in control. Without LDPE modification, the melt curtain may show neck-in above 80 mm at a 300 mm die-to-nip distance, increasing edge trim and reducing adhesion to the substrate.

When HPR1018HA replaces HPR2018HA in coextruded film, where is the inflection point in dart impact versus line speed?

At constant screw speed and die geometry, the lower melt flow rate of HPR1018HA increases residence time and specific energy input. The higher viscosity also improves bubble stability under high blow-up ratios, but it can limit maximum line speed when the extruder is torque-limited. In a three-layer line with 45 mm extruders and 30:1 L/D screws, substitution of HPR1018HA into the skin layers at 2.5 BUR frequently maintains dart impact values at 650 g to 800 g in 40 μm film, whereas the 2.0 g/10 min HPR2018HA may fall toward 500 g to 650 g at equivalent gauge and output. The trade-off is a measurable reduction in maximum screw speed before motor amperage reaches the 90% continuous-duty limit; converters often increase barrel temperatures by 5 °C to 10 °C to recover throughput. Published data for this specific grade combination is limited, and the actual inflection point is extrusion-line dependent.

In blown-film conversion, film gauge variation below ±2% is achievable only when die lip temperature variation is held below ±1.5 °C; radial melt temperature differences greater than 3 °C across a 200 mm die produce visible bands and reduce Elmendorf tear uniformity by more than 10%. Melt pressure should be recorded before the screen pack. A pressure increase of more than 10% over 24 h at constant throughput indicates solids plugging or screen pack contamination; the screen pack should be changed when pressure drop exceeds 250 bar. For bubble stability, a dual-lip air ring with internal bubble cooling is recommended when the blow-up ratio exceeds 2.5:1; without internal bubble cooling, the low melt strength of metallocene LLDPE can cause oscillation at the frost line and produce alternating thick-thin bands. Frost line height is normally maintained between 1.5 and 4 times the die diameter; lower settings reduce orientation and dart impact, while higher settings increase bubble instability.

Metallocene linear low-density polyethylene lacks the long-chain branching present in low-density polyethylene. In stretch film, this means lower strain hardening and lower melt strength; however, HPR1018HA can be used as a cling-layer or core-layer modifier if an adequate bubble stabilization system is available. The resin is not a primary high-cling resin; its density and crystallinity produce a cling force that is typically below 100 g when measured by film-to-film cling methodology, and it requires the addition of a tackifier or a polyisobutylene-based cling masterbatch at 1 wt% to 3 wt% to reach machine-grade cling levels. Published data for this specific configuration is limited; converter evaluations are required before commercial use.

For applications requiring food-contact compliance, the base polyolefin falls under 21 CFR 177.1520 and EU 10/2011; however, the converter remains responsible for verifying overall migration limits on the finished printed or laminated structure. The material is subject to REACH registration obligations and is supplied with a safety data sheet that lists the stabilizer package. Polyethylene resins do not require routine pre-drying unless stored under conditions where surface condensation forms; where bagged pellets have been exposed to relative humidity above 60%, drying at 60 °C to 70 °C for 2 h in a desiccant hopper is sufficient to eliminate surface moisture and prevent bubble pinholes. During changeover from polar polymers or from PVC, the extruder should be purged with a fractional-melt high-density polyethylene or a dedicated commercial purge compound; residual polar polymer can generate hydrochloric acid and degrade the metallocene resin. The grade is not recommended for hot-fill containers, autoclave components, or continuous service above 70 °C without long-term oxidative aging data; the upper service temperature is governed by antioxidant consumption and not by immediate melting. Coextrusion with ethylene-vinyl alcohol copolymers requires maleic anhydride-grafted tie layers and should not be attempted without evaluation of interlayer adhesion under ASTM F904.

Silo-to-silo transfer of metallocene LLDPE is sensitive to fines generation. Because the pellets have a narrow molecular weight distribution, the melt is more prone to shear-induced surface roughness at high screw speeds; pellet feed zones should be maintained at 40 °C to 60 °C to prevent moisture condensation, and conveying air should be dried to below -20 °C dew point to avoid fines adhering to the hopper wall. In film conversion, edge trim and start-up scrap are reprocessed at rates of 5 wt% to 15 wt%; higher reuse may reduce dart impact and raise gel counts because antioxidant depletion is non-linear. Vacuum conveying systems should use a minimum transport velocity of 20 m/s to prevent streaming; dense-phase systems operating below 10 m/s are preferred for pellet attrition control.