Sinopec Qilu mLLDPE QHM32F is a metallocene-catalyzed linear low-density polyethylene film resin produced by Qilu Petrochemical Company. The product is classified as an ethylene/1-hexene copolymer, with a nominal density of 0.918 g/cm³ and a melt mass-flow rate of 1.0 g/10 min determined under ISO 1133-1:2022 at 190 °C and 2.16 kg piston load. The base polymer is identified by CAS 9002-88-4. The metallocene catalyst system yields a narrower molecular-weight distribution and a more uniform intermolecular comonomer distribution than conventional Ziegler-Natta linear low-density polyethylene. QHM32F is designed for blown-film applications requiring high dart impact resistance, low haze, reduced seal-initiation temperature, and controlled extractable levels. Typical end uses include high-clarity food packaging, heavy-duty sacks, form-fill-seal structures, lamination sealant webs, and agricultural films. The grade is used both as a neat resin and in blends with LDPE or other LLDPE grades to adjust melt strength and bubble behaviour.

The resin’s solid-state behaviour is directly linked to short-chain branching architecture. In conventional Ziegler-Natta LLDPE, comonomer is concentrated preferentially in the low-molecular-weight fraction, leaving the high-molecular-weight fraction relatively linear and increasing crystallite-size heterogeneity. QHM32F, by contrast, distributes 1-hexene more evenly across the molecular-weight distribution, reducing the population of low-melting crystallites and producing a more uniform lamellar structure. This change is measurable as lower thickness-normalised haze under ASTM D1003-13 and higher dart impact under ASTM D1709-16a, provided that melt temperature, frost-line height, and blow-up ratio remain within the stabilised processing window. The same narrow molecular-weight distribution also reduces shear-thinning; apparent shear viscosity measured by capillary rheometry under ISO 11443 at 190 °C and 1,000 s⁻¹ falls in the range of 300–600 Pa·s, which is typical for a 1.0 g/10 min metallocene film resin.

What processing envelope governs stable bubble formation on high-stalk film lines?

On a 90 mm grooved-feed single-screw extruder with an L/D of 30:1, a barrier screw, and a Maddock mixing section, QHM32F is typically processed with a barrel temperature profile from 170 °C in the feed zone to 210 °C in the metering zone, with a die temperature of 200–220 °C. Melt temperature measured at the die entrance should be maintained between 195 °C and 220 °C. Sustained operation above 240 °C increases the probability of oxidised gel formation and surface haze, and extended hold time at melt temperatures above 220 °C should be limited to less than 20 min. The lower extensional strain hardening of metallocene LLDPE compared with LDPE narrows the stable bubble window, so die gap, frost-line height, and air-ring setting require closer control than for a conventional high-pressure LDPE grade.

A die gap of 1.5–2.5 mm is recommended for monolayer and multilayer blown-film lines. Narrower gaps increase shear stress at the die lip and can promote sharkskin melt fracture; wider gaps reduce shear stress but may lower machine-direction orientation and tensile properties. A blow-up ratio of 2.0:1 to 3.0:1 and a frost-line height of 3–6 die diameters are typical. Chilled air at 10–15 °C from a dual-lip air ring improves bubble stability, while internal bubble cooling is generally required to maintain output rates above 150 kg/h on larger lines. If sharkskin appears, increasing the die gap or reducing screw speed is preferred before raising melt temperature, because QHM32F has limited shear-thinning and may deteriorate rapidly at excessive temperatures. Fluoropolymer processing aids can be used at 200–800 mg/kg to reduce die pressure and delay melt fracture, but their use must be validated for food-contact compliance and film surface properties.

No desiccant drying is normally required for QHM32F. If condensation occurs during cold-weather storage, pellets may be purged with dry air at or below 50 °C for 2 h. Storage should avoid prolonged exposure to direct sunlight and ambient temperatures above 40 °C. Because the resin has a narrow molecular-weight distribution, bubble flutter and instability are common when output is increased too rapidly or when air-ring velocity is unbalanced; adding 10–20 wt% LDPE improves bubble stability at the expense of some haze and dart impact. Additives containing free primary or secondary amines should not be dry-blended into QHM32F without oxidative-stability testing, as amine chemistry can interact with catalyst residues and alter discoloration behaviour and additive performance.

Supplied physical properties and comparative film performance data

The following values are drawn from supplier technical literature and represent typical data rather than maximum or minimum specifications. Lot acceptance should use the current certificate of analysis and the relevant test method designations.

Dart impact, haze, and gloss values are thickness-dependent and shift with blow-up ratio, frost-line height, internal bubble cooling, and blend composition. Direct comparison between film grades is therefore valid only when sample preparation and film thickness are matched. On a 40 µm three-layer blown-film line, QHM32F typically shows a haze reduction of 30–50% relative to a butene Ziegler-Natta LLDPE of equivalent density and melt index, and an increase in ASTM D1709 dart impact of 60–100%. Seal-initiation temperature, measured under ASTM F2029-16 on 50 µm blown film, is commonly 8–12 °C lower than that of an equivalent butene LLDPE. However, the same narrow molecular-weight distribution increases melt elasticity at the die and reduces bubble stability; on a 90 mm extruder at equal screw speed, specific energy input can be 5–10% higher than for a broad-MWD grade.

For cast-film applications, published data for this specific configuration is limited. Most supplier film-property data for QHM32F are generated on blown-film lines, and translating those values to cast-film performance requires independent evaluation because cooling rates and orientation profiles differ substantially.

The comparative values are compiled from supplier literature and published blown-film comparisons for metallocene hexene LLDPE versus Ziegler-Natta butene LLDPE. Absolute values vary with line geometry, die gap, blow-up ratio, and blend composition. In food-contact applications, the final film must be evaluated under FDA 21 CFR 177.1520 and, for European Union markets, under EU Regulation (EU) No 10/2011 with overall migration testing according to EN 1186-1:2002. The base olefin polymer is generally covered under the olefin polymer provisions; however, antioxidant packages, slip agents, antiblock agents, and processing aids require separate compliance verification from the supplier.

When QHM32F replaces conventional butene LLDPE in heavy-duty sack and lamination structures

In a three-layer heavy-duty sack structure with a total thickness of 120 µm and a layer ratio of 20:60:20, QHM32F is commonly specified in the core or outer layers where dart impact and tear resistance are limiting. The lower seal-initiation temperature allows heat-seal jaw temperatures to be reduced by 5–10 °C in high-speed horizontal form-fill-seal equipment, reducing thermal distortion of neighbouring laminate layers. In lamination sealant webs, corona discharge surface treatment to a wetting tension of 38–42 mN/m under ISO 8296 is usually applied before solventless or solvent-based lamination. The narrower molecular-weight distribution of QHM32F improves seal integrity and lowers the incidence of channel leakers, but seal strength should be verified under ASTM F88/F88M because final seal strength depends on jaw pressure, dwell time, and film thickness.

Compared with QHM22F metallocene grade, which is typically supplied at a higher melt flow rate near 2.0 g/10 min, QHM32F has higher molecular weight, lower melt fluidity, and superior dart impact and tensile toughness. QHM32F is therefore selected where heavy-duty mechanical strength, puncture resistance, or downgauging potential is more important than maximum output on thin-gauge lines. Compared with LDPE, QHM32F provides higher tensile stress at break and lower seal-initiation temperature but exhibits lower melt strength and greater sensitivity to bubble instability. In applications where melt strength is the controlling processing factor, a portion of LDPE or a broader-MWD LLDPE is added. The optimum blend ratio depends on die diameter, frost-line distance, air-ring design, and output target; typical LDPE addition levels range from 10 wt% to 30 wt%.

The grade is not recommended for injection moulding or rotational moulding because its narrow molecular-weight distribution and high viscosity reduce mould filling and surface replication. For converters running thin-gauge automatic packaging lines, the resin’s lower shear-thinning means screw speed increases may not deliver the same throughput gain as with a conventional broad-MWD LLDPE. Die pressure rise can be 10–20% at equal melt temperature, and this must be accommodated within the extruder’s maximum die pressure rating. If a line operates near its pressure limit, a wider die gap or a lower melt-index grade may be necessary. Published data for very thin films below 20 µm using QHM32F are limited; converters should run structured trials on their own lines because film gauge, bubble cooling rate, and air-ring configuration strongly influence property retention.