SABIC LLDPE 6335BE is a butene-comonomer linear low-density polyethylene pellet resin. The nominal density is 0.933 g/cm³ at 23°C per ISO 1183-1:2019, and the melt mass-flow rate is 3.5 g/10 min at 190°C/2.16 kg per ISO 1133-1:2022. The grade is positioned for blown-film products in which higher stiffness than a 0.918 g/cm³ C4-LLDPE is needed without moving to a medium-density polyethylene. Primary uses include lamination film, general-purpose packaging, collation shrink film, and stiffness-sensitive liners.

Product specifications for 6335BE are controlled by density and MFR as the two primary melt-state release parameters. The producer additionally reports lot-level ash content, additive loading, and visual gel count on downstream converter lines. Public certification does not include a single value for environmental stress-crack resistance because the property is article-specific. Batch-to-batch MFR variation is generally maintained within ±0.3 g/10 min under ISO 1133-1:2022; density variation is typically ±0.002 g/cm³ under ISO 1183-1:2019. This level of control allows stable gauge and melt pressure on continuous film lines.

What Polymer Architecture and Chain-Branching Pattern Are Implied by the Density and Melt Flow Ratio?

Density of 0.933 g/cm³ reflects a short-chain branch content sufficient to reduce crystallinity below HDPE but retain a higher crystalline fraction than commodity film grades at 0.918 g/cm³. The comonomer is butene, producing ethyl branches after incorporation; conventional Ziegler-Natta catalysis provides a heterogeneous comonomer distribution. Low-molecular-weight fractions are branch-rich and high-molecular-weight fractions are branch-poor. This distribution broadens the melting range and increases the number of tie chains relative to a uniform branching distribution. The melt flow ratio between 21.6 kg and 2.16 kg loads is not disclosed in the public datasheet, so the MFR alone does not fully define molecular weight distribution.

The molecular weight distribution of conventional Ziegler-Natta LLDPE is broad and skewed toward lower molecular weight. This skew reduces melt viscosity at high shear and helps maintain drawdown in thin films. The high-molecular-weight tail provides melt strength and tear resistance. Because 6335BE is a butene grade, the concentration of long-chain branching is negligible; melt strength is therefore lower than LDPE and lower than some metallocene grades with long-chain branching. Processing operations that require high bubble stability or deep thermoforming should account for this limitation.

Differential scanning calorimetry per ISO 11357-3:2018 on a compression-moulded specimen typically yields a peak melting temperature in the 122–125°C range. The crystalline fraction, estimated from a heat of fusion of 293 J/g for fully crystalline polyethylene, is approximately 55–60%. This crystalline content raises secant modulus relative to 0.918 g/cm³ LLDPE but also raises the heat-seal initiation temperature. Published producer data for a 25 µm blown film list tensile yield stress near 17 MPa machine direction and 16 MPa transverse direction per ISO 527-3:2018. Elongation at break is reported above 600% machine direction and above 700% transverse direction. Dart drop impact measured under ISO 7765-1:2004 method A is in the range 110–130 g for the same film gauge. These values are gauge-, orientation-, and conditioning-dependent and should not be used as article specifications.

When Melt Fracture and Bubble Instability Narrow the Processing Window on Blown-Film Lines

On a 60 mm single-screw extruder with L/D 30, die diameter 200 mm, die gap 1.2 mm, and blow-up ratio 2.5:1, stable extrusion of 6335BE is obtained at barrel temperatures from 180°C to 220°C with the die set between 190°C and 210°C. At melt temperatures below 185°C, high output can produce sharkskin on the bubble surface. At melt temperatures above 240°C, residence time in the die should not exceed 10 min because thermal-oxidative gel formation accelerates. Bubble instability appears when the blow-up ratio exceeds 3.0:1; the recommended BUR range is 2.2:1 to 2.8:1. Frost line height from the die face is typically maintained at 800–1,100 mm. At take-off speeds above 150 m/min, draw resonance may occur. Lowering the die gap from 1.5 mm to 1.0 mm or adding 10–20% LDPE can restore stability.

Barrel temperature profile is typically ramped from 170°C at the feed throat to 220°C at the die. Specific energy consumption on a 60 mm extruder at 120 kg/h is generally in the range of 0.25–0.30 kWh/kg; higher output reduces specific energy but increases melt temperature due to shear heating. The use of a grooved-feed section is not required for this MFR, but a barrier screw with mixing elements improves homogenization of the stabilizer package. Filter packs of 40/60/80 mesh are common to protect the die from gels and solidified skins. Output is usually limited by bubble cooling rather than extruder torque. Bubble instability may occur when air-ring velocity exceeds 5–8 m/s because the low melt strength cannot withstand high turbulence. A single-lip air ring with iris adjustment is generally preferred over a high-velocity dual-lip air ring for this density/MFR combination.

Die-lip build-up is a recognized limitation of conventional Ziegler-Natta LLDPE grades. During runs longer than 72 h, low-molecular-weight species can deposit on the outer die lip and produce oxidized die lines. On a 200 mm die, die-lip cleaning after every 24–48 h is typical for film grades in this MFR range. A fluoropolymer polymer processing aid at 400–800 ppm can extend run time by coating the die land and reducing melt fracture. The processing aid must be pre-dispersed as a concentrate because undispersed fluoropolymer creates localized slip layers that can reduce seal strength.

In stiffness-limited industrial packaging, the 0.933 g/cm³ density permits downgauging from 50 µm to 40 µm in some converter trials, but this is not a universal replacement rule. At 40 µm, dart impact falls below 100 g in some trials under ISO 7765-1:2004; the article must then be validated for drop resistance under distribution conditions. Failure mode analysis from production films shows brittle failure when the blow-up ratio is too low and machine-direction orientation is excessive. Adjusting BUR from 2.0:1 to 2.5:1 can shift fracture from brittle to ductile. In lamination film, the higher density of 6335BE provides a secant modulus increase of approximately 20–30% relative to a 0.918 g/cm³ C4-LLDPE at equivalent gauge. However, the downgauging limit is constrained by puncture and tear propagation. Elmendorf tear for a 25 µm film is typically 130–160 gf in the machine direction and 350–420 gf in the transverse direction per ISO 6383-2; the transverse-direction value is lower than a comparable C6-LLDPE. In sharp-edged product packaging, a C6-LLDPE or metallocene grade with higher tear strength may be required.

Seal Initiation and Adhesion Responses in Lamination Structures

Seal initiation temperature of 6335BE in a 25 µm film is approximately 112–116°C using 5 N/mm² sealing pressure and 0.5 s dwell time in accordance with ASTM F88/F88M. The seal plateau remains broad; a measurable seal-strength drop does not occur until the seal temperature reaches 150°C unless the film has been exposed to surface contamination. In lamination, oxidized polyethylene surfaces may require additional corona treatment. The higher density of 0.933 g/cm³ reduces the diffusion of flexible-chain oligomers into the seal interface compared with lower-density grades, which can shift the seal initiation temperature upward by 4–6°C relative to a 0.918 g/cm³ C4-LLDPE.

For extrusion lamination, the melt temperature is typically set at 200–215°C on a 55 mm L/D 30 line. Neck-in is greater than LDPE, and edge bead control requires die lip adjustment. Because of lower melt strength, the resin is not a drop-in replacement for tubular LDPE in high-speed extrusion coating. On a 55 mm line at 150 m/min, neck-in is typically 15–25 mm greater than a tubular LDPE of 4.0 g/10 min; this boundary governs material selection for coating and laminating.

Film Performance Boundaries Are Shaped by Tear and Impact Trade-Offs

Compared with a C4-LLDPE of 0.918 g/cm³ and similar MFR, 6335BE provides higher modulus and higher seal initiation temperature, but lower dart impact and lower Elmendorf tear. The stiffness increase comes directly from density; the impact penalty becomes more pronounced at low temperature. At -10°C, some high-speed converting operations observe a ductile-to-brittle transition in machine-direction failures, while the 0.918 g/cm³ grade remains ductile in the same film gauge. Compared with a C6-LLDPE of 0.918 g/cm³, 6335BE has a narrower ESCR window and lower tear propagation resistance. In frozen-food packaging where a brittle failure at -20°C is unacceptable, C6-LLDPE grades are generally preferred. Compared with a metallocene LLDPE of similar density and MFR, 6335BE offers broader processing latitude and lower extruder torque but lower clarity and lower dart impact. The metallocene grade typically shows better organoleptics and lower extractable content due to more uniform comonomer incorporation.

For commodity hygiene film, lamination film, and label film where stiffness and cost are primary, 6335BE is selected. For heavy-duty sacks requiring high dart and tear, the resin is often blended with 15% LDPE or coextruded with a C6-LLDPE skin to balance bubble stability and abuse resistance. The ESCR difference requires caution. Because 6335BE has higher crystallinity, its slow crack growth resistance under stress is lower than a lower-density C4-LLDPE. Under ASTM D1693 bend-strip testing at 50°C in Igepal CO-630, a 0.918 g/cm³ C4-LLDPE typically exceeds 500 h at 50% stress-cracking agent concentration, while 6335BE may fail earlier depending on molded-in stress. This limits its use in detergent or surfactant packaging. Public datasheet values for ESCR are not given; converters must run article-specific validation.

Migration of antioxidants and processing aids from 6335BE films follows Fickian diffusion within the polyolefin matrix. Diffusion coefficients are temperature-dependent; the rate increases by roughly an order of magnitude from 20°C to 60°C for common phenolic stabilizers. This matters for fatty-food contact, where migration testing must be conducted at the intended-use temperature rather than accelerated conditions. Because 6335BE has higher density than 0.918 g/cm³ grades, diffusivity is slightly reduced by the higher crystalline tortuosity.

Regulatory status for food contact must be verified for the specific supply lot and additive package. The base polyethylene may fall under FDA 21 CFR 177.1520(c) when the article meets extractive and density requirements, but finished-article compliance is the converter’s responsibility. The producer’s standard formulation has no intentionally added substances of very high concern above 0.1% w/w under REACH (EC) No 1907/2006 and no intentionally added RoHS Directive 2011/65/EU restricted substances. For repeated-use articles, migration testing under EU Regulation No 10/2011 may be required depending on food simulant and time-temperature parameters.

Storage of 6335BE should follow standard polyolefin practice: keep away from direct sunlight, store at temperatures below 50°C, and avoid contact with high-pressure steam sterilization. Pre-drying is not normally required for blown-film extrusion when sealed bags are used and ambient relative humidity is below 60%. If pellets are exposed to condensation, a dehumidified-air hopper dryer at 70–80°C for 2–4 h may be used; exceeding 80°C risks pellet softening and feed-throat bridging. The resin should not be purged with PVC or other chlorine-containing polymers because of corrosion risk. Additive packages should be verified with the producer for antagonistic interactions with the stabilizer system before compounding.