Borouge Borstar LLDPE FB2230 is a bimodal linear low-density polyethylene produced through the Borstar dual-reactor cascade. Manufacturer-published nominal values include a density of 922 kg/m³ measured in accordance with ISO 1183-1 and a melt flow rate of 0.22 g/10 min measured in accordance with ISO 1133-1 at 190 °C/2.16 kg. The resin is supplied as pellets containing antioxidant and processing-stabilizer packages; the stabilizer formulation is proprietary and is not disclosed in the public datasheet. The material is intended for blown-film applications in which impact resistance, stiffness, and processability must be balanced. Its bimodal molecular-weight distribution separates the high-molecular-weight fraction, which contributes stress-crack resistance and film toughness, from the low-molecular-weight fraction, which contributes shear-thinning and reduced extrusion back-pressure. This separation differentiates FB2230 from single-reactor LLDPE grades, which distribute comonomer and molecular weight more uniformly and frequently require a compromise between toughness and melt processability.

What Distinguishes the Bimodal Structure from Conventional Single-Reactor LLDPE?

The primary differentiation is rheological rather than solely compositional. A single-reactor LLDPE with an equivalent density and MFR typically exhibits a narrower shear-thinning response because the molecular-weight distribution is more symmetric. In contrast, a dual-reactor product contains a pronounced low-molecular-weight tail. At apparent shear rates encountered in spiral-mandrel and side-fed blown-film dies, commonly 100 to 500 s⁻¹, that low-molecular-weight tail reduces apparent viscosity and die pressure. Bimodal resins of this density and MFR class can therefore retain bubble stability at higher screw speeds before reaching the maximum melt pressure of the die and melt filter; however, published FB2230-specific capillary or slit-rheometry data are limited.

Mechanically, the high-molecular-weight fraction resists extensional failure during bubble expansion. This molecular weight distribution can raise dart impact and puncture resistance at equivalent tensile stiffness compared with a conventional LLDPE of similar density. The same architectural principle is used in slow-crack-growth-resistant polyethylene pipe grades, but its film application focuses on bubble stability and downgauging. Compared with high-pressure LDPE, FB2230 provides higher tensile strength and puncture resistance at comparable thickness, while optical clarity and pure high-stalk bubble stability are generally lower. FB2230 is not a metallocene LLDPE and should not be assumed to provide equal optical clarity or low seal-initiation temperature. When seal performance below 100 °C is required, metallocene or lower-density grades are usually evaluated instead.

Film Property Standards and Typical Published Values

Film properties are line-dependent and should be verified on the converting line rather than inferred from pellet data. Density and melt flow rate are product-release parameters. Film tensile properties are typically measured in accordance with ISO 527-3, tear resistance with ISO 6383-2, and dart impact strength with ISO 7765-2. Puncture resistance can be measured with ASTM D5748. Published FB2230-specific values for dart impact, tear, and puncture are not consistently available in public technical literature; users should request lot-specific data from Borouge before setting specification limits.

Specification based on pellet density alone is insufficient for film performance because cooling rate, blow-up ratio, and frost-line height influence crystallinity and orientation. The 922 kg/m³ density anchor indicates a stiffness level appropriate for heavy-duty film, but the actual tensile modulus of blown film will depend on processing history. A resin with this density and MFR is not optimized for high-clarity applications or for seal initiation at very low heat-seal temperatures.

On production-scale blown-film extruders with L/D ratios between 24:1 and 30:1, FB2230 is processed at melt temperatures in the range of 190 °C to 240 °C. Barrel profiles should be adjusted to avoid excessive low-temperature shearing or high-temperature degradation. Die gap settings are typically 1.6 mm to 2.5 mm for this density and MFR class; blow-up ratios from 2.0:1 to 3.5:1 are used for monolayer and coextruded structures. Frost-line height must be set by bubble stability rather than by fixed values, because the high-molecular-weight fraction increases melt strength but also responds to cooling rate. Sudden changes in air-ring velocity or frost-line height can produce periodic thickness variation; this effect is more visible on high-stalk geometry.

High-stalk operation is commonly used to increase the distance between the die and the frost line, allowing the high-molecular-weight chains to relax before crystallization. On lines configured for high-stalk, a neck height of 4 to 8 die diameters is often used, but the FB2230-specific optimum depends on bubble diameter, die diameter, and air-ring geometry. Published setup data for this specific resin is limited.

Pre-drying is not required under controlled warehouse conditions because polyethylene is not hygroscopic. Condensation on cold pellets entering a warm feed throat should be avoided when ambient RH exceeds 60%. Equipment with polished screws and low-compression barrier sections can process the material, but older general-purpose screws designed for LDPE may generate excessive shear heating. A screen pack with a 100-mesh layer downstream of a coarse breaker plate reduces melt contamination without creating excessive pressure; the exact mesh configuration depends on die pressure limits and extruder condition.

When Internal Bubble Cooling Is Used with FB2230

Internal bubble cooling is relevant for high-output campaigns because polyethylene melts of this density and MFR class retain heat. Cooling air from the internal bubble cooler must be balanced with external air-ring flow; an imbalance creates asymmetric quench and can generate gauge variation of ±5% or greater. On lines with internal bubble cooling, exhaust air temperature should be monitored at the bubble surface rather than at the die exit. Stable internal bubble pressure and controlled exhaust flow reduce blocking at the collapsing frame. Published FB2230-specific internal bubble cooling settings are limited; operators generally establish limits by measuring film gauge profile and bubble diameter rather than by fixed pressure settings.

For high-stalk production, internal bubble cooling may be reduced during start-up until the stalk geometry stabilizes. The high-molecular-weight fraction provides melt strength, but rapid cooling can lock in machine-direction orientation, shifting tear balance. When machine-direction tear drops below process-defined limits, cooling air temperature and cooling air velocity should be adjusted in increments no greater than 10% while holding extruder speed constant.

Manufacturer technical literature identifies principal applications for FB2230 as heavy-duty sacks, agricultural film, and protective packaging blown-film structures. In heavy-duty sacks, films of 100 µm to 200 µm thickness are evaluated for penetration resistance and tensile strength at yield according to ISO 527-3. In agricultural film, outdoor weathering is governed by the stabilizer package and not solely by the base resin; producers typically add UV-stabilizer masterbatch during extrusion. For frozen-food packaging, low-temperature impact testing is run according to ISO 7765-2; however, published FB2230-specific dart impact values at -20 °C should be obtained from the manufacturer because public data are limited.

In coextruded structures, FB2230 may be placed in outer or inner layers where toughness and gauge reduction are needed. It is not typically selected for a low-seal-initiation sealant layer because higher-density LLDPE generally seals at higher temperatures than lower-density metallocene grades. Converters should verify hot-tack and seal-strength performance on the actual film line using thermocouple-instrumented seal bars rather than assuming transfer from laboratory data.

Limitations, Incompatibilities, and Compliance Boundaries

FB2230 should not be held above 260 °C for extended periods because oxidative degradation can generate aldehydes and reduce molecular weight. It should not be combined with unsaturated additives or pro-oxidant systems when the film is intended for long-term storage, because interaction with the undisclosed stabilizer package cannot be predicted. Avoid contact with strongly oxidizing fillers and chlorinated solvents during purging. Food-contact status depends on the specific lot, the film structure, and migration testing; the base resin may be suitable under FDA 21 CFR 177.1520 and EU Regulation 10/2011, but converters must request the manufacturer’s grade-specific declaration and perform end-article compliance testing. RoHS compliance is typically limited to heavy-metal content and does not address food-contact obligations.

Storage of pellets should be indoors at ambient temperature below 40 °C and protected from direct sunlight. If material is stored for more than 6 months, the manufacturer’s stabilizer aging limits should be re-checked before extrusion.