Baofeng Energy M mLLDPE M2310 is a metallocene-catalysed linear low-density polyethylene resin manufactured by Ningxia Baofeng Energy Group for blown film extrusion. The grade is characterised by a nominal melt mass-flow rate of 1.0 g/10 min when tested in accordance with ISO 1133-1:2022 at 190 °C under a 2.16 kg load and a nominal density of 0.923 g/cm³ when determined by ISO 1183-1:2019. The resin is intended for monolayer and coextruded film structures, including heavy-duty industrial bags, agricultural silage wrap, lamination film, and high-strength liners. The metallocene catalysis produces a narrower molecular weight distribution and more uniform comonomer placement than conventional Ziegler-Natta C4-LLDPE, which alters the processing, sealing, optical, and mechanical response of the film. Unlike standard butene-based LLDPE grades with equivalent melt flow rate and density, M2310 exhibits a lower seal initiation temperature and higher dart impact at the same gauge, but it also generates higher die pressure and a narrower stable bubble window. The following sections address processing conditions, representative property data, seal and extractables performance, substitution against C4-LLDPE, and long-run gel control.

The product designation M2310 follows a nominal melt flow and density convention used within the Baofeng metallocene series. The resin is supplied as free-flowing pellets suitable for railcar, bulk truck, and silo handling. Specific additive formulation and packaging bulk density values should be confirmed against the batch-specific certificate of analysis because antioxidant, slip, and antiblock loadings influence coefficient of friction, haze development, and seal response.

Which Processing Window Controls Bubble Stability and Output in M2310 Film Lines?

M2310 is processed on conventional single-screw blown film lines equipped with barrier screws and, in most production applications, internal bubble cooling. On a 55 mm grooved-feed extruder with an L/D ratio of 30:1 and a 250 mm die, a stable bubble is maintained at melt temperatures of 190–215 °C and a die pressure range of 28–34 MPa. A typical temperature profile from feed throat to die is 180 °C, 190 °C, 200 °C, 205 °C, and 205 °C. The die gap is normally set at 1.6–2.0 mm, with a blow-up ratio between 2.2:1 and 2.8:1. Frost line height is typically maintained at 6–8 die diameters for 40 µm monolayer film.

Because the molecular weight distribution of metallocene LLDPE is narrow, shear thinning is less pronounced than in conventional Ziegler-Natta C4-LLDPE. At 190 °C and the same nominal melt mass-flow rate, die pressure in M2310 can be 10–15% higher than that of a standard butene LLDPE. This difference increases motor load and may limit throughput on older extruders with inadequate drive capacity. Above 230 °C, film oxidation accelerates and can produce yellowing, gel formation, and die lip deposit. Below 180 °C, melt pressure frequently exceeds 35 MPa, and screw shear heating can create local temperature spikes even when barrel setpoints remain low. The practical response is to widen the die gap to 1.8–2.0 mm and to use a lower compression barrier screw with mixing elements that avoid excessive melt residence time. Internal bubble cooling raises output by 20–30% on 55–75 mm lines but changes frost line position and can destabilise the bubble if the air exchange volume is not adjusted in steps of 5–10% per hour.

The screw speed and residence time are critical parameters. On the 55 mm line described above, output of 85 kg/h at 95 rpm produced a melt pressure of 31 MPa and a melt temperature of 207 °C. When screw speed was raised above 110 rpm, melt temperature increased to 218 °C and bubble stability decreased. This indicates that the throughput-limiting factor is not plastication capacity but viscous shear heating and bubble cooling. Converters with high-output lines should use barrier screws with deeper feed channels and separate mixing elements to keep melt temperature below 210 °C.

When M2310 is run as a skin layer in coextruded structures, the recommended skin layer thickness is at least 8 µm to avoid tear propagation from the core layer. The resin is compatible with polyethylene extrusion equipment, but residual high-density or propylene-based purging compounds must be flushed completely; incompatibility with long-residence-time hot runners is not a polymer chemistry limitation but a viscosity and melt stability constraint. Published data for very high-output internal bubble cooling configurations above 200 kg/h on a 75 mm die is limited; converter trials are required to establish line-specific limits.

Mechanical Property Targets for 40 µm Monolayer Blown Film

The values in Table 1 are representative of 40 µm monolayer film produced on a 55 mm grooved-feed blown film line with a 250 mm die, 1.6 mm die gap, 2.5:1 blow-up ratio, and frost line height of 8 die diameters. Specimens were conditioned at 23 °C and 50% RH for 48 h in accordance with ISO 291. Film properties are direction-dependent; machine direction and transverse direction values are reported where applicable.

The tensile properties were measured with a jaw separation speed of 500 mm/min and a gauge length of 50 mm for thin film specimens in accordance with ASTM D882-18. Elmendorf tear was measured on a pendulum tear tester with a 6400 g pendulum. Dart drop impact was determined with a 38 mm diameter stainless steel dart and a 660 mm drop height using method A of ASTM D1709-22. Haze and gloss were measured on a hazemeter and a 60° specular gloss meter calibrated against primary standards. These representative values are not to be interpreted as producer specification limits; batch-release values may differ according to the producer's certificate of analysis.

A 40 µm monolayer M2310 film was heat-sealed on a laboratory flat-platen sealer with 40 mm platens at 0.5 MPa pressure and 0.5 s dwell. Seal initiation temperature, defined as the temperature at which seal strength reaches 2.0 N/25 mm, was 105 °C when tested in accordance with ASTM F88/F88M-23. Hot tack strength measured by ASTM F1921-18 at 115 °C was 4.5 N/25 mm. By comparison, a conventional Ziegler-Natta C4-LLDPE with the same nominal melt mass-flow rate and density typically requires a seal initiation temperature of 112–115 °C. The lower seal initiation temperature allows converters to run form-fill-seal equipment at lower sealing bar setpoints or to increase line speed while maintaining the same seal strength. The hexane-extractable fraction of 40 µm film, measured by the extraction procedures described in FDA 21 CFR 177.1520(c) 3.2a, is below 1.0%. This value supports food-contact suitability when the film is used in accordance with the producer's food-contact statement and applicable regional migration limits under EU Regulation (EU) No 10/2011. The resin is not designated for medical implant, parenteral, or autoclave-stable device applications, and it should not be used where sustained contact with oxidizing acids or aromatic hydrocarbons is expected without prior chemical resistance testing.

After heat sealing, the seal strength of M2310 continues to rise as the melt recrystallises. On a 40 µm film sealed at 110 °C and cooled under ambient conditions, seal strength measured 5.2 N/25 mm at 1 h after sealing and 6.0 N/25 mm at 24 h using ASTM F88/F88M-23. This cold-seal development is typical of metallocene LLDPE and differs from conventional C4-LLDPE, which usually shows a smaller post-seal strength increase over the same period. The result is relevant for high-speed packaging where the film is handled before complete seal crystallisation.

When M2310 Is Substituted for Conventional C4-LLDPE in High-Strength Industrial Bags

In heavy-duty bag structures, M2310 is commonly evaluated as a drop-in replacement for conventional butene-based C4-LLDPE in blends with high-density polyethylene or as a pure resin layer. Table 2 compares representative 40 µm film properties for M2310 and a conventional C4-LLDPE of equivalent melt index and density. The comparative data are generated on the same blown film line and conditioned according to ISO 291.

The substitution effect is most visible in dart impact. On a 65 mm high-output blown film line with a 300 mm die and 2.5:1 blow-up ratio, a 60 µm C4-LLDPE/HDPE heavy-duty bag film was replaced by a 45 µm M2310 film without reduction in drop impact performance as measured by ASTM D1709-22. The reduction in gauge lowers film mass per bag by approximately 25%, but the converter must verify coefficient of friction and bending stiffness because metallocene LLDPE typically has lower secant modulus than high-density polyethylene. Blends of M2310 with HDPE above 20–30 wt% may reverse the dart impact advantage and increase haze. If higher stiffness is required, a higher-density metallocene grade or a separate HDPE core layer in coextrusion is preferred over raising HDPE concentration in the monolayer.

Sealing performance also differs. On vertical form-fill-seal bag machines with 35 mm sealing bars and 0.3 s dwell, M2310 reaches a 2.0 N/25 mm seal at 105 °C, whereas the C4-LLDPE control requires 112 °C. The practical benefit is a reduction in sealing energy and a wider operating margin before overheating causes film distortion at the seal. The hot tack plateau of M2310 is also broader, allowing faster package cycling before the seal has fully cooled. Converters measuring seal strength on a 500 N tensile test machine with 25 mm wide specimens and a separation speed of 200 mm/min should apply ASTM F88/F88M-23 consistently because peel angle and unsupported tail length influence the reported force.

Within the Baofeng metallocene LLDPE portfolio, M2310 is positioned for blown film applications requiring a nominal melt mass-flow rate of 1.0 g/10 min. Cast film converters generally select a higher melt mass-flow rate metallocene grade because reduced viscosity lowers extruder motor load and supports higher line speeds on chill-roll lines. M2310 can be converted on cast film equipment if the die pressure remains within the extruder design limit, but throughput may be lower than a dedicated cast-film metallocene grade. Published data for M2310 on cast film lines with slot dies above 1.5 m width is limited.

Die Build-Up and Gel Control in Long-Run Blown Film Conversion

Extended campaigns with M2310 require attention to die lip deposit and gel formation. On a 75 mm grooved-feed extruder with 30:1 L/D and a 400 mm die, die lip build-up appeared after 72 h of continuous operation when the die gap was set below 1.2 mm and melt temperature was held at 215 °C. The deposit was identified as oxidised low-molecular-weight polyethylene. Increasing the die gap to 1.6 mm and reducing melt temperature to 195 °C extended the continuous run to 168 h before cleaning was required. Fluoropolymer processing aid at 300–500 ppm reduced the deposit but can lower surface wetting tension below 38 mN/m, which may affect water-based ink adhesion and lamination bond strength. If surface printing is required, corona treatment to at least 40 mN/m is recommended, and the treatment level should be measured with Dyne test solutions according to ISO 8296.

Gel count, measured on 40 µm film by an optical gel counter with a lower detection limit of 200 µm, remained below 5 gels/m² when the extruder was purged with a cleanout polyethylene for 30 min after grade changes from high-density polyethylene. The resin should not be blended with amine-based antistatic or slip concentrates that contain free primary or secondary amines because these can react with oxidation products and increase yellowing. Recycled edge trim from M2310 film can be added back at up to 20 wt% without increasing gel count above 5 gels/m², provided the regrind is dry and free of paper, label stock, and polyamide or polyester contamination. Above 20 wt% recycled trim, dart impact may decline and the narrow processing window becomes more sensitive to bubble oscillation. Pre-drying is not required for polyethylene resin under normal storage conditions; however, surface condensation can occur when cold resin is moved into a warm humid compounding area, and silo transfer should include clean dry-air conveying.