LDPE Grade Codes Decoded: What 2426H, 1C7A and 2102TX00 Actually Mean

Low-density polyethylene (LDPE) is a high-pressure branched polyolefin with a density range that conventionally spans 0.915 g/cm³ to 0.935 g/cm³. The designations 2426H, 1C7A, and 2102TX00 are supplier-specific commercial grade codes rather than universal chemical descriptors. Their embedded digits and suffixes acquire technical meaning only when read against the producer technical data sheet, the lot certificate of analysis, and the intended conversion route. In blown film, cast film, extrusion coating, and shrink film operations, a grade code is decoded through melt flow rate, density, additive package, and molecular architecture. Without those parameters, the alphanumeric sequence remains inert.

Melt flow rate for LDPE is measured at 190 °C under a 2.16 kg piston load according to ISO 1133-1:2022 or ASTM D1238-20. Density is determined by ISO 1183-2:2019 or ASTM D1505-23. Tensile properties on film are obtained with ISO 527-3:2018 or ASTM D882-18, while dart drop impact resistance is tested under ASTM D1709. Optical haze is measured by ASTM D1003-21, and coefficient of friction by ISO 8295:1995 or ASTM D1894-19. These methods anchor grade-to-grade comparison because lot-to-lot variation and blown film gauge can shift reported tensile and impact values by 10% to 15% even for the same nominal designation.

How Melt Flow Rate and Density Partition the LDPE Grade Field

Melt flow rate is an inverse indicator of molecular weight under low-shear conditions. Low-flow LDPE grades with values near 2 g/10 min generally possess higher molecular weight, higher extensional viscosity, and stronger bubble stability in heavy-gauge film. High-flow grades near 7 g/10 min reduce extruder head pressure and favour high line speeds, but they sacrifice dart drop strength and stress crack resistance. The three designations occupy different segments of that continuum. Published datasheets for 2426H typically list a nominal melt flow rate of 1.9 g/10 min to 2.2 g/10 min and a density near 0.924 g/cm³. The grade is therefore positioned as a heavy-duty blown film resin. The 1C7A designation, by contrast, is associated with a nominal melt flow rate around 7.0 g/10 min and a density near 0.918 g/cm³, placing it in the high-flow, thin-gauge film segment. The 2102TX00 designation is reported on producer technical data sheets as an intermediate-flow film grade with a nominal melt flow rate near 2.0 g/10 min and density near 0.922 g/cm³.

Density differences of only 0.006 g/cm³ are not negligible in film conversion. Moving from 0.918 g/cm³ to 0.924 g/cm³ raises crystallinity and modulus while reducing low-temperature toughness and optical clarity. In high-clarity shrink and display packaging, density is kept low enough to limit spherulitic haze but high enough to maintain film stiffness during handling. The selection logic is therefore not linear: melt flow rate controls processability and drawdown, while density modulates stiffness, optics, and sealing behaviour. A grade such as 2102TX00 combines intermediate flow with moderate density because clarity and shrink performance demand a compromise between melt strength and crystallisation speed.

Slip and antiblock additive packages are embedded in many LDPE grade suffixes. Erucamide slip agents migrate to the film surface over hours to days after extrusion, reducing the coefficient of friction to the 0.05 to 0.15 range in matured film. Synthetic silica antiblock particles at addition levels between 500 ppm and 1500 ppm create surface asperities that prevent film-to-film blocking on rewind. These additives do not appear in the alphanumeric code in a standardised way, but producer documentation frequently uses terminal letters to distinguish slip, antiblock, or high-clarity packages. For the three grades under consideration, the suffix differences must be verified against the certificate of analysis because the same base resin may be offered with different additive variants.

What Does the 2426H Designation Indicate in Blown Film Equipment?

The 2426H designation is decoded in production practice as a low-flow, high-melt-strength LDPE for heavy-duty sacks, agricultural film, and shrink film with demanding bubble stability. On a 90 mm grooved-feed blown film extruder with an L/D ratio of 30:1 and a 250 mm spiral mandrel die, the grade is typically processed at a melt temperature of 165 °C to 175 °C. A die gap of 1.2 mm to 2.0 mm and a blow-up ratio of 2.0:1 to 3.0:1 are common settings. At those conditions, the frost line height is usually maintained between 600 mm and 900 mm above the die face. Exceeding 185 °C for extended residence time increases the risk of oxidation gel formation, while dropping below 160 °C can raise screw motor load and generate unmelted resin particles that appear as gel defects in film.

Mechanical data reported for 2426H in 50 µm blown film typically fall in the range of 18 MPa to 24 MPa tensile strength at break, with dart drop impact values between 110 g and 160 g under ASTM D1709 condition A. Haze values are commonly reported between 6% and 8% on 50 µm film. These values support use in heavy-duty packaging where puncture resistance and tear resistance are more important than optical clarity. The principal limitation is gauge reduction: below 25 µm, the low melt flow rate increases gauge variation and can destabilise the bubble under high drawdown. In those thin-gauge applications, a higher-flow LDPE such as 1C7A is generally preferred because it permits faster screw recovery and thinner webs without excessive die pressure.

Why 1C7A Runs Differently Through High-Speed Extrusion Coating Lines

1C7A is decoded as a high-melt-flow LDPE with a nominal melt flow rate around 7.0 g/10 min and a density near 0.918 g/cm³. The higher flow rate reduces melt viscosity, lowers extruder head pressure, and permits high throughput on thin cast film, extrusion coating, and lamination lines. On a 120 mm single-screw extruder with an L/D ratio of 30:1 and a 2400 mm slot die, melt temperatures of 280 °C to 320 °C are typical for LDPE extrusion coating to promote oxidation and adhesion to paper or board. Processing at that temperature narrows the operating window because extended residence time can form degradation gels, while insufficient temperature reduces adhesion to the substrate. Line speed and coating weight interact directly: at a coating weight of 15 g/m² and a line speed above 150 m/min, the melt curtain must resist thinning and edge neck-in.

The relationship between melt flow rate and coating performance is not direct. Higher MFI lowers shear viscosity, but neck-in and drawdown are governed more strongly by long-chain branching and molecular weight distribution. A coating-grade LDPE with an MFI near 7 g/10 min may still exhibit acceptable neck-in if its long-chain branching is controlled during high-pressure polymerisation. Published data for 1C7A in high-speed coating configurations is limited, and the grade is more frequently used in thin blown film and cast film where its lower viscosity translates into reduced motor load and improved melt conveying. In those applications, film gauge can be reduced to 20 µm or below with less bubble instability than low-flow 2426H, but dart drop impact and tensile strength are lower. The operational boundary is therefore clear: 1C7A is not a direct substitute for 2426H in heavy-duty sack film where puncture resistance controls specification compliance.

The 2102TX00 Grade and Optical Properties in Shrink Film

2102TX00 is decoded from typical producer datasheets as an intermediate-flow LDPE with a nominal melt flow rate near 2.0 g/10 min and density near 0.922 g/cm³. The code is most commonly encountered in high-clarity shrink film, lamination film, and display packaging where optical defects are rejected at low tolerance levels. In tubular shrink film production, the blown film is quenched, re-heated, and oriented in the transverse direction. Free shrink is measured under ASTM D2732, while shrink tension is quantified by ASTM D2838. The intermediate density of 0.922 g/cm³ balances film stiffness against optical clarity: densities above 0.925 g/cm³ increase crystallinity and haze, while densities below 0.919 g/cm³ reduce shrink force and may produce insufficient film memory.

Optical performance is controlled by haze and gloss. Haze is tested under ASTM D1003-21 and is typically reported between 5% and 6% for 50 µm film of 2102TX00. Gloss at 45° is measured by ASTM D2457 and is sensitive to die lines, surface roughness, and crystallite size. Gel defects are not governed by a single global film standard, but inline camera systems used on production lines classify gels by size, with 50 µm to 100 µm gels being common rejects in high-clarity film. Maintaining melt temperature below 175 °C in the barrel and minimising residence time are standard operational controls to limit degradation gels. The grade is not hygroscopic, so pre-drying is not required for moisture removal, but hopper temperature control is necessary to prevent fines and streamers at high ambient humidity above 60% relative humidity.

The tabulated values are typical published datasheet ranges rather than specification limits. Blown film gauge, bubble cooling rate, die geometry, and additive bloom all shift the measured values. A comparative decision should therefore use the producer certificate of analysis and the converter’s own film samples rather than a single nominal datasheet figure.

Regulatory compliance for these LDPE grades is application-specific. In food contact, LDPE may be evaluated under FDA 21 CFR 177.1520(c) for olefin polymers, provided the material is used within the specified conditions of use and any relevant migration limits. In the European Union, food contact materials must comply with Regulation (EU) No 10/2011 and its amendments, including an overall migration limit of 10 mg/dm² for plastic materials under specified simulant conditions. REACH obligations under Regulation (EC) No 1907/2006 require suppliers to communicate substances of very high concern at concentrations above 0.1 wt%. These compliance requirements do not alter the grade code; they restrict how the converted film or coating may be placed on the market.

When blending the three designations or recycling edge trim, melt flow index ratios above 3:1 can introduce local viscosity mismatch. On a capillary rheometer at 190 °C, LDPE film grades typically exhibit sharkskin onset at apparent wall shear stresses between 0.10 MPa and 0.30 MPa. A melt stream containing a 7 g/10 min grade dispersed into a 2 g/10 min grade may display early melt fracture at the die lip if the high-flow fraction evacuates the die channel faster than the high-molecular-weight fraction. That failure appears as periodic surface roughness and is not corrected by increasing melt temperature alone; die land length, land gap, or throughput must be adjusted. The practical decoding of 2426H, 1C7A, and 2102TX00 therefore extends beyond the grade name into rheological compatibility with the specific die and line configuration.