Linear low-density polyethylene (LLDPE) is a semicrystalline ethylene-α-olefin copolymer with a density range of 0.918–0.940 g/cm³ under ASTM D1505 or ISO 1183-1. The α-olefin—butene, hexene, or octene—generates short-chain branches that disrupt crystallinity and govern stiffness, tear, dart impact, and seal initiation temperature. Indian LLDPE Producers: Reliance Relene, IOCL and GAIL Codes Compared require careful decoding of density-first numeric sequences because grade codes do not transparently report comonomer type, molecular weight distribution, or additive package. Melt flow rate measured at 190 °C, 2.16 kg by ASTM D1238 or ISO 1133-1 is the principal lot-to-lot consistency parameter, but a single melt flow rate value does not guarantee equivalent bubble stability or mechanical performance.

Reliance Relene film-grade designations typically embed a nominal density prefix and a melt-flow suffix. In Indian market convention, a leading 20 corresponds to nominal density 0.920 g/cm³, 24 to 0.924 g/cm³, and 26 to 0.926 g/cm³; a suffix such as 010 corresponds to nominal melt flow rate 1.0 g/10 min, and 040 to 4.0 g/10 min. The same density-first convention appears in IOCL Indothene literature and in GAIL G-Lex product sheets, although the application-letter position and brand prefix are not harmonized across the three Indian producers.

Does the Indian LLDPE Code Suffix Reliably Indicate Melt Flow Rate?

The suffix in Indian LLDPE codes is a nominal target, not a specification-lot value. Certificates of analysis for Reliance Relene, IOCL Indothene, and GAIL G-Lex grades typically report melt flow rate against ASTM D1238 or ISO 1133-1 and density against ASTM D1505 or ISO 1183-1, with lot-to-lot variation generally controlled within ±10% of nominal melt flow rate and ±0.002 g/cm³ of nominal density. A converter cannot use the suffix alone to select a film structure; the producer’s technical datasheet must also be checked for whether the grade is a butene- or hexene-copolymer because the code rarely reports the α-olefin type.

On an Indian blown-film line with a grooved-feed single-screw extruder of 55 mm diameter and 28:1 L/D, a 0.920 g/cm³, 1.0 g/10 min LLDPE processes within a melt-temperature window of 190–220 °C. At 180 °C or below, sharkskin and die-lip buildup increase; above 240 °C, gel particles from oxidative degradation and additive decomposition raise screen-pack pressure and create optical defects. A die gap of 1.8–2.5 mm is required because LLDPE has lower melt strength than LDPE; a narrower gap raises shear stress at the die lip and intensifies melt fracture. Bubble stability is controlled by frost line height, normally 6–10 die diameters, and blow-up ratio, normally 2.0:1–3.0:1.

At a specific output of 1.0 kg/h per mm die circumference on a 250 mm die, bubble flutter is governed by frost line height and blow-up ratio. A narrow frost line of 5 die diameters increases quench rate and improves optical clarity but lowers dart impact; a tall frost line of 10 die diameters allows molecular relaxation and improves bubble stability but increases blocking tendency in a high-slip package. These process responses are not encoded in the Indian LLDPE grade designations and must be established through a production-scale trial.

Code Architecture for Reliance Relene, IOCL Indothene, and GAIL G-Lex

Reliance Relene, IOCL Indothene, and GAIL G-Lex grade codes share a density-first, melt-flow-second skeleton, but the application descriptor is not identical. Reliance’s Relene literature commonly places an application letter—F for film, M for moulding, R for rotational moulding—after the density prefix. IOCL’s Indothene datasheets may retain an analogous F/M descriptor but can order the density digits differently or include a plant identifier. GAIL’s G-Lex nomenclature adds a brand prefix and may use a letter string that identifies product family or comonomer before the numeric density and melt-flow block. Published data for the complete grade slate is limited; therefore direct code-to-code replacement across Reliance, IOCL, and GAIL should be verified against the current certificate of analysis and the producer’s regulatory statement.

Because the grade code does not encode comonomer type, a film converter comparing Indian producers should request tensile, dart impact, and hot-tack data from the grade datasheet. A butene-copolymer LLDPE at 0.920 g/cm³ may show lower dart impact and Elmendorf tear than a hexene-copolymer LLDPE at the same density; the difference is polymerized into the short-chain branching distribution and is not visible from the code. When switching between Indian producer grades, blown-film bubble stability often changes even when density and melt flow rate are identical on the datasheet. This is because molecular weight distribution and long-chain branching—or the lack of it—affect elongational viscosity and bubble response.

The molecular weight distribution of Indian LLDPE grades is measured indirectly through melt flow rate ratio or rheological polydispersity; typical extrusion-film grades show a melt index ratio of 22–30 when the high-load melt index is measured at 190 °C, 21.6 kg by ASTM D1238 procedure B. A higher melt index ratio generally indicates broader molecular weight distribution and can improve bubble stability, but it may also increase melt fracture and reduce dart impact. Published data for this specific configuration is limited, and producer-to-producer differences in catalyst and process technology prevent a code-only equivalence judgment.

When a producer has not disclosed the α-olefin, differential scanning calorimetry under ISO 11357-3 at 10 °C/min can provide indirect evidence: butene-copolymer LLDPE often shows a broader melting peak and lower peak temperature than a hexene-copolymer LLDPE at the same density. The melting peak temperature for film-grade LLDPE typically falls between 120–126 °C, and a shift of 2–3 °C may be meaningful. However, the DSC thermogram is also affected by thermal history and additive package; therefore this is a confirmatory tool, not a substitute for the producer’s code and datasheet.

Rotational moulding grades of Indian LLDPE generally carry melt flow rates between 3.0–6.0 g/10 min and density between 0.934–0.940 g/cm³. On a carousel rotational moulding machine with oven set point 280–310 °C, the peak internal air temperature should reach 190–200 °C for complete densification; a grade coded as a 26M040-type LLDPE may require longer cycle time than a 24M040-type because higher density raises the peak crystallization temperature and alters wall-thickness distribution. Field experience shows that part-wall porosity increases if the peak internal air temperature remains below 185 °C for more than 2 min; this is a processing boundary, not a code property.

When a Converter Requires a Narrow Density Window

LLDPE density shifts as small as 0.002 g/cm³ alter flexural modulus and seal initiation temperature enough to affect film machine settings and end-use specifications. For a converter running high-speed form-fill-seal packaging, a density change from 0.920 g/cm³ to 0.922 g/cm³ may raise heat-seal initiation temperature by several degrees and increase film modulus; if the grade is replaced by another Indian producer with the same melt flow suffix but a different density prefix, the jaw temperature must be adjusted and the sealed seam may fail under burst testing. The seal-through-contamination response is further governed by the additive package and comonomer type, neither of which is recovered from the code alone.

Injection moulding grades with codes in the density-prefix range of 17–20 and melt-flow suffix of 20–50 may be used for thin-wall containers and housewares. On a 120 t injection moulding machine with a general-purpose polyolefin screw, melt temperature 200–230 °C, mould temperature 15–40 °C, and injection pressure 60–100 MPa are typical. Warpage of thin-wall parts increases if mould cooling varies by more than 5 °C across the cavity. Producer codes with different application letters may refer to equivalent flow but different impact modification; the code alone does not identify notched Izod impact value under ASTM D256, and a grade substitution must be confirmed with the datasheet.

For food-contact film, Indian producer regulatory statements generally cite FDA 21 CFR 177.1520 and EU Regulation (EU) 10/2011 for polyethylene, but the exact additive package—slip, antiblock, and process stabilizer—is producer-specific and must be confirmed with the certificate of compliance. LLDPE is not inherently hygroscopic; however, if sacks are stored at relative humidity above 60%, surface moisture can create pinholes in blown film, and a pre-drying step at 60–70 °C for 1–2 h can reduce bubble breakage. Contamination with polypropylene above 2–3 wt% causes delamination and haze due to incompatibility in the melt phase. These limitations are operational boundaries that are not encoded in Indian LLDPE designation strings.