LyondellBasell and Basell LDPE 2427H: What Buyers Ask First

Specification screening for LyondellBasell and Basell LDPE 2427H routinely begins with the melt mass-flow rate and nominal density, because those two values determine whether the resin can be dropped into an existing blown-film recipe without reformulating bubble stability or downstream gauge control. Procurement teams request the certificate of analysis against ISO 1133-1 and ISO 1183-1 before release; a density offset of 0.0005 g/cm³ may be invisible in silo inventory but can shift the tear balance and optics of a 40 µm film. Typical datasheet values reviewed by buyers place the melt flow rate in the 1.8–2.2 g/10 min range and density near 0.923–0.925 g/cm³. The grade retains the Basell designation in many purchasing systems and is used in shrink film, collation film, and heavy-duty packaging. A generic database value for MFR should not replace the production lot certificate, because only the certificate confirms whether the material falls inside the agreed specification band.

Because LDPE 2427H is a high-pressure low-density polyethylene with long-chain branching, processability is not captured by melt flow rate alone. Converters running the grade on a 70 mm or 90 mm grooved-feed extruder with an L/D ratio of 28:1 to 30:1 observe that a lot at the upper MFR boundary reduces head pressure and may require lower screw speed to hold a 2.0:1 blow-up ratio, while a lot at the lower boundary raises melt temperature through viscous dissipation. The first-buyer question is whether the certified MFR falls inside the converter’s established processing window; a deviation of ±0.2 g/10 min is frequently manageable on a 30:1 barrier screw but problematic on a short 24:1 general-purpose screw.

Why is the melt mass-flow rate checked before film physical properties?

The priority given to melt flow rate reflects the sensitivity of blown-film bubble stability to shear and extensional viscosity. A change of 0.2 g/10 min alters the pressure drop across the die and the melt temperature measured at the die lip. On high-speed lines running 40–60 µm film at 120–250 kg/h, this shift can move the frost-line height outside the stable operating band, producing gauge bands or bubble-break events. The certificate value should be read together with the lot-to-lot consistency record; a standard deviation of ±0.05 g/10 min over 12 months is a more reliable indicator of extruder stability than a single average value.

Nominal density is read with MFR because LDPE 2427H density near 0.924 g/cm³ corresponds to a moderately branched short-chain architecture that yields a crystalline mass fraction of roughly 40–45 % by differential scanning calorimetry heat of fusion. This structural interpretation is not a specification, but it explains why the grade balances stiffness and tear strength in film. A first-buyer audit should request the density method and conditioning; the difference between ISO 1183-1 immersion and ISO 1183-2 density gradient results can be as high as 0.0005 g/cm³.

Buyers requesting first-order technical data often ask whether the grade is autoclave or tubular, because reactor configuration influences long-chain branching, gel level, and processability. The 2427H designation is historically associated with high-pressure LDPE technology; however, the reactor configuration should be confirmed with the supplier technical datasheet because it affects the balance between dart drop and tensile properties. Without this confirmation, conversion from an autoclave LDPE to a tubular LDPE can produce differences in melt strength even when MFR and density are identical.

Extruder temperature profile and backpressure limits

Blown-film processing of LDPE 2427H typically uses barrel zone settings of 160 °C to 190 °C and die zone settings of 170 °C to 195 °C, with the adapter kept no more than 10 °C above the die to avoid stagnation-induced gel formation. On a 250 kg/h line with a 160 mm die and 1.2 mm die gap, backpressure at the screen pack is monitored against the virgin-resin baseline; a rise of more than 30 % across a 200-mesh screen pack during a production run indicates melt contamination, degraded antioxidant residues, or crosslinked material from excessive residence time. Melt temperatures above 210 °C are generally avoided because LDPE can begin thermo-oxidative chain scission and crosslinking in the presence of oxygen, producing visible gel defects in film.

On high-stalk bubble configurations used for shrink film, LDPE 2427H is often run at a blow-up ratio between 2.0:1 and 3.0:1, with frost-line height adjusted from 3 to 6 die diameters. The long-chain branching gives the bubble sufficient tension at low melt strength; however, too high a frost line can overstabilize the bubble and reduce transverse direction orientation. Operators confirm that the cooling ring airflow and ambient air temperature do not vary by more than ±5 °C across the die circumference because uneven quench rates are a primary source of gauge bands and roll hardness variation on film rewind.

When LDPE 2427H is blended with LLDPE on a blown-film line

LDPE 2427H is frequently used as a 10–30 wt% blend component with C6- or C8-LLDPE to improve bubble stability and melt strength without switching to a broader molecular weight LLDPE. The processing conflict is that LDPE addition lowers the onset of melt fracture but also reduces dart drop and Elmendorf tear resistance of the finished film. A buyer asking first about blending should compare the blend’s melt flow rate and density against the pure LLDPE baseline; if LDPE 2427H is added at 20 wt%, the blend density typically rises by less than 0.001 g/cm³, while the melt flow rate may shift by 0.1–0.3 g/10 min depending on the LLDPE comonomer type. Published data for this specific blend ratio are limited; supplier-supported trial designs generally include a full factorial of die gap and output rate rather than a single dart-drop prediction.

First-buyer requests also ask whether 2427H is delivered with slip and antiblock. The base resin is normally stabilized with a phenolic antioxidant system; slip and antiblock are not universally present. Converters requiring a coefficient of friction below 0.20 for automatic packaging lines must specify the desired erucamide or oleamide slip masterbatch addition. An incorrect additivation level can take 24–72 h to equilibrate after extrusion and can cause ink adhesion failure during surface printing.

Food-contact and REACH documentation for first orders

Compliance documents are requested before resin qualification. For LDPE 2427H used in food packaging, the supplier statement should reference FDA 21 CFR 177.1520(c) for olefin polymers and specify the condition of use, including maximum service temperature and food type. Under EU Regulation 10/2011, an overall migration limit of 10 mg/dm² applies; specific migration limits are not normally a concern for an unfilled polyolefin grade unless the converter adds masterbatch. REACH registration under EC 1907/2006 and absence of candidate list substances above 0.1 wt% should be confirmed on the safety data sheet and supplier declaration.

Pellet handling and lot-to-lot variation are checked by production engineers because railcar unloading and hopper conveying are sensitive to pellet geometry and bulk density. LDPE pellets with a bulk density between 480 and 540 kg/m³ are typical; a lower bulk density lot may reduce gravimetric throughput and require vacuum conveying adjustments. Buyers often request pellet size distribution from the certificate of analysis when the resin is fed through a central vacuum system with long conveying lines, because excessive fines above 500 µm can accumulate in rotary feeders and cause feed instability.

Processors that run LDPE 2427H in thin-gauge film at high output rates may request extensional rheology data because shear viscosity alone does not predict bubble stability. The strain-hardening response is driven by long-chain branching, and 2427H typically exhibits a pronounced upswing in extensional viscosity at Hencky strain rates above 0.5–1.0 s⁻¹ when measured by a capillary breakup or uniaxial extensional rheometer. Two lots with identical ISO 1133-1 values can still differ in melt strength due to autoclave reactor temperature distribution and chain-transfer agent control, so a downgauging trial should compare elongational viscosity at 190 °C rather than MFR alone.

LDPE is not hygroscopic in the manner of polyamide or polyester, and LDPE 2427H does not require pre-drying when stored in dry, closed silos. Surface moisture from cold-to-warm condensation can generate bubble defects and splay; in high-humidity conditions above 60 % RH, pellets may be passed through a hopper dryer at 60 °C to 70 °C for 1–2 h before extrusion. The drying temperature should not exceed 80 °C because the antioxidant package and the polymer surface can be adversely affected during extended residence in a hot-air hopper.

In heavy-duty shrink film, the strain-hardening response of LDPE 2427H is used in the core layer of a three-layer structure at a die gap of 1.6–2.0 mm and a blow-up ratio of 2.5:1 to 3.5:1. The long-stalk bubble creates transverse direction orientation, and the resin’s melt strength lowers bubble-break frequency at gauges below 50 µm when compared with a fractional melt index linear grade. Buyers evaluating this grade for high-gloss printed collation ask for the supplier’s gel count and optical gel rating. Gel-count targets vary by converter and end market, but a common incoming inspection threshold is fewer than 10 gel particles per square meter above 300 µm; this criterion should be agreed with the supplier before trial.

Extrusion coating inquiries for this grade are less common. LDPE 2427H is a film-grade resin; when evaluated for coating onto paper or aluminum foil, neck-in and draw-down are more dependent on melt elasticity than MFR. Published data for this specific configuration is limited; buyers typically switch to a higher MFR LDPE coating grade if the line speed exceeds 150 m/min.

Heat-seal performance of LDPE 2427H is often compared with LLDPE in film structures. The low-density backbone gives a lower seal initiation temperature, often reported in a range of 95–110 °C for unfilled film; specific values vary with gauge, seal pressure, and dwell time. A converter asking about 2427H for lamination sealant webs should request hot-tack data from the film line because hot-tack strength is affected by jaw temperature, dwell time, and cooling rate more than by the resin’s MFR alone. Seal initiation values are measured on the finished film, not on pellets, and should not be taken from resin datasheets as a weld-seal guarantee.

First-order trials with LDPE 2427H should begin with a purge of 2–3 hopper loads of the incumbent LDPE if changeover is made on the same blown-film line. Operators then run a reference lot at fixed screw speed, die gap, and blow-up ratio, recording melt pressure, melt temperature, amperage, and film thickness profile before any formulation change. Because the resin’s melt elasticity is temperature-sensitive, processing personnel should not adjust barrel temperatures and screw speed simultaneously; a single-variable change protocol separates lot effects from machine drift.

After film production, the coefficient of friction of LDPE 2427H film may change during storage as slip additives migrate to the surface. Quality checks for coefficient of friction by ISO 8295 should be delayed for 24–72 h; values measured immediately off-line are not representative of final packaging performance. If the grade is used without slip/antiblock, the coefficient of friction can exceed 0.50 and cause jamming in form-fill-seal machines.

Optical acceptance for 2427H is evaluated on 50 µm film using ASTM D1003 for haze and ASTM D2457 or ISO 2813 for 20° gloss. The base resin without slip/antiblock may show haze below 8 %; after slip/antiblock masterbatch addition, haze can rise to 12–18 %, depending on antiblock particle size and dispersion. Buyers should specify the final additive package in the inquiry because optical properties cannot be evaluated independently of the formulation.

Quality laboratories often characterize LDPE 2427H by Fourier-transform infrared spectroscopy to confirm the absence of carbonyl bands associated with oxidative degradation, and by differential scanning calorimetry for melting peak and crystallinity. A broad melting peak with a maximum between 108 °C and 112 °C is typical for LDPE of this density; an unusual shoulder or elevated carbonyl index above 0.5 may indicate regrind contamination. These analytical checks supplement, but do not replace, the melt flow and density data on the certificate of analysis.

Cross-contamination with polypropylene or other polymers in railcar or silo transfer can compromise film opticals and sealing. A contamination level as low as 20 ppm of high-density polyethylene crystals can form unmelted gel-like specks at LDPE processing temperatures. LDPE 2427H melts below the processing temperature of HDPE, so HDPE contamination may remain as a solid inclusion at 190 °C, creating optical defects in 25 µm film. First-buyer logistics should confirm that the carrier is dedicated or cleaned to the agreed polymer class.

Surface polarity of LDPE is low; without corona treatment, the surface energy is typically below 32 mN/m, and water-based inks do not wet reliably. Converters commonly treat film to 38–42 mN/m for lamination or printing, measured by ISO 8296 test inks. LDPE 2427H film that contains slip additives can lose treatment level over time; therefore, treatment should be measured at the point of use.