Braskem HDPE L50V5A is a high-density polyethylene grade designated for extrusion blow molding of rigid containers and technical hollow parts. The material belongs to the low-melt-index HDPE class; class-typical melt mass-flow rate is approximately 0.5 g/10 min at 190 °C under a 2.16 kg load according to ISO 1133-1:2022, with solid-state density near 0.955 g/cm³ when measured by ISO 1183-1:2019. These figures are class-typical reference points and should be verified against the current lot certificate because production-site and catalyst-system variation can shift results within the specification band. The grade is selected where high melt viscosity, controlled parison hang time, and stress-cracking resistance are required rather than thin-wall injection flow. Typical applications include industrial containers, transport drums, automotive fluid reservoirs, canisters, and recreational hollow parts in which wall-thickness distribution, drop impact, and environmental stress-cracking resistance are evaluated.

The complete designation, Braskem HDPE L50V5A, identifies the supplier, polymer class, and grade suffix. The alphanumeric suffix cannot be interpreted without the supplier’s technical datasheet, although the low melt-index class indicates a molecular weight distribution and comonomer architecture intended for blow molding rather than injection molding or thin-film extrusion. The difference from other Braskem HDPE grades lies primarily in melt index, molecular weight distribution, and the resulting balance between melt strength and flow. Low-melt-index blow-molding grades are formulated to resist parison sag while retaining sufficient shear thinning for extruder throughput.

Mechanical property evaluations for low-melt-index HDPE blow-molding grades with density near 0.955 g/cm³ commonly show tensile yield stress in the range of 23 MPa to 28 MPa when tested at 50 mm/min according to ISO 527-2:2012, flexural modulus between 900 MPa and 1,200 MPa according to ISO 178:2019, and notched Charpy impact at 23 °C above 15 kJ/m² according to ISO 179-1:2020. Environmental stress-cracking resistance under ASTM D1693-15 Condition B in 100% Igepal CO-630 at 50 °C frequently exceeds 100 h for this molecular-weight class, although actual F50 values depend on comonomer content, molecular weight distribution, and production lot. These ranges are not a substitute for the Braskem datasheet but serve as an initial basis for dimensioning and validation testing.

Melt Temperature, Die Gap, and Extruder Configuration Determine Blow Moldability

For continuous-extrusion shuttle blow molders, a grooved-barrel extruder with screw diameter of 60 mm and length-to-diameter ratio of 24:1 is a common production configuration. The die-head melt temperature is typically maintained between 190 °C and 230 °C for HDPE grades of this melt-index class. Temperatures above 240 °C can increase oxidative gel formation and reduce melt strength; temperatures below 170 °C can elevate head pressure, reduce output, and produce surface roughness known as melt fracture. The die gap is generally set from 1.5 mm to 3.0 mm depending on container shot weight and parison programming. For a 60 L drum with shot weight above 1.8 kg, parison programming with a diverging die bushing and axial mandrel adjustment is used to compensate for sag-induced thinning. These processing conditions are generic to low-melt-index HDPE blow molding; exact set points for L50V5A should be taken from Braskem’s processing guide.

Under parison extrusion shear rates of 10 s⁻¹ to 100 s⁻¹, melt viscosity is high enough to limit sag in large-diameter parisons. Shear-thinning behavior allows die-head pressure to remain below the extruder maximum despite the low melt index; a typical die-entrance pressure is on the order of 20 MPa to 35 MPa for clean screens and a melt temperature near 200 °C. Published data for this specific grade’s rheology are limited; capillary rheometry according to ISO 11443:2021 is recommended before commissioning new tooling. Die swell of HDPE in this class is commonly 1.2 to 1.6 times the die diameter, requiring die bushing diameters smaller than the intended parison diameter. Excessive die swell can be reduced by increasing melt temperature or reducing mandrel length, but both adjustments affect parison sag.

Capillary rheometry is performed at 190 °C and 210 °C over apparent shear rates from 10 s⁻¹ to 1,000 s⁻¹. The Bagley correction is applied to calculate wall shear stress, and the Rabinowitsch correction converts apparent shear rate to wall shear rate. For HDPE of this melt-index class, the melt is pseudoplastic with a power-law index commonly between 0.30 and 0.50 across the parison extrusion range. A low power-law index permits higher throughput at moderate die-head pressure, while high zero-shear viscosity sustains parison hang time. If a converter changes to a grade with a narrower molecular weight distribution, die swell and parison sag response will differ even if the melt flow rate is identical.

How Does L50V5A Differ from HDPE Grade Families with Higher Melt Flow?

The primary difference is melt mass-flow rate. Higher-melt-flow HDPE bottle grades with melt flow rates of 1.5 g/10 min to 3.0 g/10 min fill thin walls at lower head pressure but exhibit greater parison sag in large shot sizes. L50V5A-class resins are selected where the container requires a minimum wall thickness above 1.5 mm and where hang time exceeds 5 s. Injection-molding HDPE grades with melt flow rates above 8 g/10 min have insufficient melt strength for conventional blow molding and should not be substituted. Differences from high-density grades with density above 0.960 g/cm³ include lower solid-state stiffness but typically higher environmental stress-cracking resistance. Therefore, L50V5A is not chosen for top-load-dominated bottles made from high-density homopolymer; it is chosen for stress-cracking-prone containers exposed to surfactants, oils, or cooling fluids.

Verification of incoming lots is usually performed against the following standard designations. The table does not list grade-specific values because those values are lot-dependent; it lists the methods used for property evaluation.

Regulatory status should be verified against the supplier’s current regulatory certificate. Polyolefin homopolymers used in food-contact applications are commonly referenced under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011, but end-use thickness, food-type simulant, and additive package determine final compliance. For automotive applications, emission requirements such as VDA 278 may apply to finished parts, not to the resin alone. No electrical or flame-retardant claims should be derived from the base polymer without a specifically amended grade.

When Coextruded Barrier Structures Are Specified Around L50V5A

In multilayer blow molding, L50V5A may serve as the structural outer and inner layers of a container whose middle barrier is ethylene-vinyl alcohol copolymer or polyamide. The processing window is constrained by the barrier layer’s thermal stability and by interfacial adhesion. Melt temperatures for the HDPE stream are typically held between 200 °C and 220 °C, while the barrier stream is maintained within its stable window, often 210 °C to 230 °C for EVOH; exceeding 240 °C risks crosslinking and gel formation in EVOH. Tie layers based on maleic anhydride-grafted polyolefins with anhydride contents around 0.1 wt% to 0.5 wt% are used to bond layers. Regrind from coextruded flash is typically incorporated into the HDPE layers only, and the barrier layer content is limited to 5 wt% to 10 wt% of the core layer to avoid delamination and viscosity mismatch. The high parison melt strength of L50V5A-class materials assists in maintaining layer thickness uniformity during the long hang time required for multilayer parisons. Published data for this specific grade in coextruded structures is limited; preproduction trials are required to establish layer distribution.

Layer thickness tolerances are strongly influenced by the melt viscosity ratio between the HDPE and the barrier resin. A viscosity mismatch exceeding 3:1 at the apparent shear rate of the die can lead to layer instabilities and uneven barrier thickness. In practice, a coextrusion trial with layer-distribution measurement by Fourier transform infrared microscopy or polarized light microscopy is used to validate layer ratios. For containers requiring drop impact resistance, the inner and outer HDPE layers are kept as the major fractions; the barrier layer is placed at 2% to 5% of total wall thickness, and tie layers each account for 1% to 2%. The low melt index of L50V5A may reduce interfacial shear heating, but processing audits should record die pressure, melt temperature at the die lip, and screw torque.

Polyethylene is hydrophobic, and equilibrium moisture uptake at 23 °C and 50% relative humidity is generally below 0.01 wt%. Nevertheless, condensation on cold pellets entering a hot hopper or high levels of moist regrind can produce surface splay and pinholes. If regrind content exceeds 30 wt% or if storage occurs at relative humidity above 60%, drying in a desiccant dryer at 80 °C for 2 h to 4 h is a common preventive measure. Additive compatibility should be evaluated before blending masterbatches; silicone-based processing aids, when used above 0.5 wt%, can alter die swell and reduce adhesion in multilayer structures. Avoid amine-based antistatic additives at levels above 0.1 wt% because amine migration can interfere with adhesion to barrier tie resins. The stabilization package is normally designed for melt temperatures up to 240 °C; extended hold-up under high shear may reduce oxidative induction time independent of the base resin.

This grade is not suitable for injection blow molding of complex preforms with flow length-to-thickness ratios above 150:1. The low melt index produces short shots and high injection pressure in narrow tooling. Converters should not substitute L50V5A into existing thin-wall injection-blow molding tools designed for resins with melt flow rates above 1.5 g/10 min. Similarly, sheet extrusion and thermoforming of thin sheet below 1 mm are outside the normal processing envelope.

On production-scale rotary wheel blow molders using an 80 mm grooved-barrel extruder with 24:1 L/D, typical defects observed with this class of low-melt-index HDPE include parison curling, fold-over, and localized thinning at the pinch-off. Parison curling often originates from mandrel misalignment or nonuniform die temperature; correction begins with mandrel centering and thermal profiling of the die head. Fold-over occurs when melt temperature is too high or die gap is too narrow for the shot weight; increasing die gap from 1.5 mm to 3.0 mm and reducing head pressure can restore parison stability. In flash-type molds, insufficient clamp force—below 150 kN for intermediate containers—can allow flash thickening and parting-line defects. These observations are not unique to L50V5A but are characteristic of blow-molding HDPE resins with melt flow rates near 0.5 g/10 min; batch-to-batch variation in melt index and molecular weight distribution should be monitored by the converter because it shifts the processing window.