Braskem HDPE HS5103 is a high-density polyethylene resin intended for extrusion blow moulding of rigid containers where environmental stress crack resistance and melt strength control the suitability window. The grade is designated by the supplier as a high-molecular-weight HDPE with a nominal density of 0.951 g/cm³ when tested according to ASTM D792-20 and a melt flow rate of 0.30 g/10 min at 190°C under a 2.16 kg load when tested according to ASTM D1238-20. These two primary indices place HS5103 in the low-melt-index segment of HDPE blow moulding polymers, separate from injection moulding HDPE with melt flow rates above 8 g/10 min and from lower-viscosity blow moulding grades selected for fast cycle times. The density-melt index combination supports slow relaxation, pronounced die swell, and delayed crystallization in the mould, all of which affect parison formation, pinch-off weld strength, and dimensional stability. The resin is commonly supplied as natural pellets, but the base polymer is not a finished article approval; end-use compliance status depends on the complete formulation, processing conditions, and article geometry.

The mechanical property profile reported for HS5103 in public technical literature includes a tensile yield strength of 26 MPa under ASTM D638-14, flexural modulus near 1100 MPa under ASTM D790-17, and notched Izod impact strength above 5.0 kJ/m² under ASTM D256-10e1. The Vicat softening temperature is listed at 126°C under ASTM D1525-17e1. Environmental stress crack resistance is specified as a screening value above 600 h in 10% Igepal at 50°C under ASTM D1693-15 condition B. Elongation at break is reported above 800%. These data are typical values and do not replace lot-specific certification; converters must verify release limits on the certificate of analysis because polymerization process variation can shift the molecular weight distribution and therefore the melt elasticity within the nominal density and melt flow rate envelope.

How Does the Rheological Profile of HS5103 Restrict Extrusion Blow Moulding Conditions?

The melt flow rate of 0.30 g/10 min reflects a high average molecular weight and a broad molecular weight distribution typical of blow moulding HDPE. The resulting shear viscosity is high at low shear rates, which increases die swell and promotes parison integrity, but it also limits plastication throughput and increases torque on the extruder drive. On a single-station shuttle blow moulder with a 60 mm grooved-barrel extruder and a 24:1 L/D ratio, typical processing begins with barrel set points from 170°C to 190°C in the metering zone, a head temperature of 185°C to 200°C, and a die temperature no higher than 200°C. Published data for this specific configuration is limited; the values are derived from equipment manufacturer technical bulletins for HDPE in the same melt index class, not from a guaranteed HS5103 processing window. At melt temperatures below 170°C, the resin may exhibit high extruder amperage, melt fracture at the die lip, and poor homogenization of regrind. At melt temperatures above 205°C, parison sag becomes the dominant defect, particularly for containers with a targeted wall thickness below 1.5 mm. The practical melt-temperature window for preserving parison stability is therefore narrow; a change of 5°C in the die zone can alter the effective parison hang time by more than 10% in high-molecular-weight blow moulding grades.

Moisture uptake is rarely the limiting variable. If the pellet is stored in an unheated silo at relative humidity below 60%, pre-drying is not required. Surface moisture can become relevant when cold pellets are transferred into a hot hopper in a humid plant; condensation on the pellet surface can generate splay, reduce melt temperature uniformity, and increase shot-to-shot weight variation. A desiccant hopper dryer set at 70°C with a residence time of 2 h is sufficient to remove surface moisture, but drying should not exceed 4 h at temperatures above 80°C because prolonged elevated-temperature exposure can initiate thermo-oxidative degradation. Regrind from edge trim and tail flash may be added up to 20 wt% without significant loss of mechanical properties when the regrind is clean, dry, and from the same HS5103 lot. Higher regrind fractions alter the die swell ratio and may increase gel counts in the finished wall; a 40 wt% regrind blend can shift the die swell ratio by 5% to 10% relative to virgin pellets, requiring adjustment of die gap or air pressure to maintain the same part weight distribution.

Extrusion blow moulding is the primary conversion route for HS5103. The grade is used for monolayer containers intended to hold household cleaning concentrates, surfactant-based detergents, agricultural chemical dilutions, and industrial liquids where slow crack growth is a potential failure mode. In monolayer structures, wall thickness typically ranges from 0.6 mm to 2.5 mm, depending on container volume and top-load requirement. The resin provides a balance between rigidity and ductility at these thicknesses, but it is not a barrier resin. Oxygen permeability of HDPE at 23°C and 0% relative humidity is generally in the range of 600 to 700 cm³·mm/(m²·day·atm) under ASTM D3985; the specific oxygen transmission rate of HS5103 is not always published in standard product literature. For oxygen-sensitive or solvent-aggressive contents, a multilayer structure with a polyamide or ethylene vinyl alcohol barrier layer, or surface fluorination, is required. HS5103 can serve as the structural and regrind layer in such coextruded systems, provided that the adhesive and barrier layers are selected to match the melt viscosity of the HDPE layer under the same die conditions.

Field experience on production-scale extrusion blow moulding lines highlights two recurring failure modes in this melt index class. The first is parison curl caused by non-uniform die temperature; a circumferential die gap variation of 0.10 mm can create wall-thickness standard deviations above 0.15 mm in a 1 L bottle, which is outside the acceptable range for stacking load. The second is insufficient pinch-off weld integrity when the mould closes at low pressure; a pinch-off temperature below 160°C can produce a brittle weld line, while a temperature above 190°C can create flash stringing and excessive tail material. Therefore, the pinch-off zone should be maintained within the melt-temperature window and the mould clamping force should be verified according to the machine manufacturer’s specification for the container footprint.

When Chemical Compatibility and Stress Cracking Govern the Material Choice Instead of Flow Length

Material selection for aggressive liquid packaging is frequently controlled by environmental stress crack resistance, not by tensile yield strength. HS5103 is documented with an ASTM D1693-15 condition B ESCR value above 600 h in 10% Igepal at 50°C. This value should be interpreted as a screening datum because field failures depend on the combination of stress, wetting agent, temperature, and article design. A container with sharp corners, deep draw areas, and high moulded-in stress can fail in service even when the resin passes the standard coupon test. Design rules therefore matter more than the single ESCR value. A minimum wall thickness of 0.8 mm at corner radii below 3.0 mm is a conservative starting point for surfactant-based contents; finished containers should be validated with a drop impact test at -18°C according to ASTM D2463 or ISO 6272-1 to confirm that the bottle does not transition to brittle fracture at refrigeration or winter transport temperatures.

The replacement of a conventional unimodal HDPE with HS5103 can support downgauging in detergent bottles only after creep rupture analysis. The critical performance variable is long-term stacking load, not short-term tensile yield. For HDPE in general, a sustained stress below 2 MPa at 23°C can produce creep deformation and eventual crack initiation if the stress concentration at the bottle shoulder exceeds the local yield stress. High-molecular-weight grades such as HS5103 are designed to retain a higher fraction of their initial modulus under long-term load than lower-molecular-weight counterparts, but published creep data for this specific configuration is limited. Any reduction in wall thickness below the qualified production geometry must be revalidated using ISO 899-1 or ASTM D2990 under the actual stacking load and temperature profile. In addition, HS5103 is not recommended for direct contact with strong oxidizing acids or aromatic hydrocarbon fuels without barrier protection because the HDPE matrix can absorb and swell in the presence of these fluids, leading to a reduction in mechanical strength even in the absence of cracking.

Compared with a higher-flow HDPE blow moulding grade in the 0.35 g/10 min to 0.45 g/10 min melt index range, HS5103 sacrifices plastication output and cycle time in exchange for higher melt strength and improved stress crack resistance. The lower melt index raises screw torque and can reduce the output rate on a 60 mm grooved-barrel extruder by as much as 10% to 15% relative to a 0.45 g/10 min resin at the same screw speed, based on equipment manufacturer estimates for the same density class. In contrast, HS5103 is not interchangeable with HDPE injection moulding grades with melt flow rates above 8 g/10 min. The low melt flow rate limits spiral flow length and increases the risk of short shots, gate blush, and burn marks in injection moulds. No published spiral flow data for HS5103 are available in standard product literature; a mouldability assessment under ISO 294-1 is required before any injection moulding attempt.

Regulatory Baseline and Test Method Documentation for HS5103

Braskem supplies HS5103 with a certificate of analysis covering melt flow rate, density, and selected mechanical properties on the release lot. In the United States, the base resin falls under the olefin polymer provisions of 21 CFR 177.1520 when the finished article meets the end-use limitations for food contact and when any added masterbatch, processing aid, or stabilizer is itself compliant. Under European Union Regulation (EU) No 10/2011, plastic food-contact articles must demonstrate overall migration below the limit of 10 mg/dm² under Annex III and Annex V test conditions specific to the food simulant and storage temperature; HS5103 itself is not a finished article approval and must be evaluated as part of the converted container. Under REACH Regulation (EC) No 1907/2006, the polymer is generally exempt from registration under Article 6(3) as a polymer substance, but monomers and intentionally added substances at or above 0.1% w/w remain subject to registration and safety data sheet obligations. The natural grade carries no intentionally added lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers; compliance with Directive 2011/65/EU should be confirmed on the supplier statement because lot-specific trace metals can vary within permitted limits.

For lot acceptance, the converter should verify pellet moisture content, bulk density, and melt flow rate after drying because transport and silo transfer can introduce fines and moisture variability. Additive packages containing high levels of calcium stearate or certain amine-based processing aids may interact with the stabilizer system; no specific incompatibility data for HS5103 are published, but the supplier should be consulted before introducing a new masterbatch or lubricant system above 2 wt%. Storage in direct sunlight for extended periods in silo bags should be avoided because ultraviolet exposure can initiate photo-oxidative chain scission and shift the melt flow rate upward. In aggressive chemical packaging, HS5103 should be combined with a validated internal or external barrier layer when the filled fluid is a strong oxidizer, an aromatic hydrocarbon, or a terpene-based formulation that exceeds the stress crack resistance limit of the standard coupon test.