Braskem HDPE GD5150K is a high-density polyethylene resin classified within the manufacturer’s extrusion blow-moulding portfolio. The grade designation identifies a pelletised product intended for continuous or accumulator blow moulding of large industrial containers, jerrycans, agricultural chemical containers, and fuel-tank bodies. Its nominal density is 0.951 g/cm³ by ASTM D1505, and the melt flow rate measured at 190 °C under a 21.6 kg load is typically 5.0 g/10 min by ASTM D1238. That combination corresponds to a high-molecular-weight HDPE with melt stiffness appropriate for large parisons. The suffix K denotes a stabilisation package; in practice, the package contributes to outdoor weathering resistance in above-grade chemical containers. The product is not a low-viscosity injection-moulding grade and is not optimised for thin-wall flow lengths below 1.5 mm.

What Processing Parameters Control Parison Sag in GD5150K?

Melt temperature control is the first variable in parison sag management. The recommended melt window is 190 °C to 230 °C, with 220 °C commonly used as an initial setpoint on continuous shuttle lines. Sustained operation above 240 °C can increase melt flow rate through oxidative chain scission and reduce die swell, producing a longer, thinner parison under the same die gap. The extruder should use a barrier screw with an L/D ratio of at least 24:1 and a compression ratio between 2.5:1 and 3.5:1. Die temperatures of 180–210 °C are typical; higher die temperatures reduce melt fracture but decrease parison strength. Blow air pressure between 0.6 MPa and 1.0 MPa is sufficient for most container sizes. When shop-floor relative humidity exceeds 60%, surface condensation on cold pellets can cause splay; a hopper dryer set to 70–80 °C for 1–2 h is advisable. Production experience on accumulator machines with 60–90 mm screw diameters shows that grooved feed zones improve throughput stability at low screw speeds. Lot-to-lot MFR variation of ±0.5 g/10 min under the 21.6 kg condition is possible, so closed-loop parison control should be recalibrated after each resin lot change.

Environmental Stress Cracking Resistance and Chemical Contact Limits

Slow crack growth is a primary failure mode in blow-moulded HDPE containers, particularly at pinch-off welds and sharp sidewall transitions. GD5150K is typically characterised by an environmental stress cracking resistance above 1000 h under ASTM D1693, Condition B, using 10% Igepal CO-630. This performance is relevant to formulations containing non-ionic surfactants, quaternary ammonium compounds, and aliphatic hydrocarbons. In practice, ESCR values measured on compression-moulded specimens do not translate directly to blow-moulded parts because moulded-in stress and wall thickness variation dominate. Chemical contact testing should be performed on finished articles at the intended temperature and fill level. The resin does not create a high-barrier layer; diesel and solvent permeation may require fluorination or coextruded EVOH when permeation limits fall below 2 g·mm/m²·day. Avoid sustained contact with strong oxidisers, chlorinated solvents, and highly aromatic fuels at temperatures above 40 °C unless specific compatibility data are available. Pinch-off weld strength is improved by land widths of 0.8–1.5 mm and compression angles of 30–45°. Post-mould annealing at 60–70 °C for 30 min may reduce residual stress in critical tanks, although it is not always economically justified.

The K stabilisation package retards photo-oxidative chain scission and surface microcracking on outdoor-stored containers. Accelerated laboratory weathering under ASTM D2565 or ISO 4892-2 typically measures retained tensile elongation after UV exposure. Stabilised HDPE of this density range may retain more than 70% of initial elongation at break after 2000 h in xenon-arc testing, but published data for this specific grade is limited. The figure should not be treated as a datasheet maximum. In actual service, carbon black or other UV-opaque pigment masterbatches further reduce light transmission. The base stabilisation does not eliminate the need for colourant selection in long-life above-ground tanks. Surface grazing remains possible at sharp mould parting lines where high orientation and residual stress coincide with UV exposure.

If Coextruded Barrier Structures Are Employed

Coextrusion of GD5150K with EVOH or polyamide barrier layers requires viscosity matching at the die lip. The resin’s shear-thinning behaviour matches best with tie-layer grades having a high-load melt flow rate in the 4–6 g/10 min range at 190 °C and 21.6 kg. A mismatch greater than 2 g/10 min under the same load can generate layer thickness oscillations and barrier discontinuities. In coextrusion heads, die temperatures should not exceed 220 °C to protect the barrier resin; the GD5150K melt may be maintained near 200–215 °C when EVOH is present. The temperature difference between structural and tie-layer melts should remain within 10 °C to limit interfacial instability. Post-extrusion regrind from barrier containers should not exceed 20 wt% in the structural layer unless the barrier domain size and compatibiliser concentration are controlled. Higher regrind levels can reduce ESCR at the pinch-off weld and generate visible delamination streaks.

Mechanical property benchmarks in blow-moulded sections remain geometry-dependent

Table 1 consolidates typical nominal values for preliminary engineering comparisons. The values are obtained from laboratory specimens and do not represent a production release specification. Finished-part properties depend on wall thickness distribution, mould temperature, and rate of cooling. The table should not replace lot-specific certificates of analysis.

The flexural modulus and top-load performance of GD5150K are greater than those of HDPE grades with density below 0.945 g/cm³. The trade-off is that ESCR generally falls as density rises; the molecular architecture and stabilisation of GD5150K seek to offset that trend for large-part blow moulding. Compared with a standard HDPE blow-moulding homopolymer, the parison hang-time stability of GD5150K supports shot sizes above 15 L without severe sag. Compared with a high-flow injection-moulding HDPE at 20 g/10 min under 2.16 kg, GD5150K has inferior spiral-flow length and is unsuitable for thin-wall caps or closures. The difference is not primarily tensile strength but melt elasticity and slow crack growth resistance.

Regression in melt-flow ratio is a useful process indicator. The melt flow ratio, determined as the quotient of MFR at 21.6 kg and MFR at 2.16 kg, is typically above 20 for broad-MWD blow-moulding HDPE. A higher ratio indicates shear thinning and good parison melt strength. If the ratio falls below 18 after repeated heat history, the material may still meet the high-load MFR specification but exhibit reduced sag resistance. Process control should therefore track MFR ratio rather than high-load MFR alone. The exact ratio for GD5150K should be obtained from the certificate of analysis; published data for this specific ratio is limited. Clean post-industrial scrap from the same grade can be incorporated at up to 30 wt% after drying and fines removal for non-critical industrial containers. Fuel-tank production often limits regrind to 10–15 wt% because repeated heat history increases the MFR and reduces ESCR. The melt-flow shift after three extrusion cycles can exceed 0.5 g/10 min at the high-load condition.

Regulatory assessment should be based on the latest Braskem safety data sheet and product compliance certificate. Polyethylene homopolymers are generally covered by EU REACH registration for polymerised substances, and the heavy-metal restrictions of Directive 2011/65/EU (RoHS) are normally met. In the United States, the resin may be referenced under 21 CFR 177.1520 as an olefin polymer for food-contact articles, but migration testing on the finished article is still required according to food type, temperature, and contact time. The grade is not marketed as a medical-grade resin. Where drinking-water contact is involved, certification under NSF/ANSI 61 or an equivalent national scheme is required and must be confirmed for the specific product.

On production accumulator machines with clamp force from 500 to 1500 kN, the parison wall distribution improves when the accumulator head uses spiral grooves rather than straight annular gaps. The high molecular weight of GD5150K means that flow marks from spiral mandrel lines relax slowly; die head tooling should avoid abrupt cross-section changes. Die swell after the die exit is typically 30–40% for HDPE blow-moulding grades, but exact values for GD5150K depend on die geometry and shear history. In continuous extrusion lines with screw diameters of 60–90 mm, throughput stability is sensitive to barrel temperature profile. A reverse profile with the rear zone at 180 °C and the front zone at 210 °C can reduce screw slip and improve melt pressure stability. The die gap should be adjusted only after melt temperature has reached equilibrium; changing die gap before thermal stabilisation produces parison length oscillations of more than 10%.

The resin’s high melt strength also affects flash trimming. Thick flash at the mould parting line may require post-mould trimming to be delayed until the part cools below 60 °C to avoid stringing. In fuel tank production, leak testing at 0.03–0.05 MPa and drop impact testing at -40 °C according to OEM specifications are typical. The tolerance to low-temperature impact is influenced by pinch-off quality, not by resin choice alone. A poorly compressed bottom weld in GD5150K can fail at -20 °C despite higher nominal impact strength. Fuel tank applications also require low-temperature impact, fire resistance, and permeability compliance under vehicle-specific standards such as UN ECE Regulation 34 or equivalent national requirements. GD5150K can be used as the structural HDPE substrate in multilayer fuel tanks, but the complete system must be tested as an assembly. The resin alone does not confer a specific fire-resistance rating. In North American passenger-vehicle applications, SHED evaporative emissions testing is generally required; the base HDPE contributes to wall stiffness, while the barrier layer controls hydrocarbon emission. Published data for this specific grade in a complete tank system is limited.

For agricultural chemical containers, moulded-in labelling and handle welds introduce additional stress concentrations. GD5150K is used in such designs because its ESCR resistance is maintained after blow moulding under slower cooling rates. Moulds should minimise sharp inside corners; root radii below 0.5 mm create localised stress that accelerates slow crack growth. When wall thickness is below 2.0 mm, coolant temperature should be uniform within ±5 °C across the mould to avoid differential shrinkage and barrel distortion. These requirements are not unique to GD5150K but become more important in large-part applications where the material’s melt strength permits high draw ratios and complex tooling.

Colour masterbatch selection affects stabilisation efficiency. Some organic pigments, particularly yellow and red azo colourants, can interact with hindered amine light stabilisers and reduce outdoor performance if incompatible packages are used. Carbon black at 2.0–2.5 wt% is an effective UV screen for HDPE exposed to sunlight. For GD5150K, masterbatch let-down ratios above 4% may alter melt viscosity and parison draw. Pigment dispersion quality should be assessed by pressure rise on a screen pack or filter test; a pressure increase above 0.5 MPa at constant throughput indicates poor dispersion that can reduce ESCR by creating agglomerate stress points.

Compared with Braskem’s general-purpose HDPE blow-moulding grades, GD5150K shifts the balance toward high ESCR and outdoor stabilisation. The density is on the high end of the blow-moulding range, which increases top-load strength and chemical resistance but reduces low-temperature impact toughness relative to lower-density HDPE. For applications where drop impact at -40 °C is the primary requirement, a lower-density HDPE with higher molecular weight may be selected. For applications where creep under top load is the primary requirement, GD5150K’s flexural modulus is advantageous. The product differs from HDPE grades used for pressure pipes such as PE100 or PE4710 because it is not formulated for long-term hydrostatic pressure at 20 °C for 50 years. The resin’s melt flow and stabilisation package are intended for blow-moulded containers, not for extruded pressure pipe. In pipe-grade HDPE, the MFR is typically below 0.5 g/10 min at 190 °C with 5 kg, whereas GD5150K has a high-load MFR of 5.0 g/10 min and is not pressure-rated under pipe standards.

The use of GD5150K in rotationally moulded articles is not a typical recommendation because the grade is pelletised for extrusion blow moulding. Published data for rotomoulding flow and sintering of this specific grade is limited. It should be converted only in blow-moulding equipment unless the manufacturer’s technical service group has qualified an alternative process. The same restriction applies to blown film and cast film operations, where the high viscosity and melt elasticity tend to produce unstable bubble behaviour or high backpressure, respectively. Injection blow moulding is also generally unsuitable because the high viscosity at injection shear rates causes short shots and high residual stress in preforms. Extrusion blow moulding remains the recommended conversion process.