Braskem (Quattor) HDPE HS-5502 is a high-density polyethylene copolymer grade specified for extrusion blow moulding of rigid containers. The legacy Quattor designation reflects the grade’s origin in the Brazilian polyolefin assets transferred to Braskem. Published nominal data place density at 0.955 g/cm³ and melt flow rate at 0.35 g/10 min under ASTM D1238 at 190 °C with 2.16 kg. The material is positioned in the high-molar-mass, low-flow branch of HDPE, where environmental stress-cracking resistance, impact toughness, and parison hang strength are more critical than rapid injection cycles. Representative end uses include blow-moulded containers for household cleaning products, agrochemicals, motor oil, pharmaceutical packaging, and cosmetic emulsions.

The grade’s density near 0.955 g/cm³ indicates controlled short-chain branching that reduces crystallinity relative to a 0.960 g/cm³ homopolymer injection resin. The resulting tie-molecule population and lamellar structure contribute to stress-cracking resistance while maintaining wall stiffness. The comonomer identity for a given lot is not always disclosed; the producer’s technical bulletin is controlling for lot-specific composition.

What Melt Rheology and Solid-State Specifications Define HS-5502?

The specification profile used for die design, container qualification, and incoming quality control is summarised below. These are producer-datasheet-aligned nominal values, not lot-specific specification limits.

The low melt flow rate of 0.30–0.40 g/10 min corresponds to high melt viscosity and good parison hang strength. In shear-thinning HDPE, apparent viscosity decreases as screw speed increases, which allows reasonable output despite the low MFR. Melt flow ratio between 21.6 kg and 2.16 kg conditions is class-typical in the range 25–35 for high-ESCR grades, indicating a broad molecular weight distribution that improves processability. Capillary rheometry data are normally required for detailed die-lip design; published data for this specific configuration is limited outside the producer’s application-support records.

In a shuttle blow-moulding cell equipped with a 70 mm single-screw extruder and 25:1 L/D grooved feed, the grade is typically run at barrel settings of 160–180 °C at the feed, 190–210 °C in the compression/metering zones, and 200–220 °C at the accumulator head. Screw speed is matched to the clamp cycle, commonly 30–60 rpm on a 70 mm machine. The high-viscosity melt generates head pressures in the range of 250–350 bar. If head pressure drops below 200 bar, output stability can suffer; if it exceeds 400 bar, melt temperature rises and the antioxidant package may be consumed prematurely.

Parison programming is used to control wall thickness in non-uniform container cross-sections. Die swell for high-molar-mass blow-moulding HDPE typically ranges from 1.3 to 1.6, though the exact value depends on die land length, die gap, melt temperature, and output. A die land length of 10–20 times the die gap is typical for reducing melt fracture. When parison sag becomes limiting, lowering the melt temperature by 5–10 °C or increasing the die gap while maintaining part weight can stabilise the parison. However, lowering the temperature too far increases die pressure and may introduce unmelts or surface roughness.

Pre-drying is not generally required for neat pellets from sealed boxes. When storage occurs at relative humidity above 60% and cold pellets are exposed to ambient air, surface condensation can introduce splay. Hopper drying at 80 °C for 2–4 h is used before processing. Melt temperatures above 240 °C should be avoided because chain scission and antioxidant depletion reduce ESCR and create odour in contained products.

Production-scale lot changes can shift die swell and ESCR within the nominal datasheet band. When re-pelletised off-spec material or post-consumer recyclate is blended, these shifts can increase. A control protocol that records melt flow ratio, density, and notched ESCR on incoming lots reduces blow-moulding start-up time and scrap. Continuous melt-pump systems are less sensitive to viscosity drift than extruder-speed-controlled systems because the pump decouples output from pressure fluctuations.

When the Grade Is Required for Aggressive and Household Chemical Packaging

The primary service demand in bleach, detergent, agrochemical, and motor-oil containers is resistance to slow crack propagation. In ASTM D1693, the resin is formed into notched specimens and bent into a fixed strain while immersed in a stress-cracking surfactant. Failure occurs when brittle cracks propagate through the notched zone. High-molar-mass HDPE with controlled short-chain branching develops tie molecules that bridge crystalline lamellae and resist crack advance. HS-5502 is positioned in the high-ESCR class, with nominal F50 values above 600 h under Condition B 100% Igepal at 50 °C; some lots may exceed 1,000 h without failure. Because ESCR testing is sensitive to notch preparation and bath temperature, F50 comparisons should be made only within a single laboratory following the same equipment calibration.

Chemical compatibility should be confirmed by immersion testing under ASTM D543 and by impact retention after exposure under ASTM D256. In continuous exposure to concentrated sodium hypochlorite above 60 °C, oxidative degradation can reduce ESCR and lead to stress crazing. Strong oxidising acids, halogens, and aromatic solvents at elevated temperature are generally outside the grade’s service envelope unless final container validation demonstrates otherwise. The polymer has no polar functionality; low-molar-mass aromatic and aliphatic species can swell the amorphous phase and reduce load-bearing capacity.

For food-contact applications, the olefin resin may be covered by FDA 21 CFR 177.1520 and EU 10/2011, provided the finished article meets migration and organoleptic requirements. These regulations do not automatically clear every formulation, and downstream pigments, masterbatches, and processing aids must be evaluated. REACH and RoHS heavy-metal restrictions are normally supported by resin manufacturing controls, but the final article manufacturer bears responsibility for conformity of the assembled container.

Comparative Position Against High-Flow Injection and Chromium-Catalysed Blow Moulding Resins

HS-5502 differs from high-flow HDPE injection grades principally in melt flow rate and ESCR. An injection grade with MFR of 8–20 g/10 min fills thin-wall moulds rapidly but may crack prematurely when exposed to surfactants or oils in a pressurised bottle thread. HS-5502 requires longer blow-moulding cycle times and may need thicker minimum wall sections, but the final container is more resistant to environmental fracture. In contrast to chromium-catalysed high-swell blow-moulding grades, HS-5502 may exhibit lower die swell and a narrower parison inflation window. Tooling designed for a high-swell chromium-catalysed HDPE should not be transferred without re-checking die gap, die pin position, and parison programming. Published data for this specific configuration is limited for side-by-side swell comparisons between HS-5502 and other Quattor/Braskem blow-moulding grades; pilot trials are required.

Compared with lower-density polyethylene grades such as LLDPE, HS-5502 offers higher top-load strength and better chemical resistance but lower environmental stress-cracking resistance than very low-density flexibles. This places the grade in rigid container applications where wall stiffness and ESCR are both relevant. In structural containers, the flexural modulus of 900–1,100 MPa allows downweighting relative to lower-modulus resins; however, thin-wall designs below 0.8 mm can lose ESCR because crack path constraints and residual stresses dominate.

Specifiers evaluating the grade against other products should request current lot-specific certificates of analysis, because nominal datasheet values do not replace specification limits. In the absence of application-specific permeation data, the rate of weight loss and stress-cracking after chemical immersion should be measured on the finished article geometry rather than on a generic resin plaque. Tests on plaques do not capture thread-root stresses and parison weld lines, which are common failure sites in blow-moulded containers.

ESCR Testing Alone Does Not Guarantee Container Fitness

A single-pass ASTM D1693 result is not sufficient to qualify a blow-moulded container for aggressive contents. The test generates a fixed strain on a small notched specimen and does not reproduce thread-root stress concentrations, weld-line orientation, or parison thickness gradients. Finished-container testing under top load, drop impact, and internal pressure after chemical exposure is required. The internal pressure test should follow ASTM D2463 or an equivalent container-specific procedure, and drop impact should follow ASTM D5276 with the container conditioned at service temperature.

The table below provides the regulatory and test-method matrix commonly used during container qualification. It is not exhaustive; application-specific chemical resistance and migration protocols may apply.

Processing conditions, colour concentrates, and recycled content can shift final container performance away from neat-resin data. Therefore, the current producer technical bulletin and lot-specific certificate of analysis remain the controlling documents. Application-specific pilot trials on production tooling are required before changing from another HDPE grade to HS-5502.