As an injection-moulding grade of high-density polyethylene, Braskem HDPE SHD0860 is supplied in pellet form and is classified as an ethylene homopolymer. Its nominal melt flow rate is 8.0 g/10 min at 190°C under a 2.16 kg load, determined in accordance with ASTM D1238-20 or ISO 1133-1:2022, and its nominal density is 0.960 g/cm³. The grade is specified for thin-wall injection-moulded articles such as caps, closures, housewares, overcaps, and technical packaging. The combination of high flow and high density permits short cycle times and wall sections from 0.6 mm to 2.5 mm, while the stiffness remains higher than that of lower-density HDPE grades. Food-contact suitability is generally addressed under FDA 21 CFR 177.1520(c) for olefin polymers, subject to end-use migration limits and conditions of use.

How Does Melt Rheology Affect Short-Shot Limits in Thin-Wall Closure Moulds?

In multi-cavity hot-runner tools, gate freeze-off is the primary short-shot mechanism when thin-wall closures are moulded from HDPE. The melt flow rate of 8.0 g/10 min is substantially higher than that of blow-moulding HDPE grades, which generally fall below 1.0 g/10 min, and this difference reduces melt viscosity and pressure drop through the runner and gate. For wall sections below 1.0 mm, the melt should be maintained between 200°C and 230°C, and injection speed should be set to produce a fill time below 0.5 s. Injection pressure in hot-runner cap tools is typically held above 80 MPa to prevent gate freeze. Mould temperature is normally set from 10°C to 30°C for rapid solidification; larger articles with dimensional stability requirements may use 40°C. Back pressure should be controlled between 0.5 MPa and 1.0 MPa to avoid excessive shear heating. A general-purpose reciprocating screw with an L/D ratio between 20:1 and 24:1 and a compression ratio between 2.5:1 and 3.0:1 is suitable. The resin does not normally require drying; if surface condensation is present, drying at 80°C for 2 h is sufficient. Melt temperatures above 250°C or residence times longer than 5 min at 230°C should be avoided because oxidative chain scission raises the melt flow rate and causes yellowing.

Multi-cavity hot-runner tooling with 1.0 mm valve-gate nozzles can exhibit gate freeze at melt temperatures below 190°C. Raising melt temperature to 210°C and holding injection pressure above 80 MPa is a standard corrective action. These settings are typical for high-flow HDPE, but published data for a specific tool configuration is limited.

Typical mechanical property values for Braskem HDPE SHD0860 are summarised in Table 1. Tensile yield strength is evaluated on Type I specimens at 50 mm/min according to ASTM D638-14. Flexural modulus is measured at 1% secant using ASTM D790-17 with a span-to-depth ratio of 16:1. Notched Izod impact is determined at 23°C on 3.2 mm specimens according to ASTM D256-23. Vicat softening temperature is measured under a 1 kg load with a 50°C/h heating rate per ASTM D1525-17.

At the nominal density of 0.960 g/cm³, the two-phase density model gives a volumetric crystallinity of approximately 0.72, assuming amorphous and crystalline HDPE densities of 0.855 g/cm³ and 1.000 g/cm³. This high crystallinity produces the flexural modulus of 1,350 MPa but reduces tie-molecule density, which is a limiting factor for environmental stress crack resistance. The manufacturer’s standard datasheet does not report an F50 ESCR value; therefore, parts under continuous hoop stress or detergent exposure should be validated by ASTM D1693 or ISO 22088-1 on the finished article.

The notched Izod value of 35 J/m at 23°C is moderate for HDPE. Low-temperature impact data are not provided in the standard datasheet. Applications requiring impact at -20°C should use instrumented puncture testing according to ISO 6603-2 or ASTM D3763 on the actual part geometry. Mould shrinkage for this density class is generally in the range of 1.5% to 2.5% in the flow direction and slightly less across flow, but exact values should be measured on the tool because shrinkage depends on wall thickness, gate design, and packing pressure.

Higher Crystallinity Raises Flexural Modulus but Lowers Slow Crack Growth Resistance

The crystalline superstructure of SHD0860 develops rapidly in a cold mould. Because the grade is a narrow-molecular-weight homopolymer with a density of 0.960 g/cm³, the orthorhombic crystallites form densely packed lamellae. Differential scanning calorimetry on HDPE of this density range typically shows a peak melting temperature between 133°C and 137°C at a heating rate of 10°C/min, with the onset of melting near 125°C. The high crystallinity is directly responsible for the Vicat softening temperature of approximately 127°C and the heat deflection temperature of 76°C at 0.455 MPa. However, the same morphological order limits interlamellar tie-molecule concentration, so slow crack growth resistance is lower than that of high-molecular-weight bimodal HDPE grades used in pressure pipe. For caps and closures without continuous hoop stress, this is acceptable. For detergent caps, press-fit closures, and chemical containers with interference fits, slow crack growth should be assessed by ASTM D1693 or ISO 22088-1 on moulded parts, not on plaque data.

Continuous service temperature under load should remain below 60°C. Short-term excursions to 80°C are tolerated only if mechanical load is low. These thermal limits are derived from the heat deflection temperature at 0.455 MPa and standard HDPE service classifications, not from creep rupture data for this specific grade.

When SHD0860 Replaces a Lower-Flow Blow-Moulding HDPE in Cap Production

When a lower-flow blow-moulding HDPE is replaced by SHD0860 in cap production, the injection pressure and fill time decrease, but the balance of properties changes. Blow-moulding HDPE grades generally exhibit melt flow rates below 1.0 g/10 min and densities from 0.950 g/cm³ to 0.956 g/cm³. Their high molecular weight provides high environmental stress crack resistance and impact strength, but their low flow makes thin-wall injection moulding difficult. SHD0860, with 8.0 g/10 min and 0.960 g/cm³, fills wall sections from 0.7 mm to 1.5 mm at lower injection pressures. The density increase from 0.956 g/cm³ to 0.960 g/cm³ contributes a measurable flexural modulus increase from roughly 900 MPa to 1,350 MPa, allowing a thinner wall for the same stiffness. The trade-off is lower slow crack growth resistance and lower notched impact at low temperature. Table 2 compares SHD0860 with general categories of lower-flow HDPE.

The values in Table 2 are representative published ranges for generic polyethylene categories, not batch guarantees for any specific grade. When the substitution is made, mould trials should include notched impact testing of tamper-evident hinges at 23°C and 0°C, and closure application testing under ASTM D5419 or an equivalent end-user protocol. If service temperatures below -20°C are required, SHD0860 is not a direct substitute without an impact modification strategy.

Under FDA 21 CFR 177.1520(c), food-contact suitability for this olefin homopolymer is established when the finished article meets the migration limits in FDA 21 CFR 176.170(c) for the intended food type and use temperature. REACH registration requirements for the polymer are generally limited because polymers are exempt from registration, but monomer and additive substances must be registered or exempted. The unpigmented resin is not an outdoor UV-stabilised product; black or coloured masterbatch may be required for exterior use. The resin should not be used in pressure pipe, fuel tanks, or continuous immersion in aromatic and chlorinated solvents. Strong oxidizers such as fuming nitric acid cause surface oxidation and stress cracking. Purging should not be performed with polyacetal or PVC unless an intermediate polyolefin purge is used, because acidic decomposition products from those resins can catalyse HDPE degradation. If the material has been stored under high humidity, drying at 80°C for 2 h before processing removes surface moisture.

Thermal Stability Boundaries During Repeated Recycling

After multiple injection-moulding cycles, the resin’s melt flow rate and oxidation level are the most sensitive indicators of process history. During a single-pass operation at 220°C with residence time under 3 min, the melt flow rate shift is typically less than 0.5 g/10 min. Repeated extrusion and pelletising raise the melt flow rate more rapidly because of cumulative shear and oxygen exposure. The processor should monitor melt flow rate after each pass according to ASTM D1238-20 and limit regrind addition to maintain the target melt flow range. If the melt flow rate exceeds 10 g/10 min, thin-wall parts may show sink marks, dimensional variability, and reduced hinge life. Processing above 250°C should be avoided; oxidative degradation accelerates and generates volatile aldehydes and ketones. Differential scanning calorimetry at 10°C/min can confirm the melting peak and detect contamination from lower-melting materials. For critical parts, melt flow ratio under 2.16 kg and 5 kg loads may provide additional information about molecular weight distribution changes, although the manufacturer’s datasheet does not state a specification for this ratio.