Sinochem Quanzhou HDPE HMN55180 is a high-molecular-weight high-density polyethylene resin supplied in pellet form for extrusion blow moulding of rigid containers in the 20–200 L range. The product is based on a hexene-1 comonomer structure, and its melt-flow behaviour is reported as a high-load melt-flow index of 5.5 g/10 min at 190 °C under a 21.6 kg load, tested according to ISO 1133-1. Density is controlled at 0.955 g/cm³ at 23 °C per ISO 1183-1. The resin’s molecular-weight distribution is bimodal, with a high-molecular-weight fraction that contributes melt strength and slow-crack growth resistance, and a controlled lower-molecular-weight fraction that reduces viscosity under shear during plastication.

Because the grade is produced by low-pressure slurry polymerisation, comonomer distribution and catalyst residues are managed within narrow limits. This controls odour and organoleptic performance in industrial packaging, although the grade is not marketed as food-contact compliant in all jurisdictions. Users must verify specific migration limits under the relevant national or regional regulation. No claim for direct food contact is made here.

What specifications distinguish HMN55180 from general-purpose HDPE blow moulding grades?

Table 1 lists representative physical properties published for HMN55180. The values are single-point typical data and do not constitute batch release limits.

The specification profile shows a balance that is uncommon in general-purpose unimodal blow moulding HDPE. The high-load melt-flow index of 5.5 g/10 min is low enough to maintain parison geometry on large tools, while density near 0.955 g/cm³ retains the stiffness needed for stack-loaded drums. Environmental stress crack resistance under 100 % Igepal at 50 °C is the key differentiator. General-purpose grades with similar density and flow frequently exhibit F50 values below 100 h; HMN55180’s typical value is above 500 h. This is achieved through high tie-molecule concentration and controlled short-chain branch distribution rather than solely through higher molecular weight.

The distinction extends to impact behaviour. At 23 °C, the notched Charpy value of 18 kJ/m² is moderate for HDPE, but the low-temperature drop impact resistance of moulded containers is more closely related to slow-crack growth resistance and the absence of weld-line weakness at the pinch-off. In blow moulded parts, the pinch-off region is a stress concentrator. HMN55180’s high-molecular-weight fraction permits a ductile pinch-off when tool temperature is maintained at 10–30 °C and clamp force is sufficient.

Melt strength, die swell, and accumulator-head performance characteristics

Processing trials on production-scale accumulator-head machines indicate that HMN55180 should be plastified at melt temperatures of 180–220 °C. The feed-throat zone is usually set at 170–180 °C, with barrel zones increasing to 200–215 °C and the die head held at 190–210 °C. Extruder screws with 24:1–30:1 L/D and barrier mixing sections provide the required melt homogeneity without excessive shear heating. In machines with 80–120 mm screw diameters, screw speed is typically reduced by 10–15 % compared with a lower-viscosity HDPE to keep melt pressure below 30 MPa and to avoid melt temperatures above 220 °C.

Die swell on annular tools is moderate to high. The observed swell ratio depends on die gap, land length, and shear rate; industrial data commonly fall between 25 % and 45 % for well-designed blow moulding dies. High die swell is a practical limitation when converting tools from a chromium-catalysed HDPE with narrow molecular-weight distribution, because the parison diameter and wall-thickness programming may require re-profiling of the diverging die gap. Published data for this specific conversion on HMN55180 is limited, and tool trials are required.

No hygroscopic drying is normally required for HDPE. However, pellets stored below the ambient dew point can carry surface condensation, producing splay in the parison. After chilled storage, the resin should be equilibrated above the dew point before entering the feed hopper. Regrind can be incorporated, but the practitioner should limit ground flash to 20–30 wt% in non-food industrial containers and screen it to remove fines and contamination.

Parison programming is effective with HMN55180 because the high-molecular-weight fraction provides a wide processing window for wall-thickness control. On a 60 L tight-head drum tool, operators often adjust wall-thickness program output by 5–10 % after switching from a lower-melt-strength HDPE. The material’s rheology permits a thicker top chime and bottom corner without excessive thinning in the sidewall, which is necessary to meet drop tests such as UN 6.1.5.3 for dangerous goods packaging.

In containers destined for hydrocarbon or solvent-containing formulations, chemical compatibility must be verified with the actual filling fluid. ESCR data under ASTM D1693-15 in 100 % Igepal is a useful screen but does not replace pack testing for specific ester-based or aromatic solvents. The grade is not recommended for direct contact with strong oxidisers or for continuous service above 60 °C, because oxidative embrittlement may reduce service life.

When HMN55180 is compared with chromium-catalysed HDPE grades of equivalent density, the hexene-copolymer structure typically yields higher notched impact and slow-crack growth resistance at the same flexural modulus. Chromium-catalysed resins may have broader short-chain branch placement and lower tie-molecule concentration, which is reflected in lower ASTM D1693 F50 values and higher notch sensitivity. However, chromium-catalysed comparators may provide lower viscosity at high shear rates and faster cycle times on small blow moulders. HMN55180 should be selected where environmental stress crack resistance and drop impact at low temperature outweigh cycle-time considerations.

Relative to small-bottle HDPE grades with melt-flow indices of 0.5–1.0 g/10 min at 2.16 kg, HMN55180 is substantially more viscous and is not suited to shuttle or wheel machines running thin-wall containers below 0.8 mm wall thickness. Attempts to force such thin walls through high melt temperature or excessive shear can degrade the polymer and produce off-spec odour and reduced ESCR. Injection moulding of thin-wall closures is outside the grade’s effective processing window; tool fill and warp are controlled poorly because of the high molecular weight.

The product is specified in non-pressure industrial containers, agricultural chemical packaging from 10 L to 60 L, and technical blow moulded parts where wall thickness exceeds 1.5 mm. In all such applications, the end user must confirm that the final moulded part meets the required transport, fill, and handling test standards. The resin’s typical properties alone are not sufficient for part certification.

Finished containers are typically evaluated under ASTM D2463-15 for drop impact and, where applicable, ASTM D1998-15 for polyethylene upright storage tanks. The resin does not by itself guarantee performance; equipment parameters, pinch-off weld geometry, and cooling rate alter orientation and residual stress. Inadequate clamping at the pinch-off produces a visible weld line and is a common field failure in high-molecular-weight HDPE containers. On 60 L drums, cooling time after extrusion may be extended by 5–10 s compared with lower-viscosity grades to set the pinch-off before de-moulding.

After chemical fill testing, the worst-case container is commonly conditioned at -18 °C for 24 h and subjected to a 3 m drop. This test condition reveals whether pinch-off welds and wall-thickness distribution are acceptable for dangerous goods packaging, although the specific protocol depends on the applicable modal transport regulation.