PetroChina Guangdong HDPE HSGC7260 is a high-density polyethylene pellet resin supplied for injection moulding. The grade designation is positioned in the high-flow segment of the Guangdong HDPE slate, with a nominal melt mass-flow rate of 7.2 g/10 min when tested at 190 °C under a 2.16 kg load according to ISO 1133-1:2022, and a nominal density of 0.960 g/cm³ when determined by ISO 1183-1:2019. The resin is typically specified for thin-wall containers, caps, closures, housewares, toys, crates, and general-purpose injection-moulded parts requiring a balance of rigidity and fast mould filling. Because commercial polyethylene production is lot-dependent, the certificate of analysis and the manufacturer’s technical datasheet should be used to confirm exact melt index, density, and additive package before tool trials.

Nominal Property Profile and Specification Benchmarks

The values in the table are representative inspection values rather than specification limits; they may shift with pigmentation, nucleation, or recycled content. The grade is usually supplied as a stabilised pellet, but processors adding masterbatch should verify that the additive carrier does not reduce the Vicat temperature below the declared value or introduce low-molecular-weight fractions that increase mould deposit formation.

Processing of HSGC7260 follows the normal envelope for high-flow HDPE injection grades. Melt temperatures between 200 °C and 260 °C and mould temperatures from 20 °C to 50 °C are common. Higher mould temperatures improve knit-line strength and surface gloss but extend cooling time. HDPE is not highly hygroscopic, but pre-drying is required at relative humidity above 60% and is commonly performed at 80 °C for 2–4 h in desiccant dryers to keep surface moisture below 0.05 wt%. Injection moulding machine set-up typically uses a compression-zone screw with 20:1 to 25:1 L/D and a back pressure of 5–10 MPa hydraulic pressure. Field reports from multi-cavity closure production indicate that shot-to-shot cushion control below 2 mm is necessary to avoid short shots at wall thicknesses below 0.8 mm; published data for this specific grade and tool configuration is limited. Processors should adjust hold pressure from the minimum required to eliminate sink marks and avoid overpacking, which raises part weight and moulded-in stress.

How Does HSGC7260 Differ from Blow Moulding and Film Extrusion Grades?

The principal difference is melt-flow rheology. HSGC7260 has a melt mass-flow rate near 7.2 g/10 min, whereas blow moulding grades such as HD5502 in the same producing region typically fall below 1.0 g/10 min, and film extrusion grades such as HD7000F may fall below 0.1 g/10 min. The higher flow rate corresponds to a lower average molecular weight, which reduces shear viscosity at injection rates above 1,000 s⁻¹. This is an advantage in filling thin-wall injection moulds and multi-cavity hot-runner systems, but it is a liability in continuous extrusion processes. Blow moulding requires high melt strength to prevent parison sag, and blown film requires bubble stability; low-viscosity HSGC7260 is therefore not interchangeable with extrusion-grade HDPE on those lines. Density also separates the grades: at 0.960 g/cm³, HSGC7260 provides higher flexural modulus than medium-density or lower-density HDPE grades, but the denser crystal structure tends to reduce low-temperature impact and environmental stress-crack resistance when compared with 0.945–0.955 g/cm³ copolymers. Within the injection moulding family, a higher-flow grade offers lower injection pressure and faster cycle time, while a lower-flow grade offers better impact and stress-crack performance in thick-walled parts.

Production-scale failure modes associated with HSGC7260 are concentrated at the boundaries of its flow advantage. In multi-drop hot-runner systems with unbalanced runner lengths, the lower viscosity allows the shorter drop to fill first, causing overpacking and flash before the longer drop fills. Tooling corrections such as runner balancing, independent valve-gate timing, or cavity pressure transducers in each cavity are required. On conventional cold-runner tools with tunnel gates, the high flow rate can generate excessive shear heating at gate diameters below 0.5 mm, raising local melt temperature by 20–40 °C and creating gate blush or degradation streaks. Reducing injection velocity or increasing gate diameter to 0.8–1.0 mm mitigates this condition. Moulders also observe that the high-density grade is more prone to post-mould shrinkage anisotropy in flat lids than lower-density grades; flatness requirements call for uniform cooling and possibly post-mould fixturing. Because HSGC7260 has lower melt strength than extrusion grades, purging after processing from high-viscosity to low-viscosity resins should be performed with a commercial purging compound rather than regrind alone to avoid screw and adapter accumulation of degraded gel.

Thin-wall packaging with wall thickness below 0.8 mm is the primary use case where the flow properties of HSGC7260 produce measurable differences. In cap and closure moulds, gates of 0.5–1.0 mm diameter are often employed because the resin can fill the cavity without requiring excessive injection pressure. The lower viscosity also permits reduced barrel temperatures relative to a 2 g/10 min HDPE, lowering energy input and reducing degradation risk. However, high flow increases the tendency to flash if the parting line is worn or the clamp tonnage is marginal. For closures, torque retention after application and ageing is evaluated using ASTM D2063-12. Food-contact applications require supplier confirmation that the formulated grade meets GB 4806.6-2016 and EU Regulation (EU) No 10/2011, including overall migration testing under the applicable simulants. Compliance with FDA 21 CFR 177.1520 may be cited for olefin polymers but is not an automatic property of every lot. The grade’s low moisture uptake means that regrind can be incorporated, but the percentage must be controlled because repeated extrusion shifts the melt flow rate upward and reduces viscosity.

Storage and handling requirements follow typical HDPE pellet practice. Sustained storage temperatures above 50 °C can block agglomerates, and ultraviolet exposure should be limited to prevent oxidative initiation. The product is insoluble in water at ambient temperatures and is not classified as hazardous under typical transport regulations, but dust from grinding or regrind operations should be controlled. For food-contact uses, the additive package, not only the base resin, determines compliance; any colour masterbatch or processing aid must also meet the relevant food-contact regulation. Supplier REACH and RoHS declarations should be requested for exports to the EU, because base resin compliance does not automatically cover formulated compounds containing external masterbatch.

When Multi-Cavity Tooling Demands Faster Cycle Times

Cycle time in injection moulding is controlled by part wall thickness and cooling efficiency. For a 1.0 mm wall section in a 10 °C chilled mould, cooling time is often in the range of 4–8 s, whereas a 2.0 mm section can require 12–18 s; these values are dependent on mould steel conductivity, coolant turbulence, and part geometry. The high melt flow of HSGC7260 allows the use of lower melt temperatures and shorter injection times, but the ejection temperature must still fall below the Vicat softening temperature before demoulding. Mould shrinkage is typically measured on standard plaques according to ISO 294-4:2018; for HSGC7260, parallel shrinkage is generally in the range of 1.5–2.0% and transverse shrinkage 1.0–1.5%, with anisotropic differences increasing as mould restraint and part geometry change. Tool designers should account for this differential shrinkage when dimensioning multi-cavity cap cores, because dimensional stability after 24 h post-mould ageing can shift by 0.1–0.3% due to post-crystallisation. If hot runners are used, valve-gate systems are preferred over thermal sprue gates to minimise stringing and improve gate cleanliness at the high flow rate.