PetroChina Fushun HDPE 2911 is an injection-moulding high-density polyethylene resin produced by PetroChina Fushun Petrochemical Company in Fushun, Liaoning. The grade is supplied as white pellets and is classified primarily by its melt mass-flow rate of approximately 20 g/10 min when measured at 190 °C under a 2.16 kg load according to ISO 1133-1:2022. The nominal density is 0.956 g/cm³ when determined by ISO 1183-1. These values define the processing identity of the product: a high-flow HDPE intended for short-cycle injection moulding of thin-walled packaging, containers, caps, closures, housewares, and general-purpose rigid articles. The high melt flow reduces injection pressure and improves cavity filling, but it also lowers melt strength compared with extrusion, blow-moulding, or pipe-grade HDPE. Consequently, Fushun HDPE 2911 is not intended for large-part blow moulding, heavy-wall pressure pipe, or applications requiring long-term creep resistance under hydrostatic stress.

What Limits Melt Flow Rate Interpretation in Thin-Wall Multi-Cavity Moulding?

The 20 g/10 min single-point value should not be interpreted as a complete viscosity curve. It is derived under low shear conditions, whereas injection moulding exposes the melt to shear rates above 1000 s^-1 in gates and thin walls. For reliable cavity-filling prediction, capillary rheometry according to ISO 11443 is required. A 1.0 mm diameter die and 20:1 length-to-diameter ratio are common test dimensions for generating shear viscosity data suitable for Moldflow input. Published data for the specific spiral flow configuration of Fushun 2911 is limited; converters should generate a capillary viscosity curve from the actual purchased lot rather than relying on the melt flow rate alone.

The high flow of this grade is achieved through a lower weight-average molecular weight and a controlled molecular weight distribution; the exact molecular architecture is proprietary. This molecular profile reduces entanglement density and lowers melt viscosity across the shear-thinning region. It also reduces zero-shear viscosity and melt strength, which explains why the product cannot replace high-molecular-weight HDPE in parison blow moulding or sheet extrusion. The polydispersity of the grade is not disclosed on all commercial data sheets, but it affects the shear-thinning slope and the onset of melt fracture at high injection velocities.

During thin-wall filling with nominal wall thickness between 1.0 mm and 1.5 mm, the narrow process window is controlled by gate freeze-off. Gate thickness below 0.5 mm may produce short shots even at high injection speed. For this high-flow HDPE class, gate thickness is commonly maintained between 0.8 mm and 1.2 mm, and gate land length is kept below 1.5 mm to avoid premature solidification. Cavity pressure transducers should record peak cavity pressures above 40 MPa but below 80 MPa to achieve adequate packing without flash. Jetting and gate blush are the most frequent visual defects when the melt temperature is too low or the gate is too small. The corrective sequence is to raise the nozzle temperature to 220 °C, increase gate diameter, or reduce first-stage injection velocity. Short shots in multi-cavity tools are often caused by runner imbalance rather than material deficiency; runner balance and gate size should be verified before increasing barrel temperature.

The tensile yield stress of 26 MPa under ISO 527-2/1A/50 indicates moderate short-term load-bearing capacity for snap-on closures, container lids, and household articles. The flexural modulus of 1100 MPa provides stiffness suitable for rigid packaging but below that of many polypropylene grades. The Vicat softening temperature of 124 °C under ISO 306/A50 defines an upper service threshold; hot-fill or microwave reheating should be validated by finished-part thermal testing rather than by raw resin data alone. For North American specification, properties may be reported under ASTM D638-14 and ASTM D790-17. The ASTM values are not numerically interchangeable with ISO data because specimen geometry, strain rate, and span-to-depth ratio differ. A direct comparison between an ISO-based Chinese datasheet and a North American ASTM-based procurement specification requires conversion testing on the same moulding batch.

Fushun 2911 versus Blow-Moulding and Piping HDPE Grades

Direct comparison with conventional blow-moulding or pipe-grade HDPE clarifies the substitution boundary. Blow-moulding HDPE grades are typically polymerised for a melt flow rate below 1.0 g/10 min, and pipe grades can be below 0.5 g/10 min. Fushun HDPE 2911 at 20 g/10 min has a significantly lower molecular weight and lower melt elasticity. In large parison blow moulding, this causes parison drawdown and uneven wall distribution before mould closure. In pipe extrusion, the hydrostatic strength and slow crack growth resistance of 2911 are inferior to PE100-rated HDPE grades; the product should not be specified for pressure piping, gas distribution, or high-stress geotechnical applications.

The reverse substitution is viable only in injection moulding. The high flow of 2911 reduces melt viscosity at the shear rates encountered in runner systems and gates. On a multi-cavity closure tool, a lower-melt-flow HDPE would require higher injection pressure, higher clamp force, or thicker walls. Fushun 2911 can fill small closures and thin-walled containers at lower cavity pressure, but the reduced molecular weight also produces lower environmental stress-crack resistance under aggressive liquids, fats, detergents, or surfactants. ASTM D1693 condition B testing is recommended before specifying the grade for detergent bottle caps, cosmetic containers, or packaging with lye-based or surfactant-rich contents. If the Fushun 2911 data sheet does not list a grade-specific ESCR value, comparative testing against a currently qualified HDPE is required rather than assuming equivalence.

Process optimisation on a 2000 kN to 3000 kN toggle-clamp injection moulding machine with a general-purpose polyolefin screw of 40 mm diameter and 20:1 to 24:1 L/D should begin with a barrel profile from 180 °C in the feed zone to 210 °C at the nozzle. Mould temperature should be maintained between 20 °C and 50 °C. Back pressure is held low, typically 0.5 MPa to 1.5 MPa, to avoid excessive shear heating and melt-pressure variability. Screw speed during recovery is adjusted to maintain a consistent cushion of 4 mm to 6 mm; larger cushions may indicate check-ring leakage or excessive decompression. Compression ratio for this grade is normally between 2.5:1 and 3.5:1; higher compression ratios may generate excessive melt temperature. A three-zone screw with a check ring and moderate mixing section is suitable. Very high-shear barrier screws are not normally required and can cause overheating.

Although HDPE 2911 is not hygroscopic, pellet surface moisture from condensation can cause splay and silver streaks. If bags are stored in high-humidity or unheated warehouses, pre-drying at 80 °C for 1 h to 2 h with dehumidified air is recommended. The resin should not be processed above 280 °C, because thermal degradation can produce gel particles and yellowing. The upper limit is also influenced by residence time and should be verified by melt flow stability trials. In medium-to-high-flow HDPE, peroxide-based purge compounds or rheology modifiers above 0.2 wt% can raise the melt flow rate further and reduce the already limited melt strength. Such additives should not be combined with Fushun 2911 unless the resulting viscosity shift is measured. Silane crosslinking systems designed for moisture-crosslinked pipe are also not applicable because the base resin lacks the melt strength and molecular weight required for pipe extrusion.

Because the base resin does not contain a UV stabiliser, outdoor parts require carbon black or a hindered amine light stabiliser package. The dispersion of the additive package should be verified by weathered specimen testing to ASTM G154 or ISO 4892-3; unstabilised parts can embrittle after a few months of outdoor exposure.

When the Fushun 2911 Grade Replaces Polypropylene Random Copolymer in Caps and Thin-Wall Packaging

In caps and thin-wall packaging, Fushun HDPE 2911 is sometimes evaluated as an alternative to polypropylene random copolymer. The choice involves trade-offs in stiffness, heat resistance, hinge performance, and low-temperature impact. The flexural modulus of 1100 MPa is lower than many PPR grades with typical values above 1300 MPa. Cap designs that rely on high radial stiffness or low deflection under top load may therefore require thicker sections or geometric reinforcement. The Vicat softening temperature of 124 °C is also below the 130 °C to 150 °C range common for PPR in hot-fill and pasteurised closures, making 2911 unsuitable for high-temperature retort applications unless the thermal load is verified by finished-part measurement.

However, HDPE 2911 can provide better low-temperature impact and reduced notch sensitivity in freezer packaging. The high flow of 20 g/10 min is suitable for multi-cavity cap moulds with hot-runner systems. Hot-runner temperature should be held between 200 °C and 240 °C, and gate temperature should not exceed 260 °C for more than 5 min during start-up to avoid resin degradation. Compared with PPR, the lower melting temperature reduces energy input, but barrel residence time control is essential because HDPE degrades if held at full temperature during production stoppage. The grade also shows different shrinkage behaviour: mould shrinkage is approximately 1.5 % to 2.0 % in the flow direction and may vary with wall thickness and gate area. Prototype tooling should use a steel-safe cavity and allow for shrinkage adjustment before final tool steel is cut.

In cap production, the relationship between melt flow and screw recovery is not linear. A high-flow HDPE may recover faster, but if back pressure is too low, melt density in the shot can vary and cause part weight drift. Moulders using 2911 in high-cavitation cap tools have observed shorter filling time than with a 0.7 g/10 min HDPE, but the cycle-time gain is limited by cooling time and demoulding rather than by filling. The clamp force requirement can be reduced because of lower injection pressure, but projected area and part geometry remain the primary clamp-force determinants. Gate area and cavity balance are critical; uneven fill in a 48-cavity tool can produce dimensional variation even when the machine barrel and hot-runner temperatures are stable.

Grade-specific documentation should be reviewed for regulatory compliance before commercial use. For food-contact packaging in China, the converter must verify compliance with GB 4806.6-2016 and any applicable positive list for additives. For the United States, FDA 21 CFR 177.1520 is relevant for olefin polymers, but actual compliance depends on the stabiliser package and conversion residues. For European Union food-contact applications, overall migration and specific migration testing under EU 10/2011 must be completed on the finished article rather than on the raw resin alone. The grade must also be evaluated for substance-of-concern compliance under REACH and RoHS when used in electrical or electronic packaging components.

Batch-to-batch variability in melt flow rate and density should be monitored by the receiving quality control laboratory. A practical incoming inspection protocol measures the melt flow rate at 190 °C/2.16 kg, density, and pellet contamination. If the melt flow rate falls outside the agreed specification window, processing conditions may shift and cavity balance may change, particularly in multi-cavity cap moulds with long flow paths. Published data for the specific application performance of Fushun 2911 is limited in peer-reviewed literature; therefore, production validation should combine supplier certificate-of-analysis data with internal rheology, mechanical testing, and end-use packaging performance testing.