PetroChina Dushanzi HD4801EX is a high-density polyethylene resin produced at the Dushanzi Petrochemical Company complex. The designation “HD” identifies the material as high-density polyethylene, while the numeric and alphabetic suffix “4801EX” is the producer’s commercial grade identifier. The suffix “EX” suggests an extrusion-oriented melt rheology, but it is not a normative classification under ISO 1043-1:2011. The material is generally supplied as stabilised pellets for extrusion and extrusion-blow moulding conversion. Publicly available lot-specific datasheets for HD4801EX are limited; therefore this introduction separates the standard HDPE specification framework from speculative lot-specific values. The manufacturer’s certificate of analysis, batch testing, and processing guidelines remain the controlling source for resin acceptance.

The grade identifier should not be interpreted as a fractional property target. The “4801” segment is a producer internal code and does not directly specify melt flow rate, density, or molecular weight. End users who rely on the suffix alone risk substituting HD4801EX into an application for which another Dushanzi HDPE grade was qualified. The supplier’s grade-selection documentation is the only valid mapping between the commercial code and the intended conversion process.

The specification suite for an HDPE extrusion resin begins with density and melt mass-flow rate because these two inputs govern screw power, melt pressure, and part stiffness. Density is determined by ISO 1183-1:2019 using an immersion method or density gradient column. For polyethylene with density not less than 0.945 g/cm³, the material is classified as high-density polyethylene. Extrusion grades in this segment commonly fall between 0.948 g/cm³ and 0.952 g/cm³, but no independent grade-specific value for HD4801EX is asserted here. The melt mass-flow rate is measured by ISO 1133-1:2022 at 190 °C and 2.16 kg load. Lower MFR values in the 0.2 g/10 min to 1.2 g/10 min band are common for HDPE extrusion and blow moulding resins because higher molecular weight increases melt strength and parison integrity. The exact MFR target for HD4801EX must be confirmed on the supplier’s certificate of analysis. Tensile yield stress is tested by ISO 527-2:2012 on type 1A specimens; for HDPE extrusion grades, yield stress is generally in the range 22 MPa to 30 MPa. Elongation at break is typically above 200 % for well-stabilised HDPE, but the result is test-speed and specimen-conditioning dependent. Flexural modulus measured by ISO 178:2019 commonly lies between 800 MPa and 1200 MPa. Vicat softening temperature under ISO 306:2022 method A50 is typically 120 °C to 128 °C. These values provide a general HDPE extrusion benchmark, not a substitute for HD4801EX lot-specific data.

Compared with a high-flow HDPE injection-moulding grade from the same production complex, HD4801EX requires lower melt temperatures and generates higher melt pressure at equivalent screw speed because of its higher molecular weight. Compared with a butene-based HDPE blown-film grade, HD4801EX may have a different short-chain branching distribution that increases stiffness but reduces dart impact; the difference is measurable by notched impact tests under ISO 179-1:2023 and by Elmendorf tear tests under ASTM D1922-15. Compared with a bimodal pressure-pipe grade, HD4801EX lacks the high environmental stress-crack resistance and creep resistance associated with a multimodal comonomer distribution; long-term hydrostatic stress classification under ISO 9080 and ISO 12162 is absent from public documentation. These comparisons are diagnostic and must be confirmed on the actual lots being compared.

How Does the Molecular Architecture of HD4801EX Influence Processing?

The processing behaviour of an extrusion-oriented HDPE is controlled primarily by molecular weight distribution and short-chain branching. HD4801EX is expected to exhibit pronounced shear thinning and elevated die swell relative to injection-moulding HDPE grades. Higher molecular weight fractions increase melt elasticity and parison stability in extrusion blow moulding, but they also reduce flow at the same melt temperature. In practice, die swell ratios of 1.2 to 1.5 are common for HDPE extrusion grades, although the exact ratio for HD4801EX must be measured on the production die. A change in die swell between lots indicates a shift in molecular architecture, not simply a change in melt flow rate. Such a shift requires adjustment of the die gap, puller speed, or parison programming to maintain wall thickness control.

Melt fracture occurs when the wall shear stress exceeds a critical value, typically in the range 0.1 MPa to 0.4 MPa for polyethylenes. The critical shear rate depends on melt temperature, die geometry, and molecular weight distribution. If sharkskin or melt fracture appears on extruded sheet or profiles, the response is to raise melt temperature within the allowed ceiling, reduce output, or use a wider die gap. Processing aids should not be added without evaluating interaction with the stabiliser package.

On a single-screw extruder with 24:1 to 30:1 L/D ratio and a barrier screw with a compression ratio of 3:1 to 4:1, the barrel temperature profile is commonly ramped from 160 °C in the feed throat to 200 °C in the metering zone. Melt temperature at the die is normally maintained between 190 °C and 220 °C for HDPE extrusion grades; excursions above 240 °C accelerate oxidative chain scission and may deplete the phenolic antioxidant package, producing aldehydes and surface defects. Screen packs of 40 mesh to 80 mesh are typically installed before the breaker plate to trap gels and unmelts. A rising melt pressure above the baseline by 20 % to 30 % at constant screw speed indicates screen blockage or inadequate plastication. Pre-drying of HD4801EX is not required when pellets are stored under dry conditions, but surface moisture from condensation can be removed with a dehumidified-air hopper at 70 °C to 80 °C for 2 h to 4 h. HDPE is not hygroscopic, so drying is an operational safeguard rather than a standard requirement.

Mechanical Performance and Slow Crack Growth Limitations

Structural performance of HD4801EX is governed by yield, creep, slow crack growth, and environmental stress cracking. Environmental stress-crack resistance is measured by ASTM D1693-15 or ISO 22088-3:2005; the test ranks formulations but does not directly predict field life. For moulded or extruded parts in contact with detergents, agricultural chemicals, or oils, the fabricator must conduct article-level validation under actual stress and chemical exposure. Creep modulus is measured by ISO 899-1:2017; designs should limit long-term strain to a region where the creep modulus remains above 50 % of the short-term modulus. Sharp corners act as stress concentrators and should be radiused to at least 1 mm to 2 mm. HDPE is not resistant to aromatic hydrocarbons, chlorinated solvents, or strong oxidising acids; contact with these media causes swelling, plasticisation, and stress cracking. The grade is generally compatible with aqueous salt solutions, dilute alkali, and many weak acids at temperatures below 40 °C, but ISO 175:2010 immersion testing on the actual grade is required for each chemical environment.

Shrinkage of HDPE after extrusion or blow moulding is anisotropic and governed by cooling rate. In thick-walled sheet or container walls, differential cooling creates a frozen-in stress gradient that can produce warpage days after demoulding. Mould design should account for HDPE mould shrinkage values generally between 1.5 % and 4 %, depending on flow direction, wall thickness, and process conditions. For HD4801EX, the exact shrinkage is grade-specific and should be obtained from pilot trials before final tooling is cut. Annealing at 80 °C to 100 °C for HDPE parts can reduce residual stress but may also cause dimensional change; the annealing time depends on wall thickness and should be determined experimentally.

Rigid packaging and technical extrusion are plausible application areas for HD4801EX if the supplier’s technical datasheet confirms the grade’s intended conversion route. Candidate products include industrial containers, accumulator-head blow-moulded parts, thick-walled sheet for thermoforming, and structural profiles. In sheet extrusion, the three-roll stack temperature is generally held between 60 °C and 90 °C to control crystallisation and sheet flatness. In profile extrusion, vacuum calibration tanks are operated with water temperatures from 15 °C to 30 °C; lower water temperature increases cooling rate but can induce residual stress. In extrusion blow moulding, mould temperatures are typically 10 °C to 30 °C to balance cycle time and surface quality. Cooling below 10 °C can create surface haze and internal stress in thick-walled articles. Published data for this specific configuration is limited; converter trials must establish the true melt pressure, output, and part-weight repeatability on the intended production line.

When Regulatory, Thermal, and Incoming Inspection Boundaries Are Applied

Regulatory status for HD4801EX is not independently confirmed in this document. High-density polyethylene grades in this family may be formulated to meet food-contact requirements under FDA 21 CFR 177.1520 and EU 10/2011, but the specific additive package and compliance documentation must be obtained from PetroChina. For non-food industrial use, the resin is subject to general chemical registration obligations under REACH and may be supplied with a compliance statement for RoHS if required by the buyer.

Oxidative stability of high-density polyethylene is provided by a primary phenolic antioxidant and a secondary phosphite processing stabiliser. The exact additive package for HD4801EX is not disclosed in public sources. Long-term thermal aging in air is evaluated by ISO 11357-6:2018 oxidation induction time or by oven aging under ISO 4577:1983. The OIT test identifies whether the active stabiliser package remains sufficient to protect the melt during multiple heat histories. Regrind use should be limited because each heat history consumes a fraction of the stabiliser and decreases the OIT. As a general boundary for HDPE extrusion grades, regrind addition up to 20 % by mass may be acceptable if the regrind is clean, dry, and generated from the same grade; higher levels should be validated by OIT and mechanical tests.

Incoming resin lots should be tested for density by ISO 1183-2:2019 and melt mass-flow rate by ISO 1133-1:2022. A shift in MFR greater than 15 % from the plant’s rolling average will alter melt pressure and output; a density shift greater than 0.003 g/cm³ may affect part stiffness and barrier. Oxidation induction time is checked by ISO 11357-6:2018 at 200 °C; values below 20 min suggest thermal stabiliser depletion or poor storage. Contamination by polypropylene, low-density polyethylene, or incompatible masterbatch can create gels, surface roughness, and reduced melt strength. In such cases, the line is purged with a high-viscosity HDPE or commercial purge compound before returning to HD4801EX. The grade’s functional operating boundary ends where pressure-pipe certification, food-contact approval, or long-term chemical resistance has not been demonstrated for the specific finished article.