ExxonMobil HDPE HD5675 is a pelletized high-density polyethylene grade intended for extrusion blow moulding of rigid containers, jerrycans, dairy bottles, and industrial packaging. Supplier technical literature identifies a nominal melt flow rate of 0.75 g/10 min at 190 °C under a 2.16 kg load according to ISO 1133-1:2022 and ASTM D1238-20, and a nominal density of 0.956 g/cm³ according to ISO 1183-1:2019 and ASTM D1505-18. These values place the grade in the high-molecular-weight fraction of HDPE blow moulding resins, where parison hang strength, die swell stability, and environmental stress-crack resistance are more process-critical than injection filling length. Because the melt flow rate is below 1 g/10 min, the grade is not intended for thin-wall injection moulding or high-speed small-part injection; published spiral-flow data for this exact grade is limited. The product is supplied as natural pellets, and the lot certificate normally records melt flow rate, density, and additive composition. A resin evaluation against the supplier’s certificate of analysis should be performed before silo qualification because batch-to-batch variation in high-density polyethylene can shift parison sag and bottle weight distribution.

Material Specification Data and Test Methods

The values in Table 1 are representative values published in supplier documentation and are not specification limits. They are measured on compression-moulded plaques under laboratory conditions; blow-moulded part properties will differ because of orientation, wall thickness, and cooling-rate history. The method editions shown are the commonly referenced versions at the time of publication; laboratories should confirm the exact method edition against the purchase specification.

The melt flow rate test is a low-stress resin identification test and does not predict extrusion blow moulding shear behaviour. For processing diagnostics, a high-load melt index or capillary rheometry sweep from 10 s⁻¹ to 1000 s⁻¹ is more informative because die entry pressure and die swell are controlled by the polymer’s high-shear viscosity and molecular weight distribution. Supplier capillary rheometry data for HD5675 is not fully reproduced in public technical bulletins; processors should request lot-specific curves when evaluating a new die-head configuration.

Which Narrow Operating Windows Govern Parison Stability and Pinch-Off Weld Strength?

In extrusion blow moulding, HD5675 is typically processed on a single-station shuttle or accumulator-head machine with a barrier screw of 24:1 L/D and a die-head melt temperature between 190 °C and 210 °C. The lower boundary is defined by melt homogeneity and parison weld quality; sustained operation below 190 °C can increase back-pressure to the extruder drive and produce frozen-in stress at the parison knit line. The upper boundary is set by oxidation and parison sag; above 215 °C, parison drop time shortens and the visible melt may develop yellowing without a catastrophic viscosity drop. The exact upper temperature depends on residence time; if an accumulator head holds resin for more than 20 min, melt temperature should be reduced toward 195 °C to limit molecular weight degradation.

Die gap settings are normally 1.5–2.5 mm for containers between 250 mL and 30 L. Parison programming is used to control wall thickness from 0.6 mm in handle pinch areas to 3.5 mm in load-bearing base corners. Blow-up ratio is generally held below 3:1; higher values may produce irregular sidewall thinning and reduce top-load performance measured by ASTM D2659-16. The low melt flow rate increases die swell compared with a 2 g/10 min blow moulding HDPE, so a new die gap must be set by trial on the target mould. Industrial trials on shuttle machines have found that a die gap reduction of 10–20 % relative to a higher-melt-flow-rate grade may be needed to maintain the same parison diameter; however, this figure is equipment-specific.

Pinch-off weld strength is controlled by clamp force, pinch-off land temperature, and melt temperature. With HD5675, insufficient clamp dwell or blunt pinch-off inserts produce a weak flash line because the high-viscosity melt resists flow into the weld. Typical blow moulder clamp forces for HDPE containers of 20 L are in the range of 100–200 kN, but the required value depends on mould geometry, flash thickness, and head pressure. Accumulator head pressure on a 75 mm extruder is commonly 28–35 MPa; a rise to 40 MPa may indicate a blocked screen pack, incorrect die land, or cold feed. Screen packs in blow moulding are frequently specified as 40/80/120 mesh to balance pressure drop with gel capture, but final selection must be validated by head-pressure measurement.

Moisture control for HD5675 differs from that required for polyamides or polyethylene terephthalate. The pellet is not hygroscopic; predrying is not a routine requirement. The dominant moisture failure mode is condensation on cold pellets when silo temperature is below the surrounding dew point. Condensed water entering the extruder feed throat vaporizes during compression and can generate pinholes, surface streaks, and reduced pinch-off weld strength. If pneumatic conveying air is not dehumidified and ambient relative humidity exceeds 60 %, hopper condensation becomes measurable. In such conditions, the pellet surface should be dried with dry air at 70–80 °C for 2–3 h before extrusion, but heated hoppers should not run continuously because oxidation can occur at residence times above 8 h. The feed throat should be kept below 40 °C; if regrind is added at more than 20 % by weight, melt temperature must be rechecked because fines and oxidized surface area lower the onset of degradation.

When HD5675 Replaces a Medium-Molecular-Weight HDPE in Extrusion Blow Moulding

Changing from a medium-molecular-weight HDPE to HD5675 is not a direct drop-in. First, the melt flow rate moves from approximately 0.95 g/10 min to 0.75 g/10 min, a reduction of about 21 %; extruder torque, head pressure, and heat generation shift higher. Second, molecular weight distribution may change die swell and parison sag independently of the melt flow rate. In blow moulding, the required adjustment is usually not a temperature increase but a die gap and parison-programming change. On a 10 L dairy-container line, a processor changing to HD5675 may observe a more stable parison length at the same drop time and slightly higher top-load values after the same wall-thickness profile, but flash thickness may increase unless the pinch-off land is maintained. These effects are not predictable from melt flow rate alone; a capillary rheometry curve and a plant trial on the target blow moulder are required.

Compared with a high-flow injection grade HDPE having a melt flow rate of 20 g/10 min, HD5675 has approximately 1/27 the melt flow rate and would fill spiral-flow moulds poorly. That comparison is useful only when an injection-grade silo is mistakenly introduced into a blow moulding line. The practical limit is the extruder drive. If a line currently processes a 0.95 g/10 min resin at 32 MPa head pressure, HD5675 may move the system to 34–36 MPa under identical molten conditions. Before changing, the processor should check the maximum continuous pressure rating of the head, the extruder motor current, and the screen pack pressure margin. If the head has no pressure transducer, a melt-pressure gauge and melt-temperature thermocouple must be installed; otherwise a pressure-limited changeover cannot be validated against documented equipment limits.

Environmental Stress-Crack Resistance Is the Principal Grade-Selection Limit

The selection of HD5675 for rigid packaging is usually driven by environmental stress-crack resistance, or ESCR, measured under ASTM D1693-15. In Condition B testing with 100 % Igepal CO-630 at 50 °C, supplier documentation reports an F50 value above 600 h for the natural pellet. The same method can show much lower values on finished containers because moulded-in orientation, cooling rate, and wall thickness change the crack-growth path. End users should therefore test bottle sections or complete containers under end-use stress rather than relying on pellet ESCR alone. In a 30 L jerrycan with a nominal wall thickness of 2.0 mm, the failure location under prolonged internal pressure is typically the pinch-off weld or a sharp base corner, not the sidewall away from stress concentrations. If the part must survive shipping at temperatures below -18 °C, drop-impact testing according to ASTM D2463-15 is more informative than ESCR because the polymer remains ductile while the weld line may embrittle.

Chemical exposure limits are application-specific. HDPE is widely used for aqueous acids, bases, and polar solvents at ambient temperature, but strong oxidizing acids, aromatic solvents, and chlorinated hydrocarbons can soften or crack the grade. Specific permeability data for HD5675 in aggressive environments is not published in supplier technical bulletins; chemical compatibility must therefore be confirmed by immersion testing under ASTM D543-20 and, for pressurized containers, by internal-pressure testing on the finished article.

Food-contact status is governed by the composition of the final article. The base resin in HD5675 can be evaluated against FDA 21 CFR 177.1520(c) item 2.1 for high-density polyethylene with density ≥0.94 g/cm³, provided extractives content and end-use conditions meet the clause. For European Union member states, a compliance declaration under Regulation (EC) No 1935/2004 is required for the finished packaging after migration testing or mathematical modelling of the complete formula. REACH obligations are covered by the polymer registrant through Regulation (EC) No 1907/2006; downstream processors must still document any intentionally added substances present above 0.1 % by weight. RoHS Directive 2011/65/EU is not directly applicable to packaging, but packaging heavy-metal limits are set in Directive 94/62/EC and require a sum concentration of lead, cadmium, mercury, and hexavalent chromium below 100 mg/kg. Table 2 summarizes the documentation a converter may have to request from the supplier or demonstrate from lot certificates.

Selecting HD5675 requires comparison against measurable failure criteria

Grade selection should be made by comparing HD5675 with the incumbent resin on the same blow moulder and test plan. The critical comparison criteria are melt flow rate, density, tensile yield strength, flexural modulus, ESCR F50, and top-load force after a fixed cooling period. HD5675 provides a documented tensile yield strength of 29 MPa and flexural modulus of 1,380 MPa, which are useful for stiffness-limited containers such as dairy bottles and household chemical bottles. Compared with lower-density copolymers, the higher density increases top-load and reduces oxygen and water-vapour transmission, but it can also reduce low-temperature drop-impact ductility if the part has sharp corners or deep pinch-off lines. A higher-density HDPE therefore requires larger corner radii and controlled pinch-off flash removal. For detergent bottles requiring a high ESCR, a medium-density or lower-density copolymer may outperform a high-density homopolymer in crack resistance while losing stiffness; HD5675 is formulated to balance these properties but remains a high-density resin with a density above 0.950 g/cm³.

The final choice must include processing cost. A low melt flow rate resin increases extruder energy input per kilogram and may reduce output on the same screw if the drive is fixed at maximum speed. The screw should have a decompression zone and an intensive mixing section, and a standard temperature profile from feed throat to die is often 170/180/190/200/205 °C for a 75 mm barrier screw. If a satellite extruder is used for a view-stripe or handle, its melt temperature should be matched to the main extruder within ±5 °C to prevent delamination at the stripe interface. Grade-specific data should be retained in the changeover record because the next lot may vary within the supplier’s specification limits and require minor die-gap adjustments.