Chevron Phillips Chemical HDPE 9607 is a high-density polyethylene copolymer commercialized within the Marlex HDPE series. The grade is specified for rigid blow molded packaging, sheet extrusion, and related applications requiring a balance of flexural modulus and melt strength. The nominal density is 0.960 g/cm³ when measured in accordance with ASTM D1505; the melt index is 0.65 g/10 min at 190 °C under 2.16 kg load using ASTM D1238. These are typical resin values, not upper or lower specification limits. Actual lot properties are controlled by the supplier certificate of analysis. The product identifier 9607 does not by itself disclose comonomer type or molecular weight distribution; such information must be confirmed with the supplier.

What separates HDPE 9607 from high-flow injection molding and fractional-melt large-part grades?

The 0.65 g/10 min melt index is approximately 8 to 45 times lower than common high-flow injection molding HDPE grades, which typically range from 5 g/10 min to 30 g/10 min. In injection molding, this low melt flow restricts thin-wall fill and favors thicker-walled parts with short flow paths. In blow molding, the same low-flow characteristic contributes to parison melt strength. Fractional-melt blow molding HDPE grades with melt indices of 0.25 g/10 min to 0.45 g/10 min are often used above 10 L container volume because they resist parison sag over long standing pars. HDPE 9607 is generally assigned to container volumes below 10 L, including dairy, automotive fluid, and household chemical containers. Published data for this specific comparison is limited to general melt-flow ranges; mold-specific flow simulation and trial runs remain necessary before tooling transfer.

Material Property Envelope and Thermal Transitions

Mechanical property data are generated on compression molded specimens prepared according to ASTM D4703. Typical tensile yield strength is reported at 29.0 MPa under ASTM D638, with elongation at break above 600%. Flexural modulus is typically on the order of 1,380 MPa under ASTM D790. Vicat softening temperature is reported near 127 °C under ASTM D1525, and brittleness temperature is below -75 °C under ASTM D746. Environmental stress-crack resistance under ASTM D1693 Condition B, 100% Igepal, exceeds 40 h. The approximate mass fraction crystallinity derived from a two-phase density model using crystalline and amorphous HDPE densities of 1.000 g/cm³ and 0.855 g/cm³ is near 75%. These values are not specification limits and depend on specimen preparation and thermal history.

Rheological estimates for an HDPE melt with 0.65 g/10 min melt index place zero-shear viscosity between 3 × 10⁴ Pa·s and 8 × 10⁴ Pa·s at 190 °C. Shear thinning under die-land shear rates of 100 s⁻¹ to 500 s⁻¹ reduces apparent viscosity by approximately 50% to 70% relative to zero-shear. This pseudoplastic response supports parison melt strength in extrusion blow molding. Published grade-specific oscillatory shear data for HDPE 9607 is limited; capillary rheometry with a 15:1 die is recommended when transferring tooling between extruder platforms.

Continuous shuttle and wheel blow molding lines process HDPE 9607 at melt temperatures of 180 °C to 220 °C, with mold temperatures held at 10 °C to 30 °C to control surface finish and freeze dimensions. Grooved-feed extruders with 70 mm screw diameter and 24:1 L/D to 30:1 L/D barrels are used. Typical barrel profiles ramp from 150 °C at the feed throat to 190 °C at the die head. Converging annular die tooling with land lengths of 10 mm to 20 mm controls die swell. Blow-pin air pressure typically ranges from 0.4 MPa to 0.7 MPa. Post-mold volumetric shrinkage is lower than in lower-density HDPE because of the higher crystalline fraction. On single-station accumulator machines, parison programming is required when container length-to-diameter ratio exceeds 2:1. Wall-thickness control becomes sensitive to die-head temperature variation exceeding ±5 °C.

If Accumulator-Head Tooling Demands Parison Melt Strength, Where Does an Operational Boundary Emerge?

Melt temperature above 220 °C in accumulator-head equipment can produce parison sag and non-uniform wall distribution in HDPE 9607. Operators may reduce die-gap opening, increase parison programming speed, or lower head temperature to 195 °C. However, head temperature below 185 °C may increase melt elasticity and generate sharkskin on the parison surface. These effects are inferred from the melt index and from standard HDPE rheological behavior. Before tooling transfer, a capillary rheometer sweep at 190 °C to 220 °C with a 15:1 die should be conducted to define wall shear stress and die swell. Wall shear stress below 0.2 MPa is generally required to avoid surface melt fracture in HDPE parison extrusion.

Sheet extrusion lines running HDPE 9607 commonly use 30:1 L/D barrier screws with polished chrome rolls at 70 °C to 90 °C. The resulting sheet is thermoformed into trays, inserts, and packaging components. Plug-assisted forming requires sheet temperatures of 160 °C to 180 °C, and trimming systems must account for higher flexural modulus relative to 0.955 g/cm³ HDPE grades. Published data for this specific configuration is limited; gauge reduction trials are required to establish part stiffness and sag resistance.

Comparative Stress-Crack and Modulus Behavior

Compared with lower-density blow molding HDPE grades, HDPE 9607 at 0.960 g/cm³ gains flexural modulus because crystallinity increases; the trade-off is lower environmental stress-crack resistance. The following table compares resin-class ranges. Values are representative and are not direct lot-to-lot comparisons.

For aggressive detergent or solvent-containing container applications, the stress-crack resistance of a 0.960 g/cm³ resin may be limiting. A lower-density or bimodal HDPE with density below 0.955 g/cm³ is often selected. Bimodal grades can combine high flexural modulus with improved slow crack growth resistance through molecular weight distribution control. HDPE 9607 is therefore not a direct replacement for bimodal pressure pipe or large-part industrial container grades unless end-use testing under ASTM D1693 and ASTM D256 demonstrates adequate stress-crack and notched impact performance.

Post-mold quality control for HDPE 9607 containers typically includes top-load testing, drop impact, and capacity evaluation on a defined platform. Top-load performance is measured with a compressive testing frame according to ASTM D2659 or equivalent. Dimensional inspection after 24 h of post-mold crystallization is required because HDPE density of 0.960 g/cm³ yields higher shrinkage anisotropy than lower-density resins. Lot-to-lot variation in melt index should be monitored with ASTM D1238; deviations beyond 0.60 g/10 min to 0.70 g/10 min may alter parison sag and wall distribution in continuous shuttle equipment. Production-scale failure modes reported for this class of HDPE include die-lip deposit formation at high shear rates and melt-temperature overshoot during cycle interruptions. Purging with a commercial polyolefin purge compound after 24 h of continuous operation may be required.

Food-contact evaluation for HDPE 9607 must be based on the supplier compliance statement and the finished article, not on nominal resin density. In the United States, olefin polymers are referenced in 21 CFR § 177.1520. In the European Union, plastic food-contact materials are subject to Regulation (EC) No 1935/2004 and Commission Regulation (EU) No 10/2011. Downstream converters must account for colorants, masterbatches, regrind, and processing aids. REACH registration for the substance is maintained by the supplier under Regulation (EC) No 1907/2006; downstream users must implement safe-use conditions from the extended safety data sheet. No claim of food-contact approval should be inferred from typical property data alone.

What operational boundaries arise from the density and melt index of HDPE 9607?

HDPE 9607 is not suitable for high-flow injection molding applications. The melt index of 0.65 g/10 min limits flow in thin-wall injection molds; when flow-length-to-thickness ratio exceeds 150:1, injection pressure can exceed 100 MPa and short shots may occur. Virgin HDPE pellets stored in dry conditions generally do not require pre-drying. However, regrind streams with moisture content above 0.05% can generate splay and voids. In high-humidity environments, desiccant drying of regrind at 70 °C to 80 °C for 2 h to 4 h is used. Aggressive peroxide masterbatches intended for viscosity reduction should be avoided because melt-phase oxidation can degrade environmental stress-crack resistance and produce inconsistent melt flow. The grade is not classified as a pressure pipe resin under ISO 4427 or ASTM D3350. It is also not formulated as a UV-stabilized grade unless explicitly stated by the supplier. For outdoor exposure, a UV stabilizer masterbatch should be validated against ASTM D2565 or ISO 4892 using the final article geometry and wall thickness.