Chevron Phillips Chemical HDPE 9513H is a high-molecular-weight, high-density polyethylene copolymer intended for extrusion blow molding of large-volume industrial containers, agricultural chemical packaging, and drum liners. The grade is manufactured as an ethylene-hexene-1 copolymer, with a nominal density of 0.951 g/cm³ when tested under ASTM D1505 and a melt flow index of 0.33 g/10 min at 190°C/2.16 kg according to ASTM D1238. Under a 21.6 kg load, the high-load melt index is typically 33 g/10 min, placing the resin in the high-load melt index class used for accumulator-head and reciprocating-screw blow molding platforms.

The nominal molecular weight distribution is broadened to provide shear thinning during extrusion without sacrificing parison melt strength. Converters should confirm lot-specific values against the certificate of analysis because nominal density and melt flow index are controlled within the manufacturer’s internal specification limits. The high-load melt index-to-melt flow index ratio is approximately 100, which provides a qualitative indication of the broad molecular weight distribution that enhances shear thinning during plastication while preserving parison integrity. This ratio should not be used as a substitute for capillary rheometry when die head design changes are evaluated.

How Does 9513H Differ from Conventional High-Load Melt Index Blow Molding Resins?

Compared with extrusion blow molding grades having a high-load melt index in the 20–25 g/10 min range, 9513H at 33 g/10 min exhibits lower viscosity under high shear, which reduces motor load during accumulator charging but still retains sufficient low-shear melt strength to limit parison sag. Against high-flow injection molding HDPE with a 2.16 kg melt index above 10 g/10 min, the product requires higher melt temperatures and generates higher die head pressure. It is not intended for thin-wall injection molded containers or closures. In blow molding, the primary functional distinction is the balance between top-load stiffness from the 0.951 g/cm³ density and environmental stress crack resistance from the hexene-1 comonomer distribution.

The density of 0.951 g/cm³ places 9513H in the medium-high stiffness range for HDPE blow molding grades. Lower-density HDPE copolymers in the 0.945–0.948 g/cm³ range generally provide higher environmental stress crack resistance but lower top-load strength. Higher-density grades near 0.954–0.958 g/cm³ may increase stiffness but can reduce resistance to cracking in chemically active service. For 9513H, the selection of 0.951 g/cm³ represents a controlled compromise between container rigidity and long-term resistance to stress cracking in industrial packaging applications.

Specification Cross-Reference and Compliance Checklist

Manufacturer-published data for the tensile yield strength and flexural modulus of this specific grade are not reproduced here because converter orientation and specimen preparation alter those values more than the resin’s nominal lot-to-lot control. For load-bearing design, ASTM D638 and ASTM D790 specimens should be cut from a molded plaque under conditions specified by the supplier and correlated with the actual wall thickness distribution of the finished article. Density and melt flow index are controlled as lot-release properties under the manufacturer’s ISO 9001 registration.

In accumulator-head blow molding lines with a 90 mm grooved-barrel extruder and a 25:1 L/D screw, the typical melt temperature range is 190–220°C for uniform parison formation. The die head is generally held at 190–210°C, and the mold temperature is maintained at 15–40°C to control surface finish and cooling time. At these conditions, the resin’s high-load melt index permits accumulator shot volumes up to 30–35 L depending on head capacity, but the actual shot size must be limited by parison length rather than by plastication rate alone. Production-scale failure modes associated with this grade include die-lip deposit, especially when the die gap is set below 1.5 mm, and moisture-induced surface defects when pellets are transferred from cold storage into high-humidity molding areas without temperature equilibration.

Pre-drying is generally unnecessary unless pellet surface condensation forms during storage in high-humidity environments above 60% RH or during cold-to-warm transfer. Moisture-related defects in HDPE blow molding are usually physical condensation rather than absorbed water. The use of a desiccant dryer is not required for routine processing, but hopper covers and temperature equilibration are recommended when ambient dew point approaches the pellet temperature.

Melt Temperature Limits and Degradation Thresholds

Maintaining melt temperature below 230°C during extended residence times is critical because high-molecular-weight HDPE undergoes thermo-oxidative chain scission at stagnant points in the accumulator head. Above 240°C, the melt can generate oxidized species that reduce environmental stress crack resistance and produce black specks in translucent articles. In practice, a temperature profile of 180°C at the feed to 220°C at the metering section is used on 80–120 mm extruders, with adapter and head zones set no higher than 210°C to minimize polymer degradation. If the melt temperature exceeds 230°C, the shot-to-shot parison length may increase due to viscosity reduction, but the final part can exhibit lower burst strength and higher gel counts.

The resin’s broad molecular weight distribution produces a shear-thinning response that permits lower melt temperatures than a narrow-distribution HDPE with the same melt flow index. However, screw recovery rate declines sharply when the melt temperature is intentionally reduced below 180°C, because the unmelted fraction increases and the extruder motor amperage rises. On 25:1 L/D screws, a compression ratio of 2.5:1–3.0:1 is typically sufficient to avoid melt-temperature overshoot while maintaining output stability.

When Backpressure Exceeds 21 MPa During Continuous Extrusion

Continuous extrusion blow molding with 9513H can produce head pressures above 21 MPa when the die gap is narrowed below 2 mm or when screen packs are added to filter gels. Under this condition, excessive shear heating raises the melt temperature and destabilizes parison thickness control. The use of a melt pump downstream of the extruder can stabilize head pressure within ±0.5 MPa and reduce surging, but the pump inlet pressure must not exceed the manufacturer’s limit for the gear pump seals. If a pressure relief or screw speed reduction is not applied, the observed failure mode is progressive die-lip drool followed by localized burn marks in the parison. Published data for this specific configuration are limited, but production-scale accumulator lines report that maintaining head pressure below 18–20 MPa and increasing the die gap to 2.5–3.5 mm is generally sufficient for uniform wall thickness.

When backpressure is allowed to remain above 21 MPa, the melt temperature can rise by 5–10°C within the accumulator due to shear heating. The resulting viscosity reduction can create short shots in programmed parisons because the programmed wall thickness is calibrated for a higher melt strength. The correction is not always achieved by raising melt temperature further; instead, the die gap should be opened and the accumulator fill rate reduced until the head pressure returns to the target band.

Environmental stress crack resistance is the primary qualification criterion for 9513H in rigid chemical packaging. Under ASTM D1693 Condition B at 100% Igepal, the nominal ESCR value of >1,000 h supports service in containers for surfactants, agricultural formulations, and diluted oxidizers, but the actual service life depends on wall thickness, mold temperature, and stress concentration at pinch-off zones. The resin’s regulatory status is governed by 21 CFR 177.1520 for olefin polymers when food-contact use is intended, and converters must verify that the final article meets migration limits under 21 CFR 177.1520(c). In European Union applications, the grade must be assessed under Regulation (EU) No 10/2011 for plastic food contact materials if the finished container is used for food contact. No conclusion about food-contact compliance is implied by these listings; the converter’s own migration testing is required.

Divergent die heads with a die gap of 2.0–3.5 mm and a land length-to-gap ratio of 10:1 are typical for 9513H in large blow molding. The die swell at normal extrusion rates is moderate, but parison programming is necessary for containers with irregular geometries because the high molecular weight broadens the sag time. The mold must be vented at the parting line to avoid air entrapment; vacuum-assisted calibration is required for dimensional tolerance below ±0.5 mm on wall thickness. The absence of post-mold annealing may be acceptable for ambient storage of empty drums, but for chemically filled containers, residual stresses at the flash line should be evaluated by a drop impact test or by a burst test under ASTM D2463-style conditions. Published data for the specific shrinkage of 9513H in heavy-wall sections is limited; mold shrinkage should be determined on the actual tool with the intended cooling rate.