Chevron Phillips Chemical HDPE HXM50100, also identified in supplier documentation as Marlex HXM50100, is a high-molecular-weight, hexene-copolymer high-density polyethylene produced for extrusion blow molding of large rigid containers. The model designation HXM50100 is specified by a nominal density of 0.950 g/cm³ under ASTM D1505 and a nominal melt index of 0.05 g/10 min under ASTM D1238 at 190°C with a 2.16 kg load. These values place the material in the high-molecular-weight HDPE range, where melt index values below 0.10 g/10 min provide elevated parison melt strength for large-part blow molding.

Supplier literature reports nominal mechanical properties that include flexural modulus near 965 MPa under ASTM D790, tensile strength at yield near 26 MPa under ASTM D638, elongation at break near 600% under ASTM D638, and Vicat softening temperature near 124°C under ASTM D1525. Low-temperature brittleness is reported below -75°C under ASTM D746. Environmental stress-crack resistance is reported as an F50 value greater than 1,000 h under ASTM D1693 condition B with 100% active stress-cracking surfactant as specified by the method. These are nominal published values; they are not lot-release specifications, and converters should obtain the current product data sheet for control limits.

Typical applications include 200 L tight-head and open-head drums, agricultural chemical containers, industrial bulk containers, and fuel tanks. In these uses, the finished container rather than the raw resin must satisfy drop impact, leakproofness, hydrostatic pressure, and stacking tests under UN 49 CFR 178.509 or equivalent transport-packaging provisions. The grade is evaluated for food-contact packaging under FDA 21 CFR 177.1520(c) and for heavy-metal restrictions under EU RoHS 2011/65/EU when supplied in natural or verified color-compounded form.

Processing behavior diverges from conventional injection molding HDPE because a melt index of 0.05 g/10 min signals high average molecular weight. Production-scale extrusion blow molding machines for this grade are generally configured with grooved feed sections, single-screw L/D ratios between 24:1 and 30:1, and accumulator or reciprocating screw heads. Grooved feed increases solids conveying and permits a cooler rear barrel zone, while downstream zones raise melt temperature to approximately 190°C to 230°C. Maintaining melt temperature below 190°C may result in incomplete knit-line fusion at the pinch-off weld; exceeding approximately 230°C may increase oxidative chain scission, reduce ESCR, and raise gel count. The operational window is wider than for shear-sensitive materials, but it is bounded by weld integrity on the low side and degradation on the high side.

Die gap settings on large-tool accumulator heads typically range from 2.0 mm to 3.5 mm. Gaps below 2.0 mm raise shear rate at the die lip and can initiate shark-skin melt fracture; gaps above 3.5 mm can increase parison sag and reduce radial wall-thickness control on large-diameter tools. High parison melt strength permits hang times in the range of 10 s to 20 s for 200 L drum parisons on accumulator machines, although hang time must be balanced against die swell, tool closure speed, and pre-blow delay. These values are starting points from industrial blow molding practice, not universal machine settings; actual settings depend on accumulator volume, die diameter, mandrel design, and tool temperature.

Compared with a standard 0.30 g/10 min HDPE injection molding grade of similar density, HXM50100 requires higher extruder torque and produces higher head pressure under the same screw speed. This is a direct consequence of molecular weight. The grade cannot be assumed to run on blow molding equipment sized for lower-viscosity HDPE. Compared with butene-copolymer HDPE blow molding resins at equivalent density and melt index, the hexene comonomer in HXM50100 introduces longer side branches that increase interlamellar tie-chain formation during crystallization. The result is a higher slow crack growth resistance in the presence of surface-active chemicals, as reflected in the ASTM D1693 condition B F50 value. Published data for this exact comparison are limited because catalyst type, molecular weight distribution, and specimen molding history also influence ESCR.

The grade’s high molecular weight and hexene comonomer architecture distinguish it from lower-viscosity high-density grades used in pallets, crates, or thin-wall injection molded closures. Those applications prioritize flow and dimensional stability, while HXM50100 prioritizes parison melt strength and slow crack growth resistance. The difference appears in high-load melt index; high-molecular-weight HDPE grades in this class commonly have high-load melt index values of 6 g/10 min to 12 g/10 min under ASTM D1238 at 21.6 kg, whereas conventional high-flow grades have higher values. Converters should not interpolate behavior from melt index alone; the molecular weight distribution and comonomer type are required.

Supplier literature reports an F50 value above 1,000 h for HXM50100 under ASTM D1693 condition B. The test uses a bent, notched specimen immersed in a specified surfactant solution at 50°C. It is a screening test, not a direct prediction of field service life. For large drums, the ESCR value is used alongside drop impact and hydraulic pressure testing because agricultural chemicals, detergent intermediates, and fuel additives can accelerate crack growth at weld lines and molded-in stresses.

The relevance of ESCR to a 200 L tight-head drum is not the resin property alone. Wall thickness distribution, pinch-off weld morphology, closure sealing, and processing-induced orientation all interact. A drum with uneven parison programming can fail hydraulic pressure under UN 49 CFR 178.509 despite a high resin ESCR. Therefore, the ESCR value positions HXM50100 as a candidate material, but type approval testing on actual production containers is the governing limitation.

Food-contact status for HDPE is established under FDA 21 CFR 177.1520(c), which permits olefin polymers for use in contact with food, subject to end-use temperature and food-simulant extraction requirements. The resin supplier can provide a food-contact statement for the natural grade. Pigmented or additive-compounded materials must be evaluated separately. Dangerous goods packaging in the United States is qualified under UN 49 CFR 178.509; the relevant tests include drop at -18°C after conditioning, leakproofness, hydrostatic pressure, and stacking. HXM50100 does not itself provide UN certification; the container design, closure system, wall thickness distribution, and molding process determine performance.

These nominal values are derived from supplier technical literature. They are not lot-release specifications and do not remove the requirement to perform grade-specific qualification on production tools.

Operational boundaries apply to moisture, regrind, and additive compatibility. HDPE is not hygroscopic in the same manner as polyamide, but surface condensation on pellets stored at ambient relative humidity above 60% can produce splay or surface defects in blow molded parts. Regrind streams should be dried at 80°C for 2 h to 4 h before processing. Regrind addition above 30% by weight may lower ESCR and impact strength because repeated shear history reduces molecular weight and tie-chain density. For UN-certified drums, many converters impose a maximum of 20% post-industrial regrind in the parison.

Contamination with polyvinyl chloride or polyacetal is a known incompatibility. Acidic decomposition products generated from these polymers at HDPE processing temperatures can catalyze degradation and create brown spots or gels. Equipment should be thoroughly purged after processing such materials. Colorant or additive masterbatches containing low-molecular-weight amides or certain surfactants can lower ESCR; when changing formulation, the blended compound should be tested under ASTM D1693 condition B rather than assuming additive compatibility.

Processing temperatures above 230°C or residence times beyond 15 min can increase gel formation and shift melt index; these boundaries become more critical with high regrind content or oxidized edge trim. Published data for the interaction between HXM50100 and specific agricultural chemical formulations are limited; compatibility testing under actual fill chemicals is required for long-term container qualification.