Dow HDPE DMDA-8007 NT 7 is a high-density polyethylene blow molding resin supplied as natural-color pellets. The product is classified by nominal density of 0.961 g/cm³ according to ISO 1183-1 and melt mass-flow rate of 0.08 g/10 min at 190°C under 2.16 kg load according to ISO 1133-1:2022. The combination of high density and low melt flow gives the resin a high stiffness-to-thickness ratio in blow molded containers and technical parts. It is specified for extrusion blow molding of rigid containers, narrow-neck bottles, industrial packaging, and automotive fluid vessels where top-load strength, dimensional consistency, and chemical resistance are limiting factors.

The resin belongs to the high-molecular-weight HDPE class. Its low melt flow index indicates higher melt viscosity than conventional blow molding grades with melt flow indices between 0.20 g/10 min and 0.35 g/10 min. At equal density, the lower melt flow index typically correlates with improved melt strength and greater die-swell retention, but it also increases extrusion torque and head pressure. These effects are not defects; they require specific extruder capacity and die-head design when DMDA-8007 NT 7 is selected.

What does the manufacturer-published property set show for DMDA-8007 NT 7 under standard conditioning?

Representative values from the manufacturer technical data sheet, determined on compression-molded or injection-molded specimens and not intended as specification limits, are summarized in the following table. Conditioning per ISO 291 at 23°C ± 2°C and 50% ± 5% relative humidity precedes testing unless the method requires otherwise.

The tensile stress at yield and flexural modulus are higher than those of a typical 0.957 g/cm³ HDPE blow molding grade because density drives crystallinity and interlamellar contact. The resin also provides a Vicat softening temperature above 125°C, which may support short-duration peak surface contact at 80°C in thick-walled containers. Continuous hot-fill service must be validated by top-load and creep testing on the actual container geometry because creep modulus declines with temperature.

Container top-load capacity can be evaluated according to ASTM D2659. Because the flexural modulus is approximately 1450 MPa, container top-load strength scales with wall thickness cubed. In practice, converters use wall thickness distribution measurements on the blow-molded part according to ISO 4591 because material distribution determines the failure mode. A uniform wall thickness of 0.8 mm ± 0.05 mm in the shoulder and sidewall is commonly targeted for consumer bottles requiring high top-load, but acceptance values are container-specific. Published data for this specific configuration is limited.

Extruder screw configuration, die-head pressure, and clamp-force boundaries

Production-scale experience on continuous shuttle and accumulator-head machines points to specific processing boundaries. A 90 mm grooved-feed extruder with 24:1 L/D and a barrier screw generates stable melt at barrel set temperatures between 180°C and 210°C. The die head is typically maintained at 205°C to 215°C. Because the melt flow index is low, the extruder drive should have sufficient torque margin. Excessive screw speed above 60 rpm on this size class may produce melt-temperature heterogeneity exceeding ±5°C, visible as parison streaking and shot-weight variation. Barrier screws with compression ratios between 2.5:1 and 3.5:1 are suitable for this resin class. Aggressive mixing elements may generate local shear heating; melt temperature measured at the die entry should not exceed 230°C to avoid oxidative chain scission.

Die swell at a 2.0 mm die gap, 12 mm land length, and 210°C melt temperature falls in the range of 55% to 75%. Tooling for neck rings, calibrated flash pockets, and handle inserts must be dimensioned accordingly. Clamp force estimation follows projected part area multiplied by cavity pressure of 0.4 MPa to 0.8 MPa. A part with projected area of 800 cm² therefore requires a clamp force of approximately 32 kN to 64 kN. Mold venting and pinch-off design must provide clean trim removal because the high-molecular-weight tail and flash remain tough at demolding.

When the resin is substituted into tools designed for lower-density HDPE grades

Compared with a typical blow molding grade at 0.957 g/cm³ and 0.20 g/10 min, DMDA-8007 NT 7 exhibits a density differential of 0.004 g/cm³ and a melt flow differential of 0.12 g/10 min. The higher density raises flexural modulus and top-load resistance at equal wall thickness, but the lower melt flow reduces fluidity. Existing tooling for lower-density grades may require an increase in melt temperature of 5°C to 10°C or a decrease in accumulator fill rate to maintain shot weight and parison length. Because the material is stiffer, blow pin alignment and mold parting line clamping become more critical to avoid wall thickness variation. Published data for this specific substitution is limited; converter trials on the target tool are mandatory.

Regrind incorporation is commonly practiced on food-contact and industrial packaging lines. Clean, dry regrind from the same resin can be added at up to 20 wt% when the reclaim stream is melt-filtered through 100 µm screens and kept free of polypropylene, paper labels, and bio-based contamination. Higher regrind levels may reduce environmental stress crack resistance. ASTM D1693 F50 values should be re-verified after any change in regrind ratio or storage time.

Regulatory status, chemical-contact limits, and black-spec/plate-out control

Dow HDPE DMDA-8007 NT 7 is reported by the manufacturer to comply with 21 CFR 177.1520(c) as an olefin polymer for direct food contact, subject to conditions of use in 21 CFR 176.170(c) Table 2. Compliance with EU Regulation (EU) No 10/2011 is declared for food-contact applications, with an overall migration limit of 10 mg/dm². The resin also meets the material restrictions of RoHS Directive 2011/65/EU and its delegated amendments for lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ethers.

For non-food chemical packaging, the environmental stress crack resistance of the resin is relevant for household and industrial detergent formulations. Containers intended for oxidizing acids, strongly aromatic hydrocarbons, or polar solvent blends require chemical compatibility testing per ASTM D543 because high-density polyethylene swells and stress-cracks in the presence of strong oxidizers and certain hydrocarbon fractions. No universal chemical-resistance claim is made; service life depends on stress level, wall thickness, and temperature.

Black spec formation is controlled by residence time and oxygen exclusion. The high melt viscosity can generate stagnant material in poorly streamlined die heads. Melt residence time should not exceed 15 min at 210°C to avoid oxidative gel formation. Periodic purging with a high-viscosity purging compound after color changes is recommended. Screen packs of 60/100/60 mesh are commonly used; screen packs above 100 mesh are generally not recommended for this melt index class because shear dissipation may increase melt temperature by more than 5°C and initiate gel formation.

Pellets supplied in sealed containers at 23°C and 50% RH do not require pre-drying. If bags are exposed to condensation during outdoor transfer, surface moisture can cause splay and voiding. Drying for 2 h at 65°C in a desiccant dryer is advised before extrusion when condensation is observed. Prolonged storage beyond 24 months or direct sunlight may shift yellowness and odor profile. Containers should be kept away from ultraviolet light and strong oxidizing atmospheres.