Dow HDPE 3364 is a high-density polyethylene resin supplied in pellet form for extrusion blow molding applications in which rigidity, melt strength, and environmental stress crack resistance are concurrent selection constraints. It is commonly specified for narrow-neck industrial containers, household chemical bottles, and thin-wall packaging that must endure drop impact and top-load compression during warehousing. The nominal density of 0.963 g/cm³ is determined by ASTM D792, and the melt flow rate is 0.64 g/10 min at 190°C/2.16 kg using ASTM D1238. The density places the grade above 0.960 g/cm³, where flexural modulus rises rapidly with density, while the melt flow rate remains low enough to maintain a stable parison on continuous extrusion machines producing bottles with depth-to-diameter ratios above 4:1. Published information for the exact molecular weight distribution of this specific product is limited; however, its flow response indicates a broader molecular weight distribution than conventional injection molding HDPE.

Typical physical property profile for Dow HDPE 3364

Property	Test method	Typical value
Density	ASTM D792	0.963 g/cm³
Melt flow rate	ASTM D1238, 190°C/2.16 kg	0.64 g/10 min
Tensile yield strength	ASTM D638, Type IV	28 MPa
Flexural modulus	ASTM D790	1,550 MPa

Property values are influenced by specimen preparation, conditioning time, and thermal history. Batch-to-batch differences may alter these values; processors should consult current supplier certificates of analysis rather than treating the values as specification limits.

What separates this resin from generic high-density grades?

The distinction is not simply density. HDPE grades of identical 0.963 g/cm³ density but narrow molecular weight distribution commonly exhibit greater parison sag at equivalent die gap settings, limiting part length and increasing sidewall variation. Dow HDPE 3364 is formulated with a controlled high-molecular-weight fraction that raises extensional viscosity at low shear while avoiding a proportional increase in die pressure at high shear. On accumulator and reciprocating screw machines, this behavior permits longer parisons with less neck thinning. Field observations from blow molding lines indicate that wall-thickness standard deviation can decrease after switching from a narrow-MWD grade, but published data collected on identical tooling across all grades is limited. The difference is most evident when the container depth-to-diameter ratio exceeds 4:1 and in oval containers where pinch-off welding depends on melt strength. This resin should not be substituted for a high-flow injection molding HDPE because its 0.64 g/10 min melt flow rate would require high injection pressure in thin-wall molds and may produce weld-line weakness.

On accumulator blow molders with 65 mm to 120 mm barrel diameters and 24:1 to 30:1 L/D ratios, Dow HDPE 3364 is typically processed with barrel zone setpoints from 180°C at the feed throat to 210°C at the adapter. Die head temperature is commonly maintained between 200°C and 220°C. Melt temperature measured with an immersion probe should remain below 225°C; sustained operation above 230°C can reduce extensional viscosity, produce parison thinning, and accelerate antioxidant depletion. Die gaps between 2.5 mm and 3.5 mm are representative for containers with nominal wall thickness from 0.6 mm to 1.5 mm. On a 65 mm, 24:1 L/D extruder, screw speeds are typically kept between 30 rpm and 70 rpm. Above 80 rpm, shear heating can raise melt temperature above 225°C unless barrel setpoints are reduced. Adapter pressures from 18 MPa to 32 MPa are common; values exceeding 38 MPa usually indicate a blocked screen pack, insufficient die temperature, or an improperly set die gap. Screen packs of 60/80/100 mesh are frequently installed to capture degraded resin and unmelts.

Pre-drying is not normally required because high-density polyethylene is not hygroscopic. If pellets stored below 10°C are transferred into a humid room, surface moisture can form and produce parison surface defects. At relative humidity above 60%, hot-air drying at 70°C for 1 h or desiccant drying at 80°C for 2 h removes surface moisture. Long-term storage above 50°C should be avoided because oxidation can consume the stabilizer package.

During high-volume production with multiple parallel extruders, batch-to-batch melt flow rate variation is controlled by the supplier, but processors may observe a die pressure shift when a new lot is introduced. If the same machine settings are retained, a lot with melt flow rate at the low end of the specification may produce higher adapter pressure and a thicker parison, while a lot at the high end may produce lower pressure and shorter parison length. Operators should monitor drive torque and parison length during lot changes and adjust barrel temperatures in 5°C increments before changing die gap. Regrind usage above 20% can reduce environmental stress crack resistance and lower top load; regrind should be tested under ASTM D1693 before production approval. Regrind particle size below 6 mm and moisture content below 0.05% reduce feed interruptions in smooth-bore hoppers.

Die pressure is governed by parison wall dimensions and drop impact requirements

Die head pressure in continuous blow molding is determined by die pin diameter, die gap, parison length, and melt temperature. For a 25 mm die pin and 3.0 mm die gap at 210°C, adapter pressure typically ranges from 22 MPa to 28 MPa. Opening the die gap to 3.5 mm reduces adapter pressure by 4–8 MPa, but the resulting lower hoop orientation may reduce top-load strength. Because the relationship between die gap and top-load is tool-specific, processors should verify container top load according to ASTM D2659 after any die gap adjustment. Die land lengths between 15 mm and 25 mm are commonly used to prevent sharkskin melt fracture and improve parison surface quality. If melt fracture appears at adapter pressures above 35 MPa, increasing die land temperature by 3–5°C is preferred to opening the die gap, because a die temperature change does not alter parison wall thickness in the same manner. Blow pin air pressure between 0.45 MPa and 0.65 MPa is typical; values below 0.40 MPa can produce incomplete bottle definition and wall-thickness variation, while values above 0.70 MPa increase clamp force demand. Mold temperatures from 8°C to 15°C are used to balance cooling rate and molded-in stress.

When Thin-Wall Containers Require a Balance of Drop Impact and Top Load

When the target wall thickness drops below 0.8 mm, Dow HDPE 3364 is selected only when top-load strength and drop impact are more critical than absolute cycle time. The melt flow rate of 0.64 g/10 min restricts parison inflation in deep recesses if blow pressure is held below 0.45 MPa, so mold venting must be adequate. Parting-line vents of 0.05 mm to 0.08 mm depth are typical for HDPE blow molding to permit air escape without flash. Lower mold temperatures reduce cycle time but can create higher residual stress near the pinch-off and reduce drop impact measured by ASTM D2463. Top load is evaluated by ASTM D2659. When compared to a higher-flow HDPE blow molding grade with melt flow rate near 0.8 g/10 min, Dow HDPE 3364 can provide higher top-load stiffness at equal wall thickness because of its density and molecular architecture, but the magnitude is determined by bottle geometry, die gap, cooling rate, and regrind level. Published data comparing two grades on identical production molds is limited; a controlled comparative trial is required before specification changes.

Environmental stress crack resistance is commonly evaluated by ASTM D1693, condition B, 100% Igepal CO-630. The test is an empirical indicator and does not predict field failure with complex chemical formulations. Dow HDPE 3364 is selected for agricultural and industrial chemical containers because its density is high enough to provide rigidity while retaining sufficient short-chain branching to slow brittle crack growth under stress. The exact comonomer content is proprietary, but the density-melt flow rate combination indicates a linear polyethylene backbone with controlled short-chain branching rather than a fully homopolymer structure. No blanket chemical compatibility claim should be derived from a single ESCR value. Containers intended for chlorinated hydrocarbons, aromatic solvents, or strong oxidizing acids should be tested under ASTM D543 or with the relevant UN 3H1 packaging protocol. Prolonged contact with aromatic hydrocarbons above 50°C and with strong oxidizing acids at elevated temperatures should be avoided because swelling and chain scission can lead to dimensional distortion and mechanical failure. For food contact use, compliance must be verified under FDA 21 CFR 177.1520 or the applicable regional regulation; published specific migration data for this grade is limited. Regulatory compliance under REACH and RoHS depends on additive selection and should be confirmed through supplier documentation.

Compared with medium-density polyethylene blow molding grades, Dow HDPE 3364 has higher flexural modulus and lower melt flow rate. This makes it unsuitable for squeeze bottles requiring low stiffness for dispensing; those applications typically use MDPE with flexural modulus below 900 MPa and melt flow rate above 0.8 g/10 min. Compared with high-density pipe extrusion grades, Dow HDPE 3364 has higher melt flow rate and lower melt strength, making it less suitable for thick-wall pipe where sag is resisted by higher molecular weight. Compared with HDPE film grades, its higher density and narrower die gap requirements reduce tear resistance and are not optimized for blown film.