ExxonMobil HDPE HTA-001HD is a high molecular weight, high-density polyethylene homopolymer supplied in pellet form and specified primarily for extrusion blow molding of large-part industrial, automotive, and packaging articles. The published typical density is 0.949 g/cm³ measured according to ASTM D1505-18, and the melt flow rate is 0.05 g/10 min at 190 °C under 2.16 kg load using ASTM D1238-20 Procedure A. Those values define a high-viscosity resin with long parison hang time and high melt strength rather than an injection molding or film-extrusion grade. Principal uses reported for this product include automotive fuel tanks where multi-layer coextrusion with ethylene-vinyl alcohol barrier layers is employed, intermediate bulk containers, large agricultural chemical bottles, and industrial drums requiring resistance to environmental stress cracking. Because the product is a homopolymer, its stiffness and chemical resistance are retained across a broad range of service temperatures, but the low-temperature impact response of the finished article remains wall-thickness and processing-orientation dependent.

Specification sheets for HTA-001HD do not use a single fixed property target across all lots; producers supply lot-to-lot acceptance ranges around the typical values. Users evaluating this grade for load-bearing containers should obtain the certificate of analysis and confirm lot-specific melt flow rate, density, and environmental stress crack resistance, because those three properties interact with blow molding cycle time and drop-impact performance at -20 °C and below. In comparison with high-melt-index HDPE injection grades with melt flow rates commonly between 2 g/10 min and 30 g/10 min, HTA-001HD imposes higher back pressure in screw plasticating, slower screw recovery, and greater shear heating at the same screw speed. These differences are not defects; they are the inherent consequence of the high molecular weight needed to maintain parison stability during large-part extrusion blow molding.

What Distinguishes HTA-001HD from Medium-Melt-Index Injection Molding HDPE?

The most direct distinction is the melt flow rate. Injection molding HDPE grades are normally formulated for spiral flow and short cycle times, with melt flow rates in the range 2–30 g/10 min and densities from 0.950 g/cm³ to 0.965 g/cm³. HTA-001HD has a melt flow rate of 0.05 g/10 min; therefore its low-shear viscosity at 190 °C is substantially higher, and its ability to replicate thin ribs, snap-fit sections, and tight-tolerance features is limited. Injection molding of HTA-001HD would require elevated melt temperature and injection pressure, yet the part would still exhibit high molded-in stress and weld-line weakness relative to an injection molding grade. In extrusion blow molding, the same high viscosity is functional because it supports the parison against gravity and reduces drawdown between the die exit and the mold close.

Published tensile yield stress for HTA-001HD is approximately 23 MPa using ASTM D638-14 Type IV specimens at 50 mm/min, with tensile elongation at break above 600%. The flexural modulus is approximately 800 MPa by ASTM D790-17. These stiffness values are comparable to other high-density polyethylene homopolymers and are not the primary differentiating feature. The primary differentiating feature is environmental stress crack resistance determined by ASTM D1693-15 under 100% Igepal, where F50 values above 600 h are reported. Medium-melt-index injection molding grades often exhibit lower ESCR because their molecular weight distribution and comonomer type are optimized for flow, not slow crack growth resistance. For this reason, HTA-001HD is not a drop-in replacement for an injection molding grade in thin-wall closures, thin-wall containers, or crates.

The product also differs from high-load melt-index film grades and pipe-grade HDPE. Film grades with bimodal molecular weight distribution and density lower than 0.941 g/cm³ are optimized for dart impact and tear, not for parison stability in heavy blow molding. Pipe-grade HDPE with melt flow rate below 0.1 g/10 min is designed for long hydrostatic strength and slow crack growth in pressurized pipe, but its additive package and extrusion conditions are not optimized for blow molding surface finish and cycle time. HTA-001HD is positioned in the extrusion blow molding segment, where the combination of density 0.949 g/cm³, melt flow rate 0.05 g/10 min, and ESCR above 600 h creates a specific balance between stiffness, processability, and slow crack growth resistance.

Table 1 values are typical and are not specification limits. Lot-to-lot acceptance is controlled by the certificate of analysis and the applicable grade specification. Test specimens are normally conditioned at 23 °C and 50% relative humidity for at least 40 h before mechanical testing, in line with ASTM D618-21 or equivalent ISO conditioning procedures.

Melt Rheology and Accumulator-Head Blow Molding Response

Production lines configured for high molecular weight HDPE blow molding typically use single-screw extruders with L/D ratios from 24:1 to 30:1 and barrier screws with mixing sections. Accumulator-head machines are preferred when the shot volume exceeds continuous extrusion capacity, because the accumulator discharges the melt rapidly through the die and minimizes parison hang time. For HTA-001HD, melt temperatures of 200 °C to 220 °C are commonly set at the die head, with barrel zones progressing from 180 °C at the feed throat to 210 °C at the metering section. If melt temperature drops below 180 °C, unmelted particles and rough parison surfaces are observed, whereas temperatures above 230 °C can produce oxidative degradation, gel particles, and yellowing. The narrow practical window requires monitoring of screw speed, back pressure, and melt temperature at the die adapter.

High molecular weight increases parison swell and melt strength. Parison swell values observed on production equipment for high molecular weight HDPE commonly range from 30% to 50%, requiring the die diameter to be smaller than the target parison diameter and the die gap to be programmed to shift weight toward the top or bottom of the part. Published swell data specific to HTA-001HD are limited; therefore tooling trials should record parison length, diameter, and weight distribution at the intended melt temperature and screw speed. Back pressure is kept low enough to avoid excessive shear heating, and head pressure is controlled by die gap, die land length, and melt temperature rather than by screw speed alone.

Moisture uptake in HDPE homopolymer pellets is generally below 0.01% by mass, but surface condensation in silos or bin trucks exposed to sudden temperature changes can cause splay and bubble defects. On lines where pellets move from 4 °C to 25 °C storage areas at relative humidity above 60%, a surface-drying step at 75–85 °C for 2 h is used before the extruder. Drying is not a substitute for proper venting; the extruder should be vented or vacuum-assisted when volatile carryover from regrind or color concentrate is present. Regrind addition up to 30% is common in non-automotive industrial containers, but ESCR and drop impact must be revalidated after regrind incorporation because repeated heat history shifts molecular weight distribution and additive package performance.

In agricultural chemical packaging, wall reductions below 1.5 mm without ESCR revalidation have produced stress cracking at the pinch-off weld and along the parting line after 12 months of ambient storage. The failure mode is slow crack growth through the thickness, accelerated by externally applied stress and surface-active fluids. Containers for glyphosate, ester-based formulations, or surfactant concentrates are tested with the actual formulation or specified surrogate solutions because the ASTM D1693-15 Igepal test does not reproduce every surfactant system. On production lines, pinch-off geometry and clamp force are as important as resin choice: insufficient compression at the pinch-off zone leaves a weak tail that can initiate cracking. HTA-001HD is selected for these applications when the container must pass a 1.2 m drop test at -18 °C after stacking or when the user requires a high-molecular-weight HDPE with ESCR above 600 h.

Industrial drums produced from HTA-001HD are commonly extrusion blow molded with a top or bottom sealing surface and a clamp ring. The parison must be oriented to maintain wall thickness above 2 mm at the chime because that region carries stack loads. Suppliers of drums, not the resin manufacturer, certify the finished container under UN dangerous-goods design-type tests. The resin contributes slow crack growth resistance and low-temperature impact, but tool design, cooling rate, and regrind level govern whether the container passes a 1.2 m drop test at -18 °C.

When High ESCR Determines Service Life in Large Industrial Containers

Environmental stress crack resistance is a threshold property for large industrial containers, automotive fuel tanks, and intermediate bulk containers because a crack can propagate through the wall over months or years under stress below the tensile yield point. In a container made from HTA-001HD, the combination of high molecular weight and minimal comonomer short-chain branching produces slow crack growth resistance, but the finished performance is also controlled by processing-induced orientation and internal stresses. The standard test ASTM D1693-15 uses notched bent specimens in 100% Igepal at 50 °C; a result above 600 h indicates that the resin can resist surface-active crack initiation. However, large-part service conditions frequently involve different loads and fluids; therefore the test is a ranking tool, not a direct service-life model.

In automotive fuel tank coextrusion, HTA-001HD is used as the outer and inner HDPE layers with an ethylene-vinyl alcohol barrier layer. Direct contact between HDPE and polyamide or EVOH without an adhesive tie layer results in delamination because HDPE is non-polar and the barrier polymers are polar. The pinch-off weld generated when the mold closes around the coextruded parison must be inspected by cross-sectional microscopy or burst testing because contamination at the weld line reduces barrier continuity. Published values for fuel-tank drop impact of HTA-001HD are configuration-specific; automotive OEM tests are conducted at -40 °C and specified impact energies but are not available from the resin datasheet alone. Users must evaluate the final tank on the production line with the actual layer thickness distribution, mold cooling, and barrier layer regrind content.

Chemical resistance of HTA-001HD follows high-density polyethylene homopolymer behaviour. The resin is not recommended for long-term contact with strong oxidizing acids, chlorinated solvents, or aromatic hydrocarbons above 60 °C. For aliphatic hydrocarbons, short-term exposure at ambient temperature is acceptable, but permeation and environmental stress cracking must be assessed for the specific fluid and wall thickness. Compared with bimodal high-density polyethylene film grades, HTA-001HD has higher density and lower melt flow, hence lower orientation-driven modulus and higher shear viscosity. Compared with hexene-1 copolymer blow molding grades with broad molecular weight distribution, HTA-001HD may have lower notched Izod at low temperatures if the wall is below 2 mm; for thick-wall containers, the difference is less significant. Direct comparative data for HTA-001HD against named alternative grades is limited in public literature, so selection should be made by compounding the specified lot with the target regrind and evaluating ESCR, drop impact, and parison sag on the intended tool.

The Extent to Which HTA-001HD Meets Contact-Sensitive Regulations

HDPE homopolymers of this density range are commonly referenced against US FDA 21 CFR 177.1520(c) item 2.1, depending on density and extraction limitations. Finished article compliance must be tested because polymerization residues, additives, colorants, and regrind affect migration. For the European Union, HDPE food-contact materials are assessed under Regulation (EU) No 10/2011 and its amendments; the overall migration limit is 10 mg/dm² for articles not intended for infants, with specific migration limits for any additives present. HTA-001HD is not sold with a universal food-contact certification; the supplier documentation for the specific lot and production location should be obtained. REACH obligations apply to the European Economic Area, and the resin supplier provides safety data sheet information for the registered substance high-density polyethylene. RoHS Directive 2011/65/EU restriction thresholds apply to the finished electronic article, not the plastic packaging material itself, but heavy-metal limits may be relevant if the container is used for electronic component packaging.

For dangerous-goods packaging, the finished drum or container is qualified as a design type under UN 1H1 for non-removable-head drums or UN 1H2 for open-head drums, and the test programme includes stack load, leakproofness, hydraulic pressure, and drop tests at -18 °C for liquids with specific gravities up to the design value. HTA-001HD contributes to those tests through impact strength and ESCR, but the resin alone cannot guarantee UN certification. Users should not extrapolate a UN performance certification from the resin datasheet.