Borealis HE3497-LS-H is a black, bimodal, high-density polyethylene compound specified for pressure pipe extrusion in water and gas distribution. Under ISO 12162, the material belongs to the PE100 class, with a minimum required strength of 10 MPa extrapolated to 50 years at 20 °C according to ISO 9080. The compound density is typically 0.959 g/cm³ when measured by ISO 1183-1:2019. The melt mass-flow rate at 190 °C and 5 kg is typically 0.22 g/10 min under ISO 1133-1:2022. Carbon black content is held between 2.0 wt% and 2.5 wt%, and carbon black dispersion is assessed under ISO 18553. These values are typical lot data and are not release specifications unless separately agreed.

The property values in the table represent the compound as supplied and include the effect of carbon black. Tensile yield stress and flexural modulus are measured on compression-moulded plaques; they do not directly predict pipe stiffness or full-scale fracture behavior. Pipe-scale performance must be verified by the pipe manufacturer using hydrostatic pressure tests, notched pipe tests, and full-scale resistance tests under the relevant product standard.

Molecular Architecture and Rheological Signature of HE3497-LS-H

The product’s bimodal molecular weight distribution is created by a dual-reactor polymerization sequence. The lower-molecular-weight fraction contributes to extruder throughput and surface quality by lowering melt viscosity at high shear rates in the die land. The higher-molecular-weight fraction increases the number of load-bearing tie molecules and is therefore linked to slow crack growth resistance. The melt flow rate of 0.22 g/10 min at 5 kg should not be interpreted as a high-viscosity obstacle; under die land shear, the material exhibits non-Newtonian shear thinning typical of bimodal high-density polyethylene. Numerical molecular weight distribution data for the exact grade are not generally published, so die design calculations should be based on capillary rheometry data supplied by the manufacturer for the specific lot in production.

The Charpy notched impact value of 11 kJ/m² at -30 °C under ISO 179-1:2010 provides a laboratory measure of toughness, but pipe impact requirements are governed separately by ISO 3127 or equivalent national methods. Low-temperature impact resistance is relevant for outdoor installation, but it is not a substitute for full-scale pipe testing.

What Distinguishes HE3497-LS-H from Standard PE100 Resins?

Relative to a general-purpose PE100 pipe grade such as Borealis HE3490-LS-H, HE3497-LS-H is differentiated by its slow crack growth resistance and low-sag melt behavior rather than by a different minimum required strength classification. Both products are PE100 under ISO 12162 and share a hydrostatic design basis of 10 MPa under ISO 9080. The difference appears primarily in sustained-load tests: the notched pipe test under ISO 13479:2022 and the full notch creep test under ISO 16770:2019 are more discriminating for the HE3497-LS-H application window than short-term tensile tests. Standard PE100 grades may pass minimum hydrostatic strength but exhibit shorter times to failure in point-load or no-sand bedding conditions. Published lot-specific comparative data for this exact formulation are limited; users should request current notched pipe and FNCT data from the supplier before selecting the grade for trenchless installation.

Compared with PE80 compounds, the PE100 classification permits higher design stress at the same temperature and service life, leading to thinner wall thickness at equal pressure rating under ISO 4427-2 or EN 12201-2. However, PE100 materials require more precise butt fusion control because the high-molecular-weight fraction increases melt viscosity at low shear. Jointing procedures under ISO 21307 must be qualified with the specific pipe and fitting combination. In North American specification practice, the material may be assigned an ASTM D3350 cell classification; users should obtain the current cell classification and pipe listing from the pipe manufacturer because the resin alone is not listed as a finished pipe.

The “-LS” designation indicates low-sag processing. In thick-wall pipes, the melt at the die exit is subjected to gravitational drawdown until the outer surface is cooled below the crystallization onset. The low-sag formulation reduces thickness eccentricity in SDR 11 and SDR 9 profiles, but it does not eliminate the need for internal cooling, calibrated vacuum sizing, and gravimetric output control.

Across incoming lots, the extrusion operation should monitor melt flow rate under ISO 1133-1:2022 at 190 °C/5 kg and compound density under ISO 1183-1:2019 before approving a silo for pipe production. A variation in MFR of ±0.03 g/10 min is often used as an internal control limit for wall-thickness consistency on coextrusion lines. The high-molecular-weight fraction can produce shear heating during melt pumping; melt temperature measured by an immersion probe at the die entry may run 5 °C to 15 °C above the barrel set point, depending on screw speed and back pressure. This behavior has been observed on grooved-feed single-screw extruders with L/D 30:1 to 37:1. Shorter extruders with L/D 25:1 may show insufficient thermal homogenization and variable melt temperature, leading to wall-thickness deviations and higher reject rates in thick-wall pipe.

Maintain Melt Temperature Below 230 °C in Thick-Wall Extrusion

Barrel temperature settings from the feed zone to the metering zone should be ramped from 180 °C to 220 °C. The die head is typically held between 210 °C and 225 °C. Melt temperature measured at the die entry should not exceed 230 °C; excursions above 250 °C initiate thermo-oxidative degradation that reduces oxidative induction time and long-term hydrostatic strength. Melt pressure at the screen pack varies with tooling and output, but production-scale L/D 30:1 extruders with grooved feed sections often operate between 250 bar and 400 bar. Pre-drying is generally not required when pellets are stored in sealed containers and moved without condensation. If surface moisture is present, drying with dried air at 80 °C for 2 h to 4 h is sufficient; drying above 90 °C risks pellet fusion.

Melt filtration for this grade commonly uses screen packs with 80/100/120 mesh configurations to remove carbon black agglomerates and crosslinked gels. Frequent screen-pack changes are required if pressure rises beyond 400 bar; a rising pressure trend indicates gel accumulation or carbon black dispersion problems. Screen pack selection should balance melt temperature rise against contaminant removal. A melt pump between the extruder and die head is recommended for thick-wall pipe because it reduces surge and stabilizes die pressure; melt pumps must be operated below the shear rate at which the high-molecular-weight fraction begins to degrade.

Die land length ratios between 10:1 and 20:1 are recommended for stabilization of the melt front and reduction of melt fracture in thick sections. Internal air cooling, vacuum sizing, and multistage water-spray cooling are used downstream. Cooling water temperature should be controlled to avoid excessive thermal residual stress; pipe manufacturers typically maintain spray-tank temperature gradients based on wall thickness and line speed. Regrind of the same grade can be incorporated, but the regrind fraction must be validated by hydrostatic regression testing under ISO 9080 and notched pipe testing under ISO 13479:2022 at the intended level.

When Trenchless Installation Demands Elevated Slow Crack Growth Resistance

Pipe-bursting, horizontal directional drilling, and direct ploughing introduce external scoring and point loads that short-term tensile data cannot capture. Slow crack growth resistance becomes the controlling material property. In qualification programs for PE100-RC-type materials, the notched pipe test under ISO 13479:2022 at 80 °C and 4 MPa and the full notch creep test under ISO 16770:2019 at 80 °C and 4 MPa in 2 % Arkopal N-100 are used to rank performance. Although the product is referred to in the market as a high slow crack growth resistant grade, published lot-specific data for the exact HE3497-LS-H configuration are limited. The conversion of laboratory FNCT or notched pipe results to field service depends on notch depth, residual stress, test fluid, and temperature extrapolation; it is not a direct prediction of pipe lifetime.

Rapid crack propagation resistance is also relevant for gas distribution at sub-zero temperatures. Small-scale RCP testing under ISO 13477 or full-scale RCP testing under ISO 13478 may be specified for gas pipes. The PE100 classification alone does not guarantee a critical pressure above the design pressure; pipe manufacturers may need to run RCP tests on the final pipe geometry and at the minimum operating temperature. Published RCP data for this exact compound in all wall thicknesses are limited.

Buried pipe installations without sand bedding or with recycled trench spoil are the primary application domain for such grades. The carbon black content of 2.0–2.5 wt% provides ultraviolet screening during outdoor storage, but dispersion quality must be confirmed on extruded pipe by ISO 18553. Poor dispersion creates local stress concentrations that can reduce slow crack growth resistance even when average carbon black content is within specification.

For drinking-water pressure pipe, the compound is specified against the raw-material requirements of ISO 4427-1 and EN 12201-1. For gas distribution pipe, the relevant frameworks are ISO 4437-1 and EN 1555-1. Raw-material compliance does not automatically certify the finished pipe; the pipe manufacturer must test extruded product for melt flow rate, density, tensile properties, oxidative induction time, hydrostatic strength, and dimensional stability. National regulatory approval for potable water contact is required for the finished pipe and cannot be inferred from resin supplier data alone.

Oxidative induction time at 210 °C of >20 min under ISO 11357-6:2018 is a typical control value for the stabilized compound. In long-term water service, design derating factors under ISO 13760 must be applied when the operating temperature exceeds 20 °C for extended periods. The PE100 classification does not confer universal resistance to oxidizing chemicals, organic solvents, or hydrocarbon condensates; exposure to such media requires separate compatibility testing on the finished pipe system.

Storage conditions should minimize water uptake and prolonged ultraviolet exposure, although carbon black provides a UV-stabilized outer layer. The pellets are incompatible with strong oxidizers and should not be mixed with high-flow polyolefins, unknown regrind, or amine-based stabilizer packages without test validation. Because slow crack growth resistance depends on the preservation of the high-molecular-weight fraction, process temperatures above 250 °C or repeated high-shear recycling can degrade the property balance even when the MFR remains within specification.