Mocom (ALBIS) PE-HD ALTECH is a compounded high-density polyethylene grade supplied as natural or pigmented granules. The designation PE-HD denotes a polymer backbone with a density of at least 0.941 g/cm³ as defined in DIN EN ISO 1043-1, and the ALTECH brand identifies a formulated compound rather than a virgin resin. For unreinforced injection-moulding grades of this class, density typically falls between 0.94 g/cm³ and 0.97 g/cm³ according to ISO 1183-1. Melt mass flow rate at 190 °C and 2.16 kg, measured according to ISO 1133-1:2022, is grade-dependent and commonly ranges from 0.2 g/10 min for high-molecular-weight extrusion types to 20 g/10 min for easy-flow injection types. Differential scanning calorimetry per ISO 11357-3 places the melting peak between 130 °C and 137 °C, with crystallinity determined by density and cooling rate. Because the matrix is non-polar and semi-crystalline, water absorption at 23 °C and 50% relative humidity is below 0.01 wt%. The compound is stabilised with a hindered phenolic and phosphite system, but the precise additive package, filler content, and melt flow rate require the grade-specific technical datasheet.

Rheological and Thermal Processing Window

Rheologically, unfilled high-density polyethylene compounds are pseudoplastic. At melt temperatures between 190 °C and 230 °C, the shear viscosity of a grade with MFR 4 g/10 min to 12 g/10 min can vary from approximately 800 Pa·s to 300 Pa·s over shear rates of 100 s⁻¹ to 1000 s⁻¹, as measured by capillary rheometry in ISO 11443. The power-law index lies between 0.35 and 0.50. On single-screw extruders with 25:1–30:1 L/D and compression ratios of 2.5:1–3.5:1, a barrel profile of 180 °C at the feed throat to 210 °C at the die is used. For injection moulding, a screw with L/D of at least 20:1, a non-return valve with a free-flow end cap, and a nozzle temperature of 190 °C to 220 °C are standard. The mould temperature is maintained between 10 °C and 50 °C, with lower mould temperatures reducing cycle time but increasing flow orientation and shrinkage anisotropy.

Because the crystallisation temperature extends from 117 °C to 124 °C, cooling of sections thicker than 4 mm occurs with a pronounced skin-core temperature gradient. The melt pressure required to compensate volumetric shrinkage in unfilled PE-HD is typically 50 MPa to 80 MPa during hold, with a screw cushion of 2 mm to 5 mm. Premature hold release produces sink marks and microvoids. Mould shrinkage after 48 h per ISO 294-4 ranges from 1.5% to 3.5% for unfilled grades and falls to 0.6%–1.2% for mineral-filled formulations. Pre-drying is not required for dry granulate; however, granulate stored below the dew point can carry surface condensation, which is removed by drying at 80 °C for 2 h using a desiccant dryer with a dew point below −20 °C.

Compounding on twin-screw extruders with 36:1–48:1 L/D and specific energy input of 0.15 kWh/kg–0.25 kWh/kg is typical for colour and stabiliser dispersion. Melt flow variability is usually held within ±10% of the nominal value when tested under ISO 1133-1. In production-scale injection moulding, the main observed failure modes are gate blush from excessive injection speed, sink marks from inadequate packing, and warpage from non-uniform mould temperature; these are controlled by closed-loop melt temperature and cushion monitoring.

What limits impact behaviour at low temperature?

Low-temperature impact resistance in PE-HD compounds is not governed by the glass transition alone. The β-relaxation of polyethylene occurs below −100 °C, but the practical ductile-brittle transition is raised by notch severity, comonomer placement, molecular weight, cooling rate, and orientation. Notched Charpy impact strength per ISO 179-1/eA at 23 °C commonly falls between 4 kJ/m² and 20 kJ/m² for unreinforced high-density polyethylene compounds, depending on molecular weight and notch radius preparation. At −30 °C, the range narrows to approximately 2 kJ/m²–6 kJ/m². Thin sections with frozen-in orientation may show higher crack propagation resistance, but notched specimens eliminate that energy contribution and represent a lower-bound condition.

Environmental stress cracking resistance is the more common field failure boundary. Under ASTM D1693 condition B, using 10% Igepal CO-630 at 50 °C, high-density polyethylene resins in this class can show F50 failure times from below 10 h for low-molecular-weight easy-flow grades to above 1000 h for bimodal, low-MFR pipe grades. Injection-moulding grades with MFR above 8 g/10 min generally trade lower ESCR for fill speed. For applications with continuous surface-active chemical exposure, a reduced melt index and a known comonomer type are more important than room-temperature impact value.

Mechanical data under ISO 527-2 and ISO 179-1 are not sufficient on their own

Representative class-level data for unreinforced PE-HD ALTECH, unfilled PE-HD, a 20 wt% talc-filled polypropylene compound, and a dry 30 wt% glass-fibre-reinforced polyamide 6 are shown below. The PE-HD ALTECH values assume no mineral filler; grade-specific filler and impact-modifier packages will shift the envelope.

The main differences between PE-HD ALTECH and unfilled PE-HD are not necessarily visible in bulk tensile data; they appear in additive retention, molecular weight distribution control, and batch-to-batch melt flow range. Relative to a 20 wt% talc-filled polypropylene, the PE-HD matrix has lower density, lower heat deflection temperature under load, and higher linear shrinkage after moulding, but higher elongation at break and lower moisture sensitivity. Relative to 30 wt% glass-fibre-reinforced polyamide 6, the PE-HD compound has a much lower tensile modulus and lower HDT, but it does not require pre-drying for moisture uptake and it resists hydrolysis in polar aqueous environments.

When mineral-filled PE-HD replaces unfilled PE-HD in thermoforming

When a mineral-filled PE-HD replaces an unfilled high-density polyethylene in extruded sheet and thermoforming, the process change involves more than a density increase. The filler raises low-shear melt viscosity and melt strength, reducing sag at the thermoforming temperature of 160 °C–200 °C. The thermal conductivity of an unfilled PE-HD is approximately 0.40 W/(m·K) to 0.45 W/(m·K); the addition of 20 wt% to 40 wt% mineral filler can increase this to 0.60 W/(m·K)–1.0 W/(m·K), reducing the sheet heating time for a given thickness. However, the same filler reduces drawability and increases the risk of local thinning at corners when the plug speed exceeds the material’s deformation rate. Published data for this specific PE-HD ALTECH configuration at filler loadings above 40 wt% is limited; processing trials on vacuum-assisted plug-assisted forming lines should therefore use starting sheet temperatures in the upper half of the crystalline melting range and an adjustable plug delay.

For parts with wall-thickness distribution requirements, a hot mould at 60 °C–90 °C and a well-controlled sheet temperature of 170 °C–190 °C are standard. Compared with unfilled PE-HD, mineral-filled grades produce reduced post-forming shrinkage and lower part-to-part dimensional variability, but cut edges can show filler-related wear on steel trim tools; hardened tool steel with Rockwell hardness of 58 HRC to 62 HRC is specified for blanking operations.

Chemical resistance of the PE-HD matrix is assessed by immersion testing under ASTM D543 at 23 °C and 60 °C. The material generally withstands dilute acids, alkalis, saline solutions, and many polar solvents with mass change below 1% after 7 days. It is not suitable for continuous contact with strong oxidising acids, aromatic hydrocarbons, or chlorinated solvents, where swelling and environmental stress cracking may occur. Outdoor weathering requires a UV-stabilised grade or a carbon black masterbatch added at 2 wt%–2.5 wt%. Melt blending with polyamide or polyester is not recommended because high interfacial tension produces gross phase separation and delamination in moulded articles.

Storage and drying boundaries are narrow. The granulate retains processability for 24 months when kept in sealed, UV-shielded packaging at 15 °C–35 °C and below 60% relative humidity. At higher humidity or after outdoor exposure, 80 °C drying for 2 h is applied only to remove surface condensation because the polymer itself is non-hygroscopic. The practical quality window for unfilled PE-HD injection moulding is set by screw recovery time, gate freeze time, and cushion stability rather than by thermal degradation. Holding at melt temperatures above 280 °C for more than 15 min can produce odour and a drop in impact strength, although the onset of thermo-oxidative degradation in properly stabilised compounds is normally above 300 °C under ISO 11357-6.