Angst+Pfister PE-HD APSOPLAST is a high-density polyethylene semi-finished stock shape used for machined components in process vessels, water treatment, food-contact tooling, and wear parts that operate in wet or chemically mild conditions. The model designation PE-HD APSOPLAST identifies the material as belonging to the PE-HD class under ISO 1043-1; it does not indicate a single fixed viscosity or stabilizer formulation. Available stock forms include sheet, round bar, and welding wire, with dimensional schedules that must be confirmed against the manufacturer’s current stock list. Because semi-finished polyethylene is produced by extrusion or pressing, batch-to-batch differences in melt-flow rate, density, and stabilization can affect machining and chemical resistance. Design calculations should therefore use the inspection certificate for the supplied lot rather than generic polyethylene data alone.

Typical unfilled PE-HD densities determined according to ISO 1183-1 fall between 0.94 g/cm³ and 0.96 g/cm³. Tensile yield strength under ISO 527-2 at 23 °C commonly lies between 18 MPa and 26 MPa, and tensile modulus is typically in the range of 800 MPa to 1,200 MPa. The material absorbs less than 0.01% water by mass after 24 h immersion under ISO 62. These values are not product-specific guarantees; they define the engineering envelope for unfilled PE-HD. If the APSOPLAST grade is pigmented, filled, or produced from recycled feedstock, the values change and must be verified.

Stock-shape tolerances depend on the manufacturing route. Extruded sheet is generally supplied with thickness tolerances conforming to DIN 16955 or equivalent; pressed sheet may exhibit wider thickness variation. Machined parts should be designed with a minimum oversize allowance of 2 mm to 3 mm per face unless the stock is stress-relieved before machining.

What Distinguishes PE-HD APSOPLAST from PE-UHMW in Sliding and Impact-Loaded Components?

In sliding and impact-loaded parts, PE-HD APSOPLAST occupies a lower molecular weight node than PE-UHMW. Standard PE-HD weight-average molar mass is commonly reported between 2 × 10⁵ g/mol and 5 × 10⁵ g/mol, while PE-UHMW grades typically fall between 3 × 10⁶ g/mol and 9 × 10⁶ g/mol. The lower molecular weight improves melt flow and machinability but reduces notched impact strength. Under ISO 179-1/1eA at 23 °C, unfilled PE-HD notched Charpy values commonly range from 4 kJ/m² to 12 kJ/m²; PE-UHMW sheets often record no break under the same test configuration. For high-energy impact pads, chain guides, or scraper blades, substitution of PE-HD APSOPLAST for PE-UHMW requires recalculation of impact energy and fatigue cycles.

In dry or lightly lubricated sliding, PE-HD has a higher wear factor than PE-UHMW. No material-specific abrasion value for every APSOPLAST stock dimension is published; if the application includes coarse slurries or high contact pressure, sand-slurry or Taber abrasion data should be obtained from the manufacturer. Frictional heating is the limiting variable. At surface velocities above 1 m/s under continuous load, interface temperatures can exceed 60 °C, causing localized softening and dimensional loss. This boundary is more restrictive for PE-HD than for PE-UHMW and must be evaluated before replacing wear strips, pump plates, or curved guides.

Compared with PA6 and POM-C stock shapes, PE-HD APSOPLAST has lower tensile strength and higher thermal expansion but lower water absorption and superior resistance to many aqueous process fluids. PA6 absorbs 2% to 3% moisture under humid conditions; PE-HD remains below 0.01% in 24 h. POM-C is stronger and dimensionally more stable but is attacked by some acid and chlorine-containing media that do not degrade PE-HD. These differences are inputs for materials selection, not rankings.

Thermal joining of PE-HD APSOPLAST is performed by hot-gas welding, extrusion welding, or heated-tool butt welding. Hot-gas welding of high-density polyethylene typically uses a nozzle gas temperature between 200 °C and 220 °C. The welding rod and base material must melt without surface oxidation. DVS 2207-1 provides welding parameters for PE-HD in hot-gas and extrusion processes. Heated-tool butt welding of sheets from 10 mm to 60 mm uses plate temperatures of 210 °C to 230 °C and cooling under pressure. Joint quality depends on gas flow, root gap, and travel speed. Oxidized surfaces, dust, or moisture at the weld interface reduce tensile strength at the joint by 20% to 30% relative to the parent sheet.

Thermal expansion is a primary design input. The coefficient of linear thermal expansion for PE-HD measured by ISO 11359-2 between 23 °C and 60 °C typically ranges from 1.1 × 10⁻⁴ K⁻¹ to 1.3 × 10⁻⁴ K⁻¹. A 500 mm sheet section heated from 20 °C to 40 °C expands by approximately 1.1 mm to 1.3 mm. Machined parts with close clearances require expansion gaps; rigid fasteners in unrelieved holes can cause buckling when temperature differentials exceed 20 °C. For tank liners and long wear strips, thermal movement must be accommodated by slotted holes or flexible supports.

When Chlorinated or Aromatic Media Replace Weak Aqueous Acids

PE-HD APSOPLAST resists many dilute acids, alkalis, salt solutions, and polar solvents at temperatures below 40 °C. Resistance is concentration-dependent and stress-dependent. Exposure to 50% sulfuric acid or 30% sodium hydroxide at room temperature generally produces low mass change in unstressed immersion tests, but oxidizing acids such as concentrated nitric acid and chromic acid cause chain scission and embrittlement. Chlorinated solvents and aromatic hydrocarbons should not be specified for continuous contact because they swell the amorphous phase. Under external stress, swelling converts to environmental stress cracking, and a component can fail below the short-term tensile strength.

Environmental stress cracking resistance is measured by ASTM D1693 or ISO 22088-3. For PE-HD, ESCR is strongly influenced by melt-flow rate, density, comonomer type, and mold-in or machining residual stress. The APSOPLAST stock shape should not be assumed to match blow-moulding grades with high ESCR unless the manufacturer’s certificate states a specific test result. In sodium hypochlorite service, dilute solutions below 35 °C can be tolerated in continuously welded tanks with no sharp notches, but published data for this specific configuration is limited. Field testing with unstressed coupons is required before production use.

Compared with PP-C homopolymer stock, PE-HD APSOPLAST has better low-temperature impact resistance but a lower heat deflection temperature. Heat deflection temperature under ISO 75-2 method B for PE-HD is generally 65 °C to 75 °C, while PP-C homopolymer can reach 90 °C to 100 °C. Therefore PP-C is used in hot water linings where PE-HD softens, while PE-HD is preferred where low-temperature ductility or higher environmental stress cracking resistance governs.

Machining PE-HD APSOPLAST requires low cutting forces and high rake angles. The material behaves as a viscoelastic solid; elastic recovery can cause the cut surface to spring back and grip the tool. In band sawing of sheets above 30 mm, a hook-tooth blade with a 10 mm to 12 mm pitch and a cutting speed near 300 m/min clears chips and reduces frictional heat. For milling, climb cutting with sharp carbide inserts and surface speeds of 150 m/min to 300 m/min produce continuous chips. High-speed steel tools are acceptable for short runs, but tool life decreases because heat generation softens the surface and causes smearing.

Dimensional control depends on thermal management. Reference dimensions should be taken at 23 °C ± 2 °C according to ISO 291. Residual stress from extrusion or pressing can cause warping after asymmetric material removal. Roughing passes should remove 70% of the stock from both faces before finishing, followed by a light final pass of 0.25 mm to 0.50 mm. This sequence reduces distortion in long wear strips, tank flanges, and pump housings. If coolant is used, it must be free of aromatic hydrocarbons and chlorinated solvents that stress-crack the surface.

Storage before machining should be in a flat, supported condition at 15 °C to 30 °C. Polyethylene oxidizes slowly and can absorb hydrocarbon vapours; storage near solvent vapours or ozone-generating equipment must be avoided. Sheets should be conditioned to 23 °C for at least 4 h before final inspection.

Regulatory Status and Oxidation-Limited Service Boundaries

Unfilled polyethylene base polymers can comply with FDA 21 CFR 177.1520 for food-contact use if produced from authorized olefin monomers and used within the specified end-use limitations. European food-contact compliance is assessed under EU 10/2011 with overall migration testing. A supplier declaration for PE-HD APSOPLAST should confirm that the stock shape contains no intentionally added PFAS, no phthalates, and no bisphenol A monomer; polyethylene does not contain BPA by monomer chemistry. Machined components must be cleaned before food service to remove cutting oils, dust, and fine particles.

Oxidation resistance limits long-term service. Lightly stabilized PE-HD exposed to hot water above 60 °C can undergo oxidative degradation, particularly in the presence of residual chlorine. Stabilization packages are proprietary and vary among stock-shape producers. Without material-specific oxidative induction time data from ISO 11357-6, continuous exposure in hot water should be limited to 50 °C. Ultraviolet exposure degrades the surface; outdoor use requires a UV-stabilized grade or carbon black loading near 2% to 2.5%. Natural PE-HD APSOPLAST is not recommended for permanent outdoor load-bearing parts unless the specification explicitly includes UV stabilization.